JP5960622B2 - RF circuit - Google Patents

Description

  The present invention relates to a high-frequency RF circuit that allows simple and low-cost mounting such as wire bonding in a power supply wiring mounting that applies a DC bias to an RF (Radio Frequency) circuit that handles a millimeter wave band or higher frequency band. is there.

  As a method for mounting a power supply pad for applying a DC voltage to an IC (Integrated Circuit), wire bonding is generally used. In an RF circuit that handles a high-frequency band, an inductance component that is parasitic outside the power supply pad is generated by wire bonding at the time of mounting. Therefore, it is necessary to design in consideration of the influence of this inductance component.

  In the prior art, in order to reduce the influence of parasitic inductance caused by wires adhering to the power supply pad of the IC, a power supply pad that inserts a capacitor element between the power supply pads on the IC or supplies a DC bias of the same level A method of reducing the influence of parasitic inductance due to mounting by using a plurality of parallel circuits (see Non-Patent Document 1) and a method of using flip-chip mounting, which is a mounting method that can obtain good electrical characteristics even in a high frequency band (See Non-Patent Document 2 and Non-Patent Document 3).

Behzad Razavi, translated by Tadahiro Kuroda, “Design and application of analog CMOS integrated circuits”, Maruzen Co., Ltd., p. 816-819, 2003 William J. et al. Dally, John W. By Paulton, translated by Tadahiro Kuroda, “Digital System Engineering Fundamentals”, Maruzen Co., Ltd., p. 38-40, 2003 Tsuru Masaomi, Tanaka Toshiyuki, Inagaki Ryuji, Taniguchi Eiji, Nakayama Masatoshi, Kameda Takuji, Suematsu Kenji, Takagi Nao, Tsubouchi Kazuo, "Prototype of 60 GHz Receiving Front-End CMOS IC with Flip-Chip", 2012 IEICE Electronics Society Convention, C-2-8, p. 34, 2012

  However, the method disclosed in Non-Patent Document 1 has a problem that the chip area increases due to an increase in the number of pads, and the methods disclosed in Non-Patent Document 2 and Non-Patent Document 3 increase the mounting cost. There was a problem.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a high-frequency RF circuit capable of suppressing an increase in chip size and an increase in mounting cost.

The high-frequency RF circuit of the present invention is formed on the semiconductor substrate, an RF circuit formed on the semiconductor substrate, a plurality of power supply pads formed on the semiconductor substrate for applying a DC bias to the RF circuit, and the semiconductor substrate. A plurality of wirings for connecting the plurality of power supply pads and the corresponding plurality of terminals of the RF circuit, and one of the wirings has a characteristic impedance of approximately 0 in a desired frequency band. For each power supply pad, between the terminal of the RF circuit to which the transmission line is connected and a power supply pad other than the power supply pad to which the transmission line is connected. It is characterized by being individually connected through a capacitive element .
Further, in one configuration example of the high-frequency RF circuit of the present invention, the transmission line has the characteristics such that a reflection characteristic viewed from a terminal of the RF circuit exists in the vicinity of impedance 0 on the Smith chart in a desired frequency band. The impedance is set.
Also, one configuration example of the high-frequency RF circuit of the present invention is characterized in that the transmission line is connected between one of the plurality of power supply pads and the corresponding terminal of the RF circuit. It is.
Further, in one configuration example of the high-frequency RF circuit of the present invention, one end of the transmission line is connected to a wiring between one of the plurality of power supply pads and the corresponding terminal of the RF circuit, The other end of the transmission line is electrically opened.
In one configuration example of the high-frequency RF circuit of the present invention, the transmission line is a microstrip line.
In one configuration example of the high-frequency RF circuit of the present invention, the transmission line is a coplanar line with GND.

  According to the present invention, a distributed constant type transmission having a characteristic impedance of approximately 0 in a desired frequency band is applied to a part or all of the wiring connecting the power supply pad and the RF circuit terminal formed on the same semiconductor substrate. By using a line, it is possible to design a high-frequency RF circuit that is less susceptible to the inductance component parasitic to the power supply pad during mounting in an RF circuit that handles a millimeter wave band or higher frequency band. Increasing the number eliminates the need for high-cost mounting such as an increase in chip size and flip-chip mounting in which parasitic inductance is unlikely to occur, and a low-cost high-frequency RF circuit can be realized.

