Monolithic integrated frequency conversion circuit with image rejection switching and superheterodyne system

Abstract

The invention belongs to the field of semiconductor device integration, and particularly relates to a monolithic integrated frequency conversion circuit with image rejection switching and a superheterodyne system, which comprise a radio frequency power division and synthesis unit, a mixer A unit, a mixer B unit, a local oscillator phase switching unit, an intermediate frequency phase switching unit and an intermediate frequency power division and synthesis unit, wherein the mixer A unit and the mixer B unit adopt the same circuit structure and parameters, numerical control phase shifters and phase shift control units are integrated in the local oscillator phase switching unit and the intermediate frequency phase switching unit, and the two branches are enabled to reach a state of relatively leading 90 degrees or lagging 90 degrees in phase by controlling the switching state of switches in the phase shift control units. According to the invention, the mirror image rejection function is realized in two modes that the radio frequency is higher than the local frequency and the radio frequency is lower than the local frequency. After the monolithic integrated frequency conversion circuit is applied to a superheterodyne system, the monolithic integrated frequency conversion circuit has better frequency selectivity, interference resistance and low spurious characteristics.

Description

Technical Field

[0001] The invention relates to the field of semiconductor device integration, and in particular to a monolithic integrated frequency conversion circuit with image suppression switching and a superheterodyne system. Background Art

[0002] In current radar systems and communication systems, frequency conversion systems exist in receivers and transmitters. Superheterodyne and low intermediate frequency are typical application architectures in transceiver systems. In order to prevent interference caused by image signals, filters are often introduced to suppress image signals. However, the use of filters for suppression will increase the size and cost of the link, so the image suppression structure proposed by Hartley is currently the most commonly used architecture. This structure achieves image suppression by first mixing the RF input signal with the two orthogonal signals of the local oscillator, then obtaining two orthogonal intermediate frequency signals through low-pass filtering, then shifting one of the intermediate frequency signals by 90°, and then superimposing it with the other intermediate frequency signal, and finally achieving the purpose of suppressing the image signal. This method of mixing the orthogonal local oscillator and the orthogonal intermediate frequency to achieve image suppression has been widely used since it was proposed.

[0003] Based on Hartley’s concept, Chang-Wan Kim et al. proposed a method to realize orthogonal signals based on polyphase filters in the paper “A 5.25-GHz Image Rejection RF Front-End Receiver With Poly-phase Filters” published in IEEE Microwave and Wireless Components Letters in 2006. The method realized the monolithic integration of the RF front-end receiver through CMOS semiconductor process and achieved the suppression of image signals. Sheng-Che Tseng et al. published a paper “Dual-Band Adjustable and Reactive I / Q Generator With Constant Resistance for Down and Up Converters” in IEEE Transactions on Microwave Theory and Techniques in 2008. The tuning range of the orthogonal generation network was increased by introducing inductors and variable capacitors. Without changing the resistance value of the orthogonal network, the image suppression function of 2.4 / 5.2GHz dual-band up-conversion and down-conversion was achieved. J. Zhang et al. published a paper “High Conversion Efficiency Photonics Generator with Constant Resistance for Down and Up Converters” in IEEE Photonics Journal in 2016. The paper "Microwave Mixer With Image Rejection Capability" proposed a microwave photonic mixer with image rejection function. Through the adjustable optical attenuator and delay line technology, the intermediate frequency orthogonal signal can be adjusted in a wider frequency range, thereby realizing the suppression of image signals in a wider frequency band of 3~20GHz. However, the above circuit architecture technologies are all based on the specific relationship between the radio frequency RF, the local oscillator frequency LO, and the intermediate frequency IF to achieve image rejection, that is, under the premise that the local oscillator frequency LO is greater than the intermediate frequency frequency IF, only condition one or condition two can be met, but not both conditions. Among them, condition one is: when the radio frequency RF is higher than the local oscillator frequency LO (RF-LO=IF and RF>LO>IF), the image signal frequency 2LO-RF=RF-2IF can be suppressed; condition two is: when the radio frequency RF is lower than the local oscillator frequency LO (LO-RF=IF and LO>RF>IF), the image signal frequency 2LO-RF=RF+2IF can be suppressed. Therefore, studying a circuit structure that can achieve image suppression when the radio frequency RF is higher or lower than the local oscillator frequency LO has positive significance for improving the hardware versatility of circuit design. Summary of the invention

[0004] The purpose of the present invention is to provide a monolithic integrated frequency conversion circuit and a superheterodyne system with image suppression switching, which is based on the phase switching concept of a local oscillator orthogonal signal and an intermediate frequency orthogonal signal, and realizes image suppression under conditions higher or lower than the local oscillator frequency LO, thereby improving the hardware versatility of the frequency conversion circuit.

