Test method of mixer

Abstract

The invention discloses a frequency mixer test method, and relates to the technical field of microwave radio frequency test, and the method comprises the following steps: S1, building a test platform; s2, calibrating the test platform; s3, testing indexes; and according to the received reflection signal and standing wave signal, port isolation test, frequency conversion loss test, port standing wave test and output 1dB compression point test are carried out on the mixer to be tested, and a test curve of each index is drawn after the test is completed. According to the method, all key indexes of the mixer can be tested at different power frequency points through one-time calibration, meanwhile, standing wave testing of the LO port under high power can be achieved, the testing efficiency and accuracy are greatly improved, and the technical problems that in the prior art, multiple times of calibration are needed in the testing process, and the testing efficiency is low are solved.

Description

Technical Field

[0001] This invention relates to the field of microwave radio frequency testing technology, and more specifically to a test method for a mixer. Background Technology

[0002] With the continuous development of aerospace technology, the demand for phased array radar is also increasing. As the core frequency conversion unit in the radio frequency / microwave system, the performance of the mixer directly determines the signal quality and stability of the entire radar system. Therefore, the testing technology of the mixer is a key link to ensure the reliable operation of the system.

[0003] Mixer performance testing has always been a key and challenging area in microwave testing. Conventional testing methods involve using a spectrum analyzer and signal source to adjust a single frequency point to test the isolation of the mixer port, and then using a vector network analyzer to test the standing wave ratio (SWR) of the mixer port. For mixers with high LO port drive power, an external control signal source is required to drive them, making it impossible to test the SWR of the LO port. This results in incomplete test performance coverage and requires multiple calibrations and manual testing, leading to low testing efficiency.

[0004] In addition, patent document CN119341664A discloses an efficient testing method and system for millimeter-wave terahertz mixers. The testing method includes: confirming the test frequency band and building a test platform; confirming the operating frequency bands of the RF, LO, and IF ports of the mixer under test; building either a first or second test platform based on the operating frequency band information of the mixer under test; controlling the output power of the terahertz S-parameter test module based on the communication between the vector network analyzer host and the terahertz S-parameter test module; and testing the characteristics of the mixer under test under different port output powers, including frequency conversion loss testing, compression point testing, port standing wave ratio testing, and isolation testing. This testing method has the advantages of simple testing process, high testing efficiency, and low testing cost. However, careful analysis reveals the following technical problems: 1. Since the LO drive power of most mixers is much higher than the power that the vector network analyzer can provide, especially for high-frequency mixers, when the local oscillator output power is higher than the power that the vector network analyzer can output, an external power amplifier must be used for testing. However, this technology does not take into account the issue of external power amplifiers, making it unsuitable for testing high-power mixers.

[0005] 2. This test method requires recalibration when testing different indicators, such as isolation test and gain compression test, which leads to low test efficiency, especially for batch device testing, the process is more cumbersome.

[0006] 3. The test method disclosed in the instruction manual allows for setting different local oscillator power and intermediate frequency to obtain information on compression point changes under different conditions. This makes the test process a point-to-point operation. If the power and frequency are changed, all indicators need to be retested, which still results in low test efficiency.

[0007] Therefore, it is necessary to propose a new technology that can reduce the calibration process and improve testing efficiency. Summary of the Invention

