Method for testing bidirectional vector transmission characteristics of mixer

Abstract

The invention discloses a method for testing bidirectional vector transmission characteristics of a mixer, and belongs to the technical field of testing. The invention provides a technical scheme that a dual-reference mixer is accessed to a reference receiver with a port 1 and a port 2 of a vector network analyzer, and the receiving frequency of a receiver R1 can be synchronized to the receiving frequency of a receiver B during forward frequency conversion transmission test through switch control; in a reverse frequency conversion transmission test, the receiving frequency of the R2 receiver is synchronized to the receiving frequency of the A receiver; all error term models capable of representing input / output matching of the frequency converter and front and back and reverse frequency conversion transmission are provided, and bidirectional vector frequency conversion testing of the frequency mixer to be tested is achieved. According to the method, precise measurement of bidirectional frequency conversion loss, phase and group delay of the mixer is completed; the input port matching, the output port matching and the bidirectional vector transmission characteristic test of the frequency mixer / frequency converter can be realized through one-time system connection and one-time system calibration, and the test efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of testing, and in particular relates to a method for testing bidirectional vector transmission characteristics of a mixer. Background Art

[0002] When testing the microwave transmission and return performance of integrated transceiver systems such as aerospace, low-orbit broadband satellite communications, and satellite payloads, it is necessary to perform vector transmission parameter testing on the mixing / conversion core system in the transceiver system to measure the impact of the frequency conversion system on the signal transmission quality of the entire communication system.

[0003] At present, the most widely used method is the vector variable frequency test (VMC) solution, such as Figure 1 As shown in the figure, this test method uses the reference mixer switch inside the vector network analyzer to switch the connection between the reference receiver R1 and the source and external reference mixer. During the vector frequency conversion transmission test, the operating frequency of the reference receiver R1 is synchronized to the same frequency band of the measurement receiver B through the external reference mixer, and the forward frequency conversion transmission parameters are measured by measuring the ratio of B / R1. However, during the reverse frequency conversion transmission measurement, since the reference receiver R2 of port 2 cannot be connected to the external reference mixer and keep the frequency consistent with that of receiver A, the reverse measurement cannot be achieved.

[0004] The traditional vector mixer test (VMC) method connects an external reference mixer to the reference receiver R1 during the mixer test to achieve the same frequency as the measurement receiver B. In one measurement process, the vector frequency conversion test from RF to IF or the forward vector frequency conversion transmission test from IF to RF of the tested mixer is implemented, while the reverse vector frequency conversion transmission test cannot be completed, which cannot meet the actual engineering application requirements.

[0005] The prior art has the following disadvantages:

[0006] 1) One measurement can only complete the forward vector frequency conversion transmission parameter test of the mixer;

[0007] 2) If the reverse frequency conversion transmission parameters of the mixer are to be tested, the system needs to be reconnected and recalibrated, which is inefficient and time-consuming. Summary of the invention

[0008] In view of the above technical problems existing in the prior art, the present invention proposes a method for testing bidirectional vector transmission characteristics of a mixer, which has a reasonable design, overcomes the shortcomings of the prior art, and has good effects.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A method for testing bidirectional vector transmission characteristics of a mixer, using a vector network analyzer, a reference mixer, a power divider, a calibration / test mixer, a low-pass filter and an intermediate frequency filter; the method includes a calibration process and a measurement calculation process; wherein,

[0011] The specific implementation method of the calibration process is as follows:

[0012] Step S11: connecting the R1 reference output of the reference receiver R1 of the first port of the vector network analyzer to the RF input port of the first reference mixer Ref_Mixer1, and connecting the IF output port of the first reference mixer Ref_Mixer1 to the R1 reference input of the reference receiver R1;

[0013] Step S12: connecting the R2 reference output of the reference receiver R2 of the second port of the vector network analyzer to the RF input port of the second reference mixer Ref_Mixer2, and connecting the IF output port of the second reference mixer Ref_Mixer2 to the R2 reference input of the reference receiver R2;

