Bidirectional nonlinear testing device and testing method

Abstract

The invention relates to the technical field of testing, in particular to a bidirectional nonlinear testing device and a bidirectional nonlinear testing method.The bidirectional nonlinear testing device comprises a signal source, a first frequency spectrograph, a second frequency spectrograph, a first duplexer, a second duplexer and a load, and the first duplexer is electrically connected with the signal source, the first frequency spectrograph and a piece to be tested; compared with an existing measuring device, the device has the advantages that on the premise that the number of signal sources is not increased, the direction of measuring the nonlinearity of the to-be-measured piece is increased, and a platform is provided for comprehensively evaluating the nonlinearity of the device.

Description

[0001] This case is a divisional application based on the invention patent filed on August 2, 2024, with application number CN202411053992.4, entitled "A Device for Forward and Reverse Nonlinear Testing and Testing Method". Technical Field

[0002] This invention relates to the field of testing technology, and in particular to a bidirectional nonlinear testing device and testing method. Background Technology

[0003] When two or more signals pass through a nonlinear device, the synthesized signal will produce an intermodulation product (IMP). When this product falls into the passband of a nearby receiver, it forms parasitic interference. Multi-band wireless communication systems, where radio frequency multiplexers are used, are a typical application of multi-band wireless communication. The nonlinearity of passive devices and their related structures is a potential source of passive intermodulation (PIM), and the passive intermodulation product (PIMP) can cause relatively serious electromagnetic interference.

[0004] Passive intermodulation measurement systems can be divided into: 1) Radiation type, suitable for the study of radiators (such as antennas, feeders, structural components), placed in an anechoic chamber or open measurement site, and greatly affected by the local signal environment; 2) Non-radiative type, suitable for research on nonlinear materials, connectors, coaxial cables, filters and waveguide devices, placed in a shielded room, with a matching load at the end.

[0005] Among them, the non-radiative type is divided into two categories: reflection (reverse) intermodulation test and propagation (forward) intermodulation test; Existing non-radiative measurement devices can only test intermodulation products in the reflected (reverse) path and cannot evaluate intermodulation products in the forward transmission. These propagating (forward) intermodulation products are coupled and received by other local antennas and enter other local receivers, thus causing intermodulation interference. In order to comprehensively improve the complex electromagnetic environment and enhance the overall electromagnetic compatibility of the communication system, the magnitude of these propagating (forward) intermodulation products also needs to be quantitatively evaluated, and the root cause needs to be located for improvement and optimization. Therefore, there is a particular need for a device and method for measuring the forward and reverse nonlinear products of a device. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a device and method for testing the forward and reverse nonlinearity of a device, which increases the direction of measuring the nonlinearity of the device under test without increasing the number of signal sources, and provides a platform for comprehensively evaluating the nonlinearity of the device.

[0007] To solve the above-mentioned technical problems, the first technical solution adopted by the present invention is as follows: A device for testing forward and reverse nonlinearity includes a signal source, a first spectrum analyzer, a second spectrum analyzer, a first duplexer, a second duplexer, and a load. The first duplexer is electrically connected to the signal source, the first spectrum analyzer, and the device under test (DUT). The second duplexer is electrically connected to the second spectrum analyzer, the load, and the DUT.

[0008] The second technical solution adopted in this invention is: A method for testing the forward and reverse nonlinearity of a device, applied to the aforementioned device forward and reverse nonlinearity testing apparatus, includes the following steps: The signal source transmits a signal, which is then transmitted to the device under test via a first duplexer. The device under test generates nonlinear energy, part of which is reflected and the other part continues to be transmitted after passing through the device under test; The reflected nonlinear energy is transmitted to the first spectrum analyzer via the first duplexer, and the reverse nonlinearity of the device under test is monitored by the first spectrum analyzer; the nonlinear energy that continues to be transmitted through the device under test is transmitted to the load and the second spectrum analyzer via the second duplexer, and the forward nonlinearity of the device under test is monitored by the second spectrum analyzer.

