Mixing circuit, transmitter and communication device

Abstract

The application provides a mixing circuit, a transmitter and a communication device. The mixing circuit comprises an I-channel digital-to-analog converter, a Q-channel digital-to-analog converter, a low-pass filter and a passive quadrature mixer; the low-pass filter comprises an active device, so that the output admittance of the mixing circuit has a frequency-dependent conductance. The consistency of the upper sideband and lower sideband gains of the mixing circuit is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of communication, and particularly relates to a mixing circuit, a transmitter and a communication device. BACKGROUND

[0002] In the related art, an I-channel digital-to-analog converter and a Q-channel digital-to-analog converter (both of which provide baseband signals with a phase difference of 90°) are connected to a mixer through a low-pass filter composed of resistors, capacitors and the like. The mixer modulates the baseband signals from the I-channel digital-to-analog converter and the Q-channel digital-to-analog converter into radio frequency signals and provides the radio frequency signals to a power amplifier in the back end, so that the power amplifier is used to drive an antenna to emit electromagnetic waves.

[0003] The mixer includes a passive quadrature mixer and an active quadrature mixer. The passive quadrature mixer has better linearity and lower noise than the active quadrature mixer, but the difference in gain of the upper sideband and the lower sideband of the frequency after mixing is larger. SUMMARY

[0004] The present application aims at the deficiencies of the prior art and provides a mixing circuit, a transmitter and a communication device.

[0005] To solve the above technical problems, the present application adopts the following technical solution: a mixing circuit, comprising an I-channel digital-to-analog converter, a Q-channel digital-to-analog converter, a low-pass filter and a passive quadrature mixer, the passive quadrature mixer being configured to obtain a radio frequency signal according to an output of the I-channel digital-to-analog converter, an output of the Q-channel digital-to-analog converter and a local oscillation signal, the low-pass filter being arranged at the front end of the passive quadrature mixer, so that the passive quadrature mixer receives low-pass filtered signals between an I-channel non-inverting input end and a Q-channel non-inverting input end and between an I-channel inverting input end and a Q-channel inverting input end, respectively; the low-pass filter contains an active device, so that the output admittance of the mixing circuit has a frequency-dependent conductance.

[0006] To solve the above technical problems, the present application adopts the following technical solution: a transmitter, comprising an antenna, a power amplification circuit and the aforementioned mixing circuit, the passive quadrature mixer being configured to provide the power amplification circuit with a radio frequency signal after mixing, and the power amplification circuit being configured to amplify the received radio frequency signal and provide the antenna with the amplified radio frequency signal.

[0007] To solve the above technical problems, the present application adopts the following technical solution: a communication device, comprising the aforementioned transmitter.

[0008] Compared with the prior art, the beneficial effects of the application are as follows: the load of the mixing circuit is usually a power amplifier, the input admittance of the power amplifier is usually irrelevant to frequency, and the output admittance of the mixing circuit is obviously relevant to frequency. In the mixing circuit of the application, the output conductance is also relevant to frequency. The sum of the output admittance of the mixing circuit and the input admittance of the load determines the gain of the mixing circuit. The real part and the imaginary part of the sum of the output admittance of the mixing circuit and the input admittance of the load are both relevant to frequency. This makes the skilled person in the art equalize or approximate the modulus of the sum of the output admittance of the mixing circuit and the input admittance of the load when debugging the mixing circuit, whether in the upper sideband or the lower sideband of the frequency after mixing, so that the gain of the mixing circuit tends to be constant with the change of frequency. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is an equivalent circuit of the mixing circuit in the related art.

[0010] Figure 2 is a circuit diagram of the complex capacitance according to the embodiment of the application.

[0011] Figure 3a is a circuit diagram of the mixing circuit according to the embodiment of the application.

[0012] Figure 3b is Figure 3a the current source mode equivalent circuit of the mixing circuit shown in FIG. 8.

[0013] Figure 4a is a circuit diagram of the mixing circuit according to the embodiment of the application.

[0014] Figure 4b is Figure 4a the current source mode equivalent circuit of the mixing circuit shown in FIG. 8.

[0015] Figures 5 to 8 are circuit diagrams of the mixing circuit according to the embodiments of the application. DETAILED DESCRIPTION

[0016] In the present application, it should be understood that terms such as "include" or "have" are intended to indicate that there exist the features, numbers, steps, actions, components, parts or combinations thereof disclosed in the specification, but do not exclude the possibility that one or more other features, numbers, steps, actions, components, parts or combinations thereof exist.