[0005] To achieve the above object, the present invention adopts the following technical solution: A monolithic integrated frequency conversion circuit with image suppression switching, comprising: a radio frequency power division and synthesis unit, a mixer A unit, a mixer B unit, a local oscillator phase switching unit, an intermediate frequency phase switching unit, and an intermediate frequency power division and synthesis unit; The combining port P1 of the RF power dividing and synthesizing unit inputs / outputs the RF signal RFSig, the first power dividing port P2 of the RF power dividing and synthesizing unit is connected to the RF port RF of the mixer A unit to transmit the signal RFA, and the second power dividing port P3 of the RF power dividing and synthesizing unit is connected to the RF port RF of the mixer B unit to transmit the signal RFB, which is used to power divide the RF signal RFSig into the signal RFA and the signal RFB or to synthesize the signal RFA and the signal RF into the RF signal RFSig; the first port Q1 of the local oscillator phase switching unit is connected to the local oscillator signal LOI, the second port Q2 is connected to the local oscillator port LO of the mixer A unit, and the third port Q3 is connected to the local oscillator port LO of the mixer B unit, which is used to provide the local oscillator orthogonal signal LOA for the mixer A unit and provide the local oscillator orthogonal signal LOB for the mixer B unit; The intermediate frequency port IF of the mixer A unit is connected to the first port Z1 of the intermediate frequency phase switching unit. The intermediate frequency port IF of the mixer B unit is connected to the second port Z2 of the intermediate frequency phase switching unit; The third port Z3 of the intermediate frequency phase switching unit is connected to the first power division port S2 of the intermediate frequency power division and synthesis unit, and the fourth port Z4 is connected to the second power division port S3 of the intermediate frequency power division and synthesis unit; The combining port S1 of the intermediate frequency power dividing and combining unit inputs / outputs IFSig.

[0006] Furthermore, the frequency conversion method implemented by the monolithic integrated frequency conversion circuit with image suppression switching supports two working modes: receiving and transmitting; In the receiving working mode, the mixer A unit and the mixer B unit are both in the down-conversion working state; the radio frequency signal RFSig is input from the combining port P1 of the radio frequency power division and synthesis unit, and the power division signal RFA is output to the RF port of the mixer A unit through the first power division port P2, and the power division signal RFB is output to the RF port of the mixer B unit through the second power division port P3; in the mixer A unit, the power division signal RFA and the local oscillator orthogonal signal LOA are mixed to generate the intermediate frequency signal IFA, and in the mixer B unit, the power division signal RFB and the local oscillator orthogonal signal LOB are mixed to generate the intermediate frequency signal IFB; the intermediate frequency signal IFA is subjected to phase shift processing by the intermediate frequency phase switching unit to generate the intermediate frequency signal IFC, and the intermediate frequency signal IFB is subjected to phase shift processing to generate the intermediate frequency signal IFD; the intermediate frequency power division and synthesis unit synthesizes the received intermediate frequency signal IFC and the intermediate frequency signal IFD to obtain the intermediate frequency signal IFSig output; In the transmitting working mode, the mixer A unit and the mixer B unit are in the up-conversion working state; the intermediate frequency signal IFSig enters from the S1 port of the intermediate frequency power division synthesis unit, and passes through the first power division port S2 and the output power division signal IFC, and outputs the power division signal IFD through the second power division port S3; after the intermediate frequency signal IFC is phase-shifted by the intermediate frequency phase switching unit, the intermediate frequency signal IFA is output and transmitted to the IF port of the mixer A unit; after the intermediate frequency signal IFD is phase-shifted by the intermediate frequency phase switching unit, the intermediate frequency signal IFB is output and transmitted to the IF port of the mixer B; in the mixer A unit, the intermediate frequency signal IFA is mixed with the local oscillator orthogonal signal LOA to generate the radio frequency signal RFA; in the mixer B unit, the intermediate frequency signal LOB is mixed with the local oscillator orthogonal signal RFB to generate the radio frequency signal RFA; after the radio frequency signals RFA and RFB are power-synthesized by the radio frequency power division synthesis unit, the radio frequency signal RFSig is output from the combining port P1 of the radio frequency power division synthesis unit.

[0007] Further, the local oscillator phase switching unit includes a local oscillator amplifying unit, a local oscillator power dividing unit, and a phase shift processing unit; The input end of the local oscillator amplifying unit is the first port Q1 of the local oscillator phase switching unit, connected to the input signal LOI, and the output end is connected to the first input end of the local oscillator power splitter unit; The first output end of the local oscillator power splitting unit is connected to the 0° / +45° local oscillator phase shifting unit, and the second output end of the local oscillator power splitting unit is connected to the 0° / -45° local oscillator phase shifting unit, for power splitting the input signal LOI into the signal LOA and the signal LOB; The phase shift processing unit includes four phase shift units and a local oscillator phase shift control unit; the four phase shift units are a 0° / +45° local oscillator phase shift unit, a 0° / -90° local oscillator phase shift unit, a 0° / -45° local oscillator phase shift unit and a 0° / +90° local oscillator phase shift unit, and the -45° (+45°-90°) and +45° (+45°+0°) phase shift functions are generated by combining the 0° / +45° local oscillator phase shift unit and the 0° / -90° local oscillator phase shift unit, and the +45° (-45°+90°) and -45° (-45°+0°) phase shift functions are generated by combining the 0° / -45° local oscillator phase shift unit and the 0° / +90° local oscillator phase shift unit; A switch is provided in the local oscillator phase shift control unit, and the switch is respectively connected to the 0° / +45° local oscillator phase shift unit, the 0° / -90° local oscillator phase shift unit, the 0° / -45° local oscillator phase shift unit and the 0° / +90° local oscillator phase shift unit; the corresponding control code can be generated according to the phase shift requirement, and the switching state of the switch is controlled by the control code to complete the phase shift operation, so as to realize the +90° phase difference or -90° phase difference of the local oscillator signal LOA and the local oscillator signal LOB; when the image suppression function is not needed, and when the two local oscillator signals LOA and LOB realize a 0° relative phase shift through the local oscillator phase shift unit, there is no orthogonal characteristic, and the image suppression function is turned off at this time.

