WO2020172893A1 - Frequency mixer and communication device - Google Patents

Abstract

A frequency mixer and a communication device, used for reducing the effects of parasitic capacitance at an input terminal of the frequency mixer on frequency mixer performance. The frequency mixer comprising: a frequency mixer circuit and a tuned circuit, the tuned circuit being connected to an input terminal of the frequency mixer circuit, wherein: the frequency mixer circuit comprising a single-balanced frequency mixer circuit or a double-balanced frequency mixer circuit; the tuned circuit and a parasitic capacitor at an input terminal of the frequency mixer circuit forming an LC parallel resonant circuit, and at least one of the capacitance value of the capacitor in the tuned circuit and the inductance value of an inductor in the tuned circuit being adjustable.

Description

Mixer and communication equipment Technical field

This application relates to the field of wireless communication technology, and in particular to a mixer and communication equipment.

Background technique

The mixer is a key component for frequency conversion in wireless communication equipment, and it is also a basic unit of the transceiver. Among them, the receiver uses a mixer to down-convert the received radio frequency (RF) signal to an intermediate frequency signal or zero-IF signal for processing, and the transmitter uses a mixer to up-convert the intermediate or zero-IF signal to a radio frequency signal to facilitate Antenna emission.

Modern communication systems have higher and higher requirements for communication rates, making the bandwidth and frequency coverage of communication signals wider and wider, and the radio frequency is also getting higher and higher. The mixer is usually realized by a pair of transistor switches. There is a parasitic capacitance at the port of the mixer used to input the signal to be processed. This parasitic capacitance affects the performance of the mixer (gain, noise figure, linearity, etc.) The influence is greater, the higher the working frequency of the mixer, the more serious the deterioration of the mixer's noise figure and linearity.

In order to solve the above problems, in the prior art, the size of the transistor switch pair in the mixer is limited to reduce the size of the parasitic capacitance at the input end thereof, thereby reducing the influence of the parasitic capacitance on the performance of the mixer. However, the method to limit the size of the transistor switch is to optimize the design of a comprehensive compromise between the gain, noise and linearity performance of the mixer. One or more of the gain, noise figure and linearity performance of the mixer will be affected. There is a certain degree of decline.

Summary of the invention

The application provides a mixer and a communication device to reduce the influence of parasitic capacitance at the input end of the mixer on the performance of the mixer.

In a first aspect, the present application provides a mixer including a tuning circuit and a mixing circuit, and the tuning circuit is connected to the input end of the mixing circuit. Wherein, the mixing circuit is a single-balanced mixing circuit or a double-balanced mixing circuit, the tuning circuit and the parasitic capacitance at the input end of the mixing circuit form an LC parallel resonant circuit, and the capacitance of the tuning circuit At least one of the capacitance value and the inductance value of the inductor in the tuning circuit is adjustable.

Through the above solution, the mixer can pass through the tuning circuit in the mixer, so that the LC resonance circuit formed by the tuning circuit and the parasitic capacitance at the input end of the mixer circuit in the mixer is at The resonance state is used to increase the impedance at the input end of the mixer circuit, so that the mixer circuit can suppress the frequency conversion of the signal input from the input end of the mixer circuit using the local oscillator signal. In the signal output by the mixer circuit, noise and nonlinear intermodulation products introduced by the parasitic capacitance at the input end of the mixer circuit can effectively improve the performance of the mixer (such as noise figure, linearity) ). Moreover, when the structure of the tuning circuit is set appropriately, the tuning circuit can increase the frequency range by cooperating with the parasitic capacitance at the input end of the mixing circuit in the mixer. The impedance at the input end of the mixer circuit in turn enables the mixer to improve the performance of the mixer in a wide frequency range.

In a possible implementation manner, the mixing circuit includes at least a pair of triode switch pairs, and the input end of the mixing circuit is the common emitter node of the triode switch pair; or, the mixing circuit includes at least A pair of metal oxide semiconductor MOS transistor switch pairs, and the input end of the mixer circuit is a common source node of the MOS transistor switch pair.

In a possible implementation manner, the resonance frequency range of the LC parallel resonant circuit is determined according to the frequency range of the local oscillator signal used when the mixing circuit 220 performs frequency conversion.

In a possible implementation manner, the frequency range of the double frequency signal of the local oscillator signal is within the resonance frequency range of the LC parallel resonant circuit.

The noise signal introduced due to the parasitic capacitance at the input end of the mixer circuit is mainly concentrated at the frequency corresponding to the even harmonic of the local oscillator signal, especially at the double frequency of the local oscillator signal. , When the frequency range of the double frequency signal of the local oscillator signal is within the resonant frequency range of the LC parallel resonant circuit, the LC parallel resonant circuit is in a resonance state, and the impedance at the input end of the mixing circuit To be larger, it can suppress the noise and nonlinear intermodulation products introduced by the parasitic capacitance at the input end of the mixer circuit in the signal output by the mixer circuit, thereby effectively improving the mixer’s performance Performance (such as noise figure, linearity).

In a possible implementation manner, the tuning circuit can be implemented in any one of the following four ways, but not limited to:

Manner 1: The tuning circuit is a switched inductance matrix, wherein the state of the switches in the switched inductance matrix is based on the resonance frequency range of the LC parallel resonant circuit and the capacitance value of the parasitic capacitance at the input end of the mixing circuit determine.

Manner 2: The tuning circuit includes a fixed inductance and a switched capacitor matrix, wherein the fixed inductance is connected in parallel with the switched capacitor matrix, and the state of the switch in the switched capacitor matrix is based on the resonance frequency range of the LC parallel resonant circuit, The inductance value of the fixed inductor and the capacitance value of the parasitic capacitance at the input end of the mixer circuit are determined.

Manner 3: The tuning circuit includes a fixed capacitor and a switch inductance matrix, wherein the fixed capacitor is connected in parallel with the switch inductance matrix, and the state of the switch in the switch inductance matrix is based on the resonance frequency range of the LC parallel resonant circuit, The capacitance value of the fixed capacitor and the capacitance value of the parasitic capacitance at the input end of the mixer circuit are determined.

Manner 4: The tuning circuit includes a switch inductance matrix and a switch inductance matrix, wherein the switch inductance matrix is connected in parallel with the switch capacitance matrix, and the state of the switch in the switch inductance matrix is based on the resonance frequency of the LC parallel resonant circuit The range and the capacitance value of the parasitic capacitance at the input end of the mixer circuit are determined, and the state of the switches in the switch inductance matrix is determined according to the resonance frequency range of the LC parallel resonant circuit and the capacitance value at the input end of the mixer circuit. The capacitance value of the parasitic capacitance is determined.