FIG. 6 is an equivalent circuit diagram that simulates an ideal power supply and an inductance that is parasitic in mounting. It is a figure which shows the circuit structure which inserts a transmission line in series between a power supply pad and RF circuit proposed by this invention. It is a figure which shows the circuit structure which inserts the transmission line which open | released one end between the power supply pad and RF circuit proposed by this invention. It is sectional drawing which shows one example of the transmission line of this invention. It is sectional drawing which shows the other example of the transmission line of this invention. It is a circuit diagram which shows the example of RF circuit which concerns on this invention. It is a figure which shows the power supply wiring equivalent circuit connected to RF circuit of FIG. It is a figure which shows the gain simulation result of the RF circuit of FIG. It is a block diagram which shows the structure of the IC chip which concerns on the 1st reference example of this invention. 1 is a block diagram showing a configuration of an IC chip according to a first embodiment of the present invention. It is a block diagram which shows the structure of the IC chip which concerns on the 2nd reference example of this invention. It is a block diagram which shows the structure of the IC chip which concerns on the 2nd Embodiment of this invention.

[Principle of the Invention]
In the high-frequency RF circuit proposed in the present invention, a transmission line having a small characteristic impedance of several Ω or less is inserted between the terminal of the RF circuit that applies a DC bias such as a power supply potential, a bias potential, and a GND potential and the power supply pad. By doing so, it is possible to reduce the influence of an inductance component parasitic on the power supply pad when an IC chip including an RF circuit is mounted on a ceramic substrate or the like. In the transmission line, the smaller the characteristic impedance (closer to 0Ω), the shorter the required line length and the less the influence of the parasitic inductance in a wide frequency band.

  In order to explain the principle of the present invention, the reflection characteristic viewed from the node 102 is considered in the circuit configuration shown in FIG. 1 in which an ideal power source 100 having an internal resistance of 0Ω and an inductor element 101 are connected in series. When the reflection characteristic is drawn on the Smith chart, as the frequency f is changed from 0 to ∞, it moves clockwise on the circumference of radius 1 from the point of impedance = 0 and converges to the point of impedance = ∞. Since the ideal power supply 100 with an internal resistance of 0Ω always has an impedance of 0, in order to obtain the same characteristics as when an ideal power supply is connected in a high-frequency RF circuit, the reflection characteristics viewed from the node 102 in the desired frequency band are Smith. It must exist near the point where impedance = 0 on the chart. However, in the millimeter wave band and the higher frequency band beyond it, only a small amount of inductance is parasitic and it moves away from the point where impedance = 0, resulting in a change in circuit characteristics.

  On the other hand, when the circuit configuration in which the transmission line 103 is further connected in series to the inductor element 101 and the ideal power source 100 as shown in FIG. 2 is used, when the reflection characteristic viewed from the node 102 is drawn on the Smith chart, the frequency is As it goes from 0 to ∞, it continues to move clockwise on the circumference of radius 1 from the point of impedance = 0 (without converging to some point), so impedance = 0 again in any frequency band Approach the point. Further, as the characteristic impedance of the transmission line 103 in FIG. 2 approaches 0Ω, the reference point that rotates clockwise on the Smith chart shifts to near 0Ω due to the influence of the transmission line 103, and thus the reflection seen from the node 102 The frequency band where the characteristic exists near the point where impedance = 0 is widened. That is, in a wide frequency band, the characteristics of the RF circuit can be brought close to the ideal power supply connection.

  In addition, when a circuit configuration is used in which one end of the transmission line 104 is connected to the connection point between the node 102 and the inductor element 101 and the other end of the transmission line 104 is opened as shown in FIG. Since it looks capacitive in the frequency band of 4 wavelengths or less, when the reflection characteristic viewed from the node 102 is drawn on the Smith chart, as the frequency is changed from 0 to ∞, on the circumference of radius 1 from the point of impedance = 0. Is moved clockwise (without converging to some point), and again approaches the point where impedance = 0 in the frequency band where transmission line length = 1/4 wavelength. At this time, as the impedance of the transmission line 104 to be used is closer to 0Ω, the reference point that rotates clockwise on the Smith chart is shifted to near 0Ω due to the influence of the transmission line 104. The frequency band existing in the vicinity of the = 0 point is widened, and the characteristics of the RF circuit can be brought close to the ideal power supply connection in a wide frequency band as in FIG.

