HK1261939B - Tunable electromagnetic coupler and modules and devices using same - Google Patents

Description

Tunable electromagnetic coupler and module and device using the same

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) and PCT Section 8 of co-pending U.S. Provisional Patent Application No. 62/329,385, filed April 29, 2016, co-pending U.S. Provisional Patent Application No. 62/463,010, filed February 24, 2017, and co-pending U.S. Provisional Patent Application No. 62/484,940, filed April 13, 2017, and each of which is incorporated herein by reference in its entirety for all purposes.

Background Art

Directional couplers are widely used in front-end module (FEM) products, such as radio transceivers, wireless handheld devices, and the like. For example, directional couplers can be used to detect and monitor electromagnetic (EM) output power. In addition, when a radio frequency (RF) signal generated by an RF source is provided to a load, such as an antenna, a portion of the RF signal may be reflected back from the load. An EM coupler may be included in the signal path between the RF source and the load to provide an indication of the forward RF power of the RF signal traveling from the RF source to the load and/or an indication of the reverse RF power reflected back from the load. EM couplers include, for example, directional couplers, bidirectional couplers, multi-band couplers (e.g., dual-band couplers), and the like.

1 , an EM coupler 100 generally has a power input port 102, a power output port 104, a coupled port 106, and an isolated port 108. The electromagnetic coupling mechanism, which may include inductive or capacitive coupling, is typically provided by two parallel or overlapping transmission lines, such as microstrip, stripline, coplanar line, or the like. A main transmission line 110 extends between the power input port 102 and the power output port 104 and provides the majority of the signal 116 from the power input port 102 to the power output port 104. A coupled line 112 extends between the coupled port 106 and the isolated port 108 and can extract a portion 114 of the power traveling between the power input port 102 and the power output port 104 for various purposes, including various measurements. When the terminating impedance is presented to the isolated port 108, an indication of the forward RF power traveling from the power input port 102 to the power output port 104 is provided at the coupled port 106.

1 , portion 114 is the portion of the main signal 116 RF power that travels from the power input port 102 to the power output port 104. EM couplers are typically rated by their coupling factor, usually expressed in decibels, which is a measure of the ratio of the power of portion 114 coupled from the power of the input signal 116. For example, a 20 dB coupler will provide a coupled signal, such as portion 114, that is 20 dB lower than the input power, or approximately 1% of the input power.

It is generally desirable to have a relatively low coupling factor so as not to unduly remove power from the primary signal, but it is also desirable for the coupling factor to be deterministic and consistent so as to allow accurate assessment of the power of the primary signal.

Summary of the Invention

Various aspects and embodiments relate to electromagnetic couplers having structures designed to allow tuning of coupler parameters and performance. As discussed in more detail below, the tuning elements can be formed from various materials (e.g., conductors or semiconductors) that are close to the transmission lines that form the tunable electromagnetic coupler, which can also be combined with various components and features to form modules, devices, and systems. The tunable electromagnetic coupler can allow for selectively adjustable coupling factors and can also advantageously achieve filtering effects, as discussed in more detail below.

According to one aspect, an electromagnetic coupler is provided. The coupler includes a first transmission line extending between an input port and an output port, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, a tuning element disposed adjacent to at least one of the first and second transmission lines, and an adjustable impedance coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port. The amplitude of the coupled signal is related to the amplitude of the input signal via a coupling factor, and the adjustable impedance is configured to adjust the coupling factor.

In some embodiments, the reference node is ground. Some embodiments include a reactive component in the impedance, while other embodiments include only a resistive component. In certain embodiments, the tuning element is configured to selectively decouple from the first transmission line and the second transmission line, for example, via a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments, a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

According to another aspect, an electromagnetic coupler module is provided, comprising a substrate having a dielectric layer with a first transmission line disposed thereon and extending between an input port and an output port, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, a tuning element disposed adjacent to at least one of the first and second transmission lines, and an adjustable impedance coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port. The amplitude of the coupled signal is related to the amplitude of the input signal via a coupling factor, and the adjustable impedance is configured to adjust the coupling factor. The module may include a protective outer surface that overmoldes the substrate, the first and second transmission lines, and at least a portion of the tuning element.

In some embodiments, the reference node is ground. Some embodiments include a reactive component in the impedance, while other embodiments include only a resistive component. In certain embodiments, the tuning element is configured to selectively decouple from the first transmission line and the second transmission line, for example, via a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments, a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Some embodiments include an antenna switch connected to one of the input port or the output port.Some embodiments include a power amplifier coupled to one of the input port and the output port.

According to another aspect, an electronic device is provided and includes a first transmission line extending between an input port and an output port, a transceiver coupled to the input port and configured to generate a transmit signal, a second transmission line adjacent to the first transmission line and extending between the coupled port and the isolated port, a tuning element disposed adjacent to at least one of the first and second transmission lines, and an adjustable impedance coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port. The input signal may be a transmit signal. The amplitude of the coupled signal is related to the amplitude of the input signal via a coupling factor, and the adjustable impedance is configured to adjust the coupling factor.

In some embodiments, the reference node is ground. Some embodiments include a reactive component in the impedance, while other embodiments include only a resistive component. In certain embodiments, the tuning element is configured to selectively decouple from the first transmission line and the second transmission line, for example, via a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments, a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Some embodiments include an antenna switch module connected to the input port or the output port and configured to direct the transmit signal to at least one of the transceiver and the antenna. Some embodiments include a power amplifier connected between the transceiver and the input port, the power amplifier configured to receive and amplify the transmit signal.

Some embodiments include an antenna coupled to the output port, the antenna configured to transmit the transmit signal and receive the receive signal. The output port may also be configured to receive the receive signal from the antenna and provide the receive signal at the input port.

