A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a s...A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a set of fractional frequencies to create multiple measuring rulers with different metric ranges to determine the values of the tens,ones,tenths,and hundredths digits of the distance.Among these rulers,the one with the lowest frequency determines the maximum metric range,while the one with the highest frequency decides the highest achievable accuracy of the position system.For all rulers,the metric accuracy is uniquely determined by the phase accuracy of the detected PIM signals.With the all-phase Fourier transform method,the phases of the PIM signals at all fractional frequencies maintain almost the same accuracy,approximately 1°(about 1/360 wavelength in the positioning accuracy)at the signal-to-noise ratio(SNR)of 10 d B.Numerical simulations verify the effectiveness of the proposed method,improving the positioning accuracy of the cable PIM up to a millimeter level with the highest fractional frequency operating at 200 MHz.展开更多
Passive intermodulation(PIM)in communication systems is an unwanted interference caused by weak nonlinear currentvoltage characteristics of radio frequency(RF)passive components.Characterization of PIM is important fo...Passive intermodulation(PIM)in communication systems is an unwanted interference caused by weak nonlinear currentvoltage characteristics of radio frequency(RF)passive components.Characterization of PIM is important for both the study of PIM mechanisms and the location/suppression of PIM sources.PIM probes,made of open-ended coaxial transmission lines,have almost the same coupling strength to carriers and PIM products,and are usually used for near-field PIM characterization.Namely,it doesn’t have any filtering capability.Therefore,it cannot stop the carrier power from entering into PIM tester’s receiver,which may trigger active intermodulation of the receiver and degrade the PIM tester’s performance.To overcome this drawback,a passive filtering coaxial probe is proposed here.Compared with existing passive coaxial PIM probes,it has stronger coupling strength for PIM products than for carriers.Thus,the probe itself can block part of the carrier power entering into the PIM tester’s receiver.This advantage helps improve PIM tester’s overall performance.Both theoretical analysis and experiments are conducted for demonstration.The proposed probe brings more possibility to PIM characterization.展开更多
Passive intermodulation（PIM） has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh...Passive intermodulation（PIM） has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh reflector antennas. This paper proposes a field-circuit coupling method to analyze the PIM level of mesh reflectors. With the existence of many metal–metal（MM） contacts in mesh reflectors, the contact nonlinearity becomes the main reason for PIM generation. To analyze these potential PIM sources, an equivalent circuit model including nonlinear components is constructed to model a single MM contact so that the transient current through the MM contact point induced by incident electromagnetic waves can be calculated. Taking the electric current as a new electromagnetic wave source, the far-field scattering can be obtained by the use of electromagnetic numerical methods or the communication link method. Finally, a comparison between simulation and experimental results is illustrated to verify the validity of the proposed method.展开更多
In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance indicators.When the other radio frequency(RF)performance of the components is well designed,passive inter...In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance indicators.When the other radio frequency(RF)performance of the components is well designed,passive intermodulation(PIM)interference may become an important factor limiting the system’s SNR.Whether it is a base station,an indoor distributed antenna system,or a satellite system,there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks.Especially for systems of high power and wide bandwidth such as 5G wireless communication,PIM interference is even more serious.Due to the complexity and uncertainty of PIM,measurement is the most important means to study and evaluate the PIM performance of wireless communication systems.In this review,the current main PIM measurement methods recommended by International Electrotechnical Commission(IEC)and other standard organizations are introduced,and several key challenges in PIM measurement and their solutions(including the design of PIM tester,the location of the PIM sources,the design of compact PIM anechoic chambers,and the evaluation methods of PIM anechoic chambers)are highlighted.These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.展开更多
In order to analyze the deleterious effects of Passive InterModulation (PIM) on high power communication satellite systems, the basic concept of PIM is introduced, and an equation for the power spectral density of the...In order to analyze the deleterious effects of Passive InterModulation (PIM) on high power communication satellite systems, the basic concept of PIM is introduced, and an equation for the power spectral density of the n-th order PIM distortion insuch systems is derived by applying flat signal-power spectrum assumption and Fourier transform method. It is indicated that PIM level generally decreases with order and the lowest frequency receive channel in the receive band is the channel of most affected by PIM interference.展开更多