  Here, as an example of the transmission lines 103 and 104 having a characteristic impedance close to 0Ω in a desired frequency band, for example, when the transmission lines 103 and 104 are formed on a semiconductor substrate capable of a multilayer wiring structure, as shown in FIG. In addition, there is a microstrip line in which only one interlayer insulating film having a relatively small thickness is used as the dielectric layer 202 between the signal line 200 and the GND 201 and the signal line width is about several tens to 100 μm.

  Further, as another example of the transmission lines 103 and 104 having a characteristic impedance close to 0Ω in a desired frequency band, as shown in FIG. 5, only the one-layer interlayer insulating film having a relatively small thickness is used as the signal line 300 and the GND 301. There is a coplanar transmission line with GND in which a dielectric layer 302 is provided between them and GND 301 is formed on both sides of the signal line 300. Thus, by using the microstrip line or the GND coplanar line, it is possible to form a transmission line having a characteristic impedance close to 0Ω with a size that can be mounted in an IC. In a process with a small number of wiring layers, it is effective to use a coplanar line structure in which the gap between the signal line 300 and the GND 301 is designed to be small.

  FIG. 6 shows a configuration of a narrowband amplifier circuit which is an example of an RF circuit. The narrowband amplifier circuit includes transistors Q1 and Q2 whose sources are connected to the power supply voltage terminal VSS, one end connected to the bias voltage terminal BIAS, the other end connected to the gate of the transistor Q1, and one end connected to the power supply. The resistor R2 is connected to the voltage terminal VDD, the other end is connected to the drain of the transistor Q1, the one end is connected to the bias voltage terminal BIAS, the other end is connected to the gate of the transistor Q2, and the other end is the power source. A resistor R4 connected to the voltage terminal VDD and having the other end connected to the drain of the transistor Q2, a capacitor element C1 having one end connected to the signal input terminal IN and the other end connected to the gate of the transistor Q1, and one end The capacitive element C2 is connected to the drain of the transistor Q1 and the other end is connected to the gate of the transistor Q2. It is connected to the drain of the static Q2, composed of a capacitor which is connected C3 Metropolitan the other end signal output terminal OUT.

As shown in FIG. 7A, only the ideal power supply 100 is connected to each of the nodes 102 (power supply voltage terminal VDD, power supply voltage terminal VSS, bias voltage terminal BIAS) of the narrowband amplifier circuit shown in FIG. A simulation result of the gain Y0 of the narrowband amplifier circuit is shown in FIG. Further, as shown in FIG. 7B, a narrowband amplifier circuit in the case where an inductor element 101 (1 nH) that simulates an inductance parasitic by mounting is added between the ideal power supply 100 and the node 102 of the narrowband amplifier circuit. The result of simulating the gain Y0 is shown in FIG. Further, as shown in FIG. 7C, a transmission line 103 having a characteristic impedance Z ₀ = 0.5Ω and a line length L = 200 μm is provided between the inductor element 101 (1 nH) and the node 102 of the narrowband amplifier circuit. FIG. 8C shows the result of simulating the gain Y0 of the narrowband amplifier circuit when added in series.

  Comparing FIG. 8A and FIG. 8B, when only the ideal power supply 100 is connected to the node 102 and when the parasitic inductance due to mounting is assumed, the characteristics of the narrowband amplifier circuit change greatly. I understand that. On the other hand, when FIG. 8A is compared with FIG. 8C, the characteristics of the narrowband amplifier circuit show almost the same values. Therefore, by using the high-frequency RF circuit proposed in the present invention, it is possible to greatly reduce the influence of the parasitic inductance on the power supply pad of the IC mounting the high-frequency RF circuit in the millimeter wave band or higher frequency band. I understand that.

