Mixer Circuit

Abstract

A mixer circuit according to the present invention comprises: a mixer (1); an LO matching circuit (6) inserted between an LO signal terminal (5) and a first terminal (2) of the mixer (1); an IF matching circuit (8) inserted between an IF signal terminal (7) and a second terminal (3) of the mixer (1); and an RF matching circuit (10) inserted between an RF signal terminal (9) and a third terminal (4) of the mixer (1). The reflection characteristics for the RF matching circuit (10) are set such that the minimum value of reflection loss appears on the high frequency side of the LO signal frequency.

Description

[Technical Field]

[0001] The present invention relates to a mixer circuit that performs frequency conversion of an electrical signal. [Background technology]

[0002] Mixers are important circuits that perform frequency conversion in wireless communication transceivers, radars, etc. In recent years, with the increase in data rates, there has been a demand for mixers that can operate at high frequencies and with a wide bandwidth.

[0003] A mixer circuit that operates at high frequencies is generally provided with matching circuits at each of the LO (Local Oscillator), IF (Intermediate Frequency), and RF (Radio Frequency) signal terminals to match with 50Ω (Non-Patent Document 1). In the example of Fig. 14, LO matching circuit 104 is provided at LO signal terminal 101 of mixer 100, IF matching circuit 105 is provided at IF signal terminal 102, and RF matching circuit 106 is provided at RF signal terminal 103.

[0004] The value obtained by normalizing the power of the RF signal or IF signal output from a mixer circuit after frequency conversion by the power of the IF signal or RF signal input to the mixer circuit before frequency conversion is called the conversion gain. The band in which the conversion gain is within -3 dB, based on the conversion gain of the mixer circuit at the LO signal frequency, is the RF band of the mixer circuit. This RF band is significantly affected by the reflection characteristics of the matching circuit, particularly the reflection characteristics of RF matching circuit 106. The reflection characteristics of RF matching circuit 106 of a conventional mixer circuit are generally designed to minimize return loss near the LO signal frequency fLO, as shown in Figure 15. BRF in Figure 15 is the desired RF band.

[0005] On the other hand, in order to broaden the RF band of the mixer circuit, it is necessary to broaden the bandwidth of the matching circuit, in particular the bandwidth of RF matching circuit 106. A conventional method for broadening the bandwidth is to use multiple stubs or capacitors in RF matching circuit 106 and design it so that multiple minimum values ​​RLmin appear in the reflection characteristics, as shown in Fig. 16. If there are four minimum values ​​RLmin of return loss, then at least four stubs or capacitors are required.

[0006] However, conventional band broadening techniques have had the problem of increasing the circuit area and increasing loss (decreasing conversion gain) because they require the use of many stubs and capacitors in RF matching circuit 106. On the other hand, in the case of mixer circuits that require compact circuits and low loss (high conversion gain), it is not possible to use many stubs and capacitors in RF matching circuit 106, making it difficult to broaden the RF band.

[0007] If RF matching circuit 106 is designed to have only one minimum value of return loss RLmin near the LO signal frequency of 270 GHz as shown in Fig. 17, the conversion gain characteristics of the mixer circuit when this RF matching circuit 106 is used will be as shown in Fig. 18. According to Figs. 17 and 18, as the LO signal frequency moves away from 270 GHz, the return loss of RF matching circuit 106 increases and the RF signal also attenuates, so the RF band becomes a narrow range of 55 GHz, from 235 GHz to 290 GHz. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Hiroshi Hamada,et al.,“300-GHz,100-Gb / s InP-HEMT wireless transceiver using a 300-GHz fundamental mixer”,2018 IEEE / MTT-S International Microwave Symposium-IMS,IEEE,2018 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above problems, and has an object to provide a mixer that can widen the RF band while maintaining a small area and low loss. [Means for solving the problem]