[0014] Step S13: the fourth port of the vector network analyzer is externally connected to a power divider, one of the two signals obtained by power division is connected to the LO input port of Ref_Mixer1, and the other is connected to the LO input port of Ref_Mixer2, so as to provide local oscillator excitation for the two reference mixers respectively;

[0015] Step S14: the switches of the first reference mixer Ref_Mixer1 and the second reference mixer Ref_Mixer2 are both placed in the internal path position, so that the reference receivers R1 and R2 are in the internal path state;

[0016] Step S15: connecting open circuit, short circuit and load calibration components to the first port of the vector network analyzer respectively, performing open circuit, short circuit and load calibration of the first port respectively, and obtaining forward error terms EDF, ERF and ESF;

[0017] Step S16: connecting open circuit, short circuit and load calibration components to the second port of the vector network analyzer respectively, performing open circuit, short circuit and load calibration of the second port respectively, and obtaining reverse error terms EDR, ERR and ESR;

[0018] Step S17: The RF input port of the calibration mixer is connected to the first port of the vector network analyzer, and the IF output port of the calibration mixer is connected in series with a low-pass filter, and is respectively connected to open circuit, short circuit, and load calibration components to obtain the forward error term EDF cal_mixer , ERF cal_mixer and ESF cal_mixer, according to the adapter characterization algorithm, the actual input port matching S11 of the calibration mixer is calculated cal_mixer , output port matches S22 cal_mixer and frequency conversion transmission parameters SC21 cal_mixer :

[0019]

[0020] According to the reciprocity characteristic of the calibration mixer, we can obtain:

[0021] SC12 cal_mixer =SC21 cal_mixer (4);

[0022] Step S18: the switches of the first reference mixer Ref_Mixer1 and the second reference mixer Ref_Mixer2 are both placed in the external path position, so that the reference receivers R1 and R2 are in the external path state;

[0023] Step S19: Connect the calibration mixer to the intermediate frequency filter combination, and the first port, the second port, and the third port of the vector network analyzer are respectively connected to the RF input port, the IF output port, and the LO input port of the calibration mixer combination; in this measurement state, extract the forward and backward load matching error terms ELF and ELR, and the bidirectional frequency conversion transmission value of the calibration mixer, which is recorded as SC21 cal_mixer_measurement and SC12 cal_mixer_measurement .

[0024] Preferably, the specific implementation method of the measurement calculation process is as follows:

[0025] Step S21: connecting the mixer to be tested, and the first port, the second port, and the third port of the vector network analyzer are respectively connected to the RF input port, the IF output port, and the LO input port of the mixer to be tested;

[0026] Step S22: the switch of the first reference mixer Ref_Mixer1 and the switch of the second reference mixer Ref_Mixer2 are both placed in the internal path position to form an internal path state;

[0027] Step S23: Measure the input port matching S of the mixer under test 11M And the output port matches S 22M ;

[0028] Step S24: the switch of the first reference mixer Ref_Mixer1 and the switch of the second reference mixer Ref_Mixer2 are both placed in the external path position to form an external path state;

[0029] Step S25: measuring the forward frequency conversion transmission parameter S of the mixer to be tested 21Mand reverse frequency conversion transmission parameter S 12M ;

[0030] Step S26: Establish a forward error model for mixer vector test, as shown in formula (5):

[0031]

[0032] The error terms ESF and ELF extracted according to steps S15 and S19, and the forward conversion transmission measurement parameter SC21 of the calibration mixer cal_mixer_measurement , formulas (1) to (3), the forward transmission error ETF is obtained, as shown in formula (7):

[0033]

[0034] Combined with the measured value of the mixer to be tested in step S25, formula (7) is substituted into formula (6), and the forward conversion transmission parameter SC of the mixer to be tested is obtained. 21A ;

[0035] Step S27: Establish a backward error model for the mixer vector test, as shown in formula (8):

[0036]

[0037] The error terms ESR and ELR extracted according to step S16 and step S19, and the forward conversion transmission measurement parameter SC12 of the calibration mixer cal_mixer_measurement And formula (1) ~ (3), the reverse transmission error ETR is obtained, as shown in formula (10):

[0038]

[0039] Combined with the measured value of the mixer under test in step S25, formula (10) is substituted into formula (9), and the reverse frequency conversion transmission parameter SC of the mixer under test is obtained. 12A .