[0017] It should also be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0018] Reference Figure 1, which shows the equivalent circuit of the mixing circuit in the related art. The inventor of the present application found that, when a low-pass filter composed of passive devices is connected between the signal source (i.e. the I-channel digital-to-analog converter and the Q-channel digital-to-analog converter) and the passive quadrature mixer, the equivalent circuit of the mixing circuit includes a current source I RF , an output resistance R and an output capacitance C driven by the current source I RF , the output admittance of the mixing circuit is denoted as Y BB , the input impedance of the power amplifier connected to the mixing circuit is denoted as Z PA , the input admittance of the power amplifier is denoted as Y PA , and the input voltage received by the power amplifier is denoted as V RF .

[0019] The output admittance Y BB of the current source I RF may be determined according to the following formula:

[0020]

[0021] wherein α and β are coefficients, R BB is the resistance value of the equivalent resistance of the low-pass filter, ω is the angular frequency, ω LO is the carrier angular frequency, and C BB is the capacitance value of the equivalent capacitance of the low-pass filter.

[0022] It can be found that the real part Y Re and the imaginary part Y Im of the input admittance Y PA of the power amplifier are basically fixed, the real part of the output admittance Y BB of the current source I RF is a constant value, and the imaginary part is a frequency-dependent value. Obviously, the imaginary part values of Y BB are different in the upper sideband and the lower sideband.

[0023] In the upper sideband, the admittance of the total load of the current source I RF is denoted as Y USB , and can be expressed according to the following formula:

[0024]

[0025] In the lower sideband, the admittance of the total load of the current source I RF is denoted as Y LSB , and can be expressed according to the following formula:

[0026]

[0027] Therefore, the input voltage V RF received by the power amplifier in the upper sideband and the lower sideband isRF The following set of equations can be used to determine:

[0028]

[0029] where ω BB is the bandwidth of the baseband signal.

[0030] Since the real part of the equivalent impedance of the low-pass filter is independent of frequency, and the real part of the input impedance of the power amplifier is also independent of frequency, this results in a large gain difference between the upper sideband and the lower sideband, i.e.

[0031] |V RF (ω LO +ω BB )|≠|V RF (ω LO -ω BB )|.

[0032] Based on the above analysis, the inventors of the present application propose that if the real part of the impedance of the low-pass filter between the signal source (i.e. the I-channel digital-to-analog converter and the Q-channel digital-to-analog converter) and the passive quadrature mixer is also frequency-dependent, then through appropriate debugging and simulation, the gain of the mixing circuit in the upper sideband and the lower sideband can be made equal or close to equal. If an active device is provided in the low-pass filter, then the equivalent resistance of the low-pass filter can be made frequency-dependent, and thus the output admittance of the mixing circuit can have a frequency-dependent conductance.

[0033] Based on this, the present application proposes a mixing circuit, comprising an I-channel digital-to-analog converter, a Q-channel digital-to-analog converter, a low-pass filter, and a passive quadrature mixer, wherein the passive quadrature mixer is used to obtain a radio frequency signal according to the output of the I-channel digital-to-analog converter, the output of the Q-channel digital-to-analog converter, and a local oscillation signal, the low-pass filter is provided at the front end of the passive quadrature mixer, so that the I-channel non-inverting input and the Q-channel non-inverting input of the passive quadrature mixer and the I-channel inverting input and the Q-channel inverting input of the passive quadrature mixer respectively receive low-pass filtered signals.

[0034] The low-pass filter contains an active device, so that the output admittance of the mixing circuit has a frequency-dependent conductance.

[0035] It should be noted that the present application does not limit the structure of the passive quadrature mixer, and those skilled in the art can design it according to the prior art.

[0036] The present application does not limit the type of low-pass filter, for example, RC low-pass filter circuits are used in the embodiments.

[0037] The application does not limit the connection mode of the passive quadrature mixer and the I-channel digital-to-analog converter and the passive quadrature mixer and the Q-channel digital-to-analog converter.