[0010] The mixer circuit of the present invention comprises a mixer configured to receive an LO signal and an IF signal as input and output an RF signal, or to receive an LO signal and an RF signal as input and output an IF signal; an LO matching circuit inserted between an LO signal terminal and a first terminal of the mixer and configured to match the impedance of the LO signal terminal with the impedance of the first terminal of the mixer as seen from the LO signal terminal; an IF matching circuit inserted between an IF signal terminal and a second terminal of the mixer and configured to match the impedance of the IF signal terminal with the impedance of the second terminal of the mixer as seen from the IF signal terminal; and an RF matching circuit inserted between an RF signal terminal and a third terminal of the mixer and configured to match the impedance of the RF signal terminal with the impedance of the third terminal of the mixer as seen from the RF signal terminal, wherein the RF matching circuit has reflection characteristics set so that a minimum value of return loss appears on the high frequency side of the frequency of the LO signal and in the vicinity of the highest frequency of a desired RF band. The desired RF band is a band in which the conversion gain is within −3 dB based on the conversion gain of the mixer circuit at the frequency of the LO signal. It is characterized by the following.

[0011] In one configuration example of the mixer circuit of the present invention, the RF matching circuit is The aforementioned The reflection characteristics are set so that a minimum value of the return loss appears near the highest frequency in the RF band, and also so that a minimum value of the return loss appears on the low-frequency side of the LO signal frequency and near the lowest frequency in the RF band. In addition, in one configuration example of the mixer circuit of the present invention, the RF matching circuit is characterized in that the reflection characteristics are set so that the minimum value of the return loss on the high frequency side is smaller than the minimum value of the return loss on the low frequency side.

[0012] The mixer circuit of the present invention includes a mixer configured to receive an LO signal and an IF signal as input and output an RF signal, or to receive an LO signal and an RF signal as input and output an IF signal; an LO matching circuit inserted between an LO signal terminal and a first terminal of the mixer and configured to match the impedance of the LO signal terminal with the impedance of the first terminal of the mixer as seen from the LO signal terminal; an IF matching circuit inserted between an IF signal terminal and a second terminal of the mixer and configured to match the impedance of the IF signal terminal with the impedance of the second terminal of the mixer as seen from the IF signal terminal; and an RF matching circuit inserted between an RF signal terminal and a third terminal of the mixer and configured to match the impedance of the RF signal terminal with the impedance of the third terminal of the mixer as seen from the RF signal terminal, wherein the IF matching circuit has reflection characteristics set so that a minimum value of return loss appears on the high frequency side higher than DC and in the vicinity of the highest frequency of a desired IF band. The desired IF band is a band from DC to a predetermined frequency that is lower than the desired RF band, and the desired RF band is a band in which the conversion gain is within −3 dB based on the conversion gain of the mixer circuit at the frequency of the LO signal. It is characterized by the following.

[0013] The mixer circuit of the present invention also includes a mixer configured to receive an LO signal and an IF signal as inputs and output an RF signal, or to receive an LO signal and an RF signal as inputs and output an IF signal, an LO matching circuit inserted between an LO signal terminal and a first terminal of the mixer and configured to match the impedance of the LO signal terminal with the impedance of the first terminal of the mixer as seen from the LO signal terminal, and an LO matching circuit inserted between an IF signal terminal and a second terminal of the mixer and configured to match the impedance of the IF signal terminal with the impedance of the second terminal of the mixer as seen from the IF signal terminal. and an RF matching circuit inserted between an RF signal terminal and a third terminal of the mixer and configured to match the impedance of the RF signal terminal with the impedance of the third terminal of the mixer as viewed from the RF signal terminal, wherein the RF matching circuit has a reflection characteristic set so that a minimum value of return loss appears on the high frequency side of the frequency of the LO signal and in the vicinity of the highest frequency of a desired RF band, and the IF matching circuit has a reflection characteristic set so that a minimum value of return loss appears on the high frequency side of DC and in the vicinity of the highest frequency of a desired IF band. The desired RF band is a band in which the conversion gain is within −3 dB based on the conversion gain of the mixer circuit at the frequency of the LO signal, and the desired IF band is a band from DC to a predetermined frequency that is lower than the RF band. It is characterized by the following.

