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Article List
2023, 21(3):257-262.
DOI: 10.11805/TKYDA2022174
Abstract:
In ground communication systems, microwave components of the base station are exposed in air for a period of time, usually influenced by temperatures, humidity, pollution and other factors. The original clean surface of the components is oxidized and contaminated, leading to poor contact and Passive Intermodulation(PIM), which interferes with the communication system. Therefore, PIM is inevitable in ground mobile communication system. In the satellite communication system, due to the long communication distance and platform limitation, the common transceiver mode should be adopted. As the receiver sensitivity increases, the requirements on PIM indexes are more strict. PIM is one of the key problems for realizing the high reliability of system. The characteristics and research progress of PIM interference in ground mobile communication and satellite microwave components are introduced, which can provide a reference for PIM research.
In ground communication systems, microwave components of the base station are exposed in air for a period of time, usually influenced by temperatures, humidity, pollution and other factors. The original clean surface of the components is oxidized and contaminated, leading to poor contact and Passive Intermodulation(PIM), which interferes with the communication system. Therefore, PIM is inevitable in ground mobile communication system. In the satellite communication system, due to the long communication distance and platform limitation, the common transceiver mode should be adopted. As the receiver sensitivity increases, the requirements on PIM indexes are more strict. PIM is one of the key problems for realizing the high reliability of system. The characteristics and research progress of PIM interference in ground mobile communication and satellite microwave components are introduced, which can provide a reference for PIM research.
2023, 21(3):263-270.
DOI: 10.11805/TKYDA2022192
Abstract:
Passive Intermodulation(PIM) is one of the key reliability problems of the microwave circuits. With the development of microwave system integration and miniaturization, the microstrip circuits are widely used in the industry and studied by the researchers. Therefore, it has great value to investigate the physical mechanisms, the evaluation methods, and the suppression technologies of the PIM interference in the microstrip circuits. The nonlinearities in the microstrip circuits are usually distributed, which are usually different from that of the cavity based microwave devices, and they are also associated with the substrate materials, the fabrication processes and the device structures. All these make it difficult to solve the PIM problems in the microstrip circuits. Though more and more PIM investigations for the mircostrip circuits have been reported in recent years, the practical high-quality circuit-design still faces challenge. In this paper, we review the recent developments about the PIM phenomenon in the microstrip circuits including the nonlinearity mechanisms, the modeling and simulation methods, and the measurement technologies, which could provide comprehensive guidance for the future study of the PIM problems in the microstrip circuits.
Passive Intermodulation(PIM) is one of the key reliability problems of the microwave circuits. With the development of microwave system integration and miniaturization, the microstrip circuits are widely used in the industry and studied by the researchers. Therefore, it has great value to investigate the physical mechanisms, the evaluation methods, and the suppression technologies of the PIM interference in the microstrip circuits. The nonlinearities in the microstrip circuits are usually distributed, which are usually different from that of the cavity based microwave devices, and they are also associated with the substrate materials, the fabrication processes and the device structures. All these make it difficult to solve the PIM problems in the microstrip circuits. Though more and more PIM investigations for the mircostrip circuits have been reported in recent years, the practical high-quality circuit-design still faces challenge. In this paper, we review the recent developments about the PIM phenomenon in the microstrip circuits including the nonlinearity mechanisms, the modeling and simulation methods, and the measurement technologies, which could provide comprehensive guidance for the future study of the PIM problems in the microstrip circuits.
3 Research progress of suppression technology of Passive Intermodulation based on contact nonlinearity
2023, 21(3):291-300.
DOI: 10.11805/TKYDA2022143
Abstract:
Wireless communication systems are increasingly developing towards high power and high sensitivity. The interference of Passive Intermodulation(PIM) on signal transmission is one of the difficult problems to be solved in the development of communication systems. Based on this, the mechanism of passive intermodulation is summarized in this paper. The research progress of passive intermodulation suppression technology from three aspects, such as reducing contact surface roughness, applying coating materials and optimizing device structure, are mainly reviewed. Moreover, the advantages and disadvantages of different suppression technologies are analyzed. Finally, the development trends of passive intermodulation suppression technology are prospected. This work aims to provide reference and guidance for relevant researchers.
