CN116260474A - Multimode RXFE circuit - Google Patents

Abstract

The application provides a multimode RXFE circuit, comprising: the low-noise amplifier comprises a first mixer, a first operational Amplifier (AMP) and two groups of feedback circuits, wherein the feedback circuits comprise feedback resistors and feedback capacitors, two gm units which are controlled by a switch are added between the low-noise amplifier (LNA) and the mixer, and the low-noise amplifier (LNA) and the gm units are separated by a value separation capacitor; the output end of the gm unit outputs an RF signal and is connected with the first input end of the mixer, and the second input end of the mixer is connected with VDD; the first output end and the second output end of the mixer are respectively connected with the forward input end and the reverse input end of the operational amplifier AMP, and the feedback circuit is connected with the operational amplifier AMP in parallel. The method and the device can adjust the gain of the output signal in real time while working with low power consumption in the communication process, and reduce the noise coefficient of the circuit, thereby improving the communication performance.

Description

A kind of multi-mode RXFE circuit

technical field

This application relates to the technical field of power electronics, in particular, to a multi-mode RXFE circuit with large bandwidth, low power consumption and low noise figure applied to the radio frequency front end of a UWB receiver.

Background technique

UWB (Ultra Wide Band) is a wireless technology that transmits data at high speed within a short distance with extremely low power. The working principle of the RF front end of the UWB receiver is shown in Figure 1, in which the box part is a block diagram of the RXFE circuit structure of the RF front end of the UWB receiver. The radio frequency signal needs to go through a series of signal processing processes from the antenna end to the digital baseband: after the UWB receiver receives the weak small signal through the antenna, when it passes through the low noise amplifier (LNA), it minimizes noise and interference signals to the weak signal. The influence of the signal and amplify the received weak signal, and then convert the frequency of the passband signal into a baseband signal with a zero-IF bandwidth of 250MHz through the mixer (MIXER), and finally through the operational amplifier, feedback resistance and feedback capacitance. TIA, amplifies the baseband signal again, the above is the function realized by the Receiver RF front-end (RXFE for short) circuit; the signal output by RXFE is filtered by a filter, and then converted to digital by ADC, and then output to the digital baseband.

In order to meet the needs of the terminal market for high-performance, high-integration, multi-mode and multi-band RF chips, the UWB receiver RF front-end circuit is also constantly moving towards high-performance, large bandwidth, low power consumption, low noise figure, multi-mode and multi-band However, since the small signal received by the antenna is relatively weak, it is necessary to amplify the small signal while reducing the influence of the interference signal and the noise of the circuit itself on the received signal. When the noise of the circuit is relatively large, the received weak signal will be lost in the noise of the circuit. Since the frequency of the transmission signal received by the receiver may be different, this requires the RXFE circuit of the RF front end of the UWB receiver to be able to process weak signals of different frequencies received by the antenna.

Contents of the invention

In view of the problems in the above content, the application provides a multi-mode RXFE circuit, which is applicable to the IEEE Std802.15.4-202 communication protocol with large bandwidth, low power consumption, and low noise. It can work in two frequency bands of 6.5GHz and 8GHz. While working with low power consumption during the communication process, the gain of the output signal can be adjusted in real time to reduce the noise figure of the circuit, thereby improving the communication performance.

In order to achieve the above object, the application provides the following technical solutions:

A multimode RXFE circuit, comprising: a low noise amplifier LNA, a first mixer, a first operational amplifier AMP, two groups of feedback circuits, the feedback circuits include a feedback resistor and a feedback capacitor, wherein:

Adding two parallel gm units controlled by a switch between the low noise amplifier LNA and the mixer, and separating the low noise amplifier LNA from the gm unit through a blocking capacitor;

The output terminal of the gm unit outputs an RF signal and is connected to the first input terminal of the mixer, and the second input terminal of the mixer is connected to VDD;

The first output terminal and the second output terminal of the mixer are respectively connected to the positive and negative input terminals of the operational amplifier AMP, and the feedback circuit is connected in parallel with the operational amplifier AMP.

Preferably, the multimode RXFE circuit also includes: a second mixer and a second operational amplifier AMP, wherein:

The second mixer is connected to the output terminal of the gm unit, and the first output terminal and the second output terminal of the second mixer are respectively connected to the positive and negative input terminals of the second operational amplifier AMP .

Preferably, the operational amplifier AMP adopts a two-stage differential input and differential output structure, a feedforward structure is adopted in the operational amplifier, and the bandwidth is compensated by adding a zero point.