[0014] In one configuration example of the mixer circuit of the present invention, the RF matching circuit is The aforementioned The reflection characteristics are set so that a minimum value of the return loss appears near the highest frequency in the RF band, and also so that a minimum value of the return loss appears on the low-frequency side of the LO signal frequency and near the lowest frequency in the RF band. In addition, in one configuration example of the mixer circuit of the present invention, the mixer is characterized in that it comprises a transistor having a gate terminal as the first terminal connected to the LO matching circuit, a source terminal connected to ground, and drain terminals as the second and third terminals connected to the IF matching circuit and the RF matching circuit. In addition, in one configuration example of the mixer circuit of the present invention, the RF matching circuit comprises a transmission line having one end connected to the RF signal terminal and the other end connected to a third terminal of the mixer, a first capacitor having one end connected to the transmission line and the other end connected to ground, and a second capacitor having a capacitance different from that of the first capacitor, arranged farther from the RF signal terminal than the first capacitor, one end connected to the transmission line and the other end connected to ground, and wherein the capacitance of the first capacitor is smaller than the capacitance of the second capacitor. [Effects of the Invention]

[0015] According to the present invention, by setting the reflection characteristics of the RF matching circuit so that a minimum value of the return loss appears on the high-frequency side of the LO signal frequency, it is possible to widen the RF band of the mixer circuit while maintaining a small area and low loss. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a circuit diagram of a mixer circuit according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the reflection characteristics of the RF matching circuit according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing specific examples of reflection characteristics of a conventional RF matching circuit and the RF matching circuit according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the conversion gain characteristics of a conventional mixer circuit and the mixer circuit according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing the reflection characteristics of an RF matching circuit according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing the reflection characteristics of an RF matching circuit according to a third embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing the reflection characteristics of a conventional IF matching circuit. [Figure 8]FIG. 8 is a diagram showing the reflection characteristics of the IF matching circuit according to the fourth embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing the reflection characteristics of an RF matching circuit and an IF matching circuit according to the fifth embodiment of the present invention. [Figure 10] FIG. 10 is a circuit diagram of a mixer circuit according to a sixth embodiment of the present invention. [Figure 11] FIG. 11 is a circuit diagram of an RF matching circuit according to a seventh embodiment of the present invention. [Figure 12] FIG. 12 is a circuit diagram of an RF matching circuit according to a seventh embodiment of the present invention. [Figure 13] FIG. 13 is a circuit diagram of an IF matching circuit according to a seventh embodiment of the present invention. [Figure 14] FIG. 14 is a circuit diagram of a conventional mixer circuit. [Figure 15] FIG. 15 is a diagram showing an example of the reflection characteristics of a conventional RF matching circuit. [Figure 16] FIG. 16 is a diagram showing another example of the reflection characteristics of a conventional RF matching circuit. [Figure 17] FIG. 17 is a diagram showing a specific example of the reflection characteristics of a conventional RF matching circuit. [Figure 18] FIG. 18 is a diagram showing the conversion gain characteristics of the mixer circuit when the RF matching circuit of FIG. 17 is used. DETAILED DESCRIPTION OF THE INVENTION

[0017] [First Example] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a circuit diagram of a mixer circuit according to a first embodiment of the present invention. The mixer circuit includes a mixer 1 that receives an LO signal and an IF signal as input and outputs an RF signal, or receives an LO signal and an RF signal as input and outputs an IF signal, an LO matching circuit 6 that is inserted between an LO signal terminal 5 and a first terminal 2 of the mixer 1 and matches the impedance of the LO signal terminal 5 to the impedance of the first terminal 2 of the mixer 1 as seen from the LO signal terminal 5, an IF matching circuit 8 that is inserted between an IF signal terminal 7 and a second terminal 3 of the mixer 1 and matches the impedance of the IF signal terminal 7 to the impedance of the second terminal 3 of the mixer 1 as seen from the IF signal terminal 7, and an RF matching circuit 10 that is inserted between an RF signal terminal 9 and a third terminal 4 of the mixer 1 and matches the impedance of the RF signal terminal 9 to the impedance of the third terminal 4 of the mixer 1 as seen from the RF signal terminal 9.