Wireless communication systems are increasingly developing towards high power and high sensitivity. The interference of Passive Intermodulation(PIM) on signal transmission is one of the difficult problems to be solved in the development of communication systems. Based on this, the mechanism of passive intermodulation is summarized in this paper. The research progress of passive intermodulation suppression technology from three aspects, such as reducing contact surface roughness, applying coating materials and optimizing device structure, are mainly reviewed. Moreover, the advantages and disadvantages of different suppression technologies are analyzed. Finally, the development trends of passive intermodulation suppression technology are prospected. This work aims to provide reference and guidance for relevant researchers.
2023, 21(3):286-290.
DOI: 10.11805/TKYDA2022193
Abstract:
The Passive Intermodulation(PIM) value of the reflector's metal mesh, an important performance parameter of high-power spaceborne mesh antenna, is tested traditionally by the radiation method which requires a large size of metal mesh sample and has a low test efficiency. A 3-port PIM test method is proposed for the metal mesh, which is carried out by adopting a waveguide testing system based on the 3-port module. A PIM performance test system based on the 3-port module is constructed in order to verify the effectiveness of this test method. The PIM performance test is carried out on two metal mesh samples of the traditional type and the improved type, respectively. The test results show that the PIM performance of the improved metal mesh sample has been improved by 50 dB than that of the traditional mesh sample. This metal mesh's PIM test system bears the characteristics of high integration, stable performance, and high system construction efficiency. The test sample size for the proposed method is reduced to about 1/10 than that of the traditional method. The proposed 3-port PIM test method provides support for the rapid research of novel low-PIM-level metal meshes.
The Passive Intermodulation(PIM) value of the reflector's metal mesh, an important performance parameter of high-power spaceborne mesh antenna, is tested traditionally by the radiation method which requires a large size of metal mesh sample and has a low test efficiency. A 3-port PIM test method is proposed for the metal mesh, which is carried out by adopting a waveguide testing system based on the 3-port module. A PIM performance test system based on the 3-port module is constructed in order to verify the effectiveness of this test method. The PIM performance test is carried out on two metal mesh samples of the traditional type and the improved type, respectively. The test results show that the PIM performance of the improved metal mesh sample has been improved by 50 dB than that of the traditional mesh sample. This metal mesh's PIM test system bears the characteristics of high integration, stable performance, and high system construction efficiency. The test sample size for the proposed method is reduced to about 1/10 than that of the traditional method. The proposed 3-port PIM test method provides support for the rapid research of novel low-PIM-level metal meshes.
2023, 21(3):271-277.
DOI: 10.11805/TKYDA2022195
Abstract:
As an important electrical connector, the reliability of spring electrical connection directly affects the electrical performance of the device. It is important to study the regularity and influencing factors of spring electrical connection for improving equipment performance and saving cost. In this paper, through software simulation and experimental measurements, the rule is tested that the contact resistance decreases with the decrease of the resistivity of the contact metal surface material and decreases with the increase of the applied force when the electrical connection parts represented by the spring are under weak external force(<2N). Through the analysis and calculation of mechanical contact theory, it is verified that the contact resistance is affected by the resistivity and external force of the material. The mechanism of contact resistance of the projectile is clearly explained, and the relationship between contact resistance of the projectile and different contact interfaces can be more accurately judged.
As an important electrical connector, the reliability of spring electrical connection directly affects the electrical performance of the device. It is important to study the regularity and influencing factors of spring electrical connection for improving equipment performance and saving cost. In this paper, through software simulation and experimental measurements, the rule is tested that the contact resistance decreases with the decrease of the resistivity of the contact metal surface material and decreases with the increase of the applied force when the electrical connection parts represented by the spring are under weak external force(<2N). Through the analysis and calculation of mechanical contact theory, it is verified that the contact resistance is affected by the resistivity and external force of the material. The mechanism of contact resistance of the projectile is clearly explained, and the relationship between contact resistance of the projectile and different contact interfaces can be more accurately judged.
2023, 21(3):278-285.
DOI: 10.11805/TKYDA2022198
Abstract:
A method is proposed to measure electrical contact Passive Intermodulation(PIM) based on a slot waveguide, which is separable and can simultaneously measure contact resistance and PIM. On this basis, the statistical behavior of metal contact PIM is investigated. Firstly, it is determined that the existence of oxide film on the surface of Device Under Test(DUT) with aluminum and silver coated aluminum, is the main reason for the producing of PIM, by characterizing the surface topography and analyzing the components. Secondly, the contact resistance(Rc) and its statistical regularities are obtained by repeating loading-unloading at some certain pressure with four-terminal sensing method. Finally, the relationship among contact resistance, PIM and contact pressure of aluminum alloy and silver coated aluminum alloy are measured by special designed slot waveguide measurement system. The experimental results show that, the contact resistance of the contact joint has the statistical characteristic under the certain pressure and its PIM value is also fluctuant. Both the contact resistance and PIM value decrease as the contact pressure increases and their fluctuant ranges decrease.