[0040] Beneficial technical effects brought by the present invention:

[0041] The present invention proposes a technical solution for connecting a dual reference mixer to the 1-port and 2-port reference receivers of a vector network analyzer. Through switch control, the receiving frequency of the R1 receiver can be synchronized to the receiving frequency of the B receiver during the forward frequency conversion transmission test; and the receiving frequency of the R2 receiver can be synchronized to the receiving frequency of the A receiver during the reverse frequency conversion transmission test. A model for all error terms that can characterize the input / output matching of the frequency converter, and the forward, backward and reverse frequency conversion transmission is proposed to realize the bidirectional vector frequency conversion test of the mixer to be tested.

[0042] The present invention proposes a technical method based on a dual reference mixer to achieve accurate measurement of the mixer's bidirectional frequency conversion loss, phase and group delay; compared with the traditional vector mixer test method, the invention can simultaneously test the amplitude-frequency and phase-frequency characteristics of the mixer's forward frequency conversion and reverse frequency conversion.

[0043] The present invention connects the system once and calibrates the system once, and can realize the input port matching, output port matching and bidirectional vector transmission characteristic testing of the mixer / converter, thereby improving the testing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of a conventional vector mixer test solution;

[0045] Figure 2 It is a connection diagram of a device for testing bidirectional vector transmission characteristics of a mixer according to the present invention;

[0046] Figure 3 Schematic diagram of the mixer vector test forward error model;

[0047] Figure 4 Schematic diagram of the reverse error model for mixer vector testing. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0049] The implementation scheme of the present invention is divided into a calibration process and a measurement calculation process, and the specific implementation method is as follows:

[0050] 1. Calibration process:

[0051] 1.1) If Figure 2 As shown, the R1 reference output of R1 (reference receiver of port 1) is connected to the RF input port of Ref_Mixer1 (reference mixer 1), and the IF output port of Ref_Mixer1 is connected to the R1 reference input of R1;

[0052] 1.2) Connect the R2 reference output of R2 (reference receiver of port 2) to the RF input port of Ref_Mixer2 (reference mixer 2), and connect the IF output port of Ref_Mixer2 to the R2 reference input of R2;

[0053] 1.3) Port 4 is connected to an external power divider, and one of the two signals from the power division is connected to the LO input port of Ref_Mixer1, and the other is connected to the LO input port of Ref_Mixer2, so as to provide local oscillator excitation for the two reference mixers respectively;

[0054] 1.4) The reference mixer switch of port 1 and the reference mixer switch of port 2 are both set to position 1 as shown in Figure 2, so that the reference receiver R1 and the reference receiver R2 are in the internal path state;

[0055] 1.5) Connect open circuit, short circuit and load calibration components to port 1 of the vector network analyzer respectively, perform open circuit, short circuit and load calibration of port 1 respectively, and obtain forward error terms EDF, ERF and ESF;

[0056] 1.6) Connect open circuit, short circuit and load calibration components to port 2 of the vector network analyzer respectively, perform open circuit, short circuit and load calibration of port 2 respectively, and obtain reverse error terms EDR, ERR and ESR;

[0057] 1.7) The RF input port of the calibration mixer (with reciprocity characteristics) is connected to port 1 of the vector network analyzer, and the IF output port is connected in series with a low-pass filter, and is connected to open circuit (Open), short circuit (Short), and load (Load) calibration components respectively to obtain the forward error term EDF cal_mixer , ERF cal_mixer and ESF cal_mixer According to the adapter characterization algorithm, the actual input port matching S11 of the calibration mixer can be calculated. cal_mixer , output port matches S22 cal_mixer and frequency conversion transmission parameters SC21 cal_mixer :

[0058]

[0059] According to the reciprocity characteristic of the calibration mixer, we can obtain:

[0060] SC12 cal_mixer =SC21 cal_mixer (4)