[0018] In this embodiment, the reflection characteristics of the RF matching circuit 10 are designed so that local minimum values ​​RLmin1 and RLmin2 of return loss appear on both the low-frequency side and the high-frequency side of the LO signal frequency fLO, as shown in Fig. 2. By designing the RF matching circuit 10 so that the return loss is large near the LO signal frequency fLO (for example, within a frequency range of ±5%) and the return loss is smallest near the highest and lowest frequencies of the desired RF band BRF, it becomes unnecessary to generate multiple local minimum values ​​in the return loss of the RF matching circuit, and it becomes possible to widen the RF band of the mixer circuit while maintaining a small area and low loss.

[0019] Assume that the frequency fLO of the LO signal is 270 GHz, the highest frequency of the desired RF band BRF is 320 GHz, and the lowest frequency of the RF band BRF is 220 GHz. The RF matching circuit 10 is designed so that the return loss is large near the LO signal frequency fLO = 270 GHz and is smallest near the highest frequency of the RF band BRF, 320 GHz, and the lowest frequency, 220 GHz. The reflection characteristics of the RF matching circuit 10 in this case are shown in Figure 3. In Figure 3, reference numeral 30 denotes the reflection characteristics of the conventional RF matching circuit 106, and reference numeral 31 denotes the reflection characteristics of the RF matching circuit 10 of this embodiment.

[0020] The conversion gain characteristics of the mixer circuit when RF matching circuits 106 and 10 are used are as shown in Fig. 4. In Fig. 4, reference numeral 40 indicates the conversion gain characteristics of the conventional mixer circuit, and reference numeral 41 indicates the conversion gain characteristics of the mixer circuit of this embodiment. According to this embodiment, the RF bandwidth is 110 GHz, which is wider than the RF bandwidth of 55 GHz of the conventional mixer circuit.

[0021] The mixer circuit of this embodiment can be applied to both up-conversion and down-conversion. When used as an up-conversion mixer, an LO signal is input to the LO signal terminal 5 and an IF signal is input to the IF signal terminal 7, and an RF signal is output from the RF signal terminal 9. When used as a down-conversion mixer, an LO signal is input to the LO signal terminal 5 and an RF signal is input to the RF signal terminal 9, and an IF signal is output from the IF signal terminal 7.

[0022] In this embodiment, it is sufficient that the minimum values ​​RLmin1 and RLmin2 of the return loss of the RF matching circuit 10 are near the highest frequency and near the lowest frequency of the desired RF band BRF, and that the maximum value RLmax of the return loss is between the two minimum values ​​RLmin1 and RLmin2. It is preferable that the maximum value RLmax of the return loss is, for example, -5 dB or more, and the minimum values ​​RLmin1 and RLmin2 of the return loss are, for example, -10 dB or less, and the loss difference between the maximum value RLmax and the minimum values ​​RLmin1 and RLmin2 is, for example, 5 dB or more.

[0023] [Second Example] As described below, a transistor is used as the mixer 1 of the first embodiment. Generally, as the frequency increases, the transconductance of the transistor decreases and the wiring loss increases, so the conversion gain of the mixer circuit decreases as the frequency increases, and flatness is lost.

[0024] Therefore, in the configuration of the first embodiment, the RF matching circuit 10 is designed so that the minimum value RLmin2 of the return loss near the highest frequency of the desired RF band BRF is smaller than the minimum value RLmin1 of the return loss near the lowest frequency of the RF band BRF, as shown in Fig. 5. As a result, in this embodiment, it is possible to widen the RF band of the mixer circuit and improve the flatness of the conversion gain characteristics.

