Passive frequency-mixing circuit, and communication device

Abstract

A passive frequency-mixing circuit, and a communication device. The frequency-mixing circuit comprises: a first switch tube and a first filter, wherein a gate electrode of the first switch tube is used for inputting a first signal, which is used for controlling the turning-on / turning-off of the first switch tube; a drain electrode of the first switch tube is used for connecting to a first end of the first filter, and a second end of the first filter is used for being grounded; and a source electrode of the first switch tube is used for inputting a second signal, and the source electrode of the first switch tube is further used for outputting a third signal, which third signal is a signal obtained after the first signal and the second signal are subjected to frequency mixing. The passive frequency-mixing circuit and communication device provided in the present application can achieve high linearity and low loss of a passive frequency mixer.

Description

Passive mixing circuit and communication equipment

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on July 17, 2023, with application number 202310876660.5, and priority to the Chinese patent application entitled “A Passive Mixing Circuit and Communication Equipment”, all contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communication technology, and in particular to a passive mixing circuit and communication equipment. Background Art

[0003] Mixers are key components for frequency conversion in wireless communication devices and are essential components of wireless transceivers. Wireless receivers use mixers to down-convert received radio frequency (RF) signals to intermediate frequency (IF) or zero-IF signals for processing, while wireless transmitters use mixers to up-convert IF or zero-IF signals to RF signals for antenna transmission.

[0004] Modern communication systems are increasingly demanding higher communication rates and ranges, resulting in wider bandwidths, higher signal powers, and higher RF frequencies. Passive mixers are typically implemented using a combination of a diode bridge stack and a balun, but this type of passive mixer fails to meet the low-loss performance requirements.

[0005] Summary of the Invention

[0006] The present application provides a passive mixer circuit and communication equipment, which can achieve the goals of high linearity and low loss of a passive mixer.

[0007] In a first aspect, the present application provides a mixing circuit, comprising a first switching transistor and a first filter. The gate of the first switching transistor is used to input a first signal, which is used to control the on / off switching of the first switching transistor. The drain of the first switching transistor is used to connect to the first end of the first filter, and the second end of the first filter is used to be grounded. The source of the first switching transistor is used to input a second signal, and the source of the first switching transistor is also used to output a third signal, which is a signal obtained by mixing the first signal and the second signal.

[0008] In this solution, mixing of the first and second signals is achieved by controlling the on / off switching of the first switching transistor using a first signal, thereby expanding the mixer's power dynamic range. By grounding the drain of the first switching transistor, a reflection circuit is formed, reducing conversion losses caused by feedthrough. A first filter is also added to the drain of the first switching transistor to filter the mixed signal output by the first switching transistor and reduce in-band ripple.

[0009] In a possible implementation, the frequency mixing circuit further includes a first resistor. The second end of the first filter is specifically configured to be connected to the first end of the first resistor, and the second end of the first resistor is configured to be grounded.

[0010] In this solution, a reflection circuit is formed by connecting the first resistor to the second end of the first filter and grounding the first resistor, thereby reducing the frequency conversion loss caused by feedthrough.

[0011] In one possible implementation, the mixing circuit further includes a second filter. The gate of the first switching tube is used to input the first signal, including: the gate of the first switching tube is used to connect to the first end of the second filter, and the second end of the second filter is used to input the first signal.

[0012] In this solution, a second filter is added to the gate of the first switching tube to select the frequency of the input first signal and reduce the in-band fluctuation.

[0013] In one possible implementation, the mixing circuit further includes a first circulator. The source of the first switching transistor is specifically configured to be connected to a first terminal of the first circulator. The second terminal of the first circulator is configured to input the second signal, and the third terminal of the first circulator is configured to output the third signal.

[0014] In this solution, the isolation between the second signal and the third signal is increased by adding a first circulator to the source of the first switching tube.

[0015] In one possible implementation, the mixing circuit further includes a second circulator, a second switching tube, and a third filter. The third end of the first circulator is used to output the third signal, including: the third end of the first circulator is used to connect to the first end of the second circulator, and the second end of the second circulator is used to output the third signal. The third end of the second circulator is used to connect to the source of the second switching tube. The gate of the second switching tube is used to input a fourth signal, and the fourth signal is used to control the on and off of the second switching tube to achieve mixing of the fourth signal and the fifth signal. The fifth signal is input from the second end of the second circulator. The output time of the third signal is different from the input time of the fifth signal. The drain of the second switching tube is used to connect to the first end of the third filter, and the second end of the third filter is used to be grounded.

[0016] This solution adds a second circulator, a second switching transistor, and a third filter. The second switching transistor is used to mix the fourth and fifth signals, and the second circulator also serves to increase isolation between the signals. Both the first and second switching transistors in this solution can mix signals. The addition of the first and second circulators allows for control of signal flow direction and increased isolation between signals. Therefore, the mixing circuit shown in this solution can perform both up-conversion and down-conversion functions.

[0017] In a possible implementation, the frequency mixing circuit further includes a second resistor. The second end of the third filter is specifically configured to be connected to the first end of the second resistor, and the second end of the second resistor is configured to be grounded.

[0018] In this solution, a reflection circuit is formed by connecting a second resistor to the second end of the third filter and grounding the second resistor.

[0019] In one possible implementation, the mixing circuit further includes a fourth filter. The gate of the second switching tube is used to input a fourth signal, including: the gate of the second switching tube is used to be connected to a first end of the fourth filter, and a second end of the fourth filter is used to input the fourth signal.

[0020] In this solution, a fourth filter is added to the gate of the second switch tube to select the frequency of the input fourth signal and reduce the in-band fluctuation.

[0021] In a possible implementation, the mixing circuit further includes a fifth filter. The second end of the first circulator is used to input the second signal, including:

[0022] The second end of the first circulator is specifically used to connect to the first end of the fifth filter, and the second end of the fifth filter is used to input the second signal.

[0023] In this solution, by connecting the fifth filter to the source of the first switching tube, the second signal input to the first switching tube is filtered to reduce in-band fluctuations.

[0024] In a possible implementation, the mixing circuit further includes a sixth filter. The source of the first switching transistor is further configured to output a third signal, including:

[0025] The source of the first switching tube is specifically used to be connected to the first end of the sixth filter, and the second end of the sixth filter is used to output the third signal.

[0026] In this solution, by connecting the sixth filter to the source of the first switching tube, the sixth signal output by the first switching tube is filtered to reduce high-order harmonics in the output signal.

[0027] In one possible implementation, the first signal is a local oscillator signal, the second signal is a baseband signal or an intermediate frequency signal, and the third signal is a radio frequency signal. The mixing circuit is configured to up-convert the second signal to obtain the third signal.

[0028] In this solution, the first signal is a local oscillator signal, the second signal is a baseband signal or an intermediate frequency signal, and the third signal is a radio frequency signal. The above-mentioned mixing circuit can realize up-conversion of the second signal.

[0029] In one possible implementation, the first signal is a local oscillator signal, the second signal is a radio frequency signal, and the third signal is a baseband signal or an intermediate frequency signal. The mixing circuit is configured to down-convert the second signal to obtain the third signal.

[0030] In this solution, the first signal is a local oscillator signal, the second signal is a radio frequency signal, and the third signal is a baseband signal or an intermediate frequency signal. The above-mentioned mixing circuit can realize down-conversion of the second signal.