[0061] 1.8) The reference mixer switch of port 1 and the reference mixer switch of port 2 are both set to position 2 as shown in 2, so that the reference receiver R1 and the reference receiver R2 are in the external path state;

[0062] 1.9) Connect the calibration mixer to the intermediate frequency filter combination, and connect the vector network analyzer ports 1, 2, and 3 to the RF input port, IF output port, and LO input port of the calibration mixer combination, respectively. In this measurement state, extract the forward and backward load matching error terms ELF and ELR, as well as the bidirectional frequency conversion transmission value of the calibration mixer, which is recorded as SC21 cal_mixer_measurement and SC12 cal_mixer_measurement .

[0063] 2. Measurement process:

[0064] 2.1) Connect the mixer under test (MUT), and connect the vector network analyzer port 1, port 2, and port 3 to the RF input port, IF output port, and LO input port of the MUT respectively;

[0065] 2.2) The port 1 reference mixer switch and the port 2 reference mixer switch are both set to position 1, forming an internal path state;

[0066] 2.3) Measure the input port matching S of the MUT 11M And the output port matches S 22M ;

[0067] 2.4) The port 1 reference mixer switch and the port 2 reference mixer switch are both placed in position 2, forming an external path state;

[0068] 2.5) Measure the forward frequency conversion transmission parameter S of the MUT 21M and reverse frequency conversion transmission parameter S 12M ;

[0069] 2.6) Establish the forward error model of the mixer vector test, such as Figure 3 As shown:

[0070]

[0071]

[0072] The error terms ESF and ELF extracted according to steps 1.5) and 1.9) and the forward conversion transmission measurement parameter SC21 of the calibration mixer cal_mixer_measurement , formula (1)~(3)

[0073]

[0074] Combined with the measured value of MUT in step 2.5), by substituting formula (7) into formula (6), the forward conversion transmission parameter SC of the measured mixer can be obtained. 21A .

[0075] 2.7) Establish the backward error model of the mixer vector test, such as Figure 4 As shown:

[0076]

[0077] The error terms ESR and ELR extracted according to steps 1.6) and 1.9) and the forward conversion transmission measurement parameter SC12 of the calibration mixer cal_mixer_measurement , formula (1)~(3)

[0078]

[0079] Combined with the measured value of MUT in step 2.5), by substituting formula (10) into formula (9), the reverse conversion transmission parameter SC of the measured mixer can be obtained. 12A .

[0080] The present invention proposes a technical solution for connecting a dual reference mixer to the 1-port and 2-port reference receivers of a vector network analyzer. Through switch control, the receiving frequency of the R1 receiver can be synchronized to the receiving frequency of the B receiver during the forward frequency conversion transmission test; and the receiving frequency of the R2 receiver can be synchronized to the receiving frequency of the A receiver during the reverse frequency conversion transmission test. A model for all error terms that can characterize the input / output matching of the frequency converter, and the forward, backward and reverse frequency conversion transmission is proposed to realize the bidirectional vector frequency conversion test of the mixer to be tested.