Some embodiments include a sensor coupled to the coupling port and configured to detect the power level of the coupled signal. Some embodiments include a baseband subsystem coupled to the transceiver and configured to provide a baseband signal to the transceiver. In some embodiments, any one of a sensor module, a memory, a baseband subsystem, a user interface, and/or a battery may be included.

In yet another aspect, an electromagnetic coupler is provided, comprising a first transmission line extending between an input port and an output port, the first transmission line configured to provide an output signal at the output port in response to receiving an input signal at the input port; a second transmission line disposed adjacent to the first transmission line and extending between the coupled port and the isolated port; a tuning element disposed adjacent to at least one of the first transmission line and the second transmission line; and an impedance including a reactive component coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port. The impedance and the tuning element are configured to filter a range of frequency components of the output signal.

In some embodiments, the reference node is ground. Some embodiments include a resistive component in the impedance. The impedance may be adjustable. In certain embodiments, the tuning element is configured to selectively decouple from the first transmission line and the second transmission line, for example, via a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments, a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

According to another aspect, an electromagnetic coupler module is provided, comprising a substrate having a dielectric layer having a first transmission line disposed thereon, the first transmission line extending between an input port and an output port; a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port; a tuning element disposed adjacent to at least one of the first and second transmission lines; and an impedance including a reactive component coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port. The impedance and the tuning element are configured to filter a range of frequency components of the output signal.

In some embodiments, the reference node is ground. Some embodiments include a resistive component in the impedance. The impedance may be adjustable. In certain embodiments, the tuning element is configured to selectively decouple from the first transmission line and the second transmission line, for example, via a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments, a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Some embodiments include an antenna switch connected to one of the input port and the output port.Some embodiments include a power amplifier coupled to one of the input port and the output port.

According to another aspect, an electronic device is provided. The electronic device includes a first transmission line extending between an input port and an output port, a transceiver coupled to the input port and configured to generate a transmit signal, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, a tuning element disposed adjacent to at least one of the first and second transmission lines, and an impedance including a reactive component coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port. The impedance and the tuning element are configured to filter a range of frequency components of the output signal.

In some embodiments, the reference node is ground. Some embodiments include a resistive component in the impedance. The impedance may be adjustable. In certain embodiments, the tuning element is configured to selectively decouple from the first transmission line and the second transmission line, for example, via a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments, a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Some embodiments include an antenna switch module connected to the input port or the output port and configured to direct the transmit signal to at least one of the transceiver and the antenna. Some embodiments include a power amplifier connected between the transceiver and the input port, the power amplifier configured to receive and amplify the transmit signal.

Some embodiments include an antenna coupled to the output port, the antenna configured to transmit the transmit signal and receive the receive signal. The output port may be configured to receive the receive signal from the antenna and provide the receive signal at the input port.

Some embodiments include a sensor coupled to the coupling port and configured to detect the power level of the coupled signal. Some embodiments include a baseband subsystem coupled to the transceiver and configured to provide a baseband signal to the transceiver. In some embodiments, any one of a sensor module, a memory, a baseband subsystem, a user interface, and/or a battery may be included.

Other aspects, embodiments, and advantages of these exemplary aspects and embodiments are discussed in detail below. The embodiments disclosed herein may be combined with other embodiments in any manner consistent with at least one of the principles disclosed herein, and references to "an embodiment," "some embodiments," "alternative embodiments," "various embodiments," "one embodiment," and the like are not necessarily mutually exclusive and are intended to indicate that the particular features, structures, or characteristics being described may be included in at least one embodiment. These terms, as they appear herein, do not necessarily all refer to the same embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings, which are not drawn to scale. The drawings are included to provide illustration and a further understanding of the various aspects and embodiments and are incorporated into and constitute a part of this specification but are not intended to be a definition of the limitations of the invention. In the drawings, each identical or nearly identical component illustrated in various figures is represented by a like numeral. For clarity, not every component is labeled in every figure. In the drawings:

FIG1 is a diagram of one example of an electromagnetic coupler;

Figure 2 is a diagram of the coupling theory;

FIG3A is a top view schematic diagram of an example of a tunable coupler;

FIG3B is a schematic end view of the tunable coupler of FIG3A ;

FIG3C is a schematic end view of an alternative example of a tunable coupler;

FIG3D is a top view schematic diagram of an alternative example of a tunable coupler;

FIG3E is a top view schematic diagram of an alternative example of a tunable coupler;

FIG4 is a side schematic diagram of a layout of an exemplary tunable coupler;

5 is a graph of coupling factor versus frequency for a series of resistors applied to a tuning element.

6 is a graph of insertion loss versus frequency for a series of capacitances applied to a tuning element.

7 is a graph of insertion loss versus frequency for a series of inductors applied to a tuning element.

FIG8 is a schematic diagram of an example of adjustable impedance;

9A-9C are block diagrams of various examples of wireless devices including tunable couplers; and

10 is a block diagram of one example of a module including a tunable coupler.

DETAILED DESCRIPTION

Conventional multilayer coupler designs, whether implemented in a laminate or semiconductor manufacturing process, are typically designed to have a specific coupling factor at a specific frequency or frequency band. By incorporating a tuning element and an adjustable ground impedance associated with the tuning element, tunable couplers, modules, and devices according to aspects disclosed herein allow for an adjustable coupling factor. The adjustability of the coupling factor can advantageously allow the coupler to be adapted to multiple frequency bands and/or multiple applications, which can allow for fewer parts to be stocked to support a range of products per band/application, and allow for adjustability to correct for manufacturing variations, which in turn increases production yield, all of which reduces costs. For example, the ground tuning element according to various aspects and examples disclosed herein provides compensation for variations in the coupling factor caused by variations in the dielectric thickness between the metal layers forming the main transmission line and the coupled line. The adjustable impedance coupled to the tuning element, i.e., a selectable impedance placed in series with the connection to ground, allows for adjustment of this compensation effect and changes in the coupling factor, thereby allowing for multiple selectable coupling factors and filtering effects based on the selected impedance. The tuning element having a selective impedance coupled to ground forms a variable electromagnetic shunt that affects the capacitive and inductive coupling between the main transmission line 110 (see, eg, FIG. 1 ) and the coupled line 112 .