A method is proposed to measure electrical contact Passive Intermodulation(PIM) based on a slot waveguide, which is separable and can simultaneously measure contact resistance and PIM. On this basis, the statistical behavior of metal contact PIM is investigated. Firstly, it is determined that the existence of oxide film on the surface of Device Under Test(DUT) with aluminum and silver coated aluminum, is the main reason for the producing of PIM, by characterizing the surface topography and analyzing the components. Secondly, the contact resistance(Rc) and its statistical regularities are obtained by repeating loading-unloading at some certain pressure with four-terminal sensing method. Finally, the relationship among contact resistance, PIM and contact pressure of aluminum alloy and silver coated aluminum alloy are measured by special designed slot waveguide measurement system. The experimental results show that, the contact resistance of the contact joint has the statistical characteristic under the certain pressure and its PIM value is also fluctuant. Both the contact resistance and PIM value decrease as the contact pressure increases and their fluctuant ranges decrease.
2023, 21(7):845-850.
DOI: 10.11805/TKYDA2022238
Abstract:
A design method of low Passive Intermodulation(PIM) coaxial connectors using noncontact inner conductors is proposed in this paper. Coaxial connectors are widely used in satellite communication systems, and their PIMs seriously affect the communication performance. Two coaxial connectors with noncontact inner conductors in S-band and C-band are designed and implemented, respectively. The measured |S11| of the proposed coaxial connectors is less than -30 dB from 2.1 GHz to 2.7 GHz in S band, and the insertion loss is better than 0.3 dB. The measured |S11| of the C band connector is less than -30 dB from 3.5 GHz to 4.2 GHz, and the insertion loss is better than 0.2 dB. The proposed coaxial connector design method with noncontact inner conductors may lower the PIM of a coaxial connector and has bright future applications in satellite communication systems.
A design method of low Passive Intermodulation(PIM) coaxial connectors using noncontact inner conductors is proposed in this paper. Coaxial connectors are widely used in satellite communication systems, and their PIMs seriously affect the communication performance. Two coaxial connectors with noncontact inner conductors in S-band and C-band are designed and implemented, respectively. The measured |S11| of the proposed coaxial connectors is less than -30 dB from 2.1 GHz to 2.7 GHz in S band, and the insertion loss is better than 0.3 dB. The measured |S11| of the C band connector is less than -30 dB from 3.5 GHz to 4.2 GHz, and the insertion loss is better than 0.2 dB. The proposed coaxial connector design method with noncontact inner conductors may lower the PIM of a coaxial connector and has bright future applications in satellite communication systems.
2023, 21(7):882-890.
DOI: 10.11805/TKYDA2023009
Abstract:
In modern wireless communication, passive intermodulation is an important factor affecting the transmission quality of communication signals. Dual-tone intermodulation testing can effectively measure the nonlinear characteristics of passive devices, but it is hard to accurately predict the nonlinear distortion of devices excited by broadband signals. A method for analyzing the Passive Intermodulation characteristics of RF connectors with broadband signal excitation is proposed. Through the dual-tone intermodulation test, the passive nonlinear transmission mathematical models of RF connectors are derived. An equivalent broadband signal considering normal distribution is provided as the excitation source to the connectors. Mathematical calculation results of the proposed model show that the broadband Passive Intermodulation power distribution is the same as the broadband signal power distribution. The bandwidth of the nth-order broadband Passive Intermodulation is n times that of the original broadband signal. It is observed that the power of Passive Intermodulation products with broadband signal excitation are higher than that of the dual-tone signal. Thus, the signal to noise ratio decreases, indicating that the PIM interference induced by the broadband signal in the transmission process is more serious compared with that induced by two Continue Wave(CW) signals. Simulations are conducted by importing the proposed broadband signal and nonlinear transfer function to an equivalent circuit. The simulation results show good consistency to the theoretical calculation, which proves the effectiveness of this analysis method.