In a possible implementation manner, the switch inductance matrix can be implemented in any one of the following three ways, but not limited to:

Manner 1. The switch inductor matrix includes a plurality of inductors connected in series, and each inductor is connected in parallel with the switch.

Manner 2. The switch inductance matrix includes a plurality of branches connected in parallel, and each branch includes an inductor and a switch connected in series with the inductor.

Manner 3: The switch inductance matrix includes at least one first inductance circuit and at least one second inductance circuit, the first inductance circuit is connected in series with the second inductance circuit, and each first inductance circuit includes a first inductance and The switch connected in series with the first inductor, and the second inductor circuit includes a switch connected in series with the second inductor.

In a possible implementation manner, the switched capacitor matrix includes a plurality of branches connected in parallel with each other, and each branch includes a capacitor and a switch connected in series with the capacitor.

In a second aspect, the present application also provides another mixer. The mixer includes an impedance adjustment circuit and a mixing circuit, and the impedance adjustment circuit is connected to the input end of the mixing circuit. Wherein, the mixer circuit is a single-balanced mixer circuit or a double-balanced mixer circuit, and the impedance adjustment circuit and the parasitic capacitance at the input end of the mixer circuit form an impedance multi-pole circuit; the impedance multi-pole circuit There are at least two target poles among the poles of the impedance function, and the frequency range of the N-multiplier signal of the local oscillator signal used when the mixer circuit performs frequency conversion is within the range determined by the frequencies corresponding to the two target poles Inside, N is an even number.

Through the above solution, the mixer can increase the impedance multi-pole circuit formed by the impedance adjustment circuit in the mixer and the parasitic capacitance at the input end of the mixer circuit in the mixer. The impedance at the input end of the mixer circuit makes it possible for the mixer circuit to use the local oscillator signal to perform frequency conversion on the signal input from the input end of the mixer circuit to suppress the signal output by the mixer circuit. The noise and nonlinear intermodulation products introduced by the parasitic capacitance at the input end of the mixer circuit can effectively improve the performance (such as noise figure, linearity) of the mixer. Moreover, when the poles of the impedance multi-pole circuit are set appropriately, the impedance multi-pole circuit can increase the impedance at the input end of the mixer circuit within a wider frequency range, thereby causing the mixing The mixer can improve the performance of the mixer in a wide frequency range.

In a possible implementation manner, the frequency range of the double frequency signal of the local oscillator signal is within a frequency range determined by the frequencies corresponding to the two target poles.

The influence of the noise signal introduced by the parasitic capacitance at the input end of the mixer on the performance of the mixer is mainly concentrated in the frequency range corresponding to the even harmonics of the local oscillator signal, especially the local The frequency range of the double frequency signal of the local oscillator signal is within the frequency range corresponding to the two target poles of the impedance multipole circuit, the impedance multipole The impedance of the circuit at the double frequency of the local oscillator signal is large, which can suppress the noise and nonlinear intermodulation introduced by the parasitic capacitance at the input end of the mixer circuit in the signal output by the mixer circuit Product product, which can effectively improve the performance of the mixer (such as noise figure, linearity).

In a possible implementation manner, the mixing circuit includes at least a pair of triode switch pairs, and the input end of the mixing circuit is the common emitter node of the triode switch pair; or, the mixing circuit includes at least A pair of metal oxide semiconductor MOS transistor switch pairs, and the input end of the mixer circuit is a common source node of the MOS transistor switch pair.

In a possible implementation manner, the impedance adjusting circuit includes a first capacitor and a coupled inductor; wherein the coupled inductor includes a first winding and a second winding, and the first winding is connected to the input terminal of the mixing circuit Connected, the second winding is connected in parallel with the first capacitor.

In a possible implementation manner, the impedance adjustment circuit further includes a second capacitor, and the second capacitor is connected in parallel with the first winding.

In a possible implementation manner, the impedance adjustment circuit further includes a resistor, and the resistor is connected in parallel with the first capacitor.

In a third aspect, the present application provides a communication device that includes a processor and the mixer described in any one of the possible implementations of the second aspect; or, the communication device includes a processor and The mixer described in any one of the possible implementation manners of the foregoing third aspect. The mixer is used to down-convert the radio frequency signal input to the mixer to obtain an intermediate frequency signal or baseband signal; the processor is used to process the intermediate frequency signal or baseband signal.

In a fourth aspect, the present application provides a communication device that includes a processor and the mixer described in any one of the possible implementations of the second aspect; or, the communication device includes a processor and The mixer described in any one of the possible implementation manners of the foregoing third aspect. Wherein, the processor is used to generate a baseband signal or an intermediate frequency signal; the mixer is used to up-convert the baseband signal to obtain a radio frequency signal when the processor generates the baseband signal; When the processor generates an intermediate frequency signal, it up-converts the intermediate frequency signal to obtain a radio frequency signal.

Description of the drawings

Figure 1 is a schematic diagram of the structure of a double-balanced mixer in the prior art;

FIG. 2 is a schematic structural diagram of a mixer provided by an embodiment of the application;

3 is one of the structural schematic diagrams of a tuning circuit in a mixer provided by an embodiment of the application;

4 is the second structural diagram of a tuning circuit in a mixer provided by an embodiment of the application;

5 is the third structural diagram of a tuning circuit in a mixer provided by an embodiment of the application;

6 is a fourth structural diagram of a tuning circuit in a mixer provided by an embodiment of the application;

FIG. 7a is one of the structural schematic diagrams of a switch inductor matrix provided by an embodiment of this application;

FIG. 7b is a second structural diagram of a switch inductor matrix provided by an embodiment of the application;

FIG. 7c is the third structural diagram of a switch inductor matrix provided by an embodiment of this application;

FIG. 7d is the fourth structural diagram of a switch inductor matrix provided by an embodiment of this application;

FIG. 7e is a schematic structural diagram of a switched capacitor matrix provided by an embodiment of the application;

FIG. 8a is one of the specific structural schematic diagrams of a mixer provided by an embodiment of this application;

FIG. 8b is the second schematic diagram of a specific structure of a mixer provided by an embodiment of this application;

FIG. 8c is the third schematic diagram of a specific structure of a mixer provided by an embodiment of this application;

FIG. 8d is a fourth schematic diagram of a specific structure of a mixer provided by an embodiment of this application;