[0038] It is noted that in the prior art, a capacitor is usually arranged between the I-channel positive-phase input end and the Q-channel positive-phase input end of the passive quadrature mixer and between the I-channel negative-phase input end and the Q-channel negative-phase input end of the passive quadrature mixer. For example, the capacitor is connected in series with a voltage amplifier, that is, one end of the capacitor is connected to the ground output end of the voltage amplifier, and then the real part and the imaginary part of the equivalent impedance between the other end of the capacitor and the ground input end of the voltage amplifier are related to the frequency. A resistor is usually arranged in a low-pass filter, and how to design a low-pass filter between the I-channel positive-phase input end and the Q-channel positive-phase input end of the passive quadrature mixer and between the I-channel negative-phase input end and the Q-channel negative-phase input end of the passive quadrature mixer is known in the art, and the internal structure of the low-pass filter is not particularly described in the application.

[0039] Reference Figure 2 It is noted that in the prior art, a capacitor is usually arranged between the I-channel positive-phase input end and the Q-channel positive-phase input end of the passive quadrature mixer and between the I-channel negative-phase input end and the Q-channel negative-phase input end of the passive quadrature mixer. For example, the capacitor is connected in series with a voltage amplifier, that is, one end of the capacitor is connected to the ground output end of the voltage amplifier, and then the real part and the imaginary part of the equivalent impedance between the other end of the capacitor and the ground input end of the voltage amplifier are related to the frequency. A resistor is usually arranged in a low-pass filter, and how to design a low-pass filter between the I-channel positive-phase input end and the Q-channel positive-phase input end of the passive quadrature mixer and between the I-channel negative-phase input end and the Q-channel negative-phase input end of the passive quadrature mixer is known in the art, and the internal structure of the low-pass filter is not particularly described in the application.

[0040] Specifically, Figure 2 The admittance Y of the complex capacitor shown in the figure is: in Y in =(j+1)ωC. Figure 2 The voltage V0 and the voltage V 90 are both ground input ends, and the phases of the signals provided by the two are different by 90°.

[0041] In some embodiments, the low-pass filter comprises a first capacitor, a second capacitor, a first voltage amplifier and a second voltage amplifier. Two ends of the first capacitor are respectively connected to the I-channel positive-phase input end of the passive quadrature mixer and the ground output end of the first voltage amplifier, and the ground input end of the first voltage amplifier is connected to the Q-channel positive-phase input end of the passive quadrature mixer. Two ends of the second capacitor are respectively connected to the Q-channel positive-phase input end of the passive quadrature mixer and the ground output end of the second voltage amplifier, and the ground input end of the second voltage amplifier is connected to the I-channel positive-phase input end of the passive quadrature mixer.

[0042] That is, connecting a complex capacitor between the I-channel non-inverting input and the Q-channel non-inverting input can improve the gain consistency of the mixer circuit in the upper sideband and the lower sideband.

[0043] In some embodiments, the low-pass filter comprises a first capacitor, a second capacitor, a first voltage amplifier and a second voltage amplifier.

[0044] The first capacitor is connected between the I-channel non-inverting input of the passive quadrature mixer and the ground output of the first voltage amplifier, and the ground input of the first voltage amplifier is connected to the Q-channel non-inverting input of the passive quadrature mixer.

[0045] The second capacitor is connected between the Q-channel non-inverting input of the passive quadrature mixer and the ground output of the second voltage amplifier, and the ground input of the second voltage amplifier is connected to the I-channel non-inverting input of the passive quadrature mixer.

[0046] Optionally, the voltage amplification coefficients of the first voltage amplifier and the second voltage amplifier are positive and negative respectively. This can make the loads of the I-channel non-inverting output and the Q-channel non-inverting output the same.

[0047] The inventor has found that when the imaginary part of the input impedance of the load of the mixer circuit is positive (has inductive characteristics), a complex capacitor can be connected between the I-channel non-inverting output and the Q-channel non-inverting output in the manner of Figure 3a , so that the real part of the output impedance of the mixer circuit increases with the increase of the frequency.

[0048] Figure 3a Only the connection mode between the I-channel non-inverting output V0 and the Q-channel non-inverting output V 90 of the mixer circuit is shown in the embodiment. It should be understood that the I-channel non-inverting output V0 is electrically connected to the I-channel non-inverting input I+ of the passive quadrature mixer, and there can be a resistor between them or they can be directly connected; the Q-channel non-inverting output V 90 is electrically connected to the Q-channel non-inverting input Q+ of the passive quadrature mixer, and there can be a resistor between them or they can be directly connected.