Capacitive and inductive coupling are briefly described with reference to FIG2 , which shows a power input port 102 , a power output port 104 , a coupled port 106 , and an isolated port 108 . The main transmission line 110 and the coupled line 112 can be considered inductors, and due to their proximity, inductive coupling exists between them. Furthermore, the proximity of the coupled line 112 to the main transmission line 110 forms a capacitor, resulting in capacitive coupling between the two lines. Both forms of coupling—inductive and capacitive—vary with the proximity between the main transmission line 110 and the coupled line 112, as well as other factors such as geometry and material selection. Accordingly, if the proximity between the main transmission line and the coupled line changes, the coupling factor of the EM coupler will vary. Modern transmission line couplers can be manufactured using lamination and/or semiconductor technology, and the transmission lines can be separated from each other by layers of dielectric material. The coupling factor and other characteristics of the EM coupler can also be altered by other elements, such as the tuning elements disclosed herein, that influence the inductive and capacitive coupling between the main transmission line and the coupled line.

Various aspects and embodiments provide a coupler that includes additional components that affect inductive and capacitive coupling to adjust the coupling factor and provide a frequency-dependent filter effect. Coupling factor variations can also be affected by variations in the spacing between the main transmission line and the coupled line, such as variations in dielectric thickness between the lines, spacing between metal traces forming the lines, or variations in line width and height, all of which are caused by design differences and variations during the manufacturing process. Obtaining a specific coupling factor is desirable because the coupled signal can be used to determine the power of the main signal, and thus the ratio of the coupled signal to the main signal (i.e., the coupling factor) can be a key factor in meeting challenging performance specifications. In mobile phone applications, the ability to accurately monitor and control signal power is crucial. As devices and components become smaller and are required to support more and wider frequency bands, the adjustability of the coupling factor and compensation for variations introduced by the manufacturing process (referred to herein as process variation) may become increasingly important. Embodiments of the EM coupler disclosed herein include additional components that function as tuning stubs to offset coupling factor variations and allow for adjustability of the coupling factor and filter effect.

It should be understood that the embodiments of the methods and apparatus discussed herein are not limited to the construction details and component arrangements set forth in the following description or shown in the accompanying drawings. The methods and apparatus can be implemented in other embodiments and can be practiced or implemented in various ways. The examples of specific implementations provided herein are for illustrative purposes only and are not restrictive. In addition, the words and terms used herein are for descriptive purposes only and should not be considered restrictive. As used herein, "include," "comprising," "having," "containing," "involving," and their variations are meant to include the items listed thereafter and their equivalents as well as additional items. References to "or" can be interpreted as inclusive, so that any term described using "or" can indicate any term in a single, more than one, and all of the terms described. Any reference to front and back, left and right, top and bottom, upper and lower, sides, ends, vertical and horizontal, etc. is intended to facilitate description and not to limit the present system and method or its components to any one positional or spatial direction.

According to certain embodiments, in an EM coupler, a coupled line can be positioned in various orientations relative to a main transmission line. One or more additional traces or transmission lines can be positioned to influence the coupling between the main transmission line and the coupled line in a manner that tends to affect the coupling factor, thereby enabling the fabricated EM coupler to have lower coupling factor variation than conventional designs, as well as allowing for adjustability of the coupling factor and the achievement of a filter effect.

Various examples of such arrangements are shown in Figures 3A-3E. Figure 3A is a top-down schematic diagram of an example of an EM coupler, showing a main transmission line 110, a coupled line 112, and a tuning element 118 coupled to ground 122 via one or more impedances 124. Figure 3B is a corresponding end view of the transmission line shown in Figure 3A. In this example, the tuning element 118 is in the same plane as the main transmission line 110, and the coupled line 112 is located in a different plane below (or above) the tuning element 118, separated by a dielectric material 120 and offset from the main transmission line 110. In an alternative example, as shown in Figure 3C, the tuning element 118 can be in the same plane as the coupled line 112, and the main transmission line 110 can be located in a different plane below (or above) the tuning element 118, separated by a dielectric material 120 and offset from the coupled line 112.

Transmission lines 110, 112, tuning element 118, and dielectric material 120 can be fabricated, for example, by lamination or deposition and etching processes. As shown in Figures 3B and 3C, the thickness of dielectric material 120 can determine the spacing or distance between the first and second planes, and therefore the spacing or distance between tuning element 118 and coupled line 112 or main transmission line 110. This spacing, the presence of tuning element 118, the value of impedance 124, and other factors all affect the capacitive and inductive coupling between the lines.

The tuning element 118 in the example of Figures 3A-3C includes a ground 122 at each end through an impedance 124, forming a partial ground plane and generating an electromagnetic shunt effect with the coupled line 112 and/or the main transmission line 110. The impedance 124 at each ground 122 allows for selective and adjustable coupling of the tuning element 118 to the ground. In some embodiments, the tuning element 118 may include one or more impedances 124, through which the tuning element 118 is coupled to the ground 122. Each impedance 124 may be an adjustable impedance and may be controlled by various embodiments of an element having a variable impedance parameter (e.g., resistance, inductance, capacitance). In some embodiments, the impedance 124 may be adjustable from zero ohms (i.e., directly connected to the ground 122) to infinite impedance (i.e., an open circuit with no connection to the ground 122) and may include or accommodate any suitable impedance therebetween, whether real or complex, including any resistance or reactance values. In some examples, adjustable impedance 124 can include multiple switching elements interconnected in a manner that selectively includes or excludes the elements from impedance 124. Such examples are discussed in more detail below with reference to FIG8. Selective switching of elements can be implemented using transistors as switching elements, such as field effect transistors or bipolar junction transistors, for example, using various manufacturing techniques. Alternative embodiments can also include switches to selectively connect tuning element 118 to an alternate node, a reference voltage, or other means other than ground 122.