[0008] Furthermore, the local oscillator amplifying unit is an active amplifier, and the phase shifts of the four local oscillator phase shifting units are all realized by using a digitally controlled phase shifter circuit.

[0009] Further, the intermediate frequency phase switching unit is a switch-controlled digitally controlled phase shifter passive circuit, which is used to perform phase shift processing on the intermediate frequency signal IFA and the intermediate frequency signal IFB, and includes: an intermediate frequency phase shift control unit, and four intermediate frequency phase shift units; The four intermediate frequency phase shift units are: 0° / +45° intermediate frequency phase shift unit, 0° / -90° intermediate frequency phase shift unit, 0° / -45° intermediate frequency phase shift unit, and 0° / +90° intermediate frequency phase shift unit. The intermediate frequency phase shift units are combined to generate -45° (+45°-90°) and +45° (+45°+0°) phase shift functions. The intermediate frequency phase shift control unit is equipped with switches, which are respectively connected to the 0° / +45° intermediate frequency phase shift unit, the 0° / -90° intermediate frequency phase shift unit, the 0° / -45° intermediate frequency phase shift unit, and the 0° / +90° intermediate frequency phase shift unit; it can generate corresponding control codes according to the phase shift requirements, and control the switching state of the switch through the control code to complete the phase shift operation, so as to achieve a +90° phase difference or a -90° phase difference between the intermediate frequency signal IFA and the intermediate frequency signal IFB; the two intermediate frequency signals can also achieve a 0° relative phase shift through the intermediate frequency phase shift unit, which does not affect the signal synthesis when the image suppression function is turned off.

[0010] Furthermore, the structures and parameters of the frequency mixing unit A and the frequency mixing unit B are the same.

[0011] Furthermore, the radio frequency power division and synthesis unit and the intermediate frequency power division and synthesis unit both adopt equal power distribution.

[0012] A superheterodyne system comprises the above-mentioned monolithic integrated frequency conversion circuit with image suppression switching.

[0013] The present invention provides a monolithic integrated frequency conversion circuit with image suppression switching, which is implemented by hybrid integrated circuit or semiconductor processes such as GaAs, GaN, CMOS, SiGe, etc., and has the advantages of high phase accuracy and better consistency. A local oscillator phase switching unit and an intermediate frequency phase switching unit are integrated therein, and both the local oscillator phase switching unit and the intermediate frequency phase switching unit are integrated with a digitally controlled phase shifter and a phase shift control unit. By controlling the switching state of the switch in the phase shift control unit, the two branches are made to be relatively advanced by 90° or delayed by 90° in phase, and then the image suppression function is realized in both modes of the radio frequency RF being higher than the local oscillator frequency LO and the radio frequency RF being lower than the local oscillator frequency LO.

[0014] In addition, in a superheterodyne system, the circuit of the present invention is used as a second frequency mixing circuit in the superheterodyne system, that is, when the system needs to work in an agile frequency conversion and anti-interference state: when the frequency of the radio frequency signal remains unchanged, another new first intermediate frequency signal frequency is generated by changing the frequency of the first local oscillator signal, and the newly generated first intermediate frequency signal frequency can be taken as the mirror frequency point corresponding to the original first intermediate frequency signal frequency. At this time, the second frequency mixing circuit can be compatible with two different first intermediate frequency signal frequency values, and the first intermediate frequency signal image suppression can still be achieved when mixing through the second frequency conversion circuit, and the second intermediate frequency frequency does not change in any way to adapt to the subsequent anti-aliasing filter of the second intermediate frequency. The agile characteristics of the first intermediate frequency signal realized by the above mode are suitable for radar frequency conversion systems with low spurious requirements. It can be seen that the superheterodyne system of the present invention has better frequency selectivity, anti-interference and low spurious characteristics after adopting the monolithic integrated frequency conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a principle block diagram of a monolithic integrated frequency conversion circuit with image suppression switching of the present invention; Figure 2 It is a principle block diagram of the local oscillator phase switching unit of the present invention; Figure 3 This is a principle block diagram of the intermediate frequency phase switching unit of the present invention; Figure 4 It is a block diagram of a superheterodyne system including a monolithic integrated frequency conversion circuit of the present invention provided in an embodiment. DETAILED DESCRIPTION

[0016] Figure 1 1 is a block diagram of the principle of a monolithic integrated frequency conversion circuit with image suppression switching according to the present invention. Figure 1 As shown, this embodiment provides a monolithic integrated frequency conversion circuit with image suppression switching, including: a radio frequency power division and synthesis unit, a mixer A unit, a mixer B unit, a local oscillator phase switching unit, an intermediate frequency phase switching unit, and an intermediate frequency power division and synthesis unit.