[0009] The beneficial effects of this invention are as follows: This solution involves setting up a signal source, a first spectrum analyzer, a second spectrum analyzer, a first duplexer, a second duplexer, and a load. The first duplexer is electrically connected to the signal source, the first spectrum analyzer, and the device under test (DUT). The second duplexer is electrically connected to the second spectrum analyzer, the load, and the DUT. During testing, the signal source transmits a signal, which, after passing through the first duplexer, delivers high-power excitation energy to the DUT. Due to the nonlinearity of the DUT, harmonic spurious energy is generated. Part of this nonlinear energy is reflected, while the remaining portion continues to be transmitted through the DUT. The reflected nonlinear energy is transmitted to the first spectrum analyzer via the first duplexer, where the reverse nonlinearity of the DUT can be monitored. The nonlinear energy continuing to be transmitted through the DUT is transmitted to the load and the second spectrum analyzer via the second duplexer, where the forward nonlinearity of the DUT can be monitored. Compared to existing measurement devices, this device increases the direction of DUT nonlinearity measurement without increasing the number of signal sources, providing a platform for comprehensively evaluating device nonlinearity. Attached Figure Description

[0010] Figure 1 This is a connection block diagram of the forward and reverse nonlinear testing device of the present invention; Figure 2 This is a flowchart of the forward and reverse nonlinear testing method for the device of the present invention; Label Explanation: 1. Signal source; 2. First spectrum analyzer; 3. Second spectrum analyzer; 4. First duplexer; 401. First bandpass filter; 402. Second bandpass filter; 5. Second duplexer; 501. Third bandpass filter; 502. Fourth bandpass filter; 6. Load; 7. First T-connector stub assembly; 701. First transmission line; 702. Second transmission line; 703. Third transmission line; 8. Second T-connector stub assembly; 801. Fourth transmission line; 802. Fifth transmission line; 803. Sixth transmission line; 9. Power amplifier; 10. Device under test. Detailed Implementation

[0011] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0012] Please refer to Figure 1 The first technical solution adopted in this invention is: A device for testing forward and reverse nonlinearity includes a signal source, a first spectrum analyzer, a second spectrum analyzer, a first duplexer, a second duplexer, and a load. The first duplexer is electrically connected to the signal source, the first spectrum analyzer, and the device under test (DUT). The second duplexer is electrically connected to the second spectrum analyzer, the load, and the DUT.

[0013] As can be seen from the above description, the beneficial effects of the present invention are as follows: This solution involves setting up a signal source, a first spectrum analyzer, a second spectrum analyzer, a first duplexer, a second duplexer, and a load. The first duplexer is electrically connected to the signal source, the first spectrum analyzer, and the device under test (DUT). The second duplexer is electrically connected to the second spectrum analyzer, the load, and the DUT. During testing, the signal source transmits a signal, which, after passing through the first duplexer, delivers high-power excitation energy to the DUT. Due to the nonlinearity of the DUT, harmonic spurious energy is generated. Part of this nonlinear energy is reflected, while the remaining portion continues to be transmitted through the DUT. The reflected nonlinear energy is transmitted to the first spectrum analyzer via the first duplexer, where the reverse nonlinearity of the DUT can be monitored. The nonlinear energy continuing to be transmitted through the DUT is transmitted to the load and the second spectrum analyzer via the second duplexer, where the forward nonlinearity of the DUT can be monitored. Compared to existing measurement devices, this device increases the direction of DUT nonlinearity measurement without increasing the number of signal sources, providing a platform for comprehensively evaluating device nonlinearity.

[0014] Furthermore, the first duplexer includes a first bandpass filter and a second bandpass filter. The first bandpass filter is electrically connected to the signal source and the device under test (DUT) respectively, and the second bandpass filter is electrically connected to the first spectrum analyzer and the DUT respectively.

[0015] Furthermore, it also includes a first T-connector stub assembly, which is a three-port microwave network. The three ports of the first T-connector stub assembly are respectively connected to a first bandpass filter, a second bandpass filter, and the device under test.

[0016] As can be seen from the above description, the first T-joint stub assembly is a three-port microwave network. The T-joint stub assembly has lower insertion loss than the coupling method using other devices, and the insertion loss of the T-joint stub assembly can be further reduced by adjusting the transmission line length. At the same time, the T-joint stub assembly can adjust the corresponding stub length according to the wavelength of the test microwave frequency, and can adapt to the nonlinear measurement of test signals of different frequencies.

[0017] Furthermore, the first T-connector stub assembly includes a first transmission line, a second transmission line, and a third transmission line. One end of the first transmission line is electrically connected to one end of the second transmission line and one end of the third transmission line, respectively. The other end of the first transmission line is electrically connected to a first bandpass filter. The other end of the second transmission line is electrically connected to a second bandpass filter. The other end of the third transmission line is electrically connected to the device under test. The lengths of the first, second, and third transmission lines are set according to the frequency of the first bandpass filter, the frequency of the second bandpass filter, the impedance of the three ports of the first T-joint stub assembly, the dielectric constant of the first transmission line, the dielectric constant of the second transmission line, and the dielectric constant of the third transmission line, so as to minimize the insertion loss of the first T-joint stub assembly.