[ First Reference Example ]
Next, the present invention will be described in detail based on reference examples and embodiments shown in the drawings. FIG. 9 is a block diagram showing a configuration of an IC chip according to the first reference example of the present invention. The IC chip 3 shown in FIG. 9 is formed on the same semiconductor substrate as the RF circuit unit 1 and the DC bias terminal 2-1 (for example, the power supply voltage terminal VDD) of the RF circuit unit 1 (core circuit unit). A transmission line 5-1 having a characteristic impedance Z ₀ of approximately 0 is inserted between the DC pad 4-1 (pad for supplying the power supply voltage VDD) and a DC bias terminal 2-2 of the RF circuit unit 1. (For example, the power supply voltage terminal VSS) and the DC pad 4-2 (pad for supplying the power supply voltage VSS) formed on the same semiconductor substrate as the RF circuit unit 1 have a characteristic impedance Z ₀ of substantially zero. A transmission line 5-2 is inserted, a DC bias terminal 2-3 (for example, a bias voltage terminal BIAS) of the RF circuit unit 1, and a DC pad 4-formed on the same semiconductor substrate as the RF circuit unit 1. 3 (Supply of bias voltage BIAS Characteristic impedance Z ₀ between the pad) of use is inserting a transmission line 5-3 of substantially 0. The configuration of the RF circuit unit 1 is as shown in FIG. As described with reference to FIGS. 4 and 5, the transmission lines 5-1 to 5-3 are formed on the same semiconductor substrate as that of the RF circuit unit 1. Between terminal 2-1 and transmission line 5-1, between terminal 2-2 and transmission line 5-2, between terminal 2-3 and transmission line 5-3, transmission line 5-1 and DC The same semiconductor substrate as that of the RF circuit unit 1 is between the pad 4-1, between the transmission line 5-2 and the DC pad 4-2, and between the transmission line 5-3 and the DC pad 4-3. They are connected by the wiring formed above.

With such a configuration, in the present reference example, it is possible to cancel the influence of the inductance parasitic on each of the DC pads 4-1 to 4-3 when the IC chip 3 is mounted on a ceramic substrate or the like. In this reference example , when the IC chip 3 is mounted on a ceramic substrate or the like, it is not necessary to use flip chip mounting, and a simple mounting method such as wire bonding can be employed. In an RF circuit that handles a band, power supply wiring can be mounted easily and at low cost without degrading the performance of the RF circuit.

[ First Embodiment ]
Next, a first embodiment of the present invention will be described. FIG. 10 is a block diagram showing the configuration of the IC chip according to the first embodiment of the present invention. The same components as those in FIG. 9 are denoted by the same reference numerals. As a difference from the first reference example , in the first reference example , the characteristic impedance Z _{0 is present} between all the DC pads 4-1 to 4-3 and the terminals 2-1 to 2-3 of the RF circuit unit 1. In this embodiment, some DC pads 4-1 (for example, pads for supplying the power supply voltage VDD) and the RF circuit section are inserted. A transmission line 5-1 having a characteristic impedance Z ₀ of approximately 0 is inserted between the DC bias terminal 2-1 (for example, the power supply voltage terminal VDD). Between the terminal 2-1 to which the transmission line 5-1 is connected and the DC pads 4-2 and 4-3 other than the DC pad 4-1 to which the transmission line 5-1 is connected. Capacitance elements 6-1 and 6-2 are connected to. The capacitive elements 6-1 and 6-2 are formed on the same semiconductor substrate as that of the RF circuit unit 1. Between the terminal 2-1 and the transmission line 5-1, between the transmission line 5-1 and the DC pad 4-1, between the terminal 2-2 and the DC pad 4-2, and between the terminal 2-3 and The DC pad 4-3 is connected by wiring formed on the same semiconductor substrate as the RF circuit unit 1.

  With such a configuration, in the present embodiment, it is possible to cancel the influence of the inductance parasitic on each of the DC pads 4-1 to 4-3 at the time of mounting while reducing the number of transmission lines to be used, In an RF circuit that handles a millimeter wave band or higher frequency band, power supply wiring can be easily and inexpensively implemented without degrading the performance of the RF circuit.

[ Second Reference Example ]
Next, a second reference example of the present invention will be described. FIG. 11 is a block diagram showing a configuration of an IC chip according to a second reference example of the present invention. The same components as those in FIGS. 9 and 10 are denoted by the same reference numerals. In the IC chip 3 shown in FIG. 11, between the DC bias terminal 2-1 and the DC pad 4-1 of the RF circuit unit 1, the transmission line 7 having a characteristic impedance Z ₀ of approximately 0 and one end open. -1 is connected, and a transmission line 7 having a characteristic impedance Z ₀ of approximately 0 and one end open between the DC bias terminal 2-2 and the DC pad 4-2 of the RF circuit unit 1 is connected. -2 is connected, and between the DC bias terminal 2-3 of the RF circuit section 1 and the DC pad 4-3, the transmission line 7 having a characteristic impedance Z ₀ of approximately 0 and one end open. -3 is connected to the other end. As described with reference to FIGS. 4 and 5, the transmission lines 7-1 to 7-3 are formed on the same semiconductor substrate as the RF circuit unit 1. Between the terminal 2-1 and the DC pad 4-1, between the terminal 2-2 and the DC pad 4-2, and between the terminal 2-3 and the DC pad 4-3, the RF circuit unit 1 is provided. Are connected by wiring formed on the same semiconductor substrate.