[0017] The combining port P1 of the RF power dividing and synthesizing unit is the input / output terminal of the RF signal RFSig, the first power dividing port P2 of the RF power dividing and synthesizing unit is connected to the RF port RF of the mixer A unit, and the second power dividing port P3 of the RF power dividing and synthesizing unit is connected to the RF port RF of the mixer B unit, and is used to power divide the RF signal RFSig into signal RFA and signal RFB or to synthesize the signal RFA and signal RFB into signal RFSig.

[0018] The first port Q1 of the local oscillator phase switching unit is connected to the local oscillator signal LOI, the second port Q2 is connected to the local oscillator port LO of the mixer A unit, and the third port Q3 is connected to the local oscillator port LO of the mixer B unit, and is used to provide the local oscillator orthogonal signal LOA for the mixer A unit and provide the local oscillator orthogonal signal LOB for the mixer B unit.

[0019] The intermediate frequency port IF of the mixer A unit is connected to the first port Z1 of the intermediate frequency phase switching unit.

[0020] The intermediate frequency port IF of the mixer B unit is connected to the second port Z2 of the intermediate frequency phase switching unit.

[0021] The third port Z3 of the intermediate frequency phase switching unit is connected to the first power division port S2 of the intermediate frequency power division and synthesis unit, and the fourth port Z4 is connected to the second power division port S3 of the intermediate frequency power division and synthesis unit.

[0022] The combining port S1 of the intermediate frequency power dividing and combining unit inputs / outputs IFSig.

[0023] The frequency conversion mode implemented by the monolithic integrated frequency conversion circuit with image suppression switching supports two working modes: receiving and transmitting.

[0024] In the receiving working mode, the mixer A unit and the mixer B unit are both in the down-conversion working state; the radio frequency signal RFSig is input from the combining port P1 of the radio frequency power division and synthesis unit, and the power division signal RFA is output to the RF port of the mixer A unit through the first power division port P2, and the power division signal RFB is output to the RF port of the mixer B unit through the second power division port P3; in the mixer A unit, the power division signal RFA and the local oscillator orthogonal signal LOA are mixed to generate the intermediate frequency signal IFA, and in the mixer B unit, the power division signal RFB and the local oscillator orthogonal signal LOB are mixed to generate the intermediate frequency signal IFB; the intermediate frequency signal IFA is subjected to phase shift processing by the intermediate frequency phase switching unit to generate the intermediate frequency signal IFC, and the intermediate frequency signal IFB is subjected to phase shift processing to generate the intermediate frequency signal IFD; the intermediate frequency power division and synthesis unit synthesizes the received intermediate frequency signal IFC and the intermediate frequency signal IFD to obtain the intermediate frequency signal IFSig output; In the transmitting working mode, the mixer A unit and the mixer B unit are in the up-conversion working state; the intermediate frequency signal IFSig enters from the S1 port of the intermediate frequency power division synthesis unit, and passes through the first power division port S2 and the output power division signal IFC, and outputs the power division signal IFD through the second power division port S3; after the intermediate frequency signal IFC is phase-shifted by the intermediate frequency phase switching unit, the intermediate frequency signal IFA is output and transmitted to the IF port of the mixer A unit; after the intermediate frequency signal IFD is phase-shifted by the intermediate frequency phase switching unit, the intermediate frequency signal IFB is output and transmitted to the IF port of the mixer B; in the mixer A unit, the intermediate frequency signal IFA is mixed with the local oscillator orthogonal signal LOA to generate the radio frequency signal RFA; in the mixer B unit, the intermediate frequency signal LOB is mixed with the local oscillator orthogonal signal RFB to generate the radio frequency signal RFA; after the radio frequency signals RFA and RFB are power-synthesized by the radio frequency power division synthesis unit, the radio frequency signal RFSig is output from the combining port P1 of the radio frequency power division synthesis unit.

[0025] Figure 2 This is a block diagram of the principle of the local oscillator phase switching unit of the present invention. Figure 2 As shown, the local oscillator phase switching unit includes: a local oscillator amplifying unit, a local oscillator power dividing unit, a 0° / +45° local oscillator phase shifting unit, a 0° / -90° local oscillator phase shifting unit, a 0° / -45° local oscillator phase shifting unit, a 0° / +90° local oscillator phase shifting unit, and a local oscillator phase shifting control unit.