The multi-mode RXFE circuit described in the present application includes: a first mixer, a first operational amplifier AMP, and two sets of feedback circuits, the feedback circuits include a feedback resistor and a feedback capacitor, wherein, in the low noise amplifier LNA and Two parallel gm units controlled by a switch are added between the mixers, and the low noise amplifier LNA and the gm unit are separated by a blocking capacitor; the output end of the gm unit outputs an RF signal, And be connected with the first input end of described mixer, the second input end of described mixer is connected with VDD; The first output end and the second output end of described mixer are respectively connected with described operational amplifier AMP The positive and negative input ends of the circuit are connected, and the feedback circuit is connected in parallel with the operational amplifier AMP. While working with low power consumption during the communication process, the present application can adjust the gain of the output signal in real time and reduce the noise figure of the circuit, thereby realizing the improvement of the communication performance.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present application. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 is a schematic structural diagram of a RXFE circuit provided by the prior art;

Fig. 2 is a schematic structural diagram of a mixer circuit provided by the prior art;

FIG. 3 is a schematic structural diagram of a multi-mode RXFE circuit provided by an embodiment of the present application;

FIG. 4 is a schematic structural diagram of a multi-mode RXFE circuit provided by an embodiment of the present application;

FIG. 5 is a schematic structural diagram of a specific implementation manner of a multi-mode RXFE circuit provided in an embodiment of the present application;

FIG. 6 is a schematic structural diagram of an operational amplifier provided in an embodiment of the present application;

FIG. 7 is a schematic structural diagram of a controllable array composed of capacitors and resistors provided by an embodiment of the present application.

Detailed ways

The applicant found in the research that when the UWB receiver is working, because the external signal is weak, the impedance should not be too high, usually 50 Ohms, otherwise the captured external signal will become smaller, which is not conducive to signal processing. At the same time, in order to ensure that the received signal will not be reflected, the RF front-end circuit of UWB is required to strictly match the impedance of the antenna. Usually, the input impedance of the low-noise amplifier (LNA) of the input stage will have a large impact on impedance matching. Influence.

Because the requirement of low noise of LNA limits the topological structure of the circuit, this means that the circuit structure of a single transistor is the input device of the signal. The gain of the LNA is adjusted by load devices such as inductors, capacitors, resistors, or feedback circuits, but the inductors and capacitors will increase the area of the circuit; increasing the equivalent impedance of the load circuit or feedback circuit will increase the circuit gain, but it will make the characteristic The impedance increases, reflecting back the signal received by the antenna. If the feedback resistance or load resistance is reduced in order to reduce signal reflection, then the LNA gain will become smaller, and the total noise figure of the mixer and TIA converted to the input terminal will become larger. If in order to meet these two requirements at the same time, increasing the width-to-length ratio of the input MOS tube will increase the power consumption of the circuit. If the gain of the LNA is too small, a subsequent TIA circuit is required to compensate the gain, and the improvement of the gain of the TIA circuit is also at the cost of sacrificing bandwidth. Therefore, the power consumption, gain, and reflection loss of the LNA are a compromise between each other, and each index is very important, which increases the difficulty of LNA design.

Due to the influence of the capacitance of the MOS tube itself, the feedthrough phenomenon between the ports often occurs in the mixer. As shown in Figure 2, for a mixer implemented based on MOS tubes, the gate-source capacitance and gate-drain capacitance will generate a feedthrough path between the LO port, the RF port, and the IF port, which will cause baseband misalignment and LO leaked. Generally, in the MIXER, the LO signal with a duty cycle of 50% is used to down-convert the received signal, but the 50% LO signal will cause the I/Q two local oscillator signals to overlap in the time domain, making the I/Q two The switch tubes of the circuit are turned on at the same time, so that the signals interfere with each other. At the same time, after the small signal received by the receiver is mixed by MIXER, the output is usually zero intermediate frequency and the bandwidth is 250MHz. It is difficult for the commonly used two-stage differential operational amplifier to maintain 250MHz while meeting the gain required by the system. If the bandwidth does not meet the requirements, the signal will be attenuated at high frequency.

For this reason, the application provides a kind of multi-mode RXFE circuit, which is suitable for large bandwidth, low power consumption and low noise of IEEE Std 802.15.4-202 communication protocol, which can work in two frequency bands of 6.5GHz and 8GHz, and is used in the communication process While working with low power consumption, it can adjust the gain of the output signal in real time, reduce the noise figure of the circuit, and improve the communication performance.