[0031] In a second aspect, the present application provides a circuit board comprising the mixing circuit shown in any one of the first aspects.

[0032] In a third aspect, the present application provides a mixer, comprising the mixing circuit shown in any one of the first aspects.

[0033] In a fourth aspect, the present application provides a communication device, comprising the mixing circuit shown in any one of the first aspects.

[0034] The solutions provided in the second to fourth aspects include the mixing circuit provided in the first aspect, and thus can achieve the same or corresponding beneficial effects as the corresponding mixing circuit in the first aspect, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0036] FIG1A and FIG1B are schematic diagrams of a radio frequency subsystem according to an embodiment of the present application;

[0037] FIG2 is a schematic diagram of a square wave signal according to an embodiment of the present application;

[0038] FIG3 is a spectrum diagram after mixing provided by an embodiment of the present application;

[0039] FIG4 is a schematic diagram showing the relationship between mixer indicators provided in an embodiment of the present application;

[0040] FIG5 is a schematic diagram of a mixer circuit provided in an embodiment of the present application;

[0041] FIG6 is a schematic diagram of another mixer circuit provided in an embodiment of the present application;

[0042] 7A, 7B, 8, and 10 are schematic diagrams of another mixer circuit provided in an embodiment of the present application;

[0043] FIG9A is a schematic diagram of up-conversion loss provided in an embodiment of the present application;

[0044] FIG9B is a schematic diagram showing the relationship between OIP3 and operating frequency according to an embodiment of the present application;

[0045] FIG11A is a schematic diagram of another up-conversion loss provided in an embodiment of the present application;

[0046] FIG11B is a schematic diagram of down-conversion loss provided in an embodiment of the present application;

[0047] FIG11C is another schematic diagram of the relationship between OIP3 and operating frequency provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] The embodiments described in this application are only part of the embodiments of this application, not all of the embodiments. Those skilled in the art will appreciate that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0049] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. In this application, "at least one" means one or more, and "a plurality" means two or more. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0050] The following is an illustrative introduction to the working principle and performance indicators of the mixer.

[0051] 1. Mixer

[0052] The mixer in the embodiments of the present application refers to a common component in radio frequency circuits used to perform frequency conversion on a target signal. This converts the carrier frequency of the target signal to a fixed frequency while maintaining the characteristics of the target signal. A mixer is a key component in a signal transceiver, used to up-convert a baseband signal or an intermediate frequency signal to generate an RF signal. Alternatively, it can down-convert an RF signal to generate a baseband signal or an intermediate frequency signal.

[0053] In order to better introduce the functions and working principles of the mixer, an embodiment of the present application exemplarily provides a schematic diagram of a radio frequency subsystem, as shown in Figures 1A and 1B.

[0054] The RF subsystem shown in Figure 1A is used to up-convert baseband or intermediate frequency signals and output RF signals. The components in Figure 1A include a digital to analog converter (DAC), a mixer, a power amplifier (PA), and an antenna. Among them, the DAC is used to convert the digital signal to be transmitted into an analog signal. The analog signal obtained after the conversion is called a baseband signal or an intermediate frequency (IF) signal. The mixer is used to up-convert the received baseband signal or IF signal to generate a radio frequency (RF) signal. The PA is used to amplify the power of the received RF signal so that the RF signal has higher transmission energy and a longer transmission distance. The antenna is used to transmit the RF signal output by the PA.

[0055] The connection relationship between the various components in Figure 1A is as follows: the output of the DAC is connected to the first input of the mixer (the port corresponding to "1" in Figure 1A), the output of the mixer (the port corresponding to "2" in Figure 1A) is connected to the input of the PA, the output of the PA is connected to the antenna, and the second input of the mixer (the port corresponding to "3" in Figure 1A) is used to input the local oscillator (LO) signal.

[0056] The mixer shown in FIG1A is specifically used to up-convert a baseband or IF signal input to the mixer so that the carrier frequency of the baseband or IF signal is equal to the frequency of the LO signal.

[0057] The RF subsystem shown in Figure 1B is used to down-convert the RF signal and output a baseband signal or IF signal. The components in Figure 1B include an analog-to-digital converter (ADC), a mixer, a low-noise amplifier (LNA), and an antenna. The ADC is used to convert the received baseband signal or IF signal into a digital signal. The mixer is used to down-convert the received RF signal to generate a baseband signal or IF signal. The LNA is used to amplify the received RF signal with low noise, increasing the sensitivity of the RF subsystem to receive signals. The antenna is used to transmit the RF signal output by the PA.

[0058] The connection relationship between the various components in Figure 1B is as follows: the antenna is connected to the input of the LNA, the first output of the LNA is connected to the first input of the mixer (the port corresponding to "1" in Figure 1B), the output of the mixer (the port corresponding to "2" in Figure 1B) is connected to the input of the ADC, and the second input of the mixer (the port corresponding to "3" in Figure 1A) is used to input the local oscillator (LO) signal.

[0059] The mixer shown in FIG1B is specifically used to down-convert the RF signal input to the mixer to obtain a baseband signal or an IF signal.

[0060] The RF subsystems shown in Figures 1A and 1B can be on the same device, chip, or circuit board, or on different devices, chips, or circuit boards. If the RF subsystems shown in Figures 1A and 1B are on the same device, chip, or circuit board, the LO signals in Figures 1A and 1B can be the same signal or different signals. This embodiment of the application does not limit whether Figures 1A and 1B are on the same device, chip, or circuit board, or whether the LO signals in Figures 1A and 1B are the same signal.

[0061] FIG1A and FIG1B exemplarily introduce the function of a mixer and the connection relationship between the mixer and other components in a radio frequency subsystem. Next, the working principle of the mixer is exemplarily introduced.

[0062] 2. Working principle of mixer

[0063] A mixer can be thought of as a multiplier. For example, it multiplies the RF and LO signals input to the mixer and outputs a signal containing difference and sum frequency components at the IF port. The calculation formula is as follows:

[0064] Among them, V IF (t) represents the signal output from the IF port, V LO Indicates the maximum amplitude of the LO signal input to the mixer, V RF Indicates the maximum amplitude of the RF signal input to the mixer. LO is the angular velocity of the LO signal, w RF is the angular velocity of the RF signal. is the phase of the LO signal, is the phase of the RF signal. The IF port outputs the difference frequency component signal as The IF port outputs the signal of the combined frequency component.

[0065] For example, the IF signal and the LO signal input to the mixer may be multiplied together to output a signal containing difference frequency and sum frequency components at the RF port, as shown in formula (1):

[0066] Among them, V RF (t) represents the signal output from the RF port, V IF Indicates the maximum amplitude of the IF signal in the input mixer, w IF is the angular velocity of the IF signal, is the phase of the IF signal. For other symbols, please refer to the relevant description of formula (1) and will not be repeated here. The signal expression of the difference frequency component output by the RF port is The signal expression of the combined frequency component output by the RF port is:

[0067] For example, if the LO signal is a square wave signal with equal amplitudes in the positive and negative half axes, the Fourier expansion of the LO signal is:

[0068] Here, n is an odd number greater than 1.

[0069] Substituting formula (3) into formula (1) we can get V IF The expression of (t) is shown in formula (4):

[0070] Here, n is an odd number greater than 1.