In modern wireless communication, passive intermodulation is an important factor affecting the transmission quality of communication signals. Dual-tone intermodulation testing can effectively measure the nonlinear characteristics of passive devices, but it is hard to accurately predict the nonlinear distortion of devices excited by broadband signals. A method for analyzing the Passive Intermodulation characteristics of RF connectors with broadband signal excitation is proposed. Through the dual-tone intermodulation test, the passive nonlinear transmission mathematical models of RF connectors are derived. An equivalent broadband signal considering normal distribution is provided as the excitation source to the connectors. Mathematical calculation results of the proposed model show that the broadband Passive Intermodulation power distribution is the same as the broadband signal power distribution. The bandwidth of the nth-order broadband Passive Intermodulation is n times that of the original broadband signal. It is observed that the power of Passive Intermodulation products with broadband signal excitation are higher than that of the dual-tone signal. Thus, the signal to noise ratio decreases, indicating that the PIM interference induced by the broadband signal in the transmission process is more serious compared with that induced by two Continue Wave(CW) signals. Simulations are conducted by importing the proposed broadband signal and nonlinear transfer function to an equivalent circuit. The simulation results show good consistency to the theoretical calculation, which proves the effectiveness of this analysis method.
2023, 21(7):850-855.
DOI: 10.11805/TKYDA2022206
Abstract:
Principles of Passive Intermodulation(PIM) production and its control method are introduced. After mainly researching and applying the PIM control technologies for the feed chain of multibeam antenna in high throughput satellite, including optimal design of high isolation of feed system, flange face choke of feed unit, PIM source control of feed array mounting plate, low PIM design of Ka-band PIM test system, etc., a Ka-band multibeam antenna achieves the goals that the 7th order PIM performance of the feed unit is controlled to ≤-135 dBm at temperatures between -60 ℃ and +100 ℃，and the performance of the feed array is controlled to ≤-140 dBm at normal temperature. The application of the product demonstrates the validity of the proposed technology for PIM control, which is of benefit to high performance antenna design.
Principles of Passive Intermodulation(PIM) production and its control method are introduced. After mainly researching and applying the PIM control technologies for the feed chain of multibeam antenna in high throughput satellite, including optimal design of high isolation of feed system, flange face choke of feed unit, PIM source control of feed array mounting plate, low PIM design of Ka-band PIM test system, etc., a Ka-band multibeam antenna achieves the goals that the 7th order PIM performance of the feed unit is controlled to ≤-135 dBm at temperatures between -60 ℃ and +100 ℃，and the performance of the feed array is controlled to ≤-140 dBm at normal temperature. The application of the product demonstrates the validity of the proposed technology for PIM control, which is of benefit to high performance antenna design.
2023, 21(7):872-876.
DOI: 10.11805/TKYDA2022197
Abstract:
Passive Intermodulation(PIM) is a subject that attracts researchers in many fields, including base station antennas and satellites. In this work, a new setup for non-contact PIM measurement is proposed, which takes a Substrate-Integrated Slotted Waveguide(SISW) designed by field reconstruction as the excitation and reception path. The SISW with field reconstruction enables a solution for the evaluation of the non-linear characteristics of samples without RF ports through far-field suppression and near-field partitioning of the carrier signal. The proposed test platform combines the finite radiation characteristics of near-field antennas and the adaptability of the gradient test area to transceiver systems in the PIM evaluation. The experimental results suggest that the proposed test method presents considerable potential for application in terms of stability and resolution.
Passive Intermodulation(PIM) is a subject that attracts researchers in many fields, including base station antennas and satellites. In this work, a new setup for non-contact PIM measurement is proposed, which takes a Substrate-Integrated Slotted Waveguide(SISW) designed by field reconstruction as the excitation and reception path. The SISW with field reconstruction enables a solution for the evaluation of the non-linear characteristics of samples without RF ports through far-field suppression and near-field partitioning of the carrier signal. The proposed test platform combines the finite radiation characteristics of near-field antennas and the adaptability of the gradient test area to transceiver systems in the PIM evaluation. The experimental results suggest that the proposed test method presents considerable potential for application in terms of stability and resolution.
2023, 21(7):877-881.
DOI: 10.11805/TKYDA2022234
Abstract:
With the development of multi-beam satellites communication and the wide application of transmit-receive technology, Passive Intermodulation(PIM) has become more seriously in the high power passive components. A PIM measurement method for phase adjustable Multiple-Input Multiple-Output(MIMO) multicarrier is presented based on that for dual carriers test according to the working mode of multi-beam satellites communication. Theories as well as experiments demonstrate the potentials and usefulness of the method. The experiments are conducted by the designed 7-channel test system under -60~60 ℃, and the PIM power level is below -155 dBm. The proposed test system has been applied to the multi-carrier components of satellites.