[0008] To address the shortcomings and defects of the existing technology, this invention proposes a test method for mixers. This method can achieve the testing of all key indicators of the mixer at different power frequencies through a single calibration, and can also achieve standing wave testing of the LO port at high power, which greatly improves the testing efficiency and accuracy, and solves the technical problem that the existing technology requires multiple calibrations and has low testing efficiency.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for testing a mixer includes the following steps: S1. Setting up the test platform The setup includes a host computer, a vector network analyzer, a spectrum analyzer, a power amplifier, a power divider, a reverse directional coupler, and a mixer under test. The vector network analyzer has a first transceiver port, a second receive port, a third transmit port, and a fourth transceiver port. The first transceiver port is connected to the RF port of the mixer under test, and the third transmit port is connected to the power amplifier. The power divider is connected to the IF port of the mixer under test, and then connected to both the spectrum analyzer and the fourth transceiver port. The reverse directional coupler is connected to the LO port of the mixer under test, and then connected to both the power amplifier and the second receive port. The host computer is connected to both the vector network analyzer and the spectrum analyzer. S2. Calibration Test Platform According to the test frequency band requirements of the mixer under test, the first transceiver port, the third transmit port and the fourth transceiver port are set to the mixer calibration mode. The calibration facets are set on the facets connected to the RF port, IF port and LO port respectively. The second receive port is set to receiver mode. The receiver calibration frequency covers the frequency range of the LO port and the RF port. The calibration facet is set on the facet of the second receive port. After the settings are completed, power calibration and receiver calibration are performed. S3. Indicator Test The control vector network analyzer outputs a local oscillator signal through the third transmit port. After being amplified by a power amplifier, the signal is input to the LO port through a reverse directional coupler to drive the mixer under test. The reflected signal from the LO port is received by the second receive port. The control vector network analyzer inputs a radio frequency signal to the RF port through the first transceiver port and receives the reflected signal from the RF port. The control fourth transceiver port transmits a test signal to the IF port and controls the spectrum analyzer and the fourth transceiver port to receive the standing wave signal reflected from the IF port. The host computer controls the vector network analyzer and the spectrum analyzer to perform port isolation, conversion loss, port standing wave, and output 1dB compression point tests on the mixer under test based on the received reflected and standing wave signals. After the tests are completed, the test curves for each indicator are plotted.

[0010] The calibration test platform also includes calibrating the input power of the spectrum analyzer using a vector network analyzer. The specific calibration process is as follows: a calibration trace is created on the test interface of the vector network analyzer, and the input power curve of the spectrum analyzer is obtained. The input power curve is compared with the calibration trace. If there is a difference between the input power curve and the calibration trace at the same frequency point, the input power at the corresponding frequency point is compensated according to the difference to achieve calibration.

[0011] The specific method for testing the aforementioned indicators is as follows: S11. Based on the received reflected signal and standing wave signal, create index traces including R1, a1, R3, R4, b1, b3, d1, d3, and d4 on the test interface of the vector network analyzer, and create the power trace Pm in the test frequency band of the mixer under test on the test interface of the spectrum analyzer. Where R1, R3, and R4 represent the source output power curves of the first transceiver port, the third transmit port, and the fourth transceiver port at the calibration end face; a1, b1, and d1 represent the power curves received by the first transceiver port, the second receive port, and the fourth transceiver port at the same frequency as the first transceiver port; b3 and d3 represent the power curves received by the second receive port and the fourth transceiver port at the same frequency band as the third transmit port; d4 represents the power curve received by the fourth transceiver port at the same frequency band as the fourth transceiver port; and Pm represents the power value of the spectrum analyzer at a specific frequency point.

[0012] S12. Use the host computer to control the vector network analyzer and spectrum analyzer to capture the values ​​of the index trace and power trace at specific frequency points, and calculate the port isolation, frequency conversion loss, port standing wave ratio and output 1dB compression point corresponding to each frequency point. After the port isolation, frequency conversion loss, port standing wave ratio and output 1dB compression point of all frequency points have been tested, plot the test curves of each index.

[0013] The formula for calculating the port isolation is: IS RF-LO =R1-(b1+ IL 2-3-2 ) IS RF-IF =R1-(P m +IL 1-2-IN ) IS LO-IF =R3-( P m + IL 1-2-IN ) In the formula, IS RF-LO IS represents the isolation between port RF and port LO. RF-IF IS represents the isolation level between port RF and port IF. LO-IF This indicates the isolation from port LO to port IF; R1, R3, and b1 represent the values ​​corresponding to each frequency point on the indicator trace, respectively; IL 2-3-2 IL represents the insertion loss value of the cable connecting the reverse directional coupler to the second receiving port. 1-2-IN This indicates the insertion loss value of the cable connecting the power divider to the fourth transceiver port. These two insertion loss values ​​can be obtained by testing after calibration.