9 is a simulation diagram of the relationship between the linearity of the mixer and the inductance value of the equivalent inductance of the switching inductance matrix provided by an embodiment of the application;

10 is a simulation diagram of the relationship between the linearity of the mixer and the inductance value of the equivalent inductance of the switching inductance matrix provided by an embodiment of the application;

FIG. 11 is a fifth schematic diagram of a specific structure of a mixer provided by an embodiment of this application;

FIG. 12 is a schematic structural diagram of another mixer provided by an embodiment of the application;

FIG. 13a is one of the schematic structural diagrams of an impedance adjusting circuit in another mixer provided by an embodiment of the application;

FIG. 13b is the second structural diagram of an impedance adjustment circuit in another mixer provided by an embodiment of the application;

FIG. 13c is the third structural diagram of an impedance adjustment circuit in another mixer provided by an embodiment of the application;

14 is a schematic diagram of a specific structure of another mixer provided by an embodiment of the application;

FIG. 15 is a schematic structural diagram of a communication device provided by an embodiment of this application.

detailed description

The mixer is usually realized by a pair of transistor switches. There is a parasitic capacitance at the port of the mixer used to input the signal to be processed. This parasitic capacitance affects the performance of the mixer (gain, noise figure, linearity, etc.) The influence is greater, the higher the working frequency of the mixer, the more serious the deterioration of the mixer's noise figure and linearity.

Take the double-balanced mixer in the receiver shown in Figure 1 as an example. The double-balanced mixer includes transistors M0-M3. The transistor M0 and the transistor M1 form a transistor switch pair, and the transistor M2 and the transistor form a transistor M3 switch. Yes, the sources of transistors M0-M3 are the input terminals of radio frequency signals (signals to be processed) RF_IN and RF_IP, the gates of transistors M0-M3 are the input terminals of local oscillator (LO) signals LON and LOP, and transistors M0-M3 The drains of are the output terminals of intermediate frequency (IF) signals IF_IN and IF_IP. Since the common source node of transistors M0 and M1 and the common source node of M2 and M3 both have parasitic capacitance Cp, the common source node of transistors M0 and M1 and the common source node of M2 and M3 become low impedance nodes, and the double balance The higher the operating frequency of the mixer, the lower the impedance at the common source node. Transistors M0-M3 charge and discharge the parasitic capacitance Cp when working, resulting in the steady-state noise current signal at the input of the local oscillator signal and the noise current signal from the transistor switch pair in the intermediate frequency signal output by the double-balanced mixer. The current signal is distributed at the even harmonics (including direct current) of the local oscillator signal. The higher the operating frequency of the double-balanced mixer, the worse the noise figure. At the same time, the low impedance caused by the parasitic capacitance Cp of the transistor switch to the common source node will also introduce the nonlinear intermodulation product of the transistor switch pair (third-order intermodulation product and second-order intermodulation product) in the intermediate frequency signal output by the double-balanced mixer. Intermodulation product). The higher the operating frequency of the double-balanced mixer, the higher the nonlinear intermodulation product, that is, the worse the linearity performance is.

In the prior art, a method of limiting the size of the transistor switch pair in the mixer is adopted to reduce the size of the parasitic capacitance at the input end thereof, thereby achieving the purpose of reducing the influence of the parasitic capacitance on the performance of the mixer. However, this method will cause one or more of the gain, noise figure, and linearity of the mixer to decrease.

In order to solve the above-mentioned problems in the prior art, the present application provides a mixer and communication equipment to reduce the mixer's performance while ensuring the mixer's performance such as gain, noise figure, and linearity. The effect of parasitic capacitance at the input on the performance of the mixer. In the embodiments of this application, improvements are mainly made to the part that implements frequency conversion in the mixer. However, it should be understood that the mixer provided in the embodiments of this application is a complete mixer and also has a known mixer. The structure of the mixer, such as input stage circuit, output stage circuit, etc., is only related to the improvement of the parasitic capacitance at the input end of the mixer where the frequency conversion part of the mixer is used to input the signal to be processed. The affected parts will be explained, and other parts will not be repeated.

In addition, it should be understood that in the description of this application, words such as “first” and “second” are only used for the purpose of distinguishing description, and cannot be understood as indicating or implying relative importance, nor can it be understood as indicating Or imply the order; "and/or" describes the association relationship of the associated objects, indicating that there can be three relationships. For example, A and/or B can mean: A alone exists, A and B exist at the same time, and B exists alone. The character "/" generally indicates that the associated objects are in an "or" relationship; "multiple" refers to two or more than two.

In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings.

As shown in FIG. 2, the present application provides a mixer 200. The mixer 200 includes a tuning circuit 210 and a mixing circuit 220, and the tuning circuit 210 is connected to the input end of the mixing circuit 220. . Wherein, the mixer circuit is a single balanced mixer circuit or a double balanced mixer circuit, the tuning circuit 220 and the parasitic capacitance Cp at the input end of the mixer circuit 210 form an LC parallel resonant circuit, and the tuning circuit At least one of the capacitance value of the capacitor in 220 and the inductance value of the inductor in the tuning circuit is adjustable.

The mixing circuit 220 is configured to use the local oscillator signal to perform frequency conversion on the signal to be processed input from the input of the mixing circuit 220, wherein the signal to be processed with different frequencies corresponds to the local signal with different frequencies. Vibration signal. Specifically, the mixing circuit 220 may use the local oscillator signal to down-convert the radio frequency signal to be processed to obtain an intermediate frequency signal or a baseband signal for subsequent signal processing; or, the mixing circuit 220 may also use the The local oscillator signal is up-converted to an intermediate frequency signal or baseband signal to be processed to obtain a radio frequency signal for antenna transmission.

In a specific implementation, the mixing circuit 220 may be implemented by a triode, and the mixing circuit 220 includes at least a pair of triode switch pairs, and the input terminal of the mixer circuit is a common emitter node of the triode switch pair. Alternatively, the mixing circuit 220 may also be implemented by a metal oxide semiconductor (MOS) transistor. In this case, the mixing circuit 220 includes at least a pair of MOS transistor switch pairs. The input terminal is the common source node of the MOS transistor switch pair.

In specific implementation, the tuning circuit 210 can be implemented by, but not limited to, any of the following two ways:

Manner 1. As shown in FIG. 3, the tuning circuit 210 is a switch inductance matrix, wherein the state of the switches in the switch inductance matrix is based on the resonance frequency range of the LC parallel resonant circuit and the input of the mixing circuit 220 The capacitance value of the parasitic capacitance Cp at the end is determined.