[0049] Figure 3a In the embodiment shown, the first capacitor C1 is connected in series with the first voltage amplifier A1, and the second capacitor C2 is connected in series with the second voltage amplifier A2. The voltage amplification coefficient of the first voltage amplifier A1 is positive, and the voltage amplification coefficient of the second voltage amplifier A2 is negative.

[0050] Figure 3aIn the shown embodiment, the type of the other parts of the low-pass filter and the internal structure of the passive quadrature mixer are not limited.

[0051] Since the complex capacitor is included in the low-pass filter, the reference Figure 3b In the current source equivalent model of the mixing circuit, the real part of the equivalent admittance of the complex capacitor increases with the frequency.

[0052] In the current source model of the mixing circuit, the output admittance Y BB It can be determined according to the following formula:

[0053]

[0054] In the admittance Y USB and the admittance Y LSB It can be expressed according to the following formula:

[0055]

[0056] Then in the upper sideband and the lower sideband, the input voltage V RF It can be determined according to the following set of formulas:

[0057]

[0058] As the capacitance value of the capacitor in the complex capacitor and / or the voltage amplification factor of the voltage amplifier are adjusted, the gain of the mixing circuit in the upper sideband and the lower sideband can be equal, that is

[0059] |V RF (ω LO +ω BB )|=|V RF (ω LO -ω BBx )|. Of course, even if other factors are considered, they cannot be completely equal, but they can be adjusted to be close to equal.

[0060] The inventors have found that when the imaginary part of the input impedance of the load of the mixing circuit is negative (capacitive), the complex capacitor can be connected between the I-channel positive input I+ and the Q-channel positive input Q+ in the manner of Figure 4a so that the output impedance of the mixing circuit exhibits a real part that decreases with the frequency.

[0061] Figure 4a In the shown embodiment, only the I-channel positive output V0 and the Q-channel positive output V 90The connection mode between the two is not limited. It should be understood that the I-channel positive output terminal V0 of the mixer is electrically connected to the I-channel positive input terminal I+ of the passive quadrature mixer, and there can be a resistor between the two or they can be directly connected; the Q-channel positive output terminal VQ of the mixer is electrically connected to the Q-channel positive input terminal Q+ of the passive quadrature mixer, and there can be a resistor between the two or they can be directly connected. 90 The connection mode between the two is not limited. It should be understood that the I-channel positive output terminal V0 of the mixer is electrically connected to the I-channel positive input terminal I+ of the passive quadrature mixer, and there can be a resistor between the two or they can be directly connected; the Q-channel positive output terminal VQ of the mixer is electrically connected to the Q-channel positive input terminal Q+ of the passive quadrature mixer, and there can be a resistor between the two or they can be directly connected.

[0062] Figure 4a In the embodiment shown, the first capacitor C1 is connected in series with the first voltage amplifier A1, and the second capacitor C2 is connected in series with the second voltage amplifier A2. The voltage amplification factor of the first voltage amplifier A1 is negative, and the voltage amplification factor of the second voltage amplifier A2 is positive.

[0063] Figure 4a In the embodiment shown, the types of other parts of the low-pass filter and the internal structure of the passive quadrature mixer are not limited.

[0064] Since the low-pass filter contains a complex capacitor, the reference Figure 4b The real part of the equivalent admittance of the complex capacitor in the current source equivalent model of the mixer circuit decreases with increasing frequency.

[0065] In the current source model of the mixer circuit, the output admittance Y BB can be determined according to the following formula:

[0066]

[0067] The admittance Y USB of the total load of the upper sideband current source and the admittance Y LSB of the total load of the lower sideband current source can be represented according to the following formula:

[0068]

[0069] The input voltage V RF obtained by the load in the upper sideband and the lower sideband can be determined according to the following set of formulas:

[0070]

[0071] By adjusting the capacitance value of the capacitor in the complex capacitor and / or the voltage amplification factor of the voltage amplifier, the gain of the mixer circuit in the upper sideband and the lower sideband can be made equal, that is, RF (ω LO +ω BB )|=|V RF (ω LO -ω BB) of course even if other factors are considered, the two cannot be completely equal, can be debugged so that the two close to equal.

[0072] It should be noted that, Figure 3a and Figure 4a In the low-pass filter, a capacitor (not shown) is further arranged between the I-channel inverting input end and the Q-channel inverting input end, which can be a conventional capacitor, rather than the complex capacitor proposed in the application.