[0071] According to formula (4), when the LO signal is a square wave signal and both the positive and negative half cycles are used, the ideal conversion loss of the mixer is 2*10*log(2 / π)=-3.92dB.

[0072] Similarly, we can substitute formula (3) into formula (1) to get V RF For the specific implementation of the expression of (t), please refer to formula (4), which will not be repeated here.

[0073] For ease of understanding, the present application embodiment provides a schematic diagram of a square wave signal, as shown in Figure 2. The expression of the square wave signal shown in Figure 2 is Where n is an odd number greater than 1, T(t) represents the amplitude of the square wave signal, and the remaining parameters are described in the aforementioned formula (1) and are not repeated here. The square wave signal shown in Figure 2 has no even harmonics.

[0074] In one possible implementation, the RF signal input to the mixer (as shown in FIG1B ) is V RF (t) = V RF cos(ω RF t), where V RF Indicates the maximum amplitude of the RF signal in the input mixer, w RF is the angular velocity of the RF signal.

[0075] RF signal V RF (t) and square wave signal V LO (t) The signal expression of the output after mixing is as follows:

[0076] in, Indicates the feedthrough of the RF signal through the mixer, Indicates the second harmonic of the RF signal after mixing. Indicates the 4th harmonic of the RF signal after mixing.

[0077] As shown in FIG3 , a spectrum diagram after mixing is provided in an embodiment of the present application. The angular velocity RF in FIG3 corresponds to the component in formula (5) as The angular velocity in Figure 3 is RF-LO or RF+LO, which corresponds to the component in formula (5) as The angular velocity in Figure 3 is 3LO-RF or 3LO+RF, which corresponds to the component in formula (5) as The angular velocity of the LO signal is greater than the angular velocity of the RF-LO signal, but less than the angular velocity of the RF signal.

[0078] 3. Mixer loss model

[0079] The embodiment of the present application also provides a model of mixer conversion loss, and the loss model is shown in formula (6): L total =L fre-diss +L tube-para +L mis-match +L conductor-diss (6)

[0080] Among them, L total Represents the total loss of the mixer frequency conversion. fre-diss is the loss caused by useless frequency. From the above description, we can know that L fre-diss About 3.92dB. tube-para It is the additional loss caused by the parasitic parameters of the tube core, mainly caused by the internal switch tube of the mixer. mis-match L is the circuit loss caused by the mixer input and output mismatch. conductor-diss It is the conductor loss, which is mainly caused by the internal circuit (conductor) of the mixer.

[0081] 4. One decibel compression output power

[0082] The one decibel compression output power in the embodiment of the present application is also referred to as P 1dB , P 1dB It means that devices such as mixers and amplifiers have a linear dynamic range. Within this range, the output power of the device increases linearly with the input power. As the input power of the device increases, it will enter the nonlinear region of the device, causing the output power of the device to no longer increase linearly with the increase of input power. The output power value of the device that is 1dB lower than the linear gain is usually called the output power P 1dB Normally, when the output power value of the device exceeds P 1dB In this case, the output power will quickly enter a maximum or fully saturated state.

[0083] 5. Third-order intercept point (IP3)

[0084] When a dual-tone signal (f1 and f2) is input into a mixer, the many combined frequency components generated by the mixer's nonlinearity may include, in addition to the fundamental component, 2f1-f2 and 2f2-f1 (generated by the cubic terms of the nonlinear components in the mixer). This combination of components caused by the mutual modulation of the dual-tone signals interferes with the desired signal, which is called intermodulation distortion, also known as third-order intermodulation (IM3).

[0085] IP3 can be divided into input third-order intermodulation (IIP3) and output third-order intermodulation (OIP3). Third-order intermodulation is measured in dBm. A mixer's IP3 is a constant determined by its inherent nonlinearity. IP3 simply describes the linearity of a mixing device and has no bearing on the input signal or the mixer's gain.

[0086] IP3 and IM3 also have the following relationship, for example: IIP3 = P in +0.5×IM3, OIP3=P out +0.5×IM 3=IIP3+G. Among them, P in is the input power of the mixer, P out is the output power of the mixer, G is the linear gain of the mixer, P out =P in +G.

[0087] In order to show P more clearly in 、P out 、OIP3、IIP3、P 1dB For the relationship between G, IM3 and the difference between output power and IM3 (IMD), please refer to FIG4 for example. FIG4 is a schematic diagram showing the relationship between mixer indicators provided in an embodiment of the present application.

[0088] As shown in Figure 4, it includes the horizontal axis, the vertical axis, the solid line representing the fundamental frequency component and the third-order intermodulation frequency component. in , the unit is dBm. The vertical axis represents P out , in dBm. The solid line representing the fundamental frequency component has a slope of 1 and its starting point is (0, G). The solid line representing the third-order intermodulation frequency component has a slope of 3 and intersects with the solid line representing the fundamental frequency component at point P, where the coordinates are (IIP3, OIP3). 1dB The power output is 1dB lower than the linear gain. IMD (dBc) means the power output is 1dB lower than the linear gain. in Under the same conditions, the difference between the output power of the fundamental frequency component and the output power of the third-order intermodulation frequency component, the output power corresponding to the third-order intermodulation frequency component is IM3.

[0089] The above content provides an exemplary introduction to the working principle and performance indicators of the mixer. Next, please refer to FIG5 , which shows a schematic diagram of a mixer circuit.

[0090] The mixer circuit shown in Figure 5 consists of two circuit sections and three ports. The two circuit sections include a diode bridge stack for frequency conversion and a balun for single-ended and differential conversion. One of the three ports is connected to the diode bridge stack, while the other two are connected to the balun. The port connected to the diode bridge stack receives the LO signal, while the two ports connected to the balun receive / transmit the IF and RF signals, respectively. For on-chip integration of passive mixers, the balun is typically a Marchand balun.

[0091] The mixer circuit shown in Figure 5 has advantages over other topologies (such as single-tube mixers, single-balanced mixers, and double-double-balanced mixers) in terms of conversion loss, isolation, spurious emissions, and cost. However, the mixer circuit shown in Figure 5 also has significant disadvantages, such as:

[0092] 1. The Marchand Balun used in the mixer circuit shown in Figure 5 requires a transmission line length proportional to the input signal wavelength (approximately a quarter-wavelength transmission line), and its operating bandwidth is inversely proportional to the transmission line width. Long signal wavelengths and wide operating bandwidths increase balun trace losses.

[0093] 2. The on-resistance of the diode in the mixer circuit shown in Figure 5 is exponentially related to the input voltage. As the input signal power increases (and the corresponding input voltage also increases), the on-resistance of the diode increases sharply. This characteristic not only increases signal loss, but also leads to poor linearity of the mixer shown in Figure 5 due to its nonlinear characteristics.

[0094] Therefore, the mixer circuit shown in FIG5 cannot meet the performance requirements of high power and high linearity.

[0095] To improve the linearity of the mixer, see Figure 6. The mixer circuit shown in Figure 6 uses appropriate biasing to cause the field effect transistor (FET) to operate in the linear resistance region, thereby extending the linearity of the mixer.

[0096] The mixer shown in Figure 6 includes a local oscillator, matching circuit, switches, a combiner / transformer, an RF signal source, an IF signal receiver / load, and an optional drain bias voltage source. The drain bias voltage source is used to operate the switches in the linear resistance region, thereby improving the linearity of the mixer shown in Figure 6.