Manner 2: As shown in FIG. 4, the tuning circuit 210 includes a fixed inductor and a switched capacitor matrix, wherein the fixed inductor is connected in parallel with the switched capacitor matrix, and the state of the switches in the switched capacitor matrix is connected in parallel according to the LC The resonant frequency range of the resonant circuit, the inductance value of the fixed inductor, and the capacitance value of the parasitic capacitance Cp at the input end of the mixer circuit 220 are determined.

Manner 3, as shown in FIG. 5, the tuning circuit 210 includes a fixed capacitor and a switch inductance matrix, wherein the fixed capacitor is connected in parallel with the switch inductance matrix, and the state of the switches in the switch inductance matrix is connected in parallel according to the LC The resonant frequency range of the resonant circuit, the capacitance value of the fixed capacitor, and the capacitance value of the parasitic capacitance Cp at the input end of the mixer circuit 220 are determined.

Manner 4. As shown in FIG. 6, the tuning circuit 210 includes a switch inductance matrix and a switch inductance matrix, wherein the switch inductance matrix is connected in parallel with the switch capacitance matrix, and the state of the switches in the switch inductance matrix is based on the The resonant frequency range of the LC parallel resonant circuit and the capacitance value of the parasitic capacitance Cp at the input of the mixing circuit 220 are determined. The state of the switches in the switch inductance matrix is determined according to the resonant frequency range of the LC parallel resonant circuit and the The capacitance value of the parasitic capacitance Cp at the input end of the mixer circuit 220 is determined.

Wherein, in the above-mentioned mode 1, mode 3, and mode 4, when the state of the switch in the switch inductance matrix (on state or off state) is different, the inductance value of the equivalent inductance corresponding to the switch inductance matrix is also different , The switch inductance matrix can be realized by, but not limited to, any of the following three ways:

Manner 1. As shown in FIG. 7a, the switch inductor matrix includes a plurality of inductors connected in series, and each inductor is connected in parallel with a switch.

Manner 2. As shown in FIG. 7b, the switch inductance matrix includes a plurality of branches connected in parallel, and each branch includes an inductor and a switch connected in series with the inductor. Wherein, the inductance value of the inductor included in each branch may be the same or different, and each branch may include one or more inductors.

Manner 3, as shown in FIG. 7c, the switch inductance matrix includes at least one first inductance circuit and at least one second inductance circuit, and each first inductance circuit includes a first inductance and a switch connected in series with the first inductance, The second inductance circuit includes a second inductance and a switch connected in series with the second inductance, and the first inductance circuit is in series with the second inductance circuit. Wherein, the inductance value of the first inductor and the inductance value of the second inductor may be the same or different.

In addition, in the above method 1, method 3, and method 4, the function of the switch inductance matrix can also be realized by other adjustable inductance circuits. For example, the adjustable inductance circuit is an adjustable inductance, and the adjustable inductance can be a sliding Adjustable inductance or magnetic core adjustable inductance; for another example, the adjustable inductance circuit is a circuit with a structure as shown in FIG. 7d.

In the second and fourth modes above, the switched capacitor matrix can be implemented as shown in FIG. 7e. The switched capacitor matrix includes a plurality of branches connected in parallel, and each branch includes a capacitor and is connected to the capacitor. Switch in series.

Taking the double-balanced circuit structure of the mixer circuit 220 as an example, when the tuning circuit 210 is implemented using the above-mentioned method 1, and the switching inductance matrix is implemented using the above-mentioned method 2, the structure of the mixer 200 is shown in FIG. 8a; when the tuning circuit 210 is implemented in the second manner above, and the switched capacitor matrix is implemented as shown in FIG. 7d, the structure of the mixer 200 is shown in FIG. 8b; when the When the circuit of the tuning circuit 210 is implemented in the third manner, and the switching inductance matrix is implemented in the foregoing manner 2, the structure of the mixer 200 is shown in FIG. 8c; when the tuning circuit 210 is implemented in the third manner, and When the switched inductance matrix is implemented using the above method 2, and the switched capacitor matrix is realized with the structure shown in FIG. 7d, the structure of the mixer 200 is shown in FIG. 8d.

It should be noted that the specific structure of the tuning circuit 210 described above is only an example and does not limit the application. Anything that can form an adjustable resonance frequency with the parasitic capacitance Cp at the input end of the mixer circuit 210 The tuning circuits of the LC parallel resonance circuit are all suitable for this application.

Further, the resonant frequency range of the LC parallel resonant circuit is determined according to the frequency range of the local oscillator signal used by the mixer circuit 220 for frequency conversion. In particular, the frequency range of the double frequency signal of the local oscillator signal is within the resonance frequency range of the LC parallel resonant circuit. The noise signal introduced due to the parasitic capacitance Cp at the input of the mixer circuit 220 is mainly concentrated at the frequency corresponding to the even harmonic of the local oscillator signal, especially at the double frequency of the local oscillator signal Therefore, when the frequency range of the double frequency signal of the local oscillator signal is within the resonant frequency range of the LC parallel resonant circuit, the LC parallel resonant circuit is in a resonance state, and the input terminal of the mixing circuit 220 The impedance at is relatively large, which can suppress the noise and nonlinear intermodulation products introduced by the parasitic capacitance at the input of the mixer circuit 220 in the signal output by the mixer circuit 220, thereby effectively improving the The performance (such as noise figure, linearity) of the mixer 200 is described. In addition, at least one of the capacitance value of the capacitor in the tuning circuit 210 and the inductance value of the inductor in the tuning circuit 210 is adjustable, that is to say, the resonance frequency of the LC parallel circuit is variable and can be adjusted according to The actual requirements of the mixer 200 cover the corresponding frequency range, and the impedance at the input end of the mixer circuit can be increased in a wider frequency range, so that the mixer can operate at a wider frequency. Within the range, the performance of the mixer can be improved.

