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Passive Inter-modulation Cancellation in FDD System

Chen, Fan LU (2017) EITM02 20161
Department of Electrical and Information Technology
Abstract
Passive inter-modulation (PIM) shows up when two or more RF signals are mixed together via the nonlinear passive devices. With the rapid development and expansion of the wireless com-munication networks, PIM is recognized as one of the most critical issues.
Especially in the base station, where several networks systems have to share the same infrastruc-ture, a few transmitted signals are physically close to each other, even they could be sharing the same antenna. So it is highly possible that several transmitted signals hit a same nonlinear junc-tion and generate PIM distortion, then the PIM distortion falls in some bands of the receivers nearby.
Even more critically, since some technologies are developed with multi-carrier or... (More)
Passive inter-modulation (PIM) shows up when two or more RF signals are mixed together via the nonlinear passive devices. With the rapid development and expansion of the wireless com-munication networks, PIM is recognized as one of the most critical issues.
Especially in the base station, where several networks systems have to share the same infrastruc-ture, a few transmitted signals are physically close to each other, even they could be sharing the same antenna. So it is highly possible that several transmitted signals hit a same nonlinear junc-tion and generate PIM distortion, then the PIM distortion falls in some bands of the receivers nearby.
Even more critically, since some technologies are developed with multi-carrier or multi-band, such as Carrier Aggregation and MIMO, the generated PIM could spread in a wide range of the spectrum and overlap with the receiver bands.
Additionally the continuous increased power of the transmitted signals and the hyper sensitivity of the received signals make PIM issue particularly critical in the base station. Even the fifth and seventh order products of PIM could cause the performance degradation on the received signals.
Isolation and shielding have been used to suppress the effect of PIM distortion, but it is costly and space-consuming solution. In this thesis, a digital self-adaptive cancellation technique is in-troduced. In the proposed technique, an estimated PIM is created based on the known baseband transmitted signal which is highly correlated to the PIM distortion present in the receiver chain, then the received signal is extracted by subtracting the estimated PIM signal from the distorted received signal in the digital domain.
Time-dependency is one of the natures of PIM, since the nonlinearity of the passive devices al-ways varies with temperature, humidity and elements age. To realize an accurate estimation of PIM distortion in real time, the adaptive filter with NLMS (Normalized Least Mean Square) and RLS (Recursive Least Squares) algorithms is used to adjust the coefficients of the filter in the cancellation block.
To ensure the expected performance of the technique to be reached, many simulations under dif-ferent situations are implemented and analyzed in Matlab. Additionally some proper simplifica-tions in the cancellation block are proceeded so that this technique can be realized in the hard-ware at a low cost in future. (Less)
Popular Abstract
Passive inter-modulation (PIM) poses a significant risk to the operational efficiency and profitability of the networks systems. It can produce the interference and hide the wanted signal, as a result the system performance is impaired severely. In this thesis, a simple and efficient technique is introduced to eliminate the PIM distortion self-adaptively. And many simulations under different situations have been implemented and analyzed to verify the feasibility of this technique. From the simulation results, this technique can offer an excellent improvement for the wanted signal, even though the original signal quality is very poor. Considering PIM is a time-varying signal, the tracking capability was tested and the result was positive as... (More)
Passive inter-modulation (PIM) poses a significant risk to the operational efficiency and profitability of the networks systems. It can produce the interference and hide the wanted signal, as a result the system performance is impaired severely. In this thesis, a simple and efficient technique is introduced to eliminate the PIM distortion self-adaptively. And many simulations under different situations have been implemented and analyzed to verify the feasibility of this technique. From the simulation results, this technique can offer an excellent improvement for the wanted signal, even though the original signal quality is very poor. Considering PIM is a time-varying signal, the tracking capability was tested and the result was positive as well. (Less)
Please use this url to cite or link to this publication:
author
Chen, Fan LU
supervisor
organization
course
EITM02 20161
year
type
H2 - Master's Degree (Two Years)
subject
report number
LU/LTH-EIT 2017-563
language
English
id
8917317
date added to LUP
2017-06-20 12:24:59
date last changed
2017-06-20 12:24:59
@misc{8917317,
  abstract     = {Passive inter-modulation (PIM) shows up when two or more RF signals are mixed together via the nonlinear passive devices. With the rapid development and expansion of the wireless com-munication networks, PIM is recognized as one of the most critical issues.
Especially in the base station, where several networks systems have to share the same infrastruc-ture, a few transmitted signals are physically close to each other, even they could be sharing the same antenna. So it is highly possible that several transmitted signals hit a same nonlinear junc-tion and generate PIM distortion, then the PIM distortion falls in some bands of the receivers nearby.
Even more critically, since some technologies are developed with multi-carrier or multi-band, such as Carrier Aggregation and MIMO, the generated PIM could spread in a wide range of the spectrum and overlap with the receiver bands.
Additionally the continuous increased power of the transmitted signals and the hyper sensitivity of the received signals make PIM issue particularly critical in the base station. Even the fifth and seventh order products of PIM could cause the performance degradation on the received signals. 
Isolation and shielding have been used to suppress the effect of PIM distortion, but it is costly and space-consuming solution. In this thesis, a digital self-adaptive cancellation technique is in-troduced. In the proposed technique, an estimated PIM is created based on the known baseband transmitted signal which is highly correlated to the PIM distortion present in the receiver chain, then the received signal is extracted by subtracting the estimated PIM signal from the distorted received signal in the digital domain.
Time-dependency is one of the natures of PIM, since the nonlinearity of the passive devices al-ways varies with temperature, humidity and elements age. To realize an accurate estimation of PIM distortion in real time, the adaptive filter with NLMS (Normalized Least Mean Square) and RLS (Recursive Least Squares) algorithms is used to adjust the coefficients of the filter in the cancellation block. 
To ensure the expected performance of the technique to be reached, many simulations under dif-ferent situations are implemented and analyzed in Matlab. Additionally some proper simplifica-tions in the cancellation block are proceeded so that this technique can be realized in the hard-ware at a low cost in future.},
  author       = {Chen, Fan},
  language     = {eng},
  note         = {Student Paper},
  title        = {Passive Inter-modulation Cancellation in FDD System},
  year         = {2017},
}