[0014] The formula for calculating the port standing wave is: P RF =R1-a1 P IF =R4-d4 P LO =R3-( IL 2-3-2 +b3) In the formula, P RF P IF and P LO These represent the standing waves (SWR) at ports RF, IF, and LO, respectively; a1, d4, and b3 represent the values ​​corresponding to each frequency point on the index trace, respectively; IL 2-3-2 This indicates the insertion loss value of the cable connecting the reverse directional coupler to the second receiving port.

[0015] The formula for calculating the frequency conversion loss is: SC RF-IF =R1-d4 In the formula, SC RF-IF This indicates the frequency conversion loss between port RF and port IF.

[0016] The 1dB compression point is calculated as follows: the power value of the fixed LO port on the index trace R3 remains unchanged, and the power value R1 of the first transceiver port is slowly increased to R1. p Meanwhile, the power value on the power trace Pm is P mLet the power difference before the power increase be ΔP0 = R1 - P. m After increasing the power value, the difference between the two power values ​​is ΔP. p =R1 p -P m When ΔP0-ΔP p When ≈1, record R1 at this time. p That is, the output 1dB compression point P1 IF .

[0017] The test platform also includes a switch, through which the host computer is connected to the vector network analyzer and the spectrum analyzer respectively.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By connecting a host computer with test instruments such as a vector network analyzer and a spectrum analyzer, the host computer can automatically control the data aggregation after testing a single frequency point. The test method is flexible and efficient, and the result curve can be generated on the host computer interface for easy test data analysis.

[0019] 2. All key performance indicators of the mixer can be tested through a single calibration. The testing method is simple, widely applicable, and greatly improves the efficiency of mass production testing of products.

[0020] 3. By using a reverse directional coupler at the LO port of the mixer, standing wave ratio (SWR) testing at the LO port under high power can be achieved. At the same time, by using a power divider at the IF port, the test results of the vector network analyzer can be used to perform calibration compensation on the receiver of the spectrum analyzer, ensuring the accuracy of the test results. Attached Figure Description Appendix Figure 1 This is a schematic diagram of the structure of the test platform that has been built. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] This invention provides a method for testing a mixer, specifically including the following steps: S1. Setting up the test platform like Figure 1As shown, the setup includes a host computer, a vector network analyzer, a spectrum analyzer, a power amplifier, a power divider, a reverse directional coupler, and a mixer under test. The vector network analyzer has a first transceiver port 1, a second receive port 2, a third transmit port 3, and a fourth transceiver port 4. The first transceiver port 1 is connected to the RF port of the mixer under test, and the third transmit port 3 is connected to the power amplifier. The power divider is connected to the IF port of the mixer under test, with port 1 of the power divider connected to the IF port. Ports 2 and 3 of the power divider are connected to the spectrum analyzer and the fourth transceiver port 4, respectively. The reverse directional coupler is connected to the LO port of the mixer under test, with port 2 of the reverse directional coupler connected to the LO port. Ports 1 and 3 of the reverse directional coupler are connected to the power amplifier and the second receive port 2, respectively. The host computer is connected to both the vector network analyzer and the spectrum analyzer.

[0023] Furthermore, the test platform also includes a switch, through which the host computer is connected to the vector network analyzer and the spectrum analyzer respectively, thereby enabling communication between the host computer and the vector network analyzer and the spectrum analyzer.

[0024] S2. Calibration Test Platform According to the test frequency band requirements of the mixer under test, the first transceiver port 1, the third transmit port 3, and the fourth transceiver port 4 are set to the mixer calibration mode, and the calibration faces are respectively set on the faces connected to the RF port, IF port, and LO port; the second receive port 2 is set to receiver mode, the receiver calibration frequency covers the frequency range of the LO port and RF port, and the calibration face is set on the face of the second receive port 2; after the settings are completed, power calibration and receiver calibration are performed.