[0018] As described above, the first T-joint stub assembly includes a first transmission line, a second transmission line, and a third transmission line. In this way, the first T-joint stub assembly can minimize the insertion loss by adjusting the length of the transmission lines, thereby enabling the transmission of stronger excitation signals, capturing weaker harmonics, and achieving good measurement results even for devices with low nonlinearity.

[0019] Furthermore, the second duplexer includes a third bandpass filter and a fourth bandpass filter, the third bandpass filter being electrically connected to the load and the device under test (DUT) respectively, and the fourth bandpass filter being electrically connected to the second spectrum analyzer and the DUT respectively.

[0020] Furthermore, it also includes a second T-connector stub assembly, which is a three-port microwave network. The three ports of the second T-connector stub assembly are respectively connected to a third bandpass filter, a fourth bandpass filter, and the device under test.

[0021] As described above, the second T-joint stub assembly is a three-port microwave network. The T-joint stub assembly has lower insertion loss than coupling methods using other devices, and the insertion loss can be further reduced by adjusting the transmission line length. In addition, the T-joint stub assembly can adjust the corresponding stub length according to the wavelength of the test microwave frequency, which can adapt to the nonlinear measurement of test signals of different frequencies.

[0022] Furthermore, the second T-connector stub assembly includes a fourth transmission line, a fifth transmission line, and a sixth transmission line. One end of the fourth transmission line is electrically connected to one end of the fifth transmission line and one end of the sixth transmission line, respectively. The other end of the fourth transmission line is electrically connected to a third bandpass filter. The other end of the fifth transmission line is electrically connected to the fourth bandpass filter. The other end of the sixth transmission line is electrically connected to the device under test. The lengths of the fourth, fifth, and sixth transmission lines are set according to the frequency of the third bandpass filter, the frequency of the fourth bandpass filter, the impedance of the three ports of the second T-joint stub assembly, the dielectric constant of the fourth transmission line, the dielectric constant of the fifth transmission line, and the dielectric constant of the sixth transmission line, so as to minimize the insertion loss of the second T-joint stub assembly.

[0023] As described above, the second T-joint stub assembly includes a fourth transmission line, a fifth transmission line, and a sixth transmission line. By adjusting the length of the transmission lines, the second T-joint stub assembly can minimize insertion loss, thereby enabling the transmission of stronger excitation signals, capturing weaker harmonics, and achieving good measurement results even for devices with low nonlinearity.

[0024] Furthermore, the load is a low intermodulation load.

[0025] As can be seen from the above description, a load with low intermodulation avoids the influence of parasitic intermodulation on device measurements.

[0026] Furthermore, it also includes a power amplifier, the input of which is electrically connected to the signal source, and the output of which is electrically connected to the first bandpass filter.

[0027] As described above, by setting a power amplifier to amplify the signal generated by the signal source, a stronger excitation signal is ensured to be input to the device under test, thereby further enhancing the detection capability of low nonlinear devices.

[0028] Please refer to Figure 2 The second technical solution adopted in this invention is: A method for testing the forward and reverse nonlinearity of a device, applied to the aforementioned device forward and reverse nonlinearity testing apparatus, includes the following steps: The signal source transmits a signal, which is then transmitted to the device under test via a first duplexer. The device under test generates nonlinear energy, part of which is reflected and the other part continues to be transmitted after passing through the device under test; The reflected nonlinear energy is transmitted to the first spectrum analyzer via the first duplexer, and the reverse nonlinearity of the device under test is monitored by the first spectrum analyzer; the nonlinear energy that continues to be transmitted through the device under test is transmitted to the load and the second spectrum analyzer via the second duplexer, and the forward nonlinearity of the device under test is monitored by the second spectrum analyzer.

[0029] Please refer to Figure 1 Embodiment 1 of the present invention is as follows: A device for testing forward and reverse nonlinearity includes a signal source 1 (with a center frequency of 120MHz, such as an IFR2025 signal source), a first spectrum analyzer 2 (with a center frequency of 360MHz, such as an E4402B spectrum analyzer), a second spectrum analyzer 3 (with a center frequency of 360MHz, such as an E4402B spectrum analyzer), a first duplexer 4, a second duplexer 5, and a load 6 (model TF200-LIM-DIN). The first duplexer 4 is electrically connected to the signal source 1, the first spectrum analyzer 2, and the device under test 10, respectively. The second duplexer 5 is electrically connected to the second spectrum analyzer 3, the load 6, and the device under test 10, respectively.