In various embodiments, the tuning element 118 can be adjustably coupled to the ground 122 via one or more impedances 124, including being directly electrically connected to or disconnected from the ground 122, thereby removing the influence of the tuning element 118 when it may not be needed. Additionally, in various embodiments, the impedances 124 and the ground 122 may be located at different locations. For example, while the impedances 124 in Figures 3A-3C are shown connected near the ends of the tuning element 118, alternative embodiments may include impedances 124 at additional or alternative locations, such as along the length of the tuning element 118, and may be coupled to the tuning element 118 at its sides, in the middle, or elsewhere.

3B , the coupled line 112 is located substantially below the tuning element 118 and offset from the main transmission line 110. In other embodiments, the coupled line 112 can be substantially below the main transmission line 110 and offset from the tuning element 118, or the coupled line 112 can be offset from each of the main transmission line 110 and the tuning element 118, or the transmission lines can be otherwise oriented relative to each other in any number of ways, such as adjacent to each other on the same plane, or otherwise. Additionally, it should be understood that the main transmission line 110, the coupled line 112, and the tuning element 118 can have various shapes and can be constructed from various materials. The main transmission line 110 and the coupled line 112 can be formed from a conductor such as a metal, and the tuning element 118 can also be formed from a conductor, but can alternatively be formed from a semiconductor or other material selected based on its effect on the coupling factor.

As described above, any of the main transmission line 110, coupled line 112, and tuning element 118 can have a variety of shapes and, in particular, need not be straight lines or confined to a particular plane. Furthermore, many variations can be made to influence the coupling factor or other effects and tailor the tuning effect of tuning element 118, including but not limited to the material, geometry (width, length, shape, etc.), and position of any of the main transmission line 110, coupled line 112, and tuning element 118.

As described herein, any physical arrangement of the main transmission line 110, coupled line 112, and tuning element 118 suitable for performing or acting in a tuning manner may be included in various embodiments. For example, FIG3D and FIG3E illustrate alternative physical arrangements of the main transmission line 110, coupled line 112, and tuning element 118. FIG3D and FIG3E each illustrate the main transmission line 110 implemented as a loop, with the coupled line 112 implemented as a loop adjacent to the main transmission line 110 and, in this example, in a different plane than the main transmission line 110, e.g., on a different layer, with a dielectric therebetween. The example of FIG3D includes the tuning element 118 in the form of a loop in the same plane as the main transmission line 110, with the end selectively switched 124 to ground 122. The tuning element 118 of the example of FIG3E also includes an adjustable impedance 124 coupled to ground 122. Alternative embodiments include numerous variations in the physical structure, materials, and arrangement of the main transmission line 110, coupled line 112, and tuning element 118.

Figures 3A-3E illustrate various physical shapes and arrangements of the main transmission line 110, coupled line 112, and tuning element 118 relative to one another, and Figure 4 illustrates an example of the location of these elements within a stack 400. Figure 4 illustrates some aspects of an exemplary construction of any of the EM couplers described herein. The example of Figure 4 includes a circuit stack 400 comprising a laminate substrate 410 and a bare die 420 mounted on and electrically connected to the laminate substrate 410 via solder bumps 412. The substrate 410 and bare die 420 are each constructed from multiple layers of conductive (e.g., metal) or semiconductor material separated by a dielectric, with interconnects between the layers passing through conductive vias. In various embodiments, the bare die 420 may be electrically connected to the substrate 410 via other arrangements, such as pins, sockets, pads, balls, solder pads, and the like. Other embodiments may include only the laminate substrate 410 without the bare die 420.

In the example of FIG4 , the main and coupled line portions of the EM coupler are implemented within a layer of substrate 410. FIG4 shows an “end view” of the main transmission line 110 and coupled line 112, as their lengths may extend perpendicular to the plane of the image. As shown, similar to the arrangement of FIG3B , coupled line 112 is formed below and on a layer offset from the main transmission line 110, and below and adjacent to tuning element 118. In an embodiment and as shown in FIG4 , tuning element 118 may be in the same layer as and adjacent to the main transmission line 110. As described above, the main transmission line 110 and coupled line 112 may be interchanged in the figure, or other physical arrangements of the elements relative to each other may be suitable. Also as described above, in some embodiments, any of the main transmission line 110, coupled line 112, or tuning element 118 may include curved or angled portions and may not be straight. In addition, the main transmission line 110, coupled line 112, and tuning element 118 can be implemented in one or more layers of either substrate 410 or bare die 420. In addition, although stack 400 has been described as substrate 410 and bare die 420, stack 400 can be equivalently described as a circuit board (e.g., 410) and a substrate (e.g., 420), or the stack can have multiple and/or additional layered structures. For example, a multi-chip module can have a substrate and multiple bare die, and the device can include a circuit board with one or more multi-chip modules mounted thereon. The main transmission line 110, coupled line 112, and tuning element 118 of any EM coupler described herein can be implemented between or across multiple layers in various structures.

Additionally, switches, grounding, filters, impedances (such as impedance 124), control circuitry, communication interfaces, and memory, among other components, may also be implemented within the stack at one or more layers of the circuit board, substrate, or die, or may be distributed among the layers, or may be external to the stack (such as stack 400), or any combination thereof.

As described above, the effect of tuning element 118, coupled to ground 122 via impedance 124, is to shunt some of the coupled power away from other elements, namely, main transmission line 110 and coupled line 112. The resistive component of impedance 124 causes tuning element 118 to shunt more or less power, thereby affecting the coupling factor. Also including a reactive component in impedance 124 can cause tuning element 118 to shunt more or less power based on frequency, thereby producing a filtering effect. Certain examples may include only a resistive component (i.e., an impedance having only real values) and no reactive component (i.e., an impedance without any complex or imaginary values). This resistive-only impedance may be implemented to allow adjustment of the coupling factor without frequency-dependent effects.

