Antenna Array Weighting for Near-Field PIM Interference Reduction
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Solution Overview
Problem
Cellular base station antennas face significant challenges with passive intermodulation (PIM) interference from external sources in rooftop environments, particularly due to the increased number of intermodulating spectral products generated when new spectrum bands are added, which can desensitize uplink receiver channels and compromise network capacity and spectral efficiency.
Innovation Solution
The implementation of a base station system with a substantially linear array of antenna elements and an antenna distribution network that applies optimized amplitude and phase weights to minimize RF coupling between the antenna and PIM sources in the near-field, allowing for independent beam tilts for downlink and uplink channels to reduce PIM interference, and utilizing customized amplitude and phase weights to minimize near-field RF coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If new spectrum bands are added to increase network capacity, then the number of intermodulating spectral products increases, but the probability that PIM products fall into uplink receiver bands increases, causing interference
Solution Approach 1:
The patent applies different amplitude and phase weights to different antenna elements in the array, creating localized variations in the radiation pattern. This allows the system to reduce PIM interference in specific frequency bands (uplink receiver bands) while maintaining or enhancing signal strength in other bands, thereby resolving the contradiction between network capacity expansion and PIM interference mitigation
Solution Approach 2:
The system dynamically adjusts the amplitude and phase parameters of each antenna element's signal to optimize the radiation pattern. By changing these parameters, the system can create nulls or reduced gain regions in directions where PIM sources are located, while maintaining high gain in directions of interest, thus reducing PIM interference without sacrificing network capacity
2Object-affected harmful factors
If antenna elements are arranged in a linear array with amplitude and phase weights, then RF coupling with PIM sources is minimized, but system complexity increases
Solution Approach 1:
The antenna distribution network is designed to perform multiple functions: it distributes signals to antenna elements, applies amplitude and phase weights for PIM reduction, and maintains compatibility with existing base station interfaces. This multi-functionality reduces the need for separate dedicated PIM mitigation hardware, thereby managing system complexity while achieving the desired interference reduction
Data Source
AI summary
A base station system may include at least one base station radio, at least one antenna, the at least one antenna including at least a first antenna comprising a linear array of antenna elements arranged in a vertical plane, and at least a one antenna distribution network for distributing radio frequency (RF) signals as component RF signals across the linear array of antenna elements of the at least the first antenna to form at least one beam in an elevation plane. In one example, the at least the one antenna feed network applies amplitude and phase weights to the component RF signals, wherein the amplitude and phase weights are selected to minimize RF coupling between the at least the first antenna and passive intermodulation sources in a near-field of the at least the first antenna.