[0025] Furthermore, it also includes using a vector network analyzer to calibrate the input power of the IN terminal of the spectrum analyzer. The specific calibration process is as follows: create a calibration trace on the test interface of the vector network analyzer and obtain the input power curve of the spectrum analyzer. Compare the input power curve with the calibration trace. If there is a difference between the input power curve and the calibration trace at the same frequency point, then compensate the input power at the corresponding frequency point according to the difference to achieve calibration.

[0026] Understandably, the aforementioned calibration traces can be directly created using a vector network analyzer, a function that is built into the vector network analyzer. Calibrating both the vector network analyzer and the spectrum analyzer ensures the accuracy of subsequent performance tests.

[0027] S3. Indicator Test The control vector network analyzer outputs a local oscillator signal through the third transmit port 3. After being amplified by a power amplifier, the signal is input to the LO port through ports 1 and 2 of the reverse directional coupler to drive the mixer under test. The second receive port 2 receives the reflected signal from the LO port through ports 2 and 3 of the reverse directional coupler. The control vector network analyzer inputs a radio frequency signal to the RF port through the first transceiver port 1 and receives the reflected signal from the RF port through the first transceiver port 1. The control fourth transceiver port 4 transmits a test signal to the IF port and controls the spectrum analyzer and the fourth transceiver port 4 to receive the standing wave signal reflected from the IF port through ports 2 and 3 of the power divider. The host computer controls the vector network analyzer and the spectrum analyzer to perform port isolation test, frequency conversion loss test, port standing wave test, and output 1dB compression point test on the mixer under test based on the received reflected signal and standing wave signal. After the test is completed, the test curves of each index are plotted.

[0028] The specific methods for testing the above indicators are as follows: S11. Based on the received reflected signal and standing wave signal, create index traces including R1, a1, R3, R4, b1, b3, d1, d3, and d4 on the test interface of the vector network analyzer, and create the power trace Pm within the test frequency band of the mixer under test on the test interface of the spectrum analyzer.

[0029] Where R1, R3, and R4 represent the source output power curves of the first transceiver port, the third transmit port, and the fourth transceiver port at the calibration end face; a1, b1, and d1 represent the power curves received by the first transceiver port, the second receive port, and the fourth transceiver port at the same frequency as the first transceiver port; b3 and d3 represent the power curves received by the second receive port and the fourth transceiver port at the same frequency band as the third transmit port; d4 represents the power curve received by the fourth transceiver port at the same frequency band as the fourth transceiver port; and Pm represents the power value of the spectrum analyzer at a specific frequency point.

[0030] Similarly, the aforementioned indicator traces and power traces Pm can be directly created using a vector network analyzer and a spectrum analyzer, respectively, as these trace creation functions are built-in features of the vector network analyzer and the spectrum analyzer.

[0031] S12. Use the host computer to control the vector network analyzer and spectrum analyzer to capture the values ​​of the index trace and power trace at specific frequency points, and calculate the port isolation, frequency conversion loss, port standing wave ratio and output 1dB compression point corresponding to each frequency point. After the port isolation, frequency conversion loss, port standing wave ratio and output 1dB compression point of all frequency points have been tested, plot the test curves of each index.

[0032] Specifically, the formula for calculating port isolation is: ISRF-LO =R1-(b1+ IL 2-3-2 ) IS RF-IF =R1-(P m +IL 1-2-IN ) IS LO-IF =R3-( P m + IL 1-2-IN ) In the formula, IS RF-LO IS represents the isolation between port RF and port LO. RF-IF IS represents the isolation level between port RF and port IF. LO-IF This indicates the isolation from port LO to port IF; R1, R3, and b1 represent the values ​​corresponding to each frequency point on the indicator trace, respectively; IL 2-3-2 IL represents the insertion loss value of the cable connecting the reverse directional coupler to the second receiving port. 1-2-IN This indicates the insertion loss value of the cable connecting the power divider to the fourth transceiver port. These two insertion loss values ​​can be obtained by testing after calibration.