Accordingly, an electromagnetic coupler having a tuning element 118 according to aspects and embodiments disclosed herein allows for tunable adjustment of the coupling factor and frequency-dependent filtering to accommodate different needs and applications, and/or to compensate for variations in the manufacturing process. The adjustable effect of the tuning element 118 is discussed with reference to the performance graphs shown in Figures 5 to 7. Figure 5 shows multiple curves of the coupling factor on the Y-axis over a range of frequencies on the X-axis. For an impedance 124 similar to, for example, that shown in Figures 3A-3B , each curve represents a different resistance value between 0 and 5 ohms. Curve 512 shows the coupling factor versus frequency for an impedance 124 of zero ohms (i.e., a direct connection to ground 122). Curve 514 shows the coupling factor versus frequency for an impedance 124 of 2 ohms, while curve 516 shows the coupling factor for an impedance 124 of 5 ohms. Intermediate curves show the coupling factors for intermediate integer resistance values of the impedance 124. The coupling factor values at a frequency of 2.00 GHz for resistive impedance 124 values of 0 to 5 ohms are shown in Table 1 in decibels.

Impedance (Ohms) Coupling factor at 2.00GHz 0.00 35.93dB 1.00 33.89dB 2.00 31.40dB 3.00 29.70dB 4.00 28.62dB 5.00 27.91dB

Table 1

As can be seen with reference to Table 1, in this example, by varying the resistive impedance 124 applied to couple the tuning element 118 to ground 122, the coupling factor can be adjusted over an 8 dB range from approximately 28 dB to 36 dB. Accordingly, varying the resistive coupling of the tuning element 118 to ground to vary the coupling factor of the electromagnetic coupler can be advantageously achieved. Including (and varying) a reactive component in the coupling to ground (e.g., impedance 124) of the tuning element 118 can advantageously impart (and vary) frequency effects (such as frequency notch filtering), as discussed further below.

Aspects and embodiments of frequency filtering can be described with reference to insertion loss. Insertion loss is the comparison of the signal power at the output of a coupler to the signal power at the input. Most of the input signal power is typically transmitted to the output port, with a relatively small amount of signal power coupled to the coupled port, resulting in insertion loss typically approaching zero decibels within the operating frequency range of the coupler. Each of Figures 6 and 7 shows multiple curves of insertion loss for a tunable coupler similar to those shown in Figures 3A-3B over a range of frequencies. Each curve represents a different capacitive impedance 124 in the case of Figure 6 and a different inductive impedance 124 in the case of Figure 7. As shown in Figures 6 and 7, at higher frequencies, the reduced signal output represents signal power that is rejected by the coupler, e.g., signal power that is not transmitted to the output port. The tuning element 118 shunts a portion of the power to ground 122 via impedance 124, which contributes to the signal power that is rejected (e.g., not transmitted to the output port). This effect is advantageously used to reject, for example, unwanted signal power within a specific frequency range.

6 , curve 610 shows the insertion loss of an impedance 124 with a capacitance of 10 picofarads (pF) versus frequency. Curve 620 shows the insertion loss of an impedance 124 with a capacitance of 6 pF. And curve 630 corresponds to an impedance 124 with a capacitance of 3 pF. The middle curve of FIG6 represents integer capacitance values. As shown in FIG6 , this example provides a coupler that can be adjusted to produce an approximately 6 dB peak reduction in signal power at adjustable frequencies from approximately 2.8 GHz (at the peak of curve 610) to greater than 6 GHz (at the peak of the curve outside the scale on the right side of FIG6 ).

Referring to FIG7 , curve 710 shows the insertion loss versus frequency for an impedance 124 having an inductance of 15 nanohenries (nH). Curve 720 shows the insertion loss for an impedance 124 having an inductance of 11 nH, and curve 730 corresponds to an impedance 124 having an inductance of 8 nH. The middle curve in FIG7 represents intermediate integer inductance values. As can be seen with reference to FIG7 , this example provides a coupler that can be adjusted to produce approximately a 15 dB peak reduction in signal power at adjustable frequencies from approximately 4.1 GHz (at the peak of curve 710 ) to greater than 6 GHz (at the peak of the curve off the scale on the right side of FIG7 ).

The graphs in Figures 6 and 7 illustrate that for various reactive impedances 124, there exists a frequency at which the input signal is significantly reduced at the output by coupling the tuning element 118 and the impedance 124 to ground 122. The graphs in Figures 6 and 7 illustrate the operation of the coupler as a notch filter, rejecting a narrow band or "notch" of frequencies. In the examples shown in Figures 6 and 7, there is an effective upper limit on the frequencies passed by the coupler. The coupler rejects higher frequencies, i.e., reduces the transmission from the input to the output, which can be useful for filtering out speech and harmonics above the intended operating band. Accordingly, adjustable frequency rejection or filtering can be achieved by variably adjusting the reactance of the impedance 124. In certain examples, the tunable coupler can include various combinations of resistance, impedance, and capacitance to provide various fixed or adjustable impedances 124 that couple the tuning element 118 to ground 122 to advantageously tune the coupling factor and/or frequency-dependent filtering effect, or to advantageously allow for adjustability of the coupling factor and/or frequency-dependent filtering effect.