For example, when the mixer 200 has a structure as shown in FIG. 8c, the working bandwidth of the mixer 200 ranges from 24.25 GHz to 29.5 GHz, that is, the input terminal of the mixer circuit 220 in the mixer 200 The frequency range of the input radio frequency signal is 24.25GHz to 29.5GHz, and when the frequency range of the local oscillator signal is 17GHz to 22.5GHz, in order to reduce the parasitic capacitance Cp at the input end of the mixer circuit 220, the frequency mixing The effect of the performance of the device 200, the resonant frequency range of the LC parallel resonant circuit composed of the switched capacitor matrix and the parasitic capacitance Cp at the input end of the mixing circuit 220 is 34GHz to 45GHz (double frequency of the local oscillator signal), By controlling the switching state in the switched capacitor matrix, the capacitance value of the equivalent capacitance of the switched capacitor matrix (the capacitance obtained after the inductances working in the switched inductance matrix are connected in parallel) can be adjusted, so that the LC parallel resonance can be realized The resonance frequency of the circuit ranges from 34 GHz to 45 GHz. At this time, the linearity simulation result of the mixer circuit 200 is shown in FIG. 9. It can be seen from FIG. 9 that if the frequency of the radio frequency signal is 29.5 GHz and the equivalent capacitance of the switched capacitor matrix is 90 fF, the LC parallel resonant circuit is in resonance, and the linearity of the mixer 200 is optimal If the frequency of the radio frequency signal is 28 GHz and the equivalent capacitance of the switched capacitor matrix is 150 fF, the LC parallel resonant circuit is in resonance, and the linearity of the mixer 200 is optimal; if the radio frequency When the frequency of the signal is 26.5 GHz and the equivalent capacitance of the switched capacitor matrix is 240 fF, the LC parallel resonant circuit is in resonance, and the linearity of the mixer 200 is optimal; if the frequency of the radio frequency signal is At 24.5 GHz, when the equivalent capacitance of the switched capacitor matrix is 360 fF, the LC parallel resonant circuit is in a resonance state, and the linearity of the mixer 200 is optimal.

For another example, when the mixer 200 has a structure as shown in FIG. 8a, the working bandwidth of the mixer 200 ranges from 24.25 GHz to 29.5 GHz, that is, the input of the mixer circuit 220 in the mixer 200 The frequency range of the radio frequency signal input from the terminal is 24.25 GHz to 29.5 GHz, and when the frequency range of the local oscillator signal is from 17 GHz to 22.5 GHz, in order to reduce the parasitic capacitance Cp at the input terminal of the mixer circuit 220 to the mixing The impact of the performance of the frequency converter 200, the resonance frequency of the LC parallel resonant circuit composed of the switch inductance matrix and the parasitic capacitance Cp at the input of the mixer circuit 220 is 34GHz to 45GHz (double frequency of the local oscillator signal) , By controlling the switching state in the switching inductance matrix, the inductance value of the equivalent inductance of the switching inductance matrix (the inductance obtained after the inductances working in the switching inductance matrix are connected in parallel) is adjusted, so as to realize the parallel connection of the LC The resonance frequency of the resonance circuit ranges from 34 GHz to 45 GHz. At this time, the linearity simulation result of the mixer circuit 200 is shown in FIG. 10. It can be seen from FIG. 10 that if the frequency of the signal to be processed is 29.5 GHz and the equivalent inductance of the switching inductance matrix is 170 pH, the LC parallel resonant circuit is in resonance and the mixer 200 has the best linearity. Excellent; if the frequency of the radio frequency signal is 28GHz and the equivalent inductance of the switching inductance matrix is 230pH, the LC parallel resonant circuit is in resonance, and the linearity of the mixer 200 is optimal; if the When the frequency of the radio frequency signal is 26.5 GHz and the equivalent inductance of the switching inductance matrix is 270 pH, the LC parallel resonant circuit is in resonance, and the linearity of the mixer 200 is optimal; if the frequency of the radio frequency signal When it is 24.5 GHz and the equivalent inductance of the switching inductance matrix is 380 pH, the LC parallel resonant circuit is in a resonance state, and the linearity of the mixer 200 is optimal.

The working principle of the mixer 200 provided in the present application will be described in detail below through a specific embodiment.

The mixer 200 is an active mixer as shown in FIG. 11. Compared with a passive mixer, the active mixer has the advantages of high gain and good noise performance. Wherein, the tuning circuit 210 in the mixer 200 includes two inductors Lp1 and Lp2 connected in series, and a switched capacitor matrix composed of two capacitors CF1, CF2 and switches connected in series. The frequency mixing in the mixer 200 The circuit 220 is realized by a differential double-balanced switch pair composed of transistors M0～M3. Under the action of the differential local oscillator signal LOP and LON, the double-balanced current commutation active mixer function is realized, and the input differential radio frequency current signal is converted into a differential Intermediate frequency current signal output, wherein the source of the transistor M0 and the source of the transistor M3, and the source of the transistor M1 and the source of the transistor M2 are used to input a differential radio frequency current signal, and the gate of the transistor M0 And the gate of the transistor M3, and the gate of the transistor M1 and the gate of the transistor M2 are used for inputting differential local oscillator signals. In addition, the mixer 200 also includes a differential input stage circuit, which converts the voltage signal input through the input terminals INP (gate of the transistor MP) and INN (gate of the transistor MN) of the differential input stage circuit into current. Signal, the inductance LDEG in the differential input stage circuit is a source-level degeneration inductance, which can provide the real impedance required for impedance matching for the differential input stage circuit, and its negative feedback effect is also beneficial to improve the linearity of the transistor MP and the transistor MN performance. The mixer 200 further includes an output stage circuit, which realizes broadband matching of the impedance of the front and rear stages through a transformer, and converts the differential intermediate frequency current signal output by the mixer circuit into an intermediate frequency voltage signal through the load impedance Rload.

When the working bandwidth of the mixer 200 ranges from 24.25 GHz to 29.5 GHz, that is, the frequency range of the radio frequency signal input from the input end of the mixer circuit 220 in the mixer 200 is from 24.25 GHz to 29.5 GHz. When the frequency range of the vibration signal is 17 GHz to 22.5 GHz, in order to reduce the influence of the parasitic capacitance Cp at the input end of the mixer circuit 220 on the performance of the mixer 200, the switch capacitor matrix and the mixer circuit 220 The resonant frequency range of the LC parallel resonant circuit composed of the parasitic capacitance Cp at the input end is 34GHz to 45GHz (double frequency of the local oscillator signal). By controlling the switching state in the switched capacitor matrix, the LC parallel resonant circuit is adjusted The size of the capacitor can further realize that the resonance frequency range of the LC parallel resonant circuit is 34GHz to 45GHz. At this time, too many capacitor matrix switches can easily reduce the quality factor Q of the LC parallel resonant circuit, so only one switch capacitor matrix is used switch. When the mixer 200 works in the high frequency Band1 (n258: 26.5 GHz-29.5 GHz), the switches in the switch capacitor matrix are disconnected, and the parasitic capacitance at the common source node of the inductor Lp1, the inductor Lp2 and the transistor switch pair The formed LC parallel resonant circuit resonates in the middle of the double frequency range of the local oscillator signal corresponding to Band1; when the mixer 200 works in the low frequency band Band2 (n257: 24.25GHz-26.5GHz), the above-mentioned switched capacitor The switches in the matrix are closed. The above-mentioned switched capacitor matrix, inductance Lp1, inductance Lp2 and the parasitic capacitance at the common source node of the transistor switch pair constitute an LC parallel resonant circuit that resonates in the middle of the double frequency range of the local oscillator signal corresponding to Band2 position.

