MIMO Antenna PIM Source Characterization via Cross-Correlation
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Solution Overview
Problem
Current detection systems for passive intermodulation (PIM) interference in Multiple Input Multiple Output (MIMO) antenna arrays are inadequate in characterizing the source of interference, leading to reduced carrier-to-interference ratio and coverage issues in wireless communication systems.
Innovation Solution
A method involving the reception of digital signals from MIMO antennas in different bands, processing to generate partial simulated PIM signals, and determining cross-correlations to identify the source of PIM interference, along with a MIMO PIM analysis test set for detecting and characterizing PIM interference by correlating simulated signals with received interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PIM detection is performed using existing methods, then the presence of PIM can be detected, but the source and characteristics of PIM interference cannot be accurately characterized
Solution Approach 1:
The patent segments the PIM detection process by separating transmit antennas into different groups (first group for first band, second group for second band) and analyzing PIM contributions from each group independently. This segmentation allows identification of which specific antenna groups contribute to PIM interference, enabling precise source characterization rather than just detecting presence.
Solution Approach 2:
The patent introduces simulated PIM signals as an intermediary element. These simulated signals are generated based on transmit signal characteristics and used as reference for correlation analysis with received signals. The simulated signals act as a mediator that bridges the gap between known transmit characteristics and unknown PIM sources, enabling accurate source identification through correlation measurement.
2Productivity
If MIMO signals are transmitted in multiple bands, then system capacity increases, but PIM interference generation increases
Solution Approach 1:
The patent implements a feedback mechanism where PIM contributions from different antenna groups are measured and correlated with simulated signals. The correlation results provide feedback information about which antenna groups are generating PIM interference. This feedback enables network operators to identify problematic antenna configurations and adjust MIMO operations to mitigate PIM while maintaining system capacity.
Solution Approach 2:
The patent analyzes PIM characteristics by examining correlation magnitudes across different parameter combinations (different antenna groups, different bands). By changing and comparing parameters such as which antenna group is active and which band is being used, the system can identify optimal configurations that minimize PIM generation while maintaining high system capacity.
3Duration of action of stationary object
If PIM interference is not characterized, then system operation continues, but coverage and carrier-to-interference ratio deteriorate
Solution Approach 1:
The patent performs preliminary PIM characterization by correlating received signals with simulated PIM signals before making operational decisions. This preliminary analysis identifies which antenna groups contribute to PIM, allowing the system to take preventive actions such as reconfiguring antenna usage or adjusting signal parameters before coverage quality deteriorates significantly.
Data Source
AI summary
A method of detecting and characterising passive intermodulation interference comprises receiving first digital signals representing respective first MIMO signal components transmitted at a first carrier frequency from each antenna of a first group of antennas, receiving second digital signals representing respective second MIMO signal components transmitted at a second carrier frequency from each antenna of a second group of antennas, and receiving third digital signals representing signals received at an antenna under analysis. The first and second digital signals are processed to determine a plurality of partial simulated PIM signals, each being generated from samples of a respective one of the MIMO signal components transmitted from one group of the first and second groups of antennas and from samples of all of the MIMO signal components transmitted from the other group of the first and second groups of antennas. A magnitude is determined of a cross-correlation between the third digital signals and each of the plurality of partial simulated PIM signals.