In order to expand the cell coverage of wireless cellular systems, the number of passive components in wireless systems has been substantially increased. There can be many passive intermodulation(PIM) pointsources eve...In order to expand the cell coverage of wireless cellular systems, the number of passive components in wireless systems has been substantially increased. There can be many passive intermodulation(PIM) pointsources even in a device or a radio link, which may add up constructively or destructively. A modified point-source model with lossy components is proposed to evaluate the superposition effect of the forward and refl ected PIM in case of series connection. The index of the series connection factor(SCF) is employed for systems that incorporate multiple PIM sources to predict the important characteristics of the cumulative PIM, such as the maximum and minimum values and the limit form. Furthermore, some initial experimental results are given out and the deviation in the above-mentioned prediction is also analyzed.展开更多
For the performance issues of satellite transceivers suffering passive intermodulation interference,a novel and effective digital suppression algorithm is presented in this paper.In contrast to analog approaches,digit...For the performance issues of satellite transceivers suffering passive intermodulation interference,a novel and effective digital suppression algorithm is presented in this paper.In contrast to analog approaches,digital passive intermodulation（PIM） suppression approaches can be easily reconfigured and therefore are highly attractive for future satellite communication systems.A simplified model of nonlinear distortion from passive microwave devices is established in consideration of the memory effect.The multiple high-order PIM products falling into the receiving band can be described as a bilinear predictor function.A suppression algorithm based on a bilinear polynomial decorrelated adaptive filter is proposed for baseband digital signal processing.In consideration of the time-varying characteristics of passive intermodulation,this algorithm can achieve the rapidness of online interference estimation and low complexity with less consumption of resources.Numerical simulation results show that the algorithm can effectively compensate the passive intermodulation interference,and achieve a high signal-to-interference ratio gain.展开更多
Passive intermodulation(PIM)interference urgently needs to be solved in the satellite communication system,owing to degrading the whole performance.Mainstream research contributions to the cancellation method for PIM ...Passive intermodulation(PIM)interference urgently needs to be solved in the satellite communication system,owing to degrading the whole performance.Mainstream research contributions to the cancellation method for PIM were focused on the analog domain,however,the PIM distortion cannot be eliminated completely with the approaches.Meanwhile,some researchers attempt to tackle the problem through digital signal processing,nevertheless,the proposed methods were not suitable for the practical satellite communication scenario.In this paper,we present a general scheme for the adaptive feedforward PIM cancellation.High-order PIM signals at baseband are estimated by modeling the PIM distortion with Hammerstein model in the digital domain.Based on the reconstructed PIM signal,we adopt the least mean square algorithm to adaptively mitigate the PIM interference for tracking the variation of PIM.The time and frequency synchronization of PIM are based on the correlation of the peak of received signals with the corresponding reconstructed PIM signal.Practical experimental results show that the scheme can effectively cancel the PIM interference,and achieve an interference suppression gain more than 20dB.展开更多
文摘A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a set of fractional frequencies to create multiple measuring rulers with different metric ranges to determine the values of the tens,ones,tenths,and hundredths digits of the distance.Among these rulers,the one with the lowest frequency determines the maximum metric range,while the one with the highest frequency decides the highest achievable accuracy of the position system.For all rulers,the metric accuracy is uniquely determined by the phase accuracy of the detected PIM signals.With the all-phase Fourier transform method,the phases of the PIM signals at all fractional frequencies maintain almost the same accuracy,approximately 1°(about 1/360 wavelength in the positioning accuracy)at the signal-to-noise ratio(SNR)of 10 d B.Numerical simulations verify the effectiveness of the proposed method,improving the positioning accuracy of the cable PIM up to a millimeter level with the highest fractional frequency operating at 200 MHz.
文摘Passive intermodulation(PIM)in communication systems is an unwanted interference caused by weak nonlinear currentvoltage characteristics of radio frequency(RF)passive components.Characterization of PIM is important for both the study of PIM mechanisms and the location/suppression of PIM sources.PIM probes,made of open-ended coaxial transmission lines,have almost the same coupling strength to carriers and PIM products,and are usually used for near-field PIM characterization.Namely,it doesn’t have any filtering capability.Therefore,it cannot stop the carrier power from entering into PIM tester’s receiver,which may trigger active intermodulation of the receiver and degrade the PIM tester’s performance.To overcome this drawback,a passive filtering coaxial probe is proposed here.Compared with existing passive coaxial PIM probes,it has stronger coupling strength for PIM products than for carriers.Thus,the probe itself can block part of the carrier power entering into the PIM tester’s receiver.This advantage helps improve PIM tester’s overall performance.Both theoretical analysis and experiments are conducted for demonstration.The proposed probe brings more possibility to PIM characterization.