Through the above solution, the mixer 200 can pass the tuning circuit 210 in the mixer 200, so that the tuning circuit 210 and the parasitic capacitance at the input end of the mixer circuit 220 in the mixer 200 The formed LC parallel resonant circuit is in resonance, and the impedance at the input end of the mixer circuit 220 is increased, so that the mixer circuit 220 uses the local oscillator signal to input the signal to the input end of the mixer circuit 220 When performing frequency conversion, it is possible to suppress noise and nonlinear intermodulation products introduced by the parasitic capacitance at the input end of the mixer circuit 220 in the signal output by the mixer circuit 220, thereby effectively improving the mixing The performance of the frequency converter 200 (such as noise figure, linearity). In addition, when the structure of the tuning circuit 210 is set appropriately, the tuning circuit can work in a wider frequency range by cooperating with the parasitic capacitance at the input end of the mixing circuit 220 in the mixer 200. , Increase the impedance at the input end of the mixer circuit, so that the mixer 200 can improve the performance of the mixer in a wider frequency range.

As shown in FIG. 12, the present application also provides another mixer 1200. The mixer 1200 includes an impedance adjustment circuit 1210 and a mixer circuit 1220, wherein the mixer circuit 1220 is a single balanced mixer circuit. Or a double-balanced mixer circuit, the impedance adjustment circuit 1210 and the parasitic capacitance at the input end of the mixer circuit 1220 form an impedance multi-pole circuit; there are at least two targets among the poles of the impedance function of the impedance multi-pole circuit For the pole, the frequency range of the N-multiplier signal of the local oscillator signal used by the mixer circuit 1220 for frequency conversion is within the range determined by the frequencies corresponding to the two target poles, and N is an even number.

Further, the frequency range determined by the frequencies corresponding to the two target poles is greater than or equal to the frequency range of the double frequency signal of the local oscillator signal. For example, if the impedance function of the impedance multi-pole circuit includes two poles, one pole corresponds to a frequency and the other pole corresponds to a frequency b (b>a), then the working bandwidth of the mixer 1200 corresponds to The frequency range of the double frequency signal of the local oscillator signal is within the frequency range [a, b] determined by the frequencies corresponding to these two poles. If the impedance function of the multi-pole circuit includes three poles, these three poles correspond to The frequencies of are respectively a, b, c (c>b>a), then the frequency ranges [a, b], [a, c] and [b, c] determined by the frequencies corresponding to these three poles are at least A frequency range makes the frequency range of the double frequency signal of the local oscillator signal corresponding to the working bandwidth of the mixer 1200 within the frequency range.

The noise signal introduced due to the parasitic capacitance Cp at the input end of the mixer 1200 is mainly concentrated in the frequency range corresponding to the even harmonics of the local oscillator signal, especially at the double frequency of the local oscillator signal Therefore, when the frequency range of the double frequency signal of the local oscillator signal is within the frequency range corresponding to the two target poles of the multi-pole circuit, the impedance multi-pole circuit is in the range of the local oscillator signal The impedance at the double frequency is large, which can suppress the noise and nonlinear intermodulation products introduced by the parasitic capacitance at the input end of the mixer circuit 1020 in the signal output by the mixer circuit 1020, thereby effectively Improve the performance (such as noise figure, linearity) of the mixer 1200. Moreover, the poles of the impedance multi-pole circuit can be set reasonably according to the frequency range of the double-frequency signal of the local oscillator signal within the working bandwidth of the mixer 1200, so that the mixer circuit 1200 can be set at a larger The impedance at the input end is relatively large within the working bandwidth of.

The mixing circuit 1220 is configured to use a local oscillator signal to perform frequency conversion on the signal to be processed input from the input terminal of the mixing circuit 1220, wherein the signal to be processed with different frequencies corresponds to the local signal with different frequencies. Vibration signal. Specifically, the mixing circuit 1220 may use the local oscillator signal to down-convert the radio frequency signal to be processed to obtain an intermediate frequency signal or a baseband signal for subsequent signal processing; or, the mixing circuit 1220 may also use the The local oscillator signal is up-converted to an intermediate frequency signal or baseband signal to be processed to obtain a radio frequency signal for antenna transmission.

In a specific implementation, the mixing circuit 1220 may be implemented by a triode, and the mixing circuit 1220 includes at least a pair of triode switch pairs, and the input terminal of the mixer circuit is the common emitter node of the triode switch pair. Alternatively, the mixing circuit 1220 can also be realized by a MOS tube. In this case, the mixing circuit 1220 includes at least a pair of MOS tube switches, and the input terminal of the mixing circuit 1220 is a pair of MOS tube switches. Common source node.

Wherein, as shown in FIG. 13a (in FIG. 13a, the mixer circuit 1220 is a double-balanced circuit structure as an example), the tuning circuit may include a first capacitor C1 and a coupling inductor, and the coupling inductor includes a first winding L1 and a second winding L2, the first winding L1 is connected to the input end of the mixing circuit 1220, and the second winding L2 is connected in parallel with the first capacitor. Specifically, the coupled inductor may be a transformer, the first winding is a primary winding of the transformer, and the second winding is a secondary winding of the transformer.

Further, as shown in FIG. 13b, the impedance adjusting circuit further includes a second capacitor C2, and the second capacitor C2 is connected in parallel with the first winding. As shown in FIG. 13c, the impedance adjusting circuit may further include a resistor R, and the resistor R is connected in parallel with the first capacitor.

It should be noted that this application does not limit the specific structure of the impedance adjustment circuit 1210. The specific structure of the impedance adjustment circuit 210 that forms an impedance multi-pole circuit with the mixer circuit 1220 described above is only an example. Any circuit that can form an impedance multi-pole circuit with the mixer circuit 1220 can be applied to this application, such as a microstrip line.