[0097] However, the mixer shown in Figure 6 also has some obvious disadvantages:

[0098] 1. When the switch operates in the triode region, intermodulation between signals can be minimized. Therefore, the bias voltage needs to be increased to prevent the switch from crossing the triode region, while also requiring the RF signal amplitude to be small.

[0099] 2. Because the RF signal and the IF signal / baseband signal are both at the drain of the switch tube, the mixer shown in Figure 6 will have a large insertion loss without adding DC bias.

[0100] In view of the problems of large insertion loss and poor linearity of the above-mentioned mixer, the embodiment of the present application exemplarily proposes another mixer that can reduce the insertion loss of the mixer and improve the linearity.

[0101] FIG7A is a schematic diagram of another mixer circuit provided in an embodiment of the present application. The mixer circuit shown in FIG7A includes a first switching tube and a first filter. The gate of the first switching tube is used to input a first signal. The drain of the first switching tube is connected to the first end of the first filter. The second end of the first filter is open. The source of the first switching tube is used to input a second signal or output a third signal. The third signal is a signal obtained by mixing the first signal and the second signal.

[0102] In a possible implementation, the first filter is a high-pass filter, configured to provide an appropriate time delay for a signal passing through the filter.

[0103] In a possible implementation, the first signal is used to control the on or off of the first switch tube, so that the first signal and the second signal are mixed.

[0104] In one possible implementation, the first signal is a square wave signal, which is divided into a positive half-cycle square wave signal and a negative half-cycle square wave signal, and the amplitudes of the positive and negative half-cycle square wave signals are equal. In the process of performing a single frequency mixing on the first signal and the second signal, usually only the mixing of the second signal and a half-cycle square wave signal can be achieved. For example, in the process of performing a single frequency mixing on the first signal and the second signal, the mixing of the second signal and the positive half-cycle square wave signal is achieved. If the mixed signal obtained by the single frequency mixing is directly output, since only the mixing of the second signal and a half-cycle square wave signal is performed, the power of the output signal will be significantly lost.

[0105] Exemplarily, the first signal is a square wave signal, and the second signal is received from the source of the first switching tube. The second signal is first mixed with the positive half-cycle square wave signal of the first signal through the first switching tube. The mixed signal (including harmonics of multiple frequencies and the second signal obtained due to filter feedthrough) is output from the drain of the first switching tube, and this signal is called the first mixed signal.

[0106] Exemplarily, when the second signal is an intermediate frequency or baseband signal, the first filter is a high-pass filter configured to pass the second signal and block the RF signal in the first mixed signal. Because the first filter cannot pass the RF signal, it forms a reflection circuit relative to the RF signal. The RF signal in the first mixed signal is reflected back to the first switching transistor and ultimately output as part of the third signal.

[0107] The output end of the first filter is grounded, which also constitutes a reflection circuit. The second signal passing through the first filter will return to the first filter again and enter the first switch tube. It can be understood that the filter will cause a certain delay to the signal during the filtering process. The second signal in the first mixing signal is output from the drain of the first switch tube and enters the first switch tube again, passing through the first filter twice in total. By adjusting the parameters of the first filter, the filtering delay of the first filter on the signal is controlled so that when the second signal in the first mixing signal enters the first switch tube again, the first signal is a negative half-cycle square wave signal, and a mixed signal of the second signal and the negative half-cycle square wave signal is output from the source of the first switch tube, and this signal is called the second mixing signal. The RF signal reflected back to the first switch tube and the second mixing signal together constitute the third signal.

[0108] For example, when the second signal is a radio frequency signal, the first filter can be a high-pass filter or a band-pass filter, configured to pass the second signal and block the intermediate frequency signal and baseband signal in the first mixed signal. Because the first filter cannot pass the intermediate frequency signal and baseband signal, the first filter forms a reflection circuit relative to the intermediate frequency signal and baseband signal. The intermediate frequency signal and baseband signal in the first mixed signal are reflected back to the first switching transistor and ultimately output as part of the third signal.

[0109] The output end of the first filter is grounded, which also constitutes a reflection circuit. The second signal passing through the first filter will return to the first filter again and enter the first switch tube. It can be understood that the filter will cause a certain delay to the signal during the filtering process. The second signal in the first mixing signal is output from the drain of the first switch tube and enters the first switch tube again, passing through the first filter twice in total. By adjusting the parameters of the first filter, the filtering delay of the first filter on the signal is controlled so that when the second signal in the first mixing signal enters the first switch tube again, the first signal is a negative half-cycle square wave signal, and a mixed signal of the second signal and the negative half-cycle square wave signal is output from the source of the first switch tube, and this signal is called the second mixing signal. The intermediate frequency signal / baseband signal reflected back to the first switch tube and the second mixing signal together constitute the third signal.

[0110] In another possible implementation, the first signal is a square wave signal, the second signal is first mixed with the square wave signal of the negative half cycle, and the second signal is passed through the first filter and reflected by the reflection circuit and then mixed with the square wave signal of the positive half cycle. The embodiment of the present application does not limit the mixing order of the second signal with the positive half cycle square wave signal and the negative half cycle square wave signal.

[0111] This solution achieves reflective mixing by reflecting the second signal back to the first switching transistor and mixing it again with the first signal, reducing signal feedthrough and frequency conversion losses. Furthermore, by adjusting the first filter parameters, the filter delay of the first filter is adjusted, so that when the second signal enters the first switching transistor for mixing again, the first signal is in the other half of the cycle. This reduces in-band fluctuations in the filtered signal and also reduces frequency conversion losses.

[0112] In one possible implementation, the first switch is a III-V compound switch, including but not limited to the following types of switches: gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), indium phosphide (InP), gallium aluminum arsenide (GaAIAs), and indium gallium phosphide (InGaP). Using III-V compound switches can improve the linearity of the mixer circuit.

[0113] Based on the frequency mixing circuit shown in FIG7A , an embodiment of the present application further provides a schematic diagram of another frequency mixing circuit, as shown in FIG7B .

[0114] The mixing circuit shown in FIG7B includes: a first switch tube, a first filter, a first resistor, a first circulator, and a second filter, wherein the first resistor, the first circulator, and the second filter are all optional.

[0115] The connection relationship of the components in the mixing circuit shown in Figure 7B is as follows: the first end of the first circulator is connected to the source of the first switching tube, the second end of the first circulator is used to input the second signal, and the third end of the first circulator is used to output the third signal. The gate of the first switching tube is connected to the first end of the second filter, and the second end of the second filter is used to input the first signal. The drain of the first switching tube is connected to the first end of the first filter, the second end of the first filter is connected to the first resistor, and the other end of the first resistor is grounded.

[0116] Exemplarily, the direction of signal flow in the first circulator is such that a signal entering from the first end of the first circulator is output from the third end of the first circulator, a signal entering from the third end of the first circulator is output from the second end of the first circulator, and a signal entering from the second end of the first circulator is output from the first end of the first circulator. Therefore, the second signal input from the second end of the first circulator can only be output from the first end of the first circulator and mixed with the first signal through the first switching device. Similarly, the signal flowing into the first end of the first circulator can only be output from the third end of the first circulator, so that the third signal obtained by mixing the first signal and the second signal can only be output from the third end of the first circulator. Therefore, adding the first circulator on the basis of FIG. 7A can reduce the leakage of the second signal or the third signal to other ports, increase the isolation between the ports, and reduce the frequency conversion loss.