FIG8 shows an example of an adjustable impedance 124. The impedance 124 circuit shown in FIG8 includes multiple banks 810, 820, 830 of impedance elements 840 that can be selectively switched 850 into the impedance 124 circuit. As shown, each bank 810, 820, 830 includes one or more impedances 840 connected in parallel, and the banks 810, 820, 830 are arranged in series with a common node 812, 822, 832 between the banks 810, 820, 830. In the example shown, at least one impedance 840 in each bank 810, 820, 830 has zero impedance, allowing each bank 810, 820, 830 to be selectively bypassed. Furthermore, if all banks 810, 820, 830 are bypassed, the impedance 124 has an overall zero impedance and is directly coupled to the node ground 122, providing a zero-ohm connection between the tuning element 118 and the ground 122. Additionally, if all switches 850 are open, impedance 124 provides an open circuit, i.e., disconnects tuning element 118 from ground 122. Each switch 850 may be formed from one or more transistors, such as field effect transistors, bipolar junction transistors, or other suitable transistor types, or from a microelectromechanical system (MEMS), or any other suitable switching element capable of selectively connecting impedance element 840 between nodes 812, 822, 832.

The switch 850 may be controlled by control logic that provides a signal voltage to, for example, one or more transistor gates, transistor bases, etc. The controller may contain memory and store switch settings (e.g., on or off, conducting or non-conducting) to control the switch 850 to establish a specific impedance value presented by the impedance 124. The controller may be part of the device and may adjust the coupling factor, the filter effect, or both in response to operating parameters of the device (such as the frequency band of operation, or feedback from other devices or components, command and control signals from other devices or components, or user-established settings).

The adjustable impedance 124 shown in FIG8 is merely one example of an adjustable impedance, and in accordance with aspects and embodiments disclosed herein, any adjustable impedance may be suitable for adjusting the coupling factor and/or filter effect of a coupler. Additionally, certain embodiments may include a fixed impedance 124 to establish a fixed coupling factor and/or filter effect. Additionally, a coupler design may include one or more impedances 124 provided during one portion of the manufacturing process that are selectively routed during another portion of the manufacturing process to produce multiple part numbers having different coupling factors and/or filter effects. Alternatively, multiple impedances 124 may be provided during one portion of the manufacturing process that are selectively connected or disconnected during another portion of the manufacturing process based on performance testing or manufacturing variation testing to provide batch manufacturing of components with a higher yield than would otherwise be the case.

As described above, the main transmission line 110, the coupled line 112, and the tuning element 118 can be straight (linear) traces, such as electrical conductors, or can be nonlinear and/or made of varying materials. One or more of the main transmission line 110, the coupled line 112, and the tuning element 118 can have bends or curves, and can be, for example, helical, spiral, or C-shaped. In certain embodiments, any or all of the main transmission line 110, the coupled line 112, and the tuning element 118 can be formed as inductor turns or can be patterned, such as a grid, sawtooth, etc. Various embodiments can include any suitable shaping and relative proximity to obtain the desired coupling factor range(s), filtering effect(s), and compensation for manufacturing variations.

In addition, one or more of the main transmission line 110, coupled lines 112, and tuning elements 118 can be segmented to have selectively adjustable lengths. For example, a set of suitable switches (e.g., FETs, MEMS) can interconnect the various sections of the transmission line, and a controller can be programmed to control the switches to selectively connect the various sections in a variety of ways to form one or more main transmission lines 110, one or more coupled lines 112, and one or more tuning elements 118, so as to be adjustable to change operational parameters or applications.

As described above, the various embodiments of the tunable couplers disclosed herein can be used in a wide variety of electronic devices. Examples of such electronic devices include, but are not limited to, consumer electronics, components of consumer electronics, electronic test equipment, cellular communication infrastructure such as base stations, mobile phones such as smartphones, telephones, televisions, computer monitors, computers, modems, handheld computers, laptop computers, tablet computers, e-book readers, wearable computers such as smart watches, personal digital assistants (PDAs), microwave ovens, refrigerators, automobiles, stereo systems, DVD players, CD players, digital music players such as MP3 players, radios, camcorders, cameras, digital cameras, portable memory chips, healthcare monitoring devices, in-vehicle electronic systems such as automotive electronic systems or avionics systems, washing machines, dryers, washer/dryers, peripheral devices, watches, clocks, and the like. Furthermore, the electronic devices may include unfinished products.

9A-9C illustrate examples of devices including a tunable EM coupler 100a, according to various embodiments described above. EM coupler 100a is configured to extract a portion of the power of an RF signal traveling between a transceiver 920 and an antenna 930. Typically, EM coupler 100a is a bidirectional coupler. As shown, in the forward or transmit direction, a power amplifier 940 receives an EM signal, such as an RF signal, from transceiver 920 and provides the amplified signal to antenna 930 via antenna switch module 950 and EM coupler 100a. Similarly, in the receive direction, a received signal is provided from antenna 930 to transceiver 920 via EM coupler 100a, antenna switch module 950, and low-noise amplifier 960. Various additional components may be included in a wireless device (such as wireless device 900 of FIG. 9A-9C ), and/or in some embodiments, a subset of the components shown may be implemented.

Power amplifier 940 amplifies the RF signal. Power amplifier 940 can be any suitable power amplifier. For example, power amplifier 940 can include one or more of the following: a single-stage power amplifier, a multi-stage power amplifier, a power amplifier implemented with one or more bipolar transistors, or a power amplifier implemented with one or more field-effect transistors. For example, power amplifier 940 can be implemented on a GaAs die, a CMOS die, or a SiGe die.

Antenna 930 can transmit amplified signals and receive signals. For example, in a cellular phone, wireless base station, etc., antenna 930 can transmit RF signals to other devices and receive RF signals from other devices. In alternative embodiments, multiple antennas can be used.

When operating in forward mode, the EM coupler 100a can extract a portion of the power of the amplified signal traveling between the power amplifier 940 and the antenna 930. For example, the EM coupler 100a can generate an indication of the forward power traveling from the power amplifier 940 to the antenna 930. When operating in reverse mode, the EM coupler 100a can generate an indication of the reflected power traveling from the antenna 930 toward the power amplifier 940, or can extract a portion of the power of the signal received by the antenna 930 from an external source. In either mode, the EM coupler 100a can provide the signal portion to the sensor 912, which provides power feedback by measuring the power of the signal portion.