The following will clearly and completely describe the technical solutions in the embodiments of the application with reference to the drawings in the embodiments of the application. Apparently, the described embodiments are only some of the embodiments of the application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

Please refer to FIG. 3 , which is a schematic structural diagram of a multi-mode RXFE circuit provided by an embodiment of the present application. As shown in Figure 3, the embodiment of the present application provides a multi-mode RXFE circuit, a low noise amplifier LNA, a first mixer, a first operational amplifier AMP, two sets of feedback circuits, the feedback circuits include a feedback resistor and a feedback capacitance, where:

Add two parallel gm units controlled by a switch between the low noise amplifier LNA and the mixer, and separate the low noise amplifier LNA from the gm unit by a blocking capacitor; the gm The output terminal of the unit outputs an RF signal and is connected to the first input terminal of the mixer, and the second input terminal of the mixer is connected to VDD; the first output terminal and the second output terminal of the mixer Terminals are respectively connected to positive and negative input terminals of the operational amplifier AMP, and the feedback circuit is connected in parallel with the operational amplifier AMP.

In the embodiment of the present application, in the part of the low noise amplifier LNA, the reflection loss is reduced by appropriately reducing the resistance value of the feedback resistor; the gm unit circuit connected after the low noise amplifier LNA, the low While the small signal gain of the noise amplifier LNA circuit is improved, the characteristic impedance of the circuit is increased to further reduce the reflection loss, and due to the increase of the gain, the noise figure of the subsequent circuit structure converted to the input terminal can be reduced; by improving the low noise The gain of the amplifier LNA and the gm unit can enable the subsequent TIA circuit to reduce the gain to widen the bandwidth under the condition that the gain requirement is met.

In the embodiment of the present application, on the basis of the circuit structure in FIG. 1 , the circuit structure is improved. As shown in FIG. 3 , two parallel gm units controlled by a switch and connected in parallel are added between the LNA and the MIXER. The LNA is separated from the gm unit by a blocking capacitor. In the LNA part, in order to reduce the reflection loss, the resistance value of the feedback resistor can be appropriately reduced. The gm unit circuit connected after the LNA will increase the small-signal gain of the LNA circuit, increase the characteristic impedance of the circuit, further reduce the reflection loss, and reduce the conversion of the subsequent circuit structure to the input due to the increase in gain. Noise Figure. The increase in the gain of the LNA and the gm unit can enable the subsequent TIA circuit to reduce the gain to widen the bandwidth under the condition of meeting the gain requirement, which provides flexibility for the index allocation and design of the overall circuit.

Further, as shown in FIG. 4, the multimode RXFE circuit further includes: a second mixer and a second operational amplifier AMP, wherein: the second mixer is connected to the output end of the gm unit, and the The first output terminal and the second output terminal of the second mixer are respectively connected to the positive and negative input terminals of the second operational amplifier AMP. The above-mentioned mixer can adopt a double-balanced structure, use a single-ended input RF signal, connect the remaining two ports of the mixer to power, and eliminate the feedthrough between the LO-RF ports at a frequency of ω _LO .

In the embodiment of this application, the LO local oscillator signal with a 25% duty cycle is used. Since the fundamental frequency Fourier coefficient of the square wave with a 25% duty cycle is 3dB smaller than that of the square wave, the I/Q channels will not be turned on at the same time. The RF current of the switch tube of the mixer is twice (6dB) that of the 50% case. In general, the LO local oscillator signal with a 25% duty cycle can increase the gain by 3dB compared with the signal with a 50% duty cycle. And the overlap time between LO+ and LO- is eliminated. The performance of the circuit such as conversion gain, noise and linearity is improved.

Further, the operational amplifier AMP adopts a two-stage differential input and differential output structure, a feedforward structure is adopted in the operational amplifier, and the bandwidth is compensated by adding a zero point.

It should be noted that in the usual UWB receiver front-end RXFE circuit, the operational amplifier in the TIA circuit uses a two-stage differential operational amplifier. In order to meet the bandwidth and gain, the current in the branch of the operational amplifier will be increased, thus increasing the For circuit power consumption, the operational amplifier in the present invention adopts a two-stage differential input and differential output structure, a feedforward structure is adopted in the operational amplifier, and the bandwidth is compensated by adding zero points to expand the bandwidth of the circuit. And due to the existence of the gm unit, the gain of the overall circuit is improved, which leaves a large margin for the design of the gain and bandwidth in the TIA circuit, and the gain of the TIA can be appropriately reduced in order to increase the output bandwidth.

In the embodiment of this application, in order to ensure that the output of the TIA will be full-scale or the output signal is too small when the input small signal is too large or too small, which will cause the UWB circuit to fail, a gain control circuit is added to the gm unit and the TIA. When the small input signal of the circuit is too large, reduce the TIA gain; when the input signal of the circuit is too small, or when the noise figure is too large, open the parallel gm unit through switch control, increase the gain of the RF front end or reduce it Noise Figure.