[0117] Exemplarily, the first resistor is a large resistor greater than 2K ohms, which is used to form a reflection circuit so that the signal passing through the first filter is reflected back to the first switching device for re-mixing, thereby reducing the frequency conversion loss caused by signal feedthrough.

[0118] Exemplarily, the second filter is a bandpass filter that performs frequency selection on the first signal, filtering out interference-band signals contained in the first signal and reducing in-band fluctuations. The second filter can also reflect the mixed signal, concentrating the signal energy near the switching transistor and reducing energy loss in the mixed signal.

[0119] In one possible implementation, the first circulator, the first resistor, and the second filter in FIG7B are all optional components. Adding any one of the first circulator, the first resistor, and the second filter to FIG7A can have corresponding beneficial effects. For details, please refer to the above-mentioned related content and will not be repeated here.

[0120] In order to help readers better understand the solutions shown in Figures 7A and 7B, the embodiment of the present application takes Figure 7B as an example to exemplarily illustrate the flow process of the signal in the mixing circuit shown in Figure 7B.

[0121] For example, please refer to Figure 7B. First, as shown by the arrow labeled "1", the first signal flows through the second filter to the gate of the first switching tube, and as shown by the arrow labeled "2", the second signal flows through the first ring device to the source of the first switching tube. Secondly, the first signal and the second signal are mixed by the first switching tube, and the first mixed signal is output from the drain of the first switching tube. As shown by the arrow labeled "3", the signal component of the first mixed signal that cannot pass through the first filter is reflected back to the first switching tube by the first filter and output from the third end of the first circulator. As shown by the arrow labeled "4", the signal component of the first mixed signal that can pass through the first filter is reflected by the first resistor, enters the first switching tube from the drain of the first switching tube, and is mixed with the first signal. The second mixed signal obtained after mixing is output from the source of the first switching tube, then input to the first end of the first circulator, and finally output from the third end of the first circulator. As indicated by the arrow numbered “5”, the signal output from the third terminal of the first circulator includes the signal component of the first mixed signal that cannot pass through the first filter and the second mixed signal.

[0122] The scheme shown in Figures 7A and 7B above, on the one hand, realizes the mixing of the first signal and the second signal by controlling the opening and closing of the switch tube by the first signal, which expands the power dynamic range of the mixer compared to the method of realizing mixing through the channel resistance of the switch tube. On the other hand, by using the drain of the switch tube as the transmitting end and reflecting and mixing the signal again by adding a large resistor, the frequency conversion loss of the mixer can be reduced. By adding a specific filter, the time delay of the signal is adjusted so that when the signal enters the first switch tube again, the first signal is a square wave signal of a different half cycle, which can also reduce the frequency conversion loss. In addition, the filter can also filter out the higher harmonics obtained after mixing and reduce the in-band fluctuation of the signal.

[0123] The solution shown in FIG7B can further include a circulator. The large bandwidth and high isolation characteristics of the circulator can expand the operating frequency range of the mixing circuit.

[0124] In order to support both up-conversion and down-conversion functions, the embodiment of the present application further provides mixing circuits as shown in FIG. 8 and FIG. 10 .

[0125] Please refer to Figure 8, which is a schematic diagram of another mixing circuit provided by an embodiment of the present application. The mixing circuit shown in Figure 8 includes: a first circulator, a first switching transistor, a first filter, a first resistor, a second filter, a second circulator, a second switching transistor, a third filter, a second resistor, and a fourth filter. The first resistor, the second resistor, the second filter, and the fourth filter are all optional components.

[0126] The connection relationship of the components in the mixing circuit shown in Figure 8 is as follows: the first end of the first circulator is connected to the source of the first switching transistor, the gate of the first switching transistor is connected to the first end of the second filter, the second end of the second filter is used to input the first signal, the drain of the first switching transistor is connected to the first end of the first filter, the second end of the first filter is connected to the first end of the first resistor, and the second end of the first resistor is grounded. The second end of the first circulator is used to input the second signal, the third end of the first circulator is connected to the first end of the second circulator, the second end of the second circulator is used to output the third signal, the third end of the second signal is connected to the source of the second switching transistor, the gate of the second switching transistor is connected to the first end of the fourth filter, the second end of the fourth filter is used to input the fourth signal, the drain of the second switching transistor is connected to the first end of the third filter, the second end of the third filter is connected to the first end of the second resistor, and the second end of the second resistor is grounded.

[0127] The direction of signal flow in the first circulator is as follows: a signal entering from the first end of the first circulator can only be output from the third end of the first circulator, a signal entering from the third end of the first circulator can only be output from the second end of the first circulator, and a signal entering from the second end of the first circulator can only be output from the first end of the first circulator. The direction of signal flow in the second circulator is as follows: a signal entering from the first end of the second circulator can only be output from the second end of the second circulator, a signal entering from the second end of the second circulator can only be output from the third end of the second circulator, and a signal entering from the third end of the second circulator can only be output from the first end of the second circulator.

[0128] In one possible implementation, the third filter is a high-pass filter, and the fourth filter is a band-pass filter. The third filter is configured to pass the fifth signal and adjust its delay, allowing the reflected fifth signal to be mixed again by the second switching transistor. The fourth filter is configured to perform frequency selection on the fourth signal, filtering out interference frequency bands within the fourth signal and reducing in-band fluctuations. The fourth filter can also reflect the mixed signal, concentrating its energy near the second switching transistor and reducing energy loss in the mixed signal.

[0129] In one possible implementation, the fourth signal and the first signal may be identical or different signals. The fourth signal and the first signal may be output from the same local oscillator or from different local oscillators. This embodiment of the present application does not limit this.

[0130] In one possible implementation, a first signal is input from the second end of the second filter, a second signal is input from the second end of the first circulator, and a third signal obtained by mixing the first signal and the second signal is output from the second end of the second circulator. For the specific implementation of mixing the first signal and the second signal to generate the third signal, please refer to the description corresponding to the mixing circuit shown in Figures 7A and 7B above, which will not be repeated here. The third signal generated by the mixing circuit shown in Figure 8 is first output from the third end of the first circulator, and input to the first end of the second circulator, and finally output from the second end of the second circulator. It can be understood that the mixing circuit shown in Figure 8, which mixes the first signal and the second signal to generate the third signal, does not require the third filter, the fourth filter, the second switch tube and the second resistor to work.

[0131] In another possible implementation, a fourth signal is input through the second terminal of the fourth filter, a fifth signal is input through the second terminal of the second circulator, and a sixth signal obtained by mixing the fourth and fifth signals is output through the second terminal of the first circulator. Furthermore, the fifth signal is a radio frequency signal, and the sixth signal is an intermediate frequency signal or a baseband signal.