[0026] The local oscillator input signal LOI enters from the input end of the local oscillator amplifier unit, and the output end of the local oscillator amplifier unit is connected to the input end of the local oscillator power splitter unit. The first output end of the local oscillator power splitter unit is connected to the input end of the 0° / +45° local oscillator phase shift unit, and the second output end is connected to the input end of the 0° / -45° local oscillator phase shift unit. The output end of the 0° / +45° local oscillator phase shift unit is connected to the input end of the 0° / -90° local oscillator phase shift unit. The output end of the 0° / -45° local oscillator phase shift unit is connected to the input end of the 0° / +90° local oscillator phase shift unit. The local oscillator phase shift control unit is respectively connected to the control end of the 0° / +45° local oscillator phase shift unit, the control end of the 0° / -90° local oscillator phase shift unit, the control end of the 0° / +90° local oscillator phase shift unit, and the control end of the 0° / +90° local oscillator phase shift unit. The output end of the 0° / -90° local oscillator phase shift unit outputs one of the local oscillator signals LOA, and the output end of the 0° / +90° local oscillator phase shift unit outputs another local oscillator signal LOB.

[0027] In this embodiment, the local oscillator amplification unit is an active amplifier, and the phase shifts of the 0° / +45° local oscillator phase shift unit, the 0° / -90° local oscillator phase shift unit, the 0° / -45° local oscillator phase shift unit, and the 0° / +90° local oscillator phase shift unit are all realized by a digitally controlled phase shifter circuit. A switch is provided inside the local oscillator phase shift control unit, and the switch is connected to the four local oscillator phase shift units respectively. When in use, the local oscillator phase shift control unit generates a control code according to the phase shift requirement to control the switching state of the switch to complete the phase shift operation, thereby realizing a +90° phase difference or a -90° phase difference between the local oscillator signal LOA and the local oscillator signal LOB.

[0028] It should be noted that, in this embodiment, the 0° / +45° local oscillator phase shift unit and the 0° / -90° local oscillator phase shift unit are configured for phase shift combination to generate -45° (+45°-90°) and +45° (+45°+0°) phase shift functions; the 0° / -45° local oscillator phase shift unit and the 0° / +90° local oscillator phase shift unit are configured for phase shift combination to generate +45° (-45°+90°) and -45° (-45°+0°) phase shift functions, so that the phase difference of the two signals can be achieved by making a difference in phase to achieve a phase difference of +90° or -90°.

[0029] Figure 3 This is a block diagram of the intermediate frequency phase switching unit of the present invention. Figure 3 As shown, the intermediate frequency phase switching unit includes: a 0° / +45° intermediate frequency phase shift unit, a 0° / -90° intermediate frequency phase shift unit, a 0° / -45° intermediate frequency phase shift unit, a 0° / +90° intermediate frequency phase shift unit, and an intermediate frequency phase shift control unit.

[0030] The intermediate frequency signal IFA is connected to the first port of the 0° / +45° intermediate frequency phase shift unit, and the second port is connected to the second port of the 0° / -90° intermediate frequency phase shift unit. The intermediate frequency signal IFB is connected to the first port of the 0° / -45° intermediate frequency phase shift unit, and the second port is connected to the second port of the 0° / +90° intermediate frequency phase shift unit. The intermediate frequency signal IFC is connected to the first port of the 0° / -90° intermediate frequency phase shift unit, and the intermediate frequency signal IFD is connected to the first port of the 0 / +90° intermediate frequency phase shift unit.

[0031] The intermediate frequency phase shift control unit is connected to the control end of the 0° / +45° intermediate frequency phase shift unit, the control end of the 0° / -90° intermediate frequency phase shift unit, the control end of the 0 / -45° intermediate frequency phase shift unit, and the control end of the 0° / +90° intermediate frequency phase shift unit respectively. The intermediate frequency phase shift control unit generates a corresponding control code according to the phase shift requirement, and controls the control end of each intermediate frequency phase shift unit through the control code to complete the phase shift operation, so as to realize the +90° phase difference or -90° phase difference of the intermediate frequency signal IFA and the intermediate frequency signal IFB.

[0032] In this embodiment, the 0° / +45° intermediate frequency phase shift unit, the 0° / -90° intermediate frequency phase shift unit, the 0° / -45° intermediate frequency phase shift unit, and the 0° / +90° intermediate frequency phase shift unit are all passive digital control phase shifters, and the intermediate frequency signal IFA and the intermediate frequency signal IFC, and the intermediate frequency signal IFB and the intermediate frequency signal IFD have bidirectional transmission characteristics. When in use, the 0° / +45° intermediate frequency phase shift unit and the 0° / -90° intermediate frequency phase shift unit are configured for phase shift combination to generate -45° (+45°-90°) and +45° (+45°+0°) phase shift functions. The 0° / -45° intermediate frequency phase shift unit and the 0° / +90° intermediate frequency phase shift unit are configured to generate +45° (-45°+90°) and -45° (-45°+0°) phase shift functions, and the intermediate frequency signal IFA and the intermediate frequency signal IFB are subtracted to achieve a +90° phase difference or a -90° phase difference.