[0033] Specifically, the formula for calculating port standing wave ratio is: P RF =R1-a1 P IF =R4-d4 P LO =R3-( IL 2-3-2 +b3) In the formula, P RF P IF and P LO These represent the standing waves (SWR) at ports RF, IF, and LO, respectively; a1, d4, and b3 represent the values ​​corresponding to each frequency point on the index trace, respectively; IL 2-3-2 This indicates the insertion loss value of the cable connecting the reverse directional coupler to the second receiving port.

[0034] Specifically, the formula for calculating frequency conversion loss is as follows: SC RF-IF =R1-d4 In the formula, SC RF-IF This indicates the frequency conversion loss between port RF and port IF.

[0035] Specifically, the 1dB compression point is calculated as follows: the power value of the fixed LO port on the indicator trace R3 remains constant, while the power value R1 of the first transceiver port is slowly increased to R1. p Meanwhile, the power value on the power trace Pm is P m Let the power difference before the power increase be ΔP0 = R1 - P. mAfter increasing the power value, the difference between the two power values ​​is ΔP. p =R1 p -P m When ΔP0-ΔP p When ≈1, record R1 at this time. p That is, the output 1dB compression point P1 IF .

[0036] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent features unless otherwise specified. All features or steps in all methods or processes disclosed may be combined in any way, except for mutually exclusive features and / or steps.

Claims

1. A method for testing a mixer, characterized in that... Includes the following steps: S1. Setting up the test platform The setup includes a host computer, a vector network analyzer, a spectrum analyzer, a power amplifier, a power divider, a reverse directional coupler, and a mixer under test. The vector network analyzer has a first transceiver port, a second receive port, a third transmit port, and a fourth transceiver port. The first transceiver port is connected to the RF port of the mixer under test, and the third transmit port is connected to the power amplifier. The power divider is connected to the IF port of the mixer under test, and then connected to both the spectrum analyzer and the fourth transceiver port. The reverse directional coupler is connected to the LO port of the mixer under test, and then connected to both the power amplifier and the second receive port. The host computer is connected to both the vector network analyzer and the spectrum analyzer. S2. Calibration Test Platform According to the test frequency band requirements of the mixer under test, the first transceiver port, the third transmit port and the fourth transceiver port are set to the mixer calibration mode. The calibration facets are set on the facets connected to the RF port, IF port and LO port respectively. The second receive port is set to receiver mode. The receiver calibration frequency covers the frequency range of the LO port and the RF port. The calibration facet is set on the facet of the second receive port. After the settings are completed, power calibration and receiver calibration are performed. S3. Indicator Test The control vector network analyzer outputs a local oscillator signal through the third transmit port. After being amplified by a power amplifier, the signal is input to the LO port through a reverse directional coupler to drive the mixer under test. The reflected signal from the LO port is received by the second receive port. The control vector network analyzer inputs a radio frequency signal to the RF port through the first transceiver port and receives the reflected signal from the RF port. The control fourth transceiver port transmits a test signal to the IF port and controls the spectrum analyzer and the fourth transceiver port to receive the standing wave signal reflected from the IF port. The host computer controls the vector network analyzer and spectrum analyzer to perform port isolation test, frequency conversion loss test, port standing wave test and output 1dB compression point test on the mixer under test based on the received reflected signal and standing wave signal, and plots the test curves of each index after the test is completed.