[0073] In some embodiments, the low-pass filter further comprises: a third capacitor, a fourth capacitor, a third voltage amplifier and a fourth voltage amplifier.

[0074] Two ends of the third capacitor are respectively connected to the I-channel inverting input end of the passive quadrature mixer and the ground output end of the third voltage amplifier, and the ground input end of the third voltage amplifier is connected to the Q-channel inverting input end of the passive quadrature mixer.

[0075] Two ends of the fourth capacitor are respectively connected to the Q-channel inverting input end of the passive quadrature mixer and the ground output end of the fourth voltage amplifier, and the ground input end of the fourth voltage amplifier is connected to the I-channel inverting input end of the passive quadrature mixer.

[0076] Optionally, the voltage amplification coefficients of the first voltage amplifier and the third voltage amplifier are both positive numbers, and the voltage amplification coefficients of the second voltage amplifier and the fourth voltage amplifier are both negative numbers; or,

[0077] The voltage amplification coefficients of the first voltage amplifier and the third voltage amplifier are both negative numbers, and the voltage amplification coefficients of the second voltage amplifier and the fourth voltage amplifier are both positive numbers. This makes the loads of the four output ends of the I and Q channels the same.

[0078] In Figure 5 In the circuit diagram shown, the I-channel digital-to-analog converter and the Q-channel digital-to-analog converter are both voltage mode (V-Mode DAC), and the passive quadrature mixer in the mixing circuit is not shown. The input admittance of the power amplifier connected to the passive quadrature mixer exhibits a negative imaginary part. Figure 5Only the I-channel non-inverting input I+, the I-channel inverting input I-, the Q-channel non-inverting input I+, and the Q-channel inverting input I- of the passive quadrature mixer are shown in the circuit diagram. The four capacitors in the low-pass filter contain two "complex capacitors", each of which contains two capacitors and two voltage amplifiers. The first capacitor C1 is connected in series with the first voltage amplifier A1 (voltage amplification factor is positive), the second capacitor C2 is connected in series with the second voltage amplifier A2 (voltage amplification factor is negative), the third capacitor C3 is connected in series with the third voltage amplifier A3 (voltage amplification factor is positive), and the fourth capacitor C4 is connected in series with the fourth voltage amplifier A4 (voltage amplification factor is negative).

[0079] In Figure 6 In the circuit diagram shown, the I-channel and Q-channel digital-to-analog converters are both voltage-mode (V-Mode DAC), and the passive quadrature mixer in the mixing circuit is not shown. The input admittance of the power amplifier connected to the passive quadrature mixer exhibits a positive imaginary part. Figure 6 Only the I-channel non-inverting input I+, the I-channel inverting input I-, the Q-channel non-inverting input I+, and the Q-channel inverting input I- of the passive quadrature mixer are shown in the circuit diagram. The four capacitors in the low-pass filter contain two "complex capacitors", each of which contains two capacitors and two voltage amplifiers. The first capacitor C1 is connected in series with the first voltage amplifier A1 (voltage amplification factor is negative), the second capacitor C2 is connected in series with the second voltage amplifier A2 (voltage amplification factor is positive), the third capacitor C3 is connected in series with the third voltage amplifier A3 (voltage amplification factor is negative), and the fourth capacitor C4 is connected in series with the fourth voltage amplifier A4 (voltage amplification factor is positive).

[0080] In Figure 7 In the circuit diagram shown, the I-channel and Q-channel digital-to-analog converters are both current-mode (I-Mode DAC), and the passive quadrature mixer in the mixing circuit is not shown. The input admittance of the power amplifier connected to the passive quadrature mixer exhibits a negative imaginary part. Figure 7 Only the I-channel non-inverting input I+, the I-channel inverting input I-, the Q-channel non-inverting input I+, and the Q-channel inverting input I- of the passive quadrature mixer are shown in the circuit diagram. The four capacitors in the low-pass filter contain two "complex capacitors", each of which contains two capacitors and two voltage amplifiers. The first capacitor C1 is connected in series with the first voltage amplifier A1 (voltage amplification factor is positive), the second capacitor C2 is connected in series with the second voltage amplifier A2 (voltage amplification factor is negative), the third capacitor C3 is connected in series with the third voltage amplifier A3 (voltage amplification factor is positive), and the fourth capacitor C4 is connected in series with the fourth voltage amplifier A4 (voltage amplification factor is negative).