The example wireless device 900 of Figures 9A-9C also includes a power management system 904 connected to the transceiver 920, which manages power for the operation of the wireless device. The power management system 904 can also control the operation of the baseband subsystem 906 and other components of the wireless device 900. The power management system 904 can manage power within the wireless device 900 by, for example, providing power to the wireless device 900 from the battery 902 or providing power to the wireless device 900 from a power connector, and controlling the charge level of the battery 902 by controlling the charge and discharge cycles and/or state of the battery 902.

In one embodiment, the baseband subsystem 906 is connected to a user interface 908 to facilitate various inputs and outputs of voice and/or data to and from the user. The baseband subsystem 906 may also be connected to a memory 910 configured to store data and/or instructions to facilitate the operation of the wireless device 900 and/or to provide storage of information for the user.

The power amplifier 940 can be used to amplify various RF or other frequency band transmission signals. For example, the power amplifier 940 can receive an enable signal that can be used to pulse the output of the power amplifier to help transmit a wireless local area network (WLAN) signal or any other suitable pulsed signal. The power amplifier 940 can be configured to amplify any of a variety of types of signals, including, for example, Global System for Mobile (GSM) signals, Code Division Multiple Access (CDMA) signals, W-CDMA signals, Long Term Evolution (LTE) signals, EDGE signals, and the like. In certain embodiments, the power amplifier 940 and associated components including switches can be fabricated on a GaAs substrate using, for example, pHEMT or BiFET transistors, or on a silicon substrate using CMOS transistors, as well as other semiconductor manufacturing technologies.

Still referring to Figures 9A-9C, the wireless device 900 may also include a tunable coupler 100a having one or more directional EM couplers for measuring the transmit power signal from the power amplifier 940 and for providing one or more coupled signals to the sensor module 912. The sensor module 912 may, in turn, send information to the transceiver 920 and/or directly to the power amplifier 940 as feedback for adjustment to adjust the power level of the power amplifier 940. In this manner, the tunable coupler 100a may be used to boost/reduce the power of a transmit signal having relatively low/high power. However, it should be understood that the tunable coupler 100a may be used in various other embodiments.

In certain embodiments of any example of the wireless device 900, transmissions from the wireless device 900 may have specified power limits and/or time slots. The power amplifier 940 may move the power envelope up and down within specified limits of power versus time. For example, a transmission time slot of a particular frequency channel may be assigned to a particular mobile phone. In such a case, the power amplifier 940 may need to adjust the power level of one or more RF power signals over time to prevent transmit signal interference during the designated receive time slot and to reduce power consumption. In such a system, as described above, the tunable coupler 100a may be used to measure the power of the power amplifier output signal to help control the power amplifier 940. The implementations shown in Figures 9A-9C are intended to be exemplary only and not limiting.

The example shown in FIG9B includes a combined module 970 that includes a tunable coupler according to aspects and embodiments described herein, combined with an antenna switch module (e.g., ASM 950). The example shown in FIG9C includes a combined module 980 that combines a tunable coupler, an antenna switch module, and a power amplifier (e.g., PA 940) as a front-end module (module 980). Additional embodiments include a front-end module that further incorporates one or more low-noise amplifiers (e.g., LNA 960) and/or sensors (e.g., sensor 912).

The embodiments of the tunable coupler 100a described herein can be implemented in a variety of different modules, including, for example, a stand-alone coupler module, a front-end module, a module combining a tunable coupler with an antenna switching network, an impedance matching module, an antenna tuning module, etc. FIG10 shows an example of a coupler module that can include any embodiment or example of a tunable coupler discussed herein.

FIG10 is a block diagram of an example of a module 1000 including an embodiment of a tunable coupler 100a. Module 1000 includes a substrate 1002 and may include various bare cores and may include packaging, such as overmolding, to provide protection and facilitate handling. Overmolding may be formed over substrate 1002 and dimensioned to substantially seal the various bare cores and components thereon. Module 1000 may also include connections from coupler 100a to the outside of the package to provide signal interconnections, such as input port connection 1004, output port connection 1006, coupled port connection 1008, and isolated port connection 1010. For example, connections 1004, 1006, 1008, and 1010 may be wire bonds or solder bumps. The embodiments of the tunable coupler disclosed herein (optionally packaged in module 1000) may be advantageously used in various electronic devices as described above.

Having described the above aspects of at least one embodiment, it will be appreciated that various changes, modifications, and improvements will readily occur to those skilled in the art. Such changes, modifications, and improvements are intended to be part of this disclosure and are intended to fall within the scope of the present invention. Accordingly, the foregoing description and accompanying drawings are intended to be exemplary only.

Claims (46)