Hereinafter, when the mixer 1200 has a structure as shown in FIG. 13c, the principle that the mixer 1200 increases the impedance at the input end of the mixer circuit 1220 through an impedance multi-pole circuit will be described in detail.

The impedance function Z _{p of} the impedance multi-pole circuit, that is, the impedance seen from the input end of the mixing circuit 1220 is as follows

Wherein, R represents the resistance value of the resistance in the impedance multi-pole circuit, C ₁ represents the capacitance value of the first capacitor in the impedance multi-pole circuit, and C ₂ represents the second capacitor in the impedance multi-pole circuit and the mixed The capacitance value of the parasitic capacitance at the input and output ends of the frequency circuit 1220 in parallel, L ₁ represents the inductance value of the primary coil of the transformer in the impedance multi-pole circuit, and L ₂ represents the secondary coil of the transformer in the impedance multi-pole circuit K is the coupling coefficient between the primary coil and the secondary coil of the transformer in the impedance multi-pole circuit.

When the resistance value R of the resistor in the impedance multi-pole circuit is large, the impedance function Z _p can be simplified as:

Wherein, the pole of the impedance function Z _p satisfies s ⁴ C ₁ C ₂ L ₁ L ₂ (1-k ² )+s ² (L ₁ C ₂ +L ₂ C ₁ )+1=0, let s=jω Let, the frequencies corresponding to the two poles of the impedance function Z _p are:

When the parameters of the first capacitor, the second capacitor, and the transformer in the impedance multi-pole circuit have appropriate values, the frequency range determined by the frequencies ω _p1 and ω _p2 corresponding to the two poles of the impedance function Z _p , namely this frequency range of the second harmonic signal LO signal within a frequency range corresponding to the two poles of the impedance function Z _p, in which case, the impedance of the multi-pole impedance circuit is large, i.e., the frequency converting circuit 220 The impedance at the input end of the mixer 1200 is relatively large, which can effectively reduce the influence of the parasitic capacitance Cp at the input end of the mixer 1200 on the performance (such as noise figure, linearity) of the mixer 200.

In addition, it should be noted that the embodiment of the present application does not limit the specific structure of the mixer circuit, and the mixer circuit may be an active mixer circuit or a passive mixer circuit.

Through the above solution, the mixer 1200 can pass an impedance multi-pole circuit formed by the impedance adjustment circuit 1210 in the mixer 1200 and the parasitic capacitance at the input end of the mixer circuit 1220 in the mixer 1200. , Increase the impedance at the input end of the mixer circuit 1220 so that the mixer circuit 1220 uses the local oscillator signal to perform frequency conversion on the signal input from the input end of the mixer circuit 1220, which can suppress the In the signal output by the mixer circuit 1220, the noise and nonlinear intermodulation products introduced by the parasitic capacitance at the input of the mixer circuit 1220 can effectively improve the performance of the mixer 1200 (such as noise figure , Linearity). Moreover, when the poles of the impedance multi-pole circuit are set appropriately, the impedance multi-pole circuit can increase the impedance at the input end of the mixer circuit 1220 in a wider frequency range, thereby causing the mixing The frequency converter 1200 can improve the performance of the mixer in a wide frequency range.

The working principle of the mixer 1200 provided in the present application will be described in detail below through a specific embodiment.

The mixer 1200 has an active mixer as shown in FIG. 12. The impedance adjustment circuit 1210 in the mixer 1200 includes a first capacitor C1, a second capacitor C2, and a transformer. The first capacitor C1 In parallel with the secondary coil of the transformer, the second capacitor C2 is connected in parallel with the input terminal of the mixing circuit 1220 and the primary coil of the transformer; the mixing circuit 1220 in the mixer 1200 is connected in parallel with the transistor M0 The differential double-balanced switch pair composed of M3 realizes the double-balanced current commutation active mixer function under the action of the differential local oscillator signal LOP and LON, and converts the input differential radio frequency current signal into a differential intermediate frequency current signal output, Wherein, the source of the transistor M0 and the source of the transistor M3, and the source of the transistor M1 and the source of the transistor M2 are used to input a differential radio frequency current signal, and the gate of the transistor M0 and the gate of the transistor M3 And the gate of the transistor M1 and the gate of the transistor M2 are used to input a differential local oscillator signal. In addition, the mixer 1200 further includes a differential input stage circuit, which converts the voltage signal input through the input terminals INP (gate of the transistor MP) and INN (gate of the transistor MN) of the differential input stage circuit into current. Signal, the inductance LDEG in the differential input stage circuit is a source-level degraded inductance, which can provide the real impedance required for impedance matching for the differential input stage circuit, and its negative feedback effect is also conducive to improving the linearity of the transistor MP and the transistor MN performance. The mixer 1200 further includes an output stage circuit that realizes broadband matching of the impedance of the front and rear stages through a transformer, and converts the differential intermediate frequency current signal output by the mixer circuit into an intermediate frequency voltage signal through the load impedance Rload.

When the working bandwidth of the mixer 1200 ranges from 24.25 GHz to 29.5 GHz, that is, the frequency range of the radio frequency signal input from the input end of the mixer circuit 1220 in the mixer 1200 is from 24.25 GHz to 29.5 GHz. When the frequency range of the vibration signal is 17 GHz to 22.5 GHz, in order to reduce the influence of the parasitic capacitance Cp at the input end of the mixer circuit 1220 on the performance of the mixer 1200, according to the above formula (2) to formula (4) , Select the inductance value of the primary coil L1 of the transformer, the secondary coil L2 of the transformer, the coupling coefficient k between the primary coil L1 of the transformer and the secondary coil L2 of the transformer, and the first capacitance The capacitance value of C1 and the capacitance value of the second capacitor make the frequency range of the double frequency signal of the local oscillator signal composed of the parasitic capacitance Cp at the input ends of the impedance adjustment circuit 1210 and the mixer circuit 1220. Within the frequency range determined by the frequencies ω _p1 and ω _p2 corresponding to the extreme points of the impedance multi-pole circuit, at this time, the impedance at the input end of the mixer circuit 1220 is at the double frequency signal of the local oscillator signal The frequency range is high impedance.

Based on the same inventive concept, the present application also provides a communication device. As shown in FIG. 15, the communication device includes a processor and the mixer described in any one of the foregoing possible implementation manners.

In a possible implementation manner, the mixer is used to down-convert the radio frequency signal input to the mixer to obtain an intermediate frequency signal or a baseband signal; the processor is used to process the intermediate frequency signal or Baseband signal.