[0081] In Figure 8In the shown circuit diagram, the I-channel digital-to-analog converter and the Q-channel digital-to-analog converter are both current-mode (I-Mode DAC), and the passive quadrature mixer in the mixing circuit is not shown. The input admittance of the power amplifier connected to the passive quadrature mixer shows a positive virtual part. Figure 8 In the shown circuit diagram, the I-channel digital-to-analog converter and the Q-channel digital-to-analog converter are both current-mode (I-Mode DAC), and the passive quadrature mixer in the mixing circuit is not shown. The input admittance of the power amplifier connected to the passive quadrature mixer shows a positive virtual part.

[0082] The various embodiments in the present application are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the difference from other embodiments.

[0083] The scope of protection of the present application is not limited to the above-described embodiments. Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the scope and spirit of the present application. If these modifications and variations belong to the scope of the claims of the present application and its equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A mixing circuit, comprising: An I-channel digital-to-analog converter, a Q-channel digital-to-analog converter, a low-pass filter and a passive quadrature mixer, the passive quadrature mixer being used to obtain a radio frequency signal according to an output of the I-channel digital-to-analog converter, an output of the Q-channel digital-to-analog converter and a local oscillation signal, the low-pass filter being arranged in front of the passive quadrature mixer, and the low-pass filter being arranged to receive a low-pass filtered signal between an I-channel non-inverting input and a Q-channel non-inverting input of the passive quadrature mixer and between an I-channel inverting input and a Q-channel inverting input of the passive quadrature mixer; The low-pass filter comprises active devices, so that the output admittance of the mixing circuit comprises a frequency-dependent conductance; wherein the low-pass filter comprises two voltage amplifiers, the two voltage amplifiers being connected in parallel between the I-channel non-inverting input and the Q-channel non-inverting input and between the I-channel inverting input and the Q-channel inverting input, and the two voltage amplifiers having opposite signal directions.

2. The frequency mixing circuit of claim 1, wherein, The low-pass filter comprises a first capacitor, a second capacitor, a first voltage amplifier and a second voltage amplifier; The two ends of the first capacitor are connected to the I-channel non-inverting input of the passive quadrature mixer and to the ground output of the first voltage amplifier, respectively, and the ground input of the first voltage amplifier is connected to the Q-channel non-inverting input of the passive quadrature mixer; The two ends of the second capacitor are connected to the Q-channel non-inverting input of the passive quadrature mixer and to the ground output of the second voltage amplifier, respectively, and the ground input of the second voltage amplifier is connected to the I-channel non-inverting input of the passive quadrature mixer.

3. The mixing circuit of claim 2, wherein, The voltage amplification coefficients of the first voltage amplifier and the second voltage amplifier are positive and negative, respectively.

4. The frequency mixing circuit of claim 2, wherein, The low-pass filter further comprises a third capacitor, a fourth capacitor, a third voltage amplifier and a fourth voltage amplifier; The two ends of the third capacitor are connected to the I-channel inverting input of the passive quadrature mixer and to the ground output of the third voltage amplifier, respectively, and the ground input of the third voltage amplifier is connected to the Q-channel inverting input of the passive quadrature mixer; The two ends of the fourth capacitor are connected to the Q-channel inverting input of the passive quadrature mixer and to the ground output of the fourth voltage amplifier, respectively, and the ground input of the fourth voltage amplifier is connected to the I-channel inverting input of the passive quadrature mixer.

5. The frequency mixing circuit of claim 4, wherein, The voltage amplification coefficients of the first voltage amplifier and the third voltage amplifier are positive, and the voltage amplification coefficients of the second voltage amplifier and the fourth voltage amplifier are negative. Alternatively, The voltage amplification coefficients of the first voltage amplifier and the third voltage amplifier are negative, and the voltage amplification coefficients of the second voltage amplifier and the fourth voltage amplifier are positive.

6. A transmitter, characterized by The mixing circuit according to claim 1 is used in a radio frequency receiver, the radio frequency receiver comprising an antenna, a power amplification circuit and the mixing circuit, the passive quadrature mixer being used to provide a mixed radio frequency signal to the power amplification circuit, and the power amplification circuit being used to amplify a received radio frequency signal and provide the amplified radio frequency signal to the antenna.

7. A communication device, characterized by The transmitter comprising the transmitter according to claim 6. The transmitter comprising the transmitter according to claim 6.

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