文摘Passive intermodulation（PIM） has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh reflector antennas. This paper proposes a field-circuit coupling method to analyze the PIM level of mesh reflectors. With the existence of many metal–metal（MM） contacts in mesh reflectors, the contact nonlinearity becomes the main reason for PIM generation. To analyze these potential PIM sources, an equivalent circuit model including nonlinear components is constructed to model a single MM contact so that the transient current through the MM contact point induced by incident electromagnetic waves can be calculated. Taking the electric current as a new electromagnetic wave source, the far-field scattering can be obtained by the use of electromagnetic numerical methods or the communication link method. Finally, a comparison between simulation and experimental results is illustrated to verify the validity of the proposed method.
文摘In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance indicators.When the other radio frequency(RF)performance of the components is well designed,passive intermodulation(PIM)interference may become an important factor limiting the system’s SNR.Whether it is a base station,an indoor distributed antenna system,or a satellite system,there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks.Especially for systems of high power and wide bandwidth such as 5G wireless communication,PIM interference is even more serious.Due to the complexity and uncertainty of PIM,measurement is the most important means to study and evaluate the PIM performance of wireless communication systems.In this review,the current main PIM measurement methods recommended by International Electrotechnical Commission(IEC)and other standard organizations are introduced,and several key challenges in PIM measurement and their solutions(including the design of PIM tester,the location of the PIM sources,the design of compact PIM anechoic chambers,and the evaluation methods of PIM anechoic chambers)are highlighted.These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.
文摘In order to analyze the deleterious effects of Passive InterModulation (PIM) on high power communication satellite systems, the basic concept of PIM is introduced, and an equation for the power spectral density of the n-th order PIM distortion insuch systems is derived by applying flat signal-power spectrum assumption and Fourier transform method. It is indicated that PIM level generally decreases with order and the lowest frequency receive channel in the receive band is the channel of most affected by PIM interference.
文摘In order to expand the cell coverage of wireless cellular systems, the number of passive components in wireless systems has been substantially increased. There can be many passive intermodulation(PIM) pointsources even in a device or a radio link, which may add up constructively or destructively. A modified point-source model with lossy components is proposed to evaluate the superposition effect of the forward and refl ected PIM in case of series connection. The index of the series connection factor(SCF) is employed for systems that incorporate multiple PIM sources to predict the important characteristics of the cumulative PIM, such as the maximum and minimum values and the limit form. Furthermore, some initial experimental results are given out and the deviation in the above-mentioned prediction is also analyzed.
基金supported by the National Natural SciencFoundation of China(Nos.U1636125,61601027)
文摘For the performance issues of satellite transceivers suffering passive intermodulation interference,a novel and effective digital suppression algorithm is presented in this paper.In contrast to analog approaches,digital passive intermodulation（PIM） suppression approaches can be easily reconfigured and therefore are highly attractive for future satellite communication systems.A simplified model of nonlinear distortion from passive microwave devices is established in consideration of the memory effect.The multiple high-order PIM products falling into the receiving band can be described as a bilinear predictor function.A suppression algorithm based on a bilinear polynomial decorrelated adaptive filter is proposed for baseband digital signal processing.In consideration of the time-varying characteristics of passive intermodulation,this algorithm can achieve the rapidness of online interference estimation and low complexity with less consumption of resources.Numerical simulation results show that the algorithm can effectively compensate the passive intermodulation interference,and achieve a high signal-to-interference ratio gain.
基金financially supported by the Joint Fund of NSFC and the General Purpose Technology Research Program under the contract U1636125,NSFC under the contract U1836201
文摘Passive intermodulation(PIM)interference urgently needs to be solved in the satellite communication system,owing to degrading the whole performance.Mainstream research contributions to the cancellation method for PIM were focused on the analog domain,however,the PIM distortion cannot be eliminated completely with the approaches.Meanwhile,some researchers attempt to tackle the problem through digital signal processing,nevertheless,the proposed methods were not suitable for the practical satellite communication scenario.In this paper,we present a general scheme for the adaptive feedforward PIM cancellation.High-order PIM signals at baseband are estimated by modeling the PIM distortion with Hammerstein model in the digital domain.Based on the reconstructed PIM signal,we adopt the least mean square algorithm to adaptively mitigate the PIM interference for tracking the variation of PIM.The time and frequency synchronization of PIM are based on the correlation of the peak of received signals with the corresponding reconstructed PIM signal.Practical experimental results show that the scheme can effectively cancel the PIM interference,and achieve an interference suppression gain more than 20dB.