[0030] The first duplexer 4 includes a first bandpass filter 401 (with a center frequency of 120MHz, which can be a filter of model XH / BPF-12085) and a second bandpass filter 402 (with a center frequency of 360MHz, which can be a filter of model XH / BPF-36085). The first bandpass filter 401 is electrically connected to the signal source 1 and the device under test 10, respectively, and the second bandpass filter 402 is electrically connected to the first spectrum analyzer 2 and the device under test 10, respectively.

[0031] It also includes a first T-connector stub assembly 7, which is a three-port microwave network. The three ports of the first T-connector stub assembly 7 are respectively connected to a first bandpass filter 401, a second bandpass filter 402, and the device under test 10.

[0032] The first T-connector stub assembly 7 includes a first transmission line 701, a second transmission line 702, and a third transmission line 703. One end of the first transmission line 701 is electrically connected to one end of the second transmission line 702 and one end of the third transmission line 703, respectively. The other end of the first transmission line 701 is electrically connected to a first bandpass filter 401. The other end of the second transmission line 702 is electrically connected to a second bandpass filter 402. The other end of the third transmission line 703 is electrically connected to the device under test 10. The lengths of the first transmission line 701, the second transmission line 702, and the third transmission line 703 are set according to the frequency of the first bandpass filter 401, the frequency of the second bandpass filter 402, the impedance of the three ports of the first T-joint stub assembly 7, the dielectric constant of the first transmission line 701, the dielectric constant of the second transmission line 702, and the dielectric constant of the third transmission line 703, so as to minimize the insertion loss of the first T-joint stub assembly 7.

[0033] The first transmission line 701, the second transmission line 702 and the third transmission line 703 are all semi-rigid wires (or other low intermodulation cables), and the first transmission line 701 and the second transmission line 702 are two semi-rigid wires of specific lengths (the length of the first transmission line 701 is 286.6 mm and the length of the second transmission line 702 is 347 mm), while the third transmission line 703 is a semi-rigid wire of unlimited length.

[0034] The second duplexer 5 includes a third bandpass filter 501 (with a center frequency of 120MHz, which can be a filter of model XH / BPF-12085) and a fourth bandpass filter 502 (with a center frequency of 360MHz, which can be a filter of model XH / BPF-36085). The third bandpass filter 501 is electrically connected to the load 6 and the device under test 10, respectively, and the fourth bandpass filter 502 is electrically connected to the second spectrum analyzer 3 and the device under test 10, respectively.

[0035] It also includes a second T-connector stub assembly 8, which is a three-port microwave network. The three ports of the second T-connector stub assembly 8 are respectively connected to a third bandpass filter 501, a fourth bandpass filter 502, and the device under test 10.

[0036] The second T-connector stub assembly 8 includes a fourth transmission line 801, a fifth transmission line 802, and a sixth transmission line 803. One end of the fourth transmission line 801 is electrically connected to one end of the fifth transmission line 802 and one end of the sixth transmission line 803, respectively. The other end of the fourth transmission line 801 is electrically connected to a third bandpass filter 501. The other end of the fifth transmission line 802 is electrically connected to the fourth bandpass filter 502. The other end of the sixth transmission line 803 is electrically connected to the device under test 10. The lengths of the fourth transmission line 801, the fifth transmission line 802, and the sixth transmission line 803 are set according to the frequency of the third bandpass filter 501, the frequency of the fourth bandpass filter 502, the impedance of the three ports of the second T-joint stub assembly 8, the dielectric constant of the fourth transmission line 801, the dielectric constant of the fifth transmission line 802, and the dielectric constant of the sixth transmission line 803, so as to minimize the insertion loss of the second T-joint stub assembly 8.

[0037] The fourth transmission line 801, the fifth transmission line 802, and the sixth transmission line 803 are all semi-rigid wires (or other low intermodulation cables), and the fourth transmission line 801 and the fifth transmission line 802 are two semi-rigid wires of specific lengths (the length of the fourth transmission line 801 is 286.6 mm, and the length of the fifth transmission line 802 is 347 mm), while the sixth transmission line 803 is a semi-rigid wire of unlimited length.

[0038] The load 6 is a low intermodulation load 6.

[0039] It also includes a power amplifier 9, the input of which is electrically connected to the signal source 1, and the output of which is electrically connected to the first bandpass filter 401.