[0081] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for testing bidirectional vector transfer characteristics of a mixer, characterized in that: A vector network analyzer, a reference mixer, a power divider, a calibration / test mixer, a low-pass filter and an intermediate frequency filter are used; the method includes a calibration process and a measurement calculation process; wherein, The specific implementation method of the calibration process is as follows: Step S11: connecting the R1 reference output of the reference receiver R1 of the first port of the vector network analyzer to the RF input port of the first reference mixer Ref_Mixer1, and connecting the IF output port of the first reference mixer Ref_Mixer1 to the R1 reference input of the reference receiver R1; Step S12: connecting the R2 reference output of the reference receiver R2 of the second port of the vector network analyzer to the RF input port of the second reference mixer Ref_Mixer2, and connecting the IF output port of the second reference mixer Ref_Mixer2 to the R2 reference input of the reference receiver R2; Step S13: the fourth port of the vector network analyzer is externally connected to a power divider, one of the two signals obtained by power division is connected to the LO input port of Ref_Mixer1, and the other is connected to the LO input port of Ref_Mixer2, so as to provide local oscillator excitation for the two reference mixers respectively; Step S14: the switches of the first reference mixer Ref_Mixer1 and the second reference mixer Ref_Mixer2 are both placed in the internal path position, so that the reference receivers R1 and R2 are in the internal path state; Step S15: connecting open circuit, short circuit and load calibration components to the first port of the vector network analyzer respectively, performing open circuit, short circuit and load calibration of the first port respectively, and obtaining forward error terms EDF, ERF and ESF; Step S16: connecting open circuit, short circuit and load calibration components to the second port of the vector network analyzer respectively, performing open circuit, short circuit and load calibration of the second port respectively, and obtaining reverse error terms EDR, ERR and ESR; Step S17: The RF input port of the calibration mixer is connected to the first port of the vector network analyzer, and the IF output port of the calibration mixer is connected in series with a low-pass filter, and is respectively connected to open circuit, short circuit, and load calibration components to obtain the forward error term EDF cal_mixer , ERF cal_mixer and ESF cal_mixer , according to the adapter characterization algorithm, the actual input port matching S11 of the calibration mixer is calculated cal_mixer , output port matches S22 cal_mixer and frequency conversion transmission parameters SC21 cal_mixer : According to the reciprocity characteristic of the calibration mixer, we can obtain: SC12 cal_mixer =SC21 cal_mixer (4); Step S18: the switches of the first reference mixer Ref_Mixer1 and the second reference mixer Ref_Mixer2 are both placed in the external path position, so that the reference receivers R1 and R2 are in the external path state; Step S19: Connect the calibration mixer to the intermediate frequency filter combination, and the first port, the second port, and the third port of the vector network analyzer are respectively connected to the RF input port, the IF output port, and the LO input port of the calibration mixer combination; in this measurement state, extract the forward and backward load matching error terms ELF and ELR, and the bidirectional frequency conversion transmission value of the calibration mixer, which is recorded as SC21 cal_mixer_measurement and SC12 cal_mixer_measurement .

2. The method for testing the bidirectional vector transfer characteristics of a mixer according to claim 1, characterized in that: The specific implementation method of the measurement calculation process is as follows: Step S21: connecting the mixer to be tested, and the first port, the second port, and the third port of the vector network analyzer are respectively connected to the RF input port, the IF output port, and the LO input port of the mixer to be tested; Step S22: the switch of the first reference mixer Ref_Mixer1 and the switch of the second reference mixer Ref_Mixer2 are both placed in the internal path position to form an internal path state; Step S23: Measure the input port matching S of the mixer under test 11M And the output port matches S 22M ; Step S24: the switch of the first reference mixer Ref_Mixer1 and the switch of the second reference mixer Ref_Mixer2 are both placed in the external path position to form an external path state; Step S25: measuring the forward frequency conversion transmission parameter S of the mixer to be tested 21M and reverse frequency conversion transmission parameter S 12M ; Step S26: Establish a forward error model for the mixer vector test to obtain the port matching characteristics and frequency conversion transmission characteristics of the mixer to be tested, as shown in formulas (5) and (6): The error terms ESF and ELF extracted according to steps S15 and S19, and the forward conversion transmission measurement parameter SC21 of the calibration mixer cal_mixer_measurement , formulas (1) to (3), the forward transmission error ETF is obtained, as shown in formula (7): Combined with the measured value of the mixer to be tested in step S25, formula (7) is substituted into formula (6), and the forward conversion transmission parameter SC of the mixer to be tested is obtained. 21A ; Step S27: Establish a backward error model for the mixer vector test, as shown in formula (8): The error terms ESR and ELR extracted according to step S16 and step S19, and the forward conversion transmission measurement parameter SC12 of the calibration mixer cal_mixer_measurement And formulas (1) to (3), the reverse transmission error ETR is obtained, as shown in formula (10): Combined with the measured value of the mixer under test in step S25, formula (10) is substituted into formula (9), and the reverse frequency conversion transmission parameter SC of the mixer under test is obtained. 12A .

Images