2. The test method for a mixer according to claim 1, characterized in that: The calibration test platform also includes calibrating the input power of the spectrum analyzer using a vector network analyzer. The specific calibration process is as follows: a calibration trace is created on the test interface of the vector network analyzer, and the input power curve of the spectrum analyzer is obtained. The input power curve is compared with the calibration trace. If there is a difference between the input power curve and the calibration trace at the same frequency point, the input power at the corresponding frequency point is compensated according to the difference to achieve calibration.

3. The test method for the mixer according to claim 1 or 2, characterized in that: The specific method for testing the aforementioned indicators is as follows: S11. Based on the received reflected signal and standing wave signal, create index traces including R1, a1, R3, R4, b1, b3, d1, d3, and d4 on the test interface of the vector network analyzer, and create the power trace Pm in the test frequency band of the mixer under test on the test interface of the spectrum analyzer. Where R1, R3, and R4 represent the source output power curves of the first transceiver port, the third transmit port, and the fourth transceiver port at the calibration end face; a1, b1, and d1 represent the power curves received by the first transceiver port, the second receive port, and the fourth transceiver port at the same frequency as the first transceiver port; b3 and d3 represent the power curves received by the second receive port and the fourth transceiver port at the same frequency band as the third transmit port; d4 represents the power curve received by the fourth transceiver port at the same frequency band as the fourth transceiver port; and Pm represents the power value of the spectrum analyzer at a specific frequency point. S12. Use the host computer to control the vector network analyzer and spectrum analyzer to capture the values ​​of the index trace and power trace at specific frequency points, and calculate the port isolation, frequency conversion loss, port standing wave ratio and output 1dB compression point corresponding to each frequency point. After the port isolation, frequency conversion loss, port standing wave ratio and output 1dB compression point of all frequency points have been tested, plot the test curves of each index.

4. The test method for the mixer according to claim 3, characterized in that: The formula for calculating the port isolation is: IS RF-LO =R1-(b1+ IL 2-3-2 ) IS RF-IF =R1-(P m +THE 1-2-IN ) IS LO-IF =R3-( P m + THE 1-2-IN ) In the formula, IS RF-LO IS represents the isolation between port RF and port LO. RF-IF IS represents the isolation level between port RF and port IF. LO-IF This indicates the isolation from port LO to port IF; R1, R3, and b1 represent the values ​​corresponding to each frequency point on the indicator trace, respectively; IL 2-3-2 IL represents the insertion loss value of the cable connecting the reverse directional coupler to the second receiving port. 1-2-IN This indicates the insertion loss value of the cable connecting the power divider to the fourth transceiver port. These two insertion loss values ​​can be obtained by testing after calibration.

5. The test method for a mixer according to claim 3, characterized in that: The formula for calculating the port standing wave is: P RF =R1-a1 P IF =R4-d4 P LO =R3-( IL 2-3-2 +b3) In the formula, P RF P IF and P LO These represent the standing waves (SWR) at ports RF, IF, and LO, respectively; a1, d4, and b3 represent the values ​​corresponding to each frequency point on the index trace, respectively; IL 2-3-2 This indicates the insertion loss value of the cable connecting the reverse directional coupler to the second receiving port.

6. The test method for a mixer according to claim 3, characterized in that: The formula for calculating the frequency conversion loss is: SC RF-IF =R1-d4 In the formula, SC RF-IF This indicates the frequency conversion loss between port RF and port IF.

7. The test method for a mixer according to claim 3, characterized in that: The 1dB compression point is calculated as follows: the power value of the fixed LO port on the index trace R3 remains unchanged, and the power value R1 of the first transceiver port is slowly increased to R1. p Meanwhile, the power value on the power trace Pm is P m Let the power difference before the power increase be ΔP0 = R1 - P. m After increasing the power value, the difference between the two power values ​​is ΔP. p =R1 p -P m When ΔP0-ΔP p When ≈1, record R1 at this time. p That is, the output 1dB compression point P1 IF .

8. The test method for a mixer according to claim 1, characterized in that: The test platform also includes a switch, through which the host computer is connected to the vector network analyzer and the spectrum analyzer respectively.

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