[0132] Exemplarily, the fifth signal input from the second end of the second circulator can be output from the third end of the second circulator to the source of the second switching tube. The fourth signal input from the fourth filter is filtered and input to the gate of the second circulator. The fourth signal achieves mixing of the fourth signal and the fifth signal by controlling the on and off of the second circulator. The fourth signal is a square wave signal including a positive half-cycle and a negative half-cycle, and the amplitudes of the positive half-cycle square wave signal and the negative half-cycle square wave signal are equal. It can be seen from the introduction of Figure 7A above that in a single mixing process, only the fifth signal can be mixed with the positive half-cycle square wave signal or the negative half-cycle square wave signal. In this example, the fifth signal is first mixed with the positive half-cycle square wave signal for introduction. The fifth signal is mixed with the positive half-cycle square wave signal, and the mixed signal is output from the drain of the second switching tube, which is called the third mixed signal. The third filter is used to block the intermediate frequency signal or baseband signal by signal components in the third mixed signal that are close in frequency to the fifth signal. Therefore, the intermediate frequency (IF) signal or baseband signal in the third mixed signal is reflected by the third filter, flows through the second switch, the third terminal of the second circulator, the first terminal of the second circulator, and the third terminal of the first circulator, and is finally output from the second terminal of the first circulator. The signal that passes through the third filter is reflected back to the third filter by the second resistor and mixed with the negative half-cycle signal of the fourth signal by the second switch. The resulting mixed signal is called the fourth mixed signal. The fourth mixed signal is output from the source of the second switch, flows through the second switch, the third terminal of the second circulator, the first terminal of the second circulator, and the third terminal of the first circulator, and is finally output from the second terminal of the first circulator. The intermediate frequency (IF) signal or baseband signal in the third mixed signal, combined with the fourth mixed signal, forms the sixth signal.

[0133] Exemplarily, the second resistor is a large resistor greater than 2K ohms, which is used to form a reflection circuit so that the signal passing through the third filter is reflected back to the second switching device for re-mixing, thereby reducing the frequency conversion loss caused by signal feedthrough.

[0134] In one possible implementation, the second switch is a III-V compound switch, including but not limited to the following types of switches: gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), indium phosphide (InP), gallium aluminum arsenide (GaAIAs), and indium gallium phosphide (InGaP). Using III-V compound switches can improve the linearity of the mixer circuit.

[0135] In another possible implementation, a fourth signal is input through the second terminal of the fourth filter, a fifth signal is input through the second terminal of the second circulator, and a sixth signal, obtained by mixing the fourth and fifth signals, is output through the second terminal of the first circulator. Furthermore, the fifth signal is an intermediate frequency signal or a baseband signal, and the sixth signal is a radio frequency signal. The specific implementation of this solution is described above and will not be further elaborated here.

[0136] It can be understood that the mixing circuit shown in FIG8 mixes the fourth signal and the fifth signal to generate the sixth signal without requiring the first filter, the second filter, the first switch tube and the first resistor to work.

[0137] In one possible implementation, the second signal and the sixth signal are intermediate frequency signals or baseband signals, and the third signal and the fifth signal are radio frequency signals. This solution can up-convert the second signal and down-convert the fifth signal.

[0138] In another possible implementation, the second signal and the sixth signal are radio frequency signals, and the third signal and the fifth signal are intermediate frequency signals or baseband signals. This solution can down-convert the second signal and up-convert the fifth signal.

[0139] In one possible implementation, the RF circuit shown in FIG8 further includes a fifth filter and / or a sixth filter. The first end of the fifth filter is connected to the second end of the first circulator, and the second end of the fifth filter is used to receive the second signal or send the sixth signal. The first end of the sixth filter is connected to the second end of the second circulator, and the second end of the sixth filter is used to send the third signal or receive the fifth signal.

[0140] The fifth and sixth filters are both used to filter the passing signal, reducing unwanted signals or higher harmonics. For example, the mixer circuit shown in Figure 8 is used to up-convert the second signal, and the generated third signal is transmitted from the second end of the second circulator. The aforementioned analysis shows that the third signal transmitted from the second end of the second circulator contains a large number of higher harmonics. Therefore, adding the sixth filter at the second end of the second circulator can reduce the number of higher harmonics in the third signal.

[0141] Similarly, the sixth filter can also filter the received fifth signal. The functions implemented by the fifth filter and the sixth filter are similar. For the function of the fifth filter, please refer to the above description of the sixth filter, which will not be repeated here.

[0142] Exemplarily, the fifth filter and the sixth filter are both bandpass filters.

[0143] Next, the embodiment of the present application exemplarily illustrates relevant experimental results of the mixing circuit shown in FIG. 8 through FIG. 9A and FIG. 9B .

[0144] Please refer to Figure 9A, which is a schematic diagram of up-conversion loss provided by an embodiment of the present application. Figure 9A exemplarily shows the conversion loss under various operating frequencies and various input powers when the mixing circuit shown in Figure 8 performs up-conversion.

[0145] As shown in FIG9A , the vertical axis of FIG9A represents conversion loss in dB. The horizontal axis of FIG9A represents operating frequency in GHz. The operating frequency in FIG9A ranges from 0.985 GHz to 1.185 GHz. The legend of FIG9A represents input power in dBm. The input powers in FIG9A include 13 dBm, 16 dBm, 19 dBm, 22 dBm, and 25 dBm.

[0146] As can be seen from Figure 9A, the relationship between operating frequency and conversion loss is that the conversion loss decreases as the operating frequency increases from 0.985 GHz to 1.115 GHz, and increases as the operating frequency increases from 1.115 GHz to 1.185 GHz.

[0147] The relationship between input power and conversion loss is that as input power increases, the conversion loss generally shows an increasing trend. When the input power is between 13dBm and 22dBm, there is no obvious pattern between the conversion loss and input power. However, when the input power reaches 25dBm, the conversion loss increases significantly. Taking input powers of 22dBm and 25dBm as an example, at the same frequency, the 25dBm input power increases by an average of approximately 0.8dB compared to the 22dBm input power. As can be seen in Figure 9A, the maximum conversion loss of 7.7dB occurs when the input power is 22dBm and the operating frequency is 1.135GHz.

[0148] Please refer to Figure 9B, which is a schematic diagram of the relationship between OIP3 and operating frequency, provided in an embodiment of the present application. As shown in Figure 9B, the horizontal axis represents the operating frequency in GHz. The vertical axis represents OIP3 in dBm. When the operating frequency is 0.985 GHz, the OIP3 is 31 dBm. As can be seen from Figure 9A, the minimum conversion loss of the mixer shown in Figure 8 is approximately 6 dB. Therefore, the IIP3 of the mixer shown in Figure 8 will be greater than 37 dBm.

[0149] The mixer circuit shown in Figure 8 first utilizes a III-V process switch as the key component for implementing the mixing function, enabling the mixer circuit to achieve high linearity. Secondly, by using a circulator and leveraging its high isolation to separate the intermediate frequency (IF) signal from the RF signal, the mixer circuit's conversion loss and in-band ripple can be reduced. Thirdly, adding a large resistor or grounding the drain of the switch to implement a reflection circuit can reduce conversion loss caused by signal feedthrough, achieving the goal of low loss in the mixer circuit. Finally, by adding a suitable filter to the drain of the switch, the signal filtering delay can be adjusted, allowing the reflected signal to be mixed with the square wave signal of the other half cycle, further reducing conversion loss. Furthermore, the filter can filter out interfering signals and reduce in-band ripple.

[0150] FIG10 is a schematic diagram of another frequency mixing circuit provided in an embodiment of the present application. Next, the other frequency mixing circuit shown in FIG10 is exemplarily introduced.