With such a configuration, in this reference example , it is possible to cancel the influence of the inductance parasitic on each of the DC pads 4-1 to 4-3 at the time of mounting, and the millimeter wave band and higher frequency bands are handled. In the RF circuit, it is possible to mount the power supply wiring easily and at low cost without degrading the performance of the RF circuit.

[ Second Embodiment ]
Next, a second embodiment will be described. FIG. 12 is a block diagram showing the configuration of an IC chip according to the second embodiment of the present invention. The same components as those in FIGS. 9 to 11 are denoted by the same reference numerals. As a difference from the second reference example , in the second reference example , the characteristic impedance Z _{0 is present} between all the DC pads 4-1 to 4-3 and the terminals 2-1 to 2-3 of the RF circuit unit 1. Is connected to the transmission lines 7-1 to 7-3 having substantially zero, in the present embodiment, some DC pads 4-1 (for example, pads for supplying the power supply voltage VDD) and the RF circuit section are connected. The other end of the transmission line 7-1 having a characteristic impedance Z ₀ of approximately 0 and one end open is connected to one DC bias terminal 2-1 (for example, the power supply voltage terminal VDD). Between the terminal 2-1 to which the transmission line 7-1 is connected and the DC pads 4-2 and 4-3 other than the DC pad 4-1 to which the transmission line 7-1 is connected. Capacitance elements 6-1 and 6-2 are connected to. Between the terminal 2-1 and the DC pad 4-1, between the terminal 2-2 and the DC pad 4-2, and between the terminal 2-3 and the DC pad 4-3, the RF circuit unit 1 is provided. Are connected by wiring formed on the same semiconductor substrate.

  With such a configuration, in the present embodiment, it is possible to cancel the influence of the inductance parasitic on each of the DC pads 4-1 to 4-3 at the time of mounting while reducing the number of transmission lines to be used, In an RF circuit that handles a millimeter wave band or higher frequency band, power supply wiring can be easily and inexpensively implemented without degrading the performance of the RF circuit.

  The present invention can be applied to a high-frequency RF circuit that handles a millimeter wave band or higher frequency band.

  DESCRIPTION OF SYMBOLS 1 ... RF circuit part, 2-1 to 2-3 ... terminal, 3 ... IC chip, 4-1 to 4-3 ... DC pad, 5-1 to 5-3, 7-1 to 7-3 ... Transmission Lines, 6-1 to 6-2... Capacitance elements.

Claims (6)

An RF circuit formed on a semiconductor substrate;
A plurality of power supply pads formed on the semiconductor substrate to apply a DC bias to the RF circuit;
Wherein formed on the semiconductor substrate, and a plurality of wire connecting the plurality of terminals of the RF circuit corresponding thereto and the plurality of power supply pads,
For one of the wires, a distributed constant transmission line having a characteristic impedance of approximately 0 in a desired frequency band is used .
An RF circuit terminal to which the transmission line is connected and a power supply pad other than the power supply pad to which the transmission line is connected are individually connected to each power supply pad via a capacitive element. A high frequency RF circuit characterized by The high-frequency RF circuit according to claim 1,
The high-frequency RF circuit, wherein the transmission line has the characteristic impedance set so that a reflection characteristic viewed from a terminal of the RF circuit exists in the vicinity of impedance 0 on a Smith chart in a desired frequency band. The high-frequency RF circuit according to claim 1 or 2,
A high-frequency RF circuit, wherein the transmission line is connected between one of the plurality of power supply pads and a corresponding terminal of the RF circuit. The high-frequency RF circuit according to claim 1 or 2,
One end of the transmission line is connected to a wiring between one of the plurality of power supply pads and the corresponding terminal of the RF circuit, and the other end of the transmission line is electrically opened. A high frequency RF circuit. In the high frequency RF circuit according to any one of claims 1 to 4,
The high-frequency RF circuit, wherein the transmission line is a microstrip line. In the high frequency RF circuit according to any one of claims 1 to 4,
The high-frequency RF circuit according to claim 1, wherein the transmission line is a coplanar line with GND.

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