With the development of multi-beam satellites communication and the wide application of transmit-receive technology, Passive Intermodulation(PIM) has become more seriously in the high power passive components. A PIM measurement method for phase adjustable Multiple-Input Multiple-Output(MIMO) multicarrier is presented based on that for dual carriers test according to the working mode of multi-beam satellites communication. Theories as well as experiments demonstrate the potentials and usefulness of the method. The experiments are conducted by the designed 7-channel test system under -60~60 ℃, and the PIM power level is below -155 dBm. The proposed test system has been applied to the multi-carrier components of satellites.
2023, 21(7):856-863.
DOI: 10.11805/TKYDA2022194
Abstract:
The uniform microstrip line is the basic structure of the microstrip circuit, and it is of great significance to establish the Passive Intermodulation(PIM) analytical model of the microstrip line. Based on the controlled source equivalence, in the lumped circuit equivalent model of the microstrip line, the distributed parasitic nonlinear PIM source in the microstrip line is modeled as a second controlled current source or voltage source, to obtain the matrix expression of the relationship between the voltage and current in the stripline PIM. The analytical calculation model of the uniform microstrip line PIM with the parasitic nonlinear mechanism is finally established. The experimental verification is carried out by comparing the transmission intermodulation and reflection intermodulation laws of nickel-plated microstrip lines with different lengths and nickel-plated microstrip lines with different concentrations of phosphorus doping. The third-order relative permeability nonlinear coefficient of nickel coatings is extracted to be 1×10-10 m2/A2 at 0.71 GHz. The proposed method based on controlled source equivalence provides a new idea for further establishing PIM models of other microstrip circuits.
The uniform microstrip line is the basic structure of the microstrip circuit, and it is of great significance to establish the Passive Intermodulation(PIM) analytical model of the microstrip line. Based on the controlled source equivalence, in the lumped circuit equivalent model of the microstrip line, the distributed parasitic nonlinear PIM source in the microstrip line is modeled as a second controlled current source or voltage source, to obtain the matrix expression of the relationship between the voltage and current in the stripline PIM. The analytical calculation model of the uniform microstrip line PIM with the parasitic nonlinear mechanism is finally established. The experimental verification is carried out by comparing the transmission intermodulation and reflection intermodulation laws of nickel-plated microstrip lines with different lengths and nickel-plated microstrip lines with different concentrations of phosphorus doping. The third-order relative permeability nonlinear coefficient of nickel coatings is extracted to be 1×10-10 m2/A2 at 0.71 GHz. The proposed method based on controlled source equivalence provides a new idea for further establishing PIM models of other microstrip circuits.
2023, 21(7):864-871.
DOI: 10.11805/TKYDA2022196
Abstract:
In modern high power communication distortion problems, the nonlinear mixing distortion effect in passive devices is always the most difficult to investigate, and it has attracted great interests in the modern high power and high density wireless communication system. Facing the typical nonlinear effect on passive device, Passive Intermodulation(PIM), this work concludes the common modeling methods and the important steps in PIM mechanism researches in recent years. In particular, targeting to the typical microscopic contact equivalence, PIM numerical transformation, and PIM prediction method in the engineered cases, the available methods are concluded for present, while a statistics based PIM prediction method for engineered device with dynamic range is proposed for the first time. This method can model the specific contact sources by using statistic strategy. The PIM prediction can be expressed as a statistical interval with the probability of each PIM value. This method can provide a big sample data for the engineered PIM prediction, and can guide the optimization of the PIM stability by controlling the detailed parameters.
In modern high power communication distortion problems, the nonlinear mixing distortion effect in passive devices is always the most difficult to investigate, and it has attracted great interests in the modern high power and high density wireless communication system. Facing the typical nonlinear effect on passive device, Passive Intermodulation(PIM), this work concludes the common modeling methods and the important steps in PIM mechanism researches in recent years. In particular, targeting to the typical microscopic contact equivalence, PIM numerical transformation, and PIM prediction method in the engineered cases, the available methods are concluded for present, while a statistics based PIM prediction method for engineered device with dynamic range is proposed for the first time. This method can model the specific contact sources by using statistic strategy. The PIM prediction can be expressed as a statistical interval with the probability of each PIM value. This method can provide a big sample data for the engineered PIM prediction, and can guide the optimization of the PIM stability by controlling the detailed parameters.
