Base Station PIM Detection Receiver Using Dual Local Oscillators
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Solution Overview
Problem
Existing methods fail to effectively detect passive intermodulation (PIM) signals generated by the non-linear mixing of two separate radio bands in wireless communication systems, particularly in base stations, which can degrade signal quality and are difficult to identify without on-site measurements.
Innovation Solution
A method and system utilizing a broadband receiver and antenna at the base station to sample and detect unknown downlink signals, employing additional receivers and antennas to separate multiple polarized signals, and scanning across a wide frequency range to calculate and measure PIM frequencies, allowing for remote monitoring and cancellation of PIM interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PIM detection methods are used, then PIM products within a single radio band can be detected, but PIM products generated by non-linear mixing of two separate radio bands cannot be detected
Solution Approach 1:
The detection receiver is configured to perform multiple functions: detecting PIM products within a single radio band and detecting PIM products generated by non-linear mixing of two separate radio bands. The system uses a first local oscillator for single-band PIM detection and a second local oscillator for cross-band PIM detection, enabling the same receiver to handle both detection scenarios.
Solution Approach 2:
The detection process is segmented into two distinct paths: one for detecting PIM products within a single radio band using a first local oscillator, and another for detecting PIM products from two separate radio bands using a second local oscillator. This segmentation allows the system to address different PIM detection scenarios with specialized processing paths.
2Measurement precision
If high dynamic range receivers are used to detect PIM signals, then detection sensitivity is improved, but system complexity and cost increase
Solution Approach 1:
A signal generator is introduced as an intermediary component that creates a composite signal containing both the first radio band signal and the second radio band signal. This composite signal is then fed to the detection receiver, which uses local oscillators to downconvert and detect PIM products. This intermediary approach simplifies the receiver requirements compared to directly detecting weak PIM signals in the presence of strong transmit signals.
Solution Approach 2:
Instead of using a high dynamic range receiver to directly detect weak PIM products in the presence of strong transmit signals, the system creates a copy of the transmit signals through the signal generator and processes them in a controlled environment. The local oscillators create downconverted copies of the signals, allowing PIM detection with simpler, lower dynamic range receivers.
3Measurement precision
If on-site measurements are performed to detect PIM, then accurate PIM identification is achieved, but operational efficiency and productivity decrease
Solution Approach 1:
The base station performs PIM detection automatically using its own resources - the detection receiver is collocated with the radio bands and uses locally generated signals and local oscillators to detect PIM products. This self-service capability eliminates the need for external measurement equipment and on-site technician visits, enabling continuous automated monitoring without impacting operational productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the detection and potential cancellation of PIM signals originating from the mixing of downlink frequencies of different radio bands, improving signal quality by identifying and mitigating interference without the need for high dynamic range receivers or complex filtering, and is independent of specific radio access technologies.
Implementation Method 1
a broadband receiver and antenna at the base station to sample and detect unknown downlink signals
Implementation Method 2
The passive intermodulation (PIM) interferences that are observed at wireless communication sites are usually generated from two or more high power carriers which are mixed together in a non-linear passive component
Data Source
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AI summary
A method and system for detecting PIM signals in a wireless communication base station are disclosed. According to one aspect, a method includes receiving radio frequency, RF, signals over a frequency band spanning a plurality of frequencies of signals transmitted by at least a first transmitter external to the base station and at least a second transmitter. The method includes determining frequencies at which signals are present among the received radio frequency signals. PIM signal frequencies are calculated based on the determined frequencies at which signals are present. The method includes determining whether the calculated PIM signal frequencies interfere with selected uplink channels.