Compared with the background technology, the multi-mode RXFE circuit provided by the embodiment of the present application has the following beneficial effects:

The traditional RXFE circuit structure has a trade-off between gain, GBW, power consumption, reflection loss, bandwidth and noise figure, and it is often considered that one loses the other in circuit design. The RXFE circuit structure proposed in the embodiment of this application reduces the power consumption, noise figure and reflection loss of the circuit while ensuring the circuit gain, and the operational amplifier designed in the TIA also greatly improves the bandwidth of the output signal , to increase the flexibility of the circuit design.

For the convenience of understanding, the embodiment of the present application provides the specific implementation shown in Figure 5. As shown in Figure 5, after the UWB receiver receives the signal, it will be transmitted to the input terminal of the low noise amplifier LNA. In order to stabilize the low noise amplifier LNA The current in I_bias is copied to the low noise amplifier LNA through the current mirror circuit. At the same time, in order to ensure that the signal of the receiver will not leak into the current mirror structure, a large resistor is added to the current mirror structure. The two ends of the resistor in the low noise amplifier LNA are connected to the output terminal and the gate of the PMOS. At the same time of feedback, the resistor and the PMOS can also act as a load.

In the embodiment of this application, the output of the low noise amplifier LNA is connected to two parallel gm units, the second gm unit is controlled by a switch, and whether the second gm unit is working is determined according to the last measured gain and noise figure . The output of the gm unit is connected to the mixer, and the mixer mixes the 25% duty cycle LO local oscillator signal input from the outside with the high-frequency signal output by the gm unit to adjust the signal to the base frequency. Finally, the signal passes through a gain controllable transimpedance amplifier (TIA) composed of an operational amplifier and a controllable gain array of negative feedback capacitors and resistors, wherein: the structure of the operational amplifier designed in the embodiment of the present application is shown in Figure 6, consisting of two It is composed of a differential operational amplifier of the first stage and a feed-forward path connecting the input and output ends of the operational amplifier. The feed-forward path compensates the bandwidth of the operational amplifier by generating zero points and widens the bandwidth of the circuit; the controllable array composed of capacitors and resistors is shown in the figure As shown in 7, the gain of the circuit is controlled by controlling the switch. At the same time, in order to ensure the stability of the circuit gain, a controllable load capacitor array is added to the input end of the TIA. While performing gain switching, by controlling the load capacitor array , to ensure the stability of the gain and to compensate the bandwidth.

An embodiment of the present application provides a multi-mode RXFE circuit, including: a first mixer, a first operational amplifier AMP, and two sets of feedback circuits, the feedback circuits include a feedback resistor and a feedback capacitor, wherein the low-noise amplifier Two parallel gm units controlled by a switch are added between the LNA and the mixer, and the low noise amplifier LNA and the gm unit are separated by a blocking capacitor; the output terminal of the gm unit outputs RF The signal is connected to the first input terminal of the mixer, and the second input terminal of the mixer is connected to VDD; the first output terminal and the second output terminal of the mixer are respectively connected to the operation The positive and negative input terminals of the amplifier AMP are connected, and the feedback circuit is connected in parallel with the operational amplifier AMP. In the embodiment of the present application, while working with low power consumption during the communication process, the gain of the output signal can be adjusted in real time to reduce the noise figure of the circuit, thereby improving the communication performance.

It should be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes none other elements specifically listed, or also include elements inherent in the process, method, commodity, or apparatus. Without more limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus that includes the element.

The above are only examples of the present application, and are not intended to limit the present application. For those skilled in the art, various modifications and changes may occur in this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims (3)

1. A multimode RXFE circuit, comprising: the low noise amplifier LNA, the first mixer, the first operational amplifier AMP, two sets of feedback circuits comprising a feedback resistor and a feedback capacitor, wherein:

adding two gm units which are controlled by a switch and are connected in parallel between the low noise amplifier LNA and the mixer, and separating the low noise amplifier LNA from the gm units by a value separation capacitor;

the output end of the gm unit outputs an RF signal and is connected with the first input end of the mixer, and the second input end of the mixer is connected with VDD;

the first output end and the second output end of the mixer are respectively connected with the forward input end and the reverse input end of the operational amplifier AMP, and the feedback circuit is connected with the operational amplifier AMP in parallel.

2. The multimode RXFE circuit according to claim 1, further comprising: a second mixer, a second operational amplifier AMP, wherein:

the second mixer is connected with the output end of the gm unit, and the first output end and the second output end of the second mixer are respectively connected with the forward and reverse input ends of the second operational amplifier AMP.

3. The multimode RXFE circuit according to claim 1, wherein the operational amplifier AMP employs a two-stage differential input differential output structure, and a feed-forward structure is employed in the operational amplifier to compensate for the bandwidth by adding zero.

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