[0040] Based on the PIMP frequency component f in the communication system PIM Statement, f PIM =mf1±nf2, harmonics can be broadly extended to be understood as a type of nonlinear energy when m=0 and n=2 or n=0 and m=2. This energy, along with the third-order intermodulation nonlinear energy when m=2 and n=1 or n=2 and m=1, can quantitatively characterize the nonlinearity of the device under test 10. Moreover, the two methods are consistent in qualitative trends. For example, if device under test A is inferior to device under test B in terms of linearity, then device under test A will also be inferior to device under test B in terms of third-order intermodulation and harmonics. In this way, the relative quality of A and B can be distinguished, which is especially important for scheme demonstration and component selection in the research, development and design of communication systems / equipment.

[0041] The testing process involves signal source 1 transmitting a 120MHz signal, which passes through linear power amplifier 9 and a first bandpass filter 401 at 120MHz. The high-power excitation energy then enters the device under test (DUT) 10. Due to the nonlinearity of DUT 10, some of the generated harmonic spurious energy (including a second harmonic at 240MHz and a third harmonic at 360MHz) is reflected, while the other part continues to be transmitted after passing through DUT 10. The reflected nonlinear energy passes through a second bandpass filter 402 at 360MHz, and the third harmonic is sent to the first spectrum analyzer 2 with a small insertion loss. At this point, the reverse nonlinearity of DUT 10 can be monitored on the first spectrum analyzer 2. The remaining excitation transmitted after passing through DUT 10 is connected to a low intermodulation load 6 through a third bandpass filter 501 at 120MHz. The third harmonic is sent to the second spectrum analyzer 3 through a fourth bandpass filter 502 at 360MHz with a small insertion loss. At this point, the forward nonlinearity of DUT 10 can be monitored on the second spectrum analyzer 3. The nonlinearity of each DUT 10 is compared using forward and reverse quantitative nonlinearity.

[0042] The device under test (DUT) 10 can be an active device or a passive device. The operating frequencies of the first T-connector stub assembly 7 and the second T-connector stub assembly 8 are both determined by the operating frequency of the DUT 10. At the same time, the excitation power output by the power amplifier 9 is also determined by the input power range of the DUT 10.

[0043] Compared with existing measurement devices, this device increases the direction of measuring the nonlinearity of the device under test 10 without increasing the number of signal sources 1, providing a platform for comprehensive evaluation of device nonlinearity.

[0044] In practice, this testing device was used to compare and analyze various specifications of RF switches, RF connectors from multiple manufacturers, and batches of 120MHz bandpass filters (with different internal metal materials, contact strengths, and other related factors). From these, the most suitable RF switches and connectors with the best forward and reverse nonlinearity were selected. The most important material selection and key process standards were also derived. This demonstrates the effectiveness of this testing device in quantitatively comparing the forward and reverse nonlinearity of devices in this frequency band. It is particularly suitable for locating and improving passive intermodulation problems, thereby helping to comprehensively improve complex electromagnetic environments and enhance the overall electromagnetic compatibility of communication systems.

[0045] The principles and methods of this device can provide inspiration and reference for the improvement of intermodulation design of other frequency band communication equipment or components.

[0046] Please refer to Figure 2 Embodiment two of the present invention is as follows: A method for testing the forward and reverse nonlinear products of a device, applied to the device forward and reverse nonlinearity testing apparatus in Example 1, is characterized by comprising the following steps: The signal source 1 transmits a signal, which is transmitted to the device under test 10 via the first duplexer 4. The device under test 10 generates nonlinear energy, part of which is reflected and the other part continues to be transmitted after passing through the device under test 10; The reflected nonlinear energy is transmitted to the first spectrum analyzer 2 via the first duplexer 4, and the reverse nonlinearity of the test device 10 is monitored by the first spectrum analyzer 2; the nonlinear energy that continues to be transmitted through the test device 10 is transmitted to the load 6 and the second spectrum analyzer 3 via the second duplexer 5, and the positive nonlinearity of the test device 10 is monitored by the second spectrum analyzer 3.