[0151] The frequency mixing circuit shown in Figure 10 includes a first filter, a second filter, a fifth filter, a sixth filter, a first switch tube, a first resistor, etc. The second filter and the first resistor are optional components.

[0152] The components in the mixing circuit shown in Figure 10 are connected as follows: the first end of the fifth filter is connected to the source of the first switching transistor, and the second end of the fifth filter is used to input the second signal. The gate of the first switching transistor is connected to the first end of the second filter, and the second end of the second filter is used to input the first signal. The drain of the first switching transistor is connected to the first end of the first filter, and the second end of the first filter is connected to the first end of the first resistor, and the second end of the first resistor is grounded. The source of the first switching transistor is also connected to the first end of the sixth filter, and the second end of the sixth filter is used to output the third signal.

[0153] Compared to the mixing circuit shown in FIG7A , the mixing circuit shown in FIG10 adds a fifth filter and a sixth filter. The specific implementation of the mixing circuit shown in FIG10 mixing the first signal and the second signal to generate the third signal is described in the aforementioned description of FIG7A and will not be repeated here.

[0154] In one possible implementation, the sixth filter is used to filter the third signal obtained by mixing the first signal and the second signal to reduce higher harmonics in the third signal. The fifth filter is used to filter the second signal to reduce interference signals in the second signal.

[0155] Exemplarily, when the second signal is an intermediate frequency signal or a baseband signal, the fifth filter is a bandpass filter, which filters the input second signal, and the second filter filters the input first signal. The signals filtered by the fifth filter and the second filter are respectively input to the source and drain of the first switching tube. This approach can filter out useless signals in the first and second signals and reduce the in-band fluctuations of the mixed signal. The sixth filter is a bandpass filter, which is used to pass the radio frequency signal (the frequency of the radio frequency signal is equal to the sum of the frequencies of the first and second signals) to reduce the interference of other higher harmonics on the signal.

[0156] Exemplarily, when the second signal is a radio frequency signal, the fifth filter is a bandpass filter, which filters the input second signal, and the second filter filters the input first signal. The signals filtered by the fifth filter and the second filter are respectively input to the source and drain of the first switching tube. This approach can filter out useless signals in the first and second signals and reduce the in-band fluctuations of the mixed signal. The sixth filter is a bandpass filter, which is used to pass an intermediate frequency signal or a baseband signal (the frequency of the intermediate frequency signal or the baseband signal is equal to the difference between the frequencies of the first and second signals) to reduce the interference of other higher harmonics on the signal.

[0157] Next, the embodiment of the present application exemplarily illustrates relevant experimental results of the mixing circuit shown in FIG. 10 through FIG. 11A , FIG. 11B , and FIG. 11C .

[0158] Please refer to Figure 11A, which is a schematic diagram of another up-conversion loss provided by an embodiment of the present application. Figure 11A exemplarily shows the conversion loss of the mixing circuit shown in Figure 10 at various operating frequencies and various input powers when performing up-conversion.

[0159] As shown in Figure 11A , the vertical axis of Figure 11A represents conversion loss in dB. The horizontal axis of Figure 11A represents operating frequency in GHz. The operating frequency in Figure 11A ranges from 0.985 GHz to 1.185 GHz. The legend of Figure 11A represents input power in dBm. The input powers in Figure 9A include 13 dBm, 16 dBm, 19 dBm, 22 dBm, and 25 dBm.

[0160] Figure 11A shows the relationship between operating frequency and conversion loss: as the operating frequency increases, the conversion loss exhibits a random oscillation. For example, when the operating frequency is between 0.985 GHz and 0.995 GHz, the conversion loss decreases as the operating frequency increases. When the operating frequency is between 0.995 GHz and 1.045 GHz, the conversion loss increases. When the operating frequency is between 1.045 GHz and 1.175 GHz, the conversion loss decreases as the operating frequency increases. When the operating frequency is between 1.175 GHz and 1.185 GHz, the conversion loss increases as the operating frequency increases.

[0161] Furthermore, Figure 11A shows that input power has little effect on conversion loss. For example, at an operating frequency of 1.085 GHz, the conversion loss for both an input power of 13 dBm and an input power of 22 dBm is approximately 5 dB. However, at some operating frequencies, the conversion loss increases with increasing input power. For example, at an operating frequency of 1.155 GHz, the conversion loss for an input power of 22 dBm is approximately 5 dB, while the conversion loss for an input power of 13 dBm is approximately 4 dB. The maximum down-conversion loss shown in Figure 11A is approximately 6 dB.

[0162] Please refer to Figure 11B, which is a schematic diagram of down-conversion loss provided by an embodiment of the present application. Figure 11B exemplarily shows the conversion loss under various operating frequencies and various input powers when the mixing circuit shown in Figure 10 performs down-conversion.

[0163] As shown in Figure 11B , the vertical axis of Figure 11B represents conversion loss in dB. The horizontal axis of Figure 11B represents operating frequency in GHz. The operating frequency in Figure 11B ranges from 3.4 GHz to 3.6 GHz. The legend of Figure 11B represents input power in dBm. The input powers in Figure 11B include 13 dBm, 16 dBm, 19 dBm, 22 dBm, and 25 dBm.

[0164] As shown in Figure 11B, the relationship between operating frequency and conversion loss is that, from 3.4 GHz to 3.6 GHz, the overall conversion loss increases with increasing operating frequency. However, there are also local areas where the conversion loss decreases with increasing operating frequency. For example, from 3.45 GHz to 3.5 GHz, the overall conversion loss decreases with increasing operating frequency. Furthermore, when the input power is 13 dBm, the overall conversion loss decreases with increasing operating frequency.

[0165] The relationship between input power and conversion loss is that, between 3.4 GHz and 3.5 GHz, there is a negative correlation between input power and conversion loss; higher input power results in lower conversion loss. Between 3.5 GHz and 3.6 GHz, there is a positive correlation between input power and conversion loss; higher input power results in higher conversion loss. Figure 11B shows that the maximum conversion loss, approximately 8 dB, occurs at an input power of 25 dBm and an operating frequency of 3.6 GHz.

[0166] Please refer to Figure 11C, which is a schematic diagram of the relationship between another OIP3 and operating frequency provided in an embodiment of the present application. As shown in Figure 11C, the horizontal axis is used to represent the operating frequency, in GHz. The vertical axis is used to represent OIP3, in dBm. When the operating frequency is 0.985GHz, the OIP3 is about 30.18dBm. As can be seen from Figure 11C, the minimum conversion loss of the mixer shown in Figure 10 is about 4dB. Therefore, the IIP3 of the mixer shown in Figure 10 will be greater than 34dBm. When the operating frequency of the mixer shown in Figure 10 is 1.085GHz, the conversion loss is about 5dB, and OIP3 is greater than 31dB. Therefore, when the operating frequency of the mixer shown in Figure 10 is 1.085GHz, the IIP3 will be greater than 36dBm.

[0167] The mixer circuit shown in Figure 10 first utilizes a III-V process switch as the key component for implementing the mixing function, enabling the mixer circuit to achieve high linearity. Secondly, adding a large resistor or grounding the drain of the switch tube to implement a reflection circuit can reduce the frequency conversion loss caused by signal feedthrough, achieving the goal of low loss in the mixer circuit. Finally, by adding a suitable filter to the drain of the switch tube, the signal filtering delay can be adjusted, allowing the reflected signal to be mixed with the square wave signal of the other half cycle, further reducing the frequency conversion loss. Furthermore, the filter can filter out interfering signals and reduce in-band fluctuations.