[0025] The minimum value RLmin1 of the return loss of the RF matching circuit 10 is, for example, about −10 dB, and the minimum value RLmin2 is, for example, preferably −15 dB or less, with the loss difference between the minimum values ​​RLmin1 and RLmin2 being, for example, 5 dB or more.

[0026] [Third Example] In the first and second embodiments, the RF matching circuit 10 was designed so that local minimum values ​​RLmin1 and RLmin2 of return loss appeared on both sides of the LO signal frequency fLO. On the other hand, in this embodiment, the RF matching circuit 10 is designed so that local minimum value RLmin2 of return loss appears only near the highest frequency in the RF band BRF that is higher than the LO signal frequency fLO, as shown in Fig. 6. This makes it possible in this embodiment to reduce the area of ​​the RF matching circuit 10, thereby achieving a wider RF band and simultaneously reducing the area and loss of the mixer circuit.

[0027] The minimum value RLmin2 of the return loss of the RF matching circuit 10 is, for example, −10 dB or less, and the maximum value RLmax of the return loss is, for example, −5 dB or more, and the loss difference between the maximum value RLmax and the minimum value RLmin2 is, for example, 5 dB or more.

[0028] [Fourth Example] The RF bandwidth of a mixer circuit is also affected by the reflection characteristics of the IF matching circuit. IF matching circuit 105 of a conventional mixer circuit is designed to minimize return loss at DC (direct current), as shown in Figure 7. However, as the frequency increases, the return loss of IF matching circuit 105 worsens, causing the IF signal to be attenuated. As a result, the RF signal converted by the mixer circuit also becomes more attenuated the further it deviates from the LO frequency, degrading the RF bandwidth.

[0029] Therefore, in the configuration of the first embodiment, as shown in FIG. 8, the IF matching circuit 8 is designed so that the return loss decreases from DC toward the higher frequency side, and the minimum value RLmin3 of the return loss appears at frequencies higher than DC. Specifically, the minimum value RLmin3 of the return loss appears near the highest frequency of the desired IF band BIF. In the case of a double-sideband mixer, the IF bandwidth is equal to half the RF bandwidth. In this embodiment, the RF band of the mixer circuit can be widened. Furthermore, in this embodiment, frequency ripple within the RF band can be suppressed.

[0030] The minimum value RLmin3 of the return loss of the IF matching circuit 8 is, for example, -10 dB or less, and the maximum value RLmax of the return loss is, for example, -5 dB or more, and the loss difference between the maximum value RLmax and the minimum value RLmin3 is, for example, 5 dB or more.

[0031] [Fifth Example] The RF band can be further broadened by combining the RF matching circuit 10 of any one of the first to third embodiments with the IF matching circuit 8 of the fourth embodiment. The example of Fig. 9 shows the reflection characteristics when the RF matching circuit 10 of the first embodiment and the IF matching circuit 8 of the fourth embodiment are used.

[0032] Furthermore, the number of design parameters increases by combining the first to fourth embodiments, which also improves ease of design. Furthermore, the combination of the first to fourth embodiments makes it possible to provide a peaking effect in which the conversion gain of the mixer circuit increases as the frequency moves away from the LO signal frequency fLO.

[0033] [Sixth Example] This embodiment shows a specific example of a mixer 1 used in the mixer circuits of the first to fifth embodiments. The mixer 1 of this embodiment is a resistive mixer, and is made up of a transistor Q1 having a gate terminal (first terminal 2) connected to an LO matching circuit 6, a source terminal connected to ground, and drain terminals (second terminal 3, third terminal 4) connected to an IF matching circuit 8 and an RF matching circuit 10, as shown in Fig. 10.

[0034] The resistive mixer has high linearity and can be configured with a single transistor Q1, allowing for a small area. Furthermore, because the resistive mixer performs multiplication using changes in the drain resistance of the transistor Q1, it is easy to design a matching circuit, particularly one that minimizes return loss on the high-frequency side.