[0033] This embodiment introduces digitally controlled phase shifters with different phase shifts in the local oscillator phase switching unit and the intermediate frequency phase switching unit, respectively, to achieve controllable phase difference between the local oscillator phase switching unit and the mixer A unit and the mixer B unit, and controllable phase difference between the intermediate frequency signals output by the orthogonal intermediate frequency, thereby achieving the image suppression switching function of the frequency conversion circuit. The image suppression function is compatible with the two situations where the radio frequency frequency RF is higher than the local oscillator frequency LO and the radio frequency frequency RF is lower than the local oscillator frequency LO, and the circuit architecture is simple and does not require complex digital circuits and algorithm calibration.

[0034] Figure 4 1 is a block diagram of a superheterodyne system including a monolithic integrated frequency conversion circuit of the present invention provided in an embodiment. Figure 4As shown, the superheterodyne system of this implementation includes a radio frequency receiving and transmitting amplification circuit, a first frequency conversion circuit, a first intermediate frequency spurious suppression filter, a first intermediate frequency bidirectional amplification circuit, a second frequency conversion circuit, and a second intermediate frequency anti-aliasing filter. The radio frequency receiving and transmitting amplification circuit is composed of a ring isolator, a low noise amplifier, a power amplifier, a receiving switch tube, a transmitting switch tube, and SP2T, wherein SP2T is a single-pole double-throw switch. VDD is a power supply port; VC1 is a receiving power modulation control signal, and VC3 is a transmitting power modulation control signal. SP2T in the radio frequency receiving and transmitting amplification circuit is used as a receiving and transmitting switching open tube, and VK1 is a receiving and transmitting switching control signal, which is used to realize the switching of receiving and transmitting working modes. In scenarios where the isolation requirement is not high, the ring isolator can also be replaced by a switching circuit. The first frequency conversion circuit is composed of a first intermediate frequency filter and a first mixer connected in sequence. The first intermediate frequency bidirectional amplifier circuit is composed of an amplifier AIF1 and four single-pole double-throw switches SP2T. The control signal of the receiving and transmitting switching is realized through the receiving and transmitting switching control signal VK1, thereby controlling the signal flow direction, and realizing the amplification function in the receiving R and transmitting T modes. The second frequency conversion circuit adopts the above-mentioned monolithic integrated frequency conversion circuit with image suppression switching.

[0035] In this superheterodyne system, f RF Indicates the frequency of the RF signal, f LO1 Indicates the frequency of the first local oscillator signal, f LO2 Indicates the second local oscillator signal frequency, f IF1 represents the frequency of the first intermediate frequency signal, f IF2 The second intermediate frequency signal frequency RF receiving and transmitting amplification circuit is used to realize the bidirectional amplification of the RF signal, and the first frequency conversion circuit is used to realize the RF signal f RF With the first local oscillator signal f LO1 The first IF spurious suppression filter is used to f RF , f LO1 , f LO2 The first intermediate frequency bidirectional amplifier circuit is used to realize the bidirectional amplification of the first intermediate frequency signal, and the second frequency conversion circuit is used to realize the radio frequency signal. f IF1 With the second local oscillator signal f LO2The second intermediate frequency anti-aliasing filter is used to suppress the second intermediate frequency out-of-band signal; wherein the implementation method of the first intermediate frequency spurious suppression filter is not limited to a single filter, and can also be implemented by a switch filter group.

[0036] The advantages of the monolithic integrated frequency conversion circuit with image suppression switching in the superheterodyne system of this embodiment are exemplified by the receiving mode and the down-conversion mixing mode: In traditional frequency conversion circuits, when the RF frequency is higher than the local oscillator frequency, f RF - f LO1 = f IF1 = f LO2 - f IF2 , the signal bandwidth is 0.08GHz, when the value f RF The frequency is 10.31GHz, f LO1 The frequency is 7.73GHz, f IF1 The frequency is 2.58GHz, f LO2 The frequency is 2.76GHz, f IF2 When the frequency is 0.18 GHz and the above equation is satisfied, there will be a fifth-order intermodulation signal 3 f LO1 -2 f RF = The spurious signal generated by 2.57GHz falls into the working bandwidth of the first intermediate frequency signal of 2.58GHz (0.08GHz), and cannot be filtered out by the first intermediate frequency spurious suppression filter. After the signal is mixed with the second local oscillator signal, a signal with a frequency of 0.19GHz is generated and enters the second intermediate frequency anti-aliasing filter, which still cannot be filtered out.