[0168] In one possible implementation, the mixing circuits shown in FIG. 8 and FIG. 10 can be reused with filters in an existing network, which can significantly reduce the cost of networking.

[0169] For example, if a filter for filtering the local oscillator signal already exists in the existing network, the second filter in the frequency mixing circuit shown in FIG10 can use the existing filter in the existing network, thereby reducing the networking cost.

[0170] For example, if a filter for filtering intermediate frequency signals or baseband signals already exists in the existing network, the fifth filter in the mixing circuit shown in FIG10 can use the existing filter in the existing network, thereby reducing networking costs.

[0171] For example, if a filter for filtering radio frequency signals already exists in the existing network, the sixth filter in the mixing circuit shown in FIG10 can use the existing filter in the existing network, thereby reducing the networking cost.

[0172] Likewise, the second filter, the fourth filter, the fifth filter, and the sixth filter in the mixer circuit shown in FIG8 can also be shared with existing filters in the network.

[0173] An embodiment of the present application further provides a circuit board, which includes the mixing circuit in FIG. 7A , FIG. 7B , FIG. 8 or FIG. 10 and possible embodiments thereof.

[0174] An embodiment of the present application further provides a mixer, which includes the mixing circuit in FIG. 7A , FIG. 7B , FIG. 8 or FIG. 10 and possible embodiments thereof.

[0175] An embodiment of the present application further provides a communication device, which includes the mixing circuit in Figure 7A, Figure 7B, Figure 8 or Figure 10 and possible embodiments thereof.

[0176] In this application, the terms "first," "second," and the like are used to distinguish between identical or similar items having substantially the same function or effect. It should be understood that "first," "second," and "nth" do not have a logical or temporal dependency, nor do they limit the quantity or order of execution. It should also be understood that although the following description uses the terms "first," "second," and the like to describe various elements, these elements should not be limited by these terms. These terms are simply used to distinguish one element from another.

[0177] It should also be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0178] It will also be understood that the term “comprise” (also known as “includes,” “including,” “comprises,” and / or “comprising”) when used in this specification specifies the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0179] It should also be understood that references throughout this specification to "one embodiment," "an embodiment," or "one possible implementation" mean that specific features, structures, or characteristics associated with that embodiment or implementation are included in at least one embodiment of the present application. Therefore, the appearance of "in one embodiment," "in an embodiment," or "one possible implementation" throughout this specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0180] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of this application and are not intended to limit them. Although this application has been described in detail with reference to the aforementioned embodiments, those skilled in the art will appreciate that they may modify the technical solutions described in the aforementioned embodiments or replace some or all of the technical features therein with equivalents. However, such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the various embodiments of this application.

Claims

1. A mixing circuit, characterized in that: The mixing circuit includes a first switch tube and a first filter; The gate of the first switch tube is used to input a first signal, and the first signal is used to control the on and off of the first switch tube; The drain of the first switch tube is used to be connected to the first end of the first filter, and the second end of the first filter is used to be grounded; The source of the first switch tube is used to input a second signal, and the source of the first switch tube is also used to output a third signal, where the third signal is a signal obtained by mixing the first signal and the second signal.

2. The mixer circuit according to claim 1, characterized in that: The frequency mixing circuit further includes a first resistor; The second end of the first filter is specifically used to be connected to the first end of the first resistor, and the second end of the first resistor is used to be grounded.

3. The mixer circuit according to claim 1 or 2, characterized in that: The mixing circuit further includes a second filter; the gate of the first switch tube is used to input a first signal, including: The gate of the first switch tube is used to be connected to the first end of the second filter, and the second end of the second filter is used to input the first signal.

4. The mixer circuit according to any one of claims 1 to 3, characterized in that: The mixing circuit also includes a first circulator; The source of the first switch tube is specifically used to connect to the first end of the first circulator; the second end of the first circulator is used to input the second signal, and the third end of the first circulator is used to output the third signal.

5. The mixer circuit according to claim 4, characterized in that: The mixing circuit also includes a second circulator, a second switch tube and a third filter; The third end of the first circulator is used to output the third signal, including: The third end of the first circulator is used to connect to the first end of the second circulator, and the second end of the second circulator is used to output the third signal; The third end of the second circulator is used to connect the source of the second switch tube; the gate of the second switch tube is used to input a fourth signal, and the fourth signal is used to control the on and off of the second switch tube to achieve mixing of the fourth signal and a fifth signal, and the fifth signal is input from the second end of the second circulator; the output time of the third signal is different from the input time of the fifth signal; The drain of the second switch tube is used to be connected to the first end of the third filter, and the second end of the third filter is used to be grounded.

6. The mixer circuit according to claim 4 or 5, characterized in that: The mixing circuit further includes a second resistor; The second end of the third filter is specifically used to be connected to the first end of the second resistor, and the second end of the second resistor is used to be grounded.

7. The mixer circuit according to any one of claims 4 to 6, characterized in that: The mixing circuit further includes a fourth filter; the gate of the second switch tube is used to input a fourth signal, including: The gate of the second switch tube is used to be connected to the first end of the fourth filter, and the second end of the fourth filter is used to input the fourth signal.

8. The mixer circuit according to any one of claims 4 to 7, characterized in that: The mixing circuit further includes a fifth filter; the second end of the first circulator is used to input the second signal, including: The second end of the first circulator is specifically used to connect to the first end of the fifth filter, and the second end of the fifth filter is used to input the second signal.

9. The mixer circuit according to any one of claims 5 to 8, characterized in that: The mixing circuit further includes a sixth filter; the second end of the second circulator is used to output the third signal, including: The second end of the second circulator is specifically used to connect to the first end of the sixth filter, and the second end of the sixth filter is used to output the third signal.

10. The mixer circuit according to any one of claims 1 to 3, characterized in that: The mixing circuit further includes a fifth filter; the source of the first switch tube is used to input a second signal, including: The source of the first switch tube is specifically used to be connected to the first end of the fifth filter, and the second end of the fifth filter is used to input the second signal.

11. The mixer circuit according to any one of claims 1 to 3 and 10, characterized in that: The mixing circuit further includes a sixth filter; the source of the first switch tube is also used to output a third signal, including: The source of the first switch tube is specifically used to be connected to the first end of the sixth filter, and the second end of the sixth filter is used to output the third signal.

12. The mixer circuit according to any one of claims 1 to 11, characterized in that: The first signal is a local oscillator signal, the second signal is a baseband signal or an intermediate frequency signal, and the third signal is a radio frequency signal; The mixing circuit is used to up-convert the second signal to obtain the third signal.

13. The mixer circuit according to any one of claims 1, 2, 3, 10 and 11, characterized in that: The first signal is a local oscillator signal, the second signal is a radio frequency signal, and the third signal is a baseband signal or an intermediate frequency signal; The frequency mixing circuit is used to down-convert the second signal to obtain the second signal.

14. A circuit board, characterized in that: The circuit board comprises the mixing circuit according to any one of claims 1-13.

15. A mixer, characterized in that: The mixer comprises the mixing circuit according to any one of claims 1 to 13.

16. A communication device, characterized in that: The device comprises a processor and the mixing circuit according to any one of claims 1 to 13.

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