[0035] [Seventh Example] This embodiment shows a specific example of a matching circuit used in the mixer circuits of the first to sixth embodiments. As shown in FIG. 11, the RF matching circuit 10 of the first and second embodiments includes a transmission line TL1 having one end connected to an RF signal terminal 9 and the other end connected to the third terminal 4 of the mixer 1, and two capacitors C1 and C2 with different capacitances that are arranged along the transmission line TL1 and have one end connected to the transmission line TL1 and the other end connected to ground. The transmission line TL1 is configured by connecting three transmission lines TL100, TL101, and TL102 in series. The capacitor C1 is connected to the connection point between the transmission lines TL100 and TL101, and the capacitor C2 is connected to the connection point between the transmission lines TL101 and TL102.

[0036] In the configuration of Figure 11, by making the capacitance of capacitor C1, which is closer to RF signal terminal 9, smaller than the capacitance of capacitor C2, it becomes easier to design RF matching circuit 10, particularly to design the minimum value of return loss on the high frequency side.

[0037] 12, the RF matching circuit 10 of the third embodiment includes a transmission line TL2 having one end connected to the RF signal terminal 9 and the other end connected to the third terminal 4 of the mixer 1, and a capacitor C3 having one end connected to the transmission line TL2 and the other end connected to ground. The transmission line TL2 is configured by connecting two transmission lines TL200 and TL201 in series. The capacitor C3 is connected to the connection point of the transmission lines TL200 and TL201.

[0038] 13, the IF matching circuit 8 of the fourth embodiment is composed of a transmission line TL3 having one end connected to the IF signal terminal 7 and the other end connected to the second terminal 3 of the mixer 1, and a capacitor C4 having one end connected to the transmission line TL3 and the other end connected to ground. The transmission line TL3 is configured by connecting two transmission lines TL300 and TL301 in series. The capacitor C4 is connected to the connection point of the transmission lines TL300 and TL301. [Industrial Applicability]

[0039] The present invention can be applied to a mixer circuit that performs frequency conversion of a signal. [Explanation of symbols]

[0040] 1...mixer, 5...LO signal terminal, 6...LO matching circuit, 7...IF signal terminal, 8...IF matching circuit, 9...RF signal terminal, 10...RF matching circuit, Q1...transistor, C1 to C4...capacitors, TL1 to TL3, TL100 to TL102, TL200, TL201, TL300, TL301...transmission lines.

Claims

1. a mixer configured to receive an LO signal and an IF signal as inputs and output an RF signal, or to receive an LO signal and an RF signal as inputs and output an IF signal; an LO matching circuit inserted between an LO signal terminal and a first terminal of the mixer, configured to match the impedance of the LO signal terminal with the impedance of the first terminal of the mixer as seen from the LO signal terminal; an IF matching circuit inserted between an IF signal terminal and a second terminal of the mixer, configured to match the impedance of the IF signal terminal with the impedance of the second terminal of the mixer as viewed from the IF signal terminal; an RF matching circuit inserted between an RF signal terminal and a third terminal of the mixer, and configured to match the impedance of the RF signal terminal with the impedance of the third terminal of the mixer as viewed from the RF signal terminal; the RF matching circuit has a reflection characteristic set so that a minimum value of reflection loss appears on the high frequency side of the LO signal frequency and in the vicinity of the highest frequency of a desired RF band; The mixer circuit is characterized in that the desired RF band is a band in which the conversion gain is within −3 dB with reference to the conversion gain of the mixer circuit at the frequency of the LO signal.

2. 2. The mixer circuit according to claim 1, The RF matching circuit has reflection characteristics set so that a minimum value of the return loss appears on the high-frequency side of the LO signal frequency and in the vicinity of the highest frequency of the RF band, and also on the low-frequency side of the LO signal frequency and in the vicinity of the lowest frequency of the RF band.