[0037] After adopting the monolithic integrated frequency conversion circuit with image suppression switching of this embodiment, the frequency is changed by the agile frequency conversion of the first local oscillator. f LO1 Higher than RF frequency f RF Satisfy the relationship f LO1 - f RF = f IF1 = f LO2 + f IF2 ,at this time, f RFThe frequency is 10.31GHz, f LO1 The frequency is 13.25GHz, f IF1 The frequency is 2.94GHz, f LO2 The frequency is 2.76GHz, f IF2 The frequency is 0.18GHz, then the fifth-order intermodulation signal 3 f LO1 -2 f RF =19.13GHz is far away from the first intermediate frequency signal frequency 2.94 GHz, so it can be filtered out by the first intermediate frequency spurious suppression filter, achieving the spurious suppression function. The above frequency calculation is just one example. As long as the intermodulation signal generated by a similar principle can be solved by the above method, it will not be listed here one by one. In the above example, regardless of the first intermediate frequency signal frequency f IF1 Whether the frequency value is 2.58 GHz or 2.94 GHz, the frequency conversion circuit with image suppression switching in this embodiment can achieve the image suppression function for the first intermediate frequency signal.

[0038] Likewise, when the received signal RF frequency f RF There is a first local oscillator f LO1 When the nearby frequency signal leaks, the above-mentioned first local oscillator agile frequency conversion method can also be used to solve the problem, by changing the frequency of the first local oscillator signal to make it meet the requirements of the first intermediate frequency f IF1 = f LO2 - f IF2 becomes f IF1 = f LO2 + f IF2 , or by the first intermediate frequency f IF1 = f LO2 + f IF2 becomes f IF1 = f LO2 - f IF2 , the spurious problem caused by the leakage of the local oscillator signal can be solved.

[0039] The present embodiment aims at innovating in the circuit architecture. The above embodiment is only one implementation form of the present invention. Those skilled in the art should understand that no matter how the circuit is specifically implemented inside each circuit unit, and no matter how the phase shift degree and the number of bits of the digitally controlled phase shifter are adjusted in other forms, all frequency conversion circuits that implement the image suppression switching function according to the circuit architecture proposed in the present invention are protected within the scope of the claims of the present invention.

Claims

1. A monolithic integrated frequency conversion circuit with image suppression switching, characterized in that: include: RF power division and synthesis unit, mixer A unit, mixer B unit, local oscillator phase switching unit, intermediate frequency phase switching unit, intermediate frequency power division and synthesis unit; The combining port P1 of the RF power dividing and synthesizing unit inputs / outputs the RF signal RFSig, the first power dividing port P2 of the RF power dividing and synthesizing unit is connected to the RF port RF of the mixer A unit to transmit the signal RFA, and the second power dividing port P3 of the RF power dividing and synthesizing unit is connected to the RF port RF of the mixer B unit to transmit the signal RFB, which is used to power divide the RF signal RFSig into the signal RFA and the signal RFB or to synthesize the signal RFA and the signal RF into the RF signal RFSig; the first port Q1 of the local oscillator phase switching unit is connected to the local oscillator signal LOI, the second port Q2 is connected to the local oscillator port LO of the mixer A unit, and the third port Q3 is connected to the local oscillator port LO of the mixer B unit, which is used to provide the local oscillator orthogonal signal LOA for the mixer A unit and provide the local oscillator orthogonal signal LOB for the mixer B unit; The intermediate frequency port IF of the mixer A unit is connected to the first port Z1 of the intermediate frequency phase switching unit; The intermediate frequency port IF of the mixer B unit is connected to the second port Z2 of the intermediate frequency phase switching unit; The third port Z3 of the intermediate frequency phase switching unit is connected to the first power division port S2 of the intermediate frequency power division and synthesis unit, and the fourth port Z4 is connected to the second power division port S3 of the intermediate frequency power division and synthesis unit; The combining port S1 of the intermediate frequency power dividing and combining unit inputs / outputs IFSig.

2. A monolithic integrated frequency conversion circuit with image suppression switching according to claim 1, characterized in that: The monolithic integrated frequency conversion circuit with image suppression switching implements a frequency conversion method that supports two working modes: receiving and transmitting; In the receiving working mode, the mixer A unit and the mixer B unit are both in the down-conversion working state; the radio frequency signal RFSig is input from the combining port P1 of the radio frequency power division and synthesis unit, and the power division signal RFA is output to the RF port of the mixer A unit through the first power division port P2, and the power division signal RFB is output to the RF port of the mixer B unit through the second power division port P3; in the mixer A unit, the power division signal RFA and the local oscillator orthogonal signal LOA are mixed to generate the intermediate frequency signal IFA, and in the mixer B unit, the power division signal RFB and the local oscillator orthogonal signal LOB are mixed to generate the intermediate frequency signal IFB; The intermediate frequency signal IFA is subjected to phase shift processing by the intermediate frequency phase switching unit to generate an intermediate frequency signal IFC, and the intermediate frequency signal IFB is subjected to phase shift processing to generate an intermediate frequency signal IFD; The intermediate frequency power division and synthesis unit synthesizes the received intermediate frequency signal IFC and the intermediate frequency signal IFD to obtain an intermediate frequency signal IFSig for output; In the transmitting working mode, the mixer A unit and the mixer B unit are in the up-conversion working state; The intermediate frequency signal IFSig enters from the S1 port of the intermediate frequency power division and synthesis unit, passes through the first power division port S2 and outputs the power division signal IFC, and outputs the power division signal IFD through the second power division port S3; After the intermediate frequency signal IFC is phase-shifted by the intermediate frequency phase switching unit, the intermediate frequency signal IFA is output and transmitted to the IF port of the mixer A unit; After the intermediate frequency signal IFD is phase-shifted by the intermediate frequency phase switching unit, the intermediate frequency signal IFB is output and transmitted to the IF port of the mixer B; in the mixer A unit, the intermediate frequency signal IFA is mixed with the local oscillator orthogonal signal LOA to generate the radio frequency signal RFA; in the mixer B unit, the intermediate frequency signal LOB is mixed with the local oscillator orthogonal signal RFB to generate the radio frequency signal RFA; after the radio frequency signals RFA and RFB are power-synthesized by the radio frequency power division and synthesis unit, the radio frequency signal RFSig is output from the combining port P1 of the radio frequency power division and synthesis unit.