1. An electromagnetic coupler, comprising: a first transmission line extending between the input port and the output port; a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, the second transmission line configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port, the amplitude of the coupled signal being related to the amplitude of the input signal by a coupling factor; a tuning element disposed adjacent to at least one of the first transmission line and the second transmission line, the tuning element being electromagnetically coupled to at least one of the first transmission line and the second transmission line; and An adjustable impedance is coupled between the tuning element and a reference node and configured to adjust the coupling factor. 2. The electromagnetic coupler according to claim 1, wherein the adjustable impedance comprises only a resistance component. 3 . The electromagnetic coupler of claim 1 , wherein the tuning element is configured to selectively electromagnetically decouple from the first transmission line and the second transmission line. 4. The electromagnetic coupler of claim 1, wherein the second transmission line is laterally offset from at least one of the first transmission line and the tuning element. 5 . The electromagnetic coupler according to claim 1 , wherein at least a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element. 6. A module comprising: a first transmission line extending between the input port and the output port; a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, the second transmission line configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port, the amplitude of the coupled signal being related to the amplitude of the input signal by a coupling factor; a tuning element disposed adjacent to at least one of the first transmission line and the second transmission line, the tuning element being electromagnetically coupled to at least one of the first transmission line and the second transmission line; and An adjustable impedance is coupled between the tuning element and a reference node and configured to adjust the coupling factor. The module of claim 6 , wherein the adjustable impedance comprises only a resistive component. 8. The module of claim 6, wherein the tuning element is configured to selectively electromagnetically decouple from the first transmission line and the second transmission line. 9. The module of claim 6, wherein the second transmission line is laterally offset from the first transmission line. 10. The module of claim 6, wherein at least a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element. 11. The module of claim 6, further comprising an antenna switch connected to one of the input port and the output port. 12. The module of claim 6, further comprising a power amplifier coupled to one of the input port and the output port. 13. An electronic device comprising: a coupler having a first transmission line extending between an input port and an output port, and a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, the second transmission line configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port, the coupled signal having an amplitude related to the input signal by a coupling factor; a tuning element disposed adjacent to at least one of the first transmission line and the second transmission line, the tuning element being electromagnetically coupled to at least one of the first transmission line and the second transmission line; an adjustable impedance coupled between the tuning element and a reference node and configured to adjust the coupling factor; and The transceiver is coupled to the input port and configured to generate the input signal as a transmission signal. The electronic device of claim 13 , wherein the adjustable impedance comprises only a resistive component. 15 . The electronic device of claim 13 , wherein the tuning element is configured to selectively electromagnetically decouple from the first transmission line and the second transmission line. 16 . The electronic device according to claim 13 , wherein at least a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element. 17 . The electronic device according to claim 13 , further comprising an antenna switch module connected to the input port or the output port and configured to direct the transmission signal to an antenna. 18 . The electronic device of claim 13 , further comprising a power amplifier connected between the transceiver and the input port, the power amplifier configured to receive and amplify the transmit signal. 19. The electronic device of claim 13, further comprising an antenna coupled to the output port, the antenna configured to transmit the transmit signal and receive a receive signal. 20. The electronic device of claim 19, wherein the output port is further configured to receive the receive signal from the antenna and provide the receive signal at the input port. 21. The electronic device of claim 13, further comprising at least one of a sensor module, a memory, a baseband subsystem, a user interface, and a battery. 22. An electromagnetic coupler, comprising: a first transmission line extending between an input port and an output port, configured to provide an output signal at the output port in response to receiving an input signal at the input port; a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, the second transmission line configured to provide a coupled signal at the coupled port in response to receiving the input signal at the input port; a tuning element disposed adjacent to at least one of the first transmission line and the second transmission line, the tuning element being electromagnetically coupled to at least one of the first transmission line and the second transmission line; and An impedance including a reactive component is coupled between the tuning element and a reference node, the impedance and tuning element being configured to filter a range of frequency components of the output signal. 23. The electromagnetic coupler of claim 22, wherein the impedance includes a resistive component. 24. The electromagnetic coupler of claim 22, wherein the impedance is adjustable. 25. The electromagnetic coupler of claim 22, wherein the tuning element is configured to selectively electromagnetically decouple from the first transmission line and the second transmission line. 26. The electromagnetic coupler of claim 22, wherein the second transmission line is laterally offset from at least one of the first transmission line and the tuning element. 27. The electromagnetic coupler of claim 22, wherein at least a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element. 28. A module comprising: a first transmission line extending between the input port and the output port; a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, the second transmission line configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port; a tuning element disposed adjacent to at least one of the first transmission line and the second transmission line, the tuning element being electromagnetically coupled to at least one of the first transmission line and the second transmission line; and An impedance including a reactive component is coupled between the tuning element and a reference node, the impedance and tuning element being configured to filter a range of frequency components of the output signal. 29. The module of claim 28, wherein the impedance comprises a resistive component. 30. The module of claim 28, wherein the impedance is adjustable. 31. The module of claim 28, wherein the tuning element is configured to selectively electromagnetically decouple from the first transmission line and the second transmission line. 32. The module of claim 28, wherein the second transmission line is laterally offset from at least one of the first transmission line and the tuning element. 33. The module of claim 28, wherein at least a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element. 34. The module of claim 28, further comprising an antenna switch connected to one of the input port and the output port. 35. The module of claim 28, further comprising a power amplifier coupled to one of the input port and the output port. 36. An electronic device comprising: a coupler having a first transmission line extending between an input port and an output port, and a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolated port, the second transmission line configured to provide a coupled signal at the coupled port in response to receiving an input signal at the input port; a tuning element disposed adjacent to at least one of the first transmission line and the second transmission line, the tuning element being electromagnetically coupled to at least one of the first transmission line and the second transmission line; an impedance including a reactive component coupled between the tuning element and a reference node, the impedance and tuning element configured to filter a range of frequency components of the output signal; and The transceiver is coupled to the input port and configured to generate the input signal as a transmission signal. 37. The electronic device of claim 36, wherein the impedance comprises a resistive component. 38. The electronic device of claim 36, wherein the impedance is adjustable. 39. The electronic device of claim 36, wherein the tuning element is configured to be selectively decoupled from the first transmission line and the second transmission line. 40. The electronic device of claim 36, wherein the second transmission line is laterally offset from at least one of the first transmission line and the tuning element. 41. The electronic device of claim 36, wherein at least a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element. 42. The electronic device of claim 36, further comprising an antenna switch module connected to the input port or the output port and configured to direct the transmit signal to an antenna. 43. The electronic device of claim 36, further comprising a power amplifier connected between the transceiver and the input port, the power amplifier configured to receive and amplify the transmit signal. 44. The electronic device of claim 36, further comprising an antenna coupled to the output port, the antenna configured to transmit the transmit signal and receive a receive signal. 45. The electronic device of claim 36, further comprising a sensor module coupled to the coupling port and configured to detect a power level of the coupled signal. 46. The electronic device of claim 36, further comprising a baseband subsystem coupled to the transceiver and configured to provide a baseband signal to the transceiver.