3. 3. The mixer circuit according to claim 2, The mixer circuit is characterized in that the RF matching circuit has reflection characteristics set so that the minimum value of the return loss on the high frequency side is smaller than the minimum value of the return loss on the low frequency side.

4. a mixer configured to receive an LO signal and an IF signal as inputs and output an RF signal, or to receive an LO signal and an RF signal as inputs and output an IF signal; an LO matching circuit inserted between an LO signal terminal and a first terminal of the mixer, configured to match the impedance of the LO signal terminal with the impedance of the first terminal of the mixer as seen from the LO signal terminal; an IF matching circuit inserted between an IF signal terminal and a second terminal of the mixer, configured to match the impedance of the IF signal terminal with the impedance of the second terminal of the mixer as viewed from the IF signal terminal; an RF matching circuit inserted between an RF signal terminal and a third terminal of the mixer, and configured to match the impedance of the RF signal terminal with the impedance of the third terminal of the mixer as viewed from the RF signal terminal; the IF matching circuit has a reflection characteristic set so that a minimum value of the reflection loss appears on the high frequency side higher than DC and in the vicinity of the highest frequency of a desired IF band; the desired IF band is a band from DC to a predetermined frequency that is lower than the desired RF band; The mixer circuit is characterized in that the desired RF band is a band in which the conversion gain is within −3 dB with reference to the conversion gain of the mixer circuit at the frequency of the LO signal.

5. a mixer configured to receive an LO signal and an IF signal as inputs and output an RF signal, or to receive an LO signal and an RF signal as inputs and output an IF signal; an LO matching circuit inserted between an LO signal terminal and a first terminal of the mixer, configured to match the impedance of the LO signal terminal with the impedance of the first terminal of the mixer as seen from the LO signal terminal; an IF matching circuit inserted between an IF signal terminal and a second terminal of the mixer, configured to match the impedance of the IF signal terminal with the impedance of the second terminal of the mixer as viewed from the IF signal terminal; an RF matching circuit inserted between an RF signal terminal and a third terminal of the mixer, and configured to match the impedance of the RF signal terminal with the impedance of the third terminal of the mixer as viewed from the RF signal terminal; the RF matching circuit has a reflection characteristic set so that a minimum value of reflection loss appears on the high frequency side of the LO signal frequency and in the vicinity of the highest frequency of a desired RF band; the IF matching circuit has a reflection characteristic set so that a minimum value of the reflection loss appears on the high frequency side higher than DC and in the vicinity of the highest frequency of a desired IF band; the desired RF band is a band in which the conversion gain is within −3 dB based on the conversion gain of the mixer circuit at the frequency of the LO signal; The mixer circuit according to claim 1, wherein the desired IF band is a band from DC to a predetermined frequency that is lower than the RF band.

6. 6. The mixer circuit according to claim 5, The RF matching circuit has reflection characteristics set so that a minimum value of the return loss appears on the high-frequency side of the LO signal frequency and in the vicinity of the highest frequency of the RF band, and also on the low-frequency side of the LO signal frequency and in the vicinity of the lowest frequency of the RF band.

7. 7. The mixer circuit according to claim 1, The mixer circuit is characterized in that the mixer comprises a transistor having a gate terminal as the first terminal connected to the LO matching circuit, a source terminal connected to ground, and drain terminals as the second and third terminals connected to the IF matching circuit and the RF matching circuit.

8. 7. The mixer circuit according to claim 2, 3, or 6, The RF matching circuit includes: a transmission line having one end connected to the RF signal terminal and the other end connected to a third terminal of the mixer; a first capacitor having one end connected to the transmission line and the other end connected to ground; a second capacitor having a capacitance different from that of the first capacitor, the second capacitor being arranged farther from the RF signal terminal than the first capacitor, one end connected to the transmission line, and the other end connected to ground; A mixer circuit, wherein the capacitance of the first capacitor is smaller than the capacitance of the second capacitor.

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