3. The monolithic integrated frequency conversion circuit with image suppression switching according to claim 1, characterized in that: The local oscillator phase switching unit includes a local oscillator amplifying unit, a local oscillator power dividing unit, and a phase shift processing unit; The input end of the local oscillator amplifying unit is the first port Q1 of the local oscillator phase switching unit, connected to the input signal LOI, and the output end is connected to the first input end of the local oscillator power splitter unit; The first output end of the local oscillator power splitting unit is connected to the 0° / +45° local oscillator phase shifting unit, and the second output end of the local oscillator power splitting unit is connected to the 0° / -45° local oscillator phase shifting unit, for power splitting the input signal LOI into the signal LOA and the signal LOB; The phase shift processing unit includes four phase shift units and a local oscillator phase shift control unit; the four phase shift units are a 0° / +45° local oscillator phase shift unit, a 0° / -90° local oscillator phase shift unit, a 0° / -45° local oscillator phase shift unit and a 0° / +90° local oscillator phase shift unit. By combining the 0° / +45° local oscillator phase shift unit and the 0° / -90° local oscillator phase shift unit, a -45° (+45°-90°) and +45° (+45°+0°) phase shift function is generated. The 0° / -45° local oscillator phase shift unit and the 0° / +90° local oscillator phase shift unit are combined. The local oscillator phase shift control unit is provided with a switch, which is respectively connected to the 0° / +45° local oscillator phase shift unit, the 0° / -90° local oscillator phase shift unit, the 0° / -45° local oscillator phase shift unit and the 0° / +90° local oscillator phase shift unit; the corresponding control code can be generated according to the phase shift requirement, and the switching state of the switch is controlled by the control code to complete the phase shift operation, so as to realize the +90° phase difference or -90° phase difference of the local oscillator signal LOA and the local oscillator signal LOB.

4. The monolithic integrated frequency conversion circuit with image suppression switching according to claim 3, characterized in that: The local oscillator amplifying unit is an active amplifier, and the phase shifts of the four local oscillator phase shifting units are all realized by using a digitally controlled phase shifter circuit.

5. The monolithic integrated frequency conversion circuit with image suppression switching according to claim 3, characterized in that: The intermediate frequency phase switching unit is a switch-controlled digitally controlled phase shifter passive circuit, which is used to perform phase shift processing on the intermediate frequency signal IFA and the intermediate frequency signal IFB, and includes: an intermediate frequency phase shift control unit, and four intermediate frequency phase shift units; The four intermediate frequency phase shift units are: 0° / +45° intermediate frequency phase shift unit, 0° / -90° intermediate frequency phase shift unit, 0° / -45° intermediate frequency phase shift unit, and 0° / +90° intermediate frequency phase shift unit. The intermediate frequency phase shift units are combined to generate 45° (+45°-90°) and +45° (+45°+0°) phase shift functions. The intermediate frequency phase shift control unit is equipped with switches, which are respectively connected to the 0° / +45° intermediate frequency phase shift unit, the 0° / -90° intermediate frequency phase shift unit, the 0° / -45° intermediate frequency phase shift unit, and the 0° / +90° intermediate frequency phase shift unit; it can generate corresponding control codes according to the phase shift requirements, and control the switching state of the switch through the control code to complete the phase shift operation, thereby achieving a +90° phase difference or a -90° phase difference between the intermediate frequency signal IFA and the intermediate frequency signal IFB.

6. The monolithic integrated frequency conversion circuit with image suppression switching according to claim 1, characterized in that: The structures and parameters of the frequency mixing unit A and the frequency mixing unit B are the same.

7. The monolithic integrated frequency conversion circuit with image suppression switching according to claim 1, characterized in that: The radio frequency power division and synthesis unit and the intermediate frequency power division and synthesis unit both adopt equal power distribution.

8. According to claim 1, a monolithic integrated frequency conversion circuit with image suppression switching is characterized in that: when the image suppression function is not needed, the two local oscillator signals can achieve a phase difference of 0°, and the two intermediate frequency signals can achieve a phase difference of 0°, and there is no image suppression function at this time.

9. A superheterodyne system, characterized in that: It comprises a monolithic integrated frequency conversion circuit with image suppression switching as claimed in any one of claims 1 to 8.

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