In another possible implementation manner, the processor is configured to generate a baseband signal or an intermediate frequency signal; the mixer is configured to up-convert the baseband signal when the processor generates the baseband signal, Obtain a radio frequency signal; when the processor generates an intermediate frequency signal, up-convert the intermediate frequency signal to obtain a radio frequency signal.

Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present application without departing from the spirit and scope of the embodiments of the present application. In this way, if these modifications and variations of the embodiments of this application fall within the scope of the claims of this application and their equivalent technologies, this application is also intended to include these modifications and variations.

Claims (18)

A mixer, characterized by comprising: a mixing circuit and a tuning circuit, the tuning circuit is connected to the input end of the mixing circuit; Wherein, the mixing circuit is a single-balanced mixing circuit or a double-balanced mixing circuit, the tuning circuit and the parasitic capacitance at the input end of the mixing circuit form an LC parallel resonant circuit, and the capacitance of the tuning circuit At least one of the capacitance value and the inductance value of the inductor in the tuning circuit is adjustable. The mixer of claim 1, wherein the mixing circuit comprises at least a pair of triode switch pairs, and the input of the mixer circuit is the common emitter node of the triode switch pair; or, The mixing circuit includes at least a pair of metal oxide semiconductor MOS transistor switch pairs, and the input terminal of the mixing circuit is a common source node of the MOS transistor switch pair. The mixer according to claim 1 or 2, wherein the resonance frequency range of the LC parallel resonant circuit is determined according to the frequency range of the local oscillator signal used when the mixer circuit performs frequency conversion. The mixer of claim 3, wherein the frequency range of the double frequency signal of the local oscillator signal is within the resonance frequency range of the LC parallel resonant circuit. The mixer according to claim 3 or 4, wherein the tuning circuit is a switch inductance matrix, wherein the state of the switches in the switch inductance matrix is based on the resonance frequency range of the LC parallel resonant circuit and the The capacitance value of the parasitic capacitance at the input end of the mixer circuit is determined. The mixer according to claim 3 or 4, wherein the tuning circuit includes a fixed inductance and a switched capacitor matrix, wherein the fixed inductance is connected in parallel with the switched capacitor matrix, and the switch The state of is determined according to the resonance frequency range of the LC parallel resonant circuit, the inductance value of the fixed inductor, and the capacitance value of the parasitic capacitance at the input end of the mixing circuit. The mixer according to claim 3 or 4, wherein the tuning circuit comprises a fixed capacitor and a switch inductance matrix, wherein the fixed capacitor is connected in parallel with the switch inductance matrix, and the switch inductance matrix is The state of is determined according to the resonance frequency range of the LC parallel resonant circuit, the capacitance value of the fixed capacitor, and the capacitance value of the parasitic capacitance at the input end of the mixer circuit. The mixer according to claim 3 or 4, wherein the tuning circuit includes a switch inductance matrix and a switch inductance matrix, wherein the switch inductance matrix is connected in parallel with the switch capacitance matrix, and the switch inductance matrix The state of the middle switch is determined according to the resonance frequency range of the LC parallel resonant circuit and the capacitance value of the parasitic capacitance at the input of the mixing circuit, and the state of the switch in the switch inductance matrix is determined according to the capacitance of the LC parallel resonant circuit. The resonant frequency range and the capacitance value of the parasitic capacitance at the input end of the mixer circuit are determined. The mixer according to claim 5, 7 or 8, wherein the switch inductance matrix comprises a plurality of inductances connected in series with each other, and each inductance is connected in parallel with the switch; or, The switch inductance matrix includes a plurality of branches connected in parallel, and each branch includes an inductor and a switch connected in series with the inductor; or, The switch inductance matrix includes at least one first inductance circuit and at least one second inductance circuit. The first inductance circuit is connected in series with the second inductance circuit. Each first inductance circuit includes a first inductance and is connected to the first inductance circuit. An inductor connected in parallel, and the second inductor circuit includes a second inductor and a switch connected in series with the second inductor. The mixer according to claim 6 or 8, wherein the switched capacitor matrix includes a plurality of branches connected in parallel with each other, and each branch includes a capacitor and a switch connected in series with the capacitor. A mixer, characterized by comprising an impedance adjustment circuit and a mixing circuit, the impedance adjustment circuit being connected to the input end of the mixing circuit; Wherein, the mixer circuit is a single-balanced mixer circuit or a double-balanced mixer circuit, and the impedance adjustment circuit and the parasitic capacitance at the input end of the mixer circuit form an impedance multi-pole circuit; the impedance multi-pole circuit There are at least two target poles among the poles of the impedance function, and the frequency range of the N-multiplier signal of the local oscillator signal used when the mixer circuit performs frequency conversion is within the range determined by the frequencies corresponding to the two target poles Inside, N is an even number. The mixer according to claim 11, wherein the mixing circuit comprises at least a pair of triode switch pairs, and the input end of the mixer circuit is the common emitter node of the triode switch pair; or, The mixing circuit includes at least a pair of metal oxide semiconductor MOS transistor switch pairs, and the input terminal of the mixing circuit is a common source node of the MOS transistor switch pair. The mixer of claim 11 or 12, wherein the range determined by the frequencies corresponding to the two target poles is greater than or equal to the frequency range of the double frequency signal of the local oscillator signal. The mixer according to any one of claims 11-13, wherein the impedance adjustment circuit includes a first capacitor and a coupled inductor; wherein the coupled inductor includes a first winding and a second winding, and the The first winding is connected to the input end of the mixing circuit, and the second winding is connected in parallel with the first capacitor. The mixer according to claim 14, wherein the impedance adjusting circuit further comprises a second capacitor, and the second capacitor is connected in parallel with the first winding. The mixer of claim 14 or 15, wherein the impedance adjusting circuit further comprises a resistor, and the resistor is connected in parallel with the first capacitor. A communication device, characterized by comprising a processor and the mixer according to any one of claims 1-16; The mixer is used to down-convert the radio frequency signal input to the mixer to obtain an intermediate frequency signal or a baseband signal; The processor is configured to process the intermediate frequency signal or baseband signal. A communication device, characterized by comprising a processor and the mixer according to any one of claims 1-16; The processor is used to generate a baseband signal or an intermediate frequency signal; The mixer is configured to up-convert the baseband signal to obtain a radio frequency signal when the processor generates the baseband signal; when the processor generates an intermediate frequency signal, up-convert the intermediate frequency signal, Get the radio frequency signal.

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