[0047] In summary, the present invention provides a bidirectional nonlinear testing device and method. By setting up a signal source, a first spectrum analyzer, a second spectrum analyzer, a first duplexer, a second duplexer, and a load, the first duplexer is electrically connected to the signal source, the first spectrum analyzer, and the device under test (DUT). The second duplexer is electrically connected to the second spectrum analyzer, the load, and the DUT. During testing, the signal source transmits a signal, which, after passing through the first duplexer, delivers high-power excitation energy to the DUT. Due to the nonlinearity of the DUT, harmonic spurious energy is generated. Part of this nonlinear energy is reflected, while the remaining portion continues to be transmitted through the DUT. The reflected nonlinear energy is transmitted to the first spectrum analyzer via the first duplexer, where the reverse nonlinearity of the DUT can be monitored. The nonlinear energy continuing to be transmitted through the DUT is transmitted to the load and the second spectrum analyzer via the second duplexer, where the forward nonlinearity of the DUT can be monitored. Compared to existing measurement devices, this device increases the direction of DUT nonlinearity measurement without increasing the number of signal sources, providing a platform for comprehensively evaluating device nonlinearity.

[0048] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention's specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A bidirectional nonlinear testing device, characterized in that, It includes a signal source, a first spectrum analyzer, a second spectrum analyzer, a first duplexer, a second duplexer, and a load. The first duplexer is electrically connected to the signal source, the first spectrum analyzer, and the device under test (DUT). The second duplexer is electrically connected to the second spectrum analyzer, the load, and the DUT. The first duplexer includes a first bandpass filter and a second bandpass filter. The first bandpass filter is electrically connected to a signal source and a device under test (DUT), respectively, and the second bandpass filter is electrically connected to a first spectrum analyzer and the DUT, respectively. It also includes a first T-connector stub assembly, which is a three-port microwave network. The three ports of the first T-connector stub assembly are respectively connected to a first bandpass filter, a second bandpass filter, and the device under test. The second duplexer includes a third bandpass filter and a fourth bandpass filter. The third bandpass filter is electrically connected to the load and the device under test (DUT) respectively, and the fourth bandpass filter is electrically connected to the second spectrum analyzer and the DUT respectively. It also includes a second T-connector stub assembly, which is a three-port microwave network. The three ports of the second T-connector stub assembly are respectively connected to a third bandpass filter, a fourth bandpass filter, and the device under test. The first T-connector stub assembly includes a first transmission line, a second transmission line, and a third transmission line. One end of the first transmission line is electrically connected to one end of the second transmission line and one end of the third transmission line, respectively. The other end of the first transmission line is electrically connected to a first bandpass filter. The other end of the second transmission line is electrically connected to a second bandpass filter. The other end of the third transmission line is electrically connected to the device under test. The lengths of the first transmission line, the second transmission line, and the third transmission line are set according to the frequency of the first bandpass filter, the frequency of the second bandpass filter, the impedance of the three ports of the first T-joint stub assembly, the dielectric constant of the first transmission line, the dielectric constant of the second transmission line, and the dielectric constant of the third transmission line, so as to minimize the insertion loss of the first T-joint stub assembly. The second T-connector stub assembly includes a fourth transmission line, a fifth transmission line, and a sixth transmission line. One end of the fourth transmission line is electrically connected to one end of the fifth transmission line and one end of the sixth transmission line, respectively. The other end of the fourth transmission line is electrically connected to a third bandpass filter. The other end of the fifth transmission line is electrically connected to the fourth bandpass filter. The other end of the sixth transmission line is electrically connected to the device under test. The lengths of the fourth, fifth, and sixth transmission lines are set according to the frequency of the third bandpass filter, the frequency of the fourth bandpass filter, the impedance of the three ports of the second T-joint stub assembly, the dielectric constant of the fourth transmission line, the dielectric constant of the fifth transmission line, and the dielectric constant of the sixth transmission line, so as to minimize the insertion loss of the second T-joint stub assembly.

2. The bidirectional nonlinear testing device according to claim 1, characterized in that, The load is a low intermodulation load.

3. The bidirectional nonlinear testing device according to claim 1, characterized in that, It also includes a power amplifier, the input of which is electrically connected to the signal source, and the output of which is electrically connected to the first bandpass filter.

4. A bidirectional nonlinear testing method, applied to the bidirectional nonlinear testing apparatus according to any one of claims 1-3, characterized in that, Includes the following steps: The signal source transmits a signal, which is then transmitted to the device under test via a first duplexer. The device under test generates nonlinear energy, part of which is reflected and the other part continues to be transmitted after passing through the device under test; The reflected nonlinear energy is transmitted to the first spectrum analyzer via the first duplexer, and the reverse nonlinearity of the device under test is monitored by the first spectrum analyzer. The nonlinear energy transmitted through the device under test is delivered to the load and the second spectrum analyzer via the second duplexer, and the positive nonlinearity of the device under test is monitored by the second spectrum analyzer.

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