Multichannel PIM Digital Cancellation Circuit
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Solution Overview
Problem
In multi-carrier base station communications systems, passive intermodulation (PIM) interference signals generated by damaged components or structural issues in antenna systems cannot be effectively cancelled in multi-transmission and multi-reception intermediate radio frequency systems with channel combiners, such as bridge or V network structures, leading to reduced receiving sensitivity and uplink throughput.
Innovation Solution
A multichannel passive intermodulation digital cancellation circuit is designed, incorporating frequency-shift variable rate modules, conversion circuits, duplexers, channel combiners, cascaded filter circuits, and PIM cancellers, which perform digital domain processing and feedback to generate PIM cancellation signals, thereby compensating for channel inconsistencies and simulating group delay characteristics to cancel PIM interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional PIM canceller is used in a multi-carrier base station system, then PIM interference in single-channel systems can be cancelled, but PIM interference signals in multi-transmission and multi-reception intermediate radio frequency systems with channel combiners cannot be cancelled
Solution Approach 1:
The patent segments the multi-channel PIM cancellation problem into multiple single-channel cancellation processes. Each channel's PIM interference is cancelled independently through separate digital signal processing paths, allowing the system to handle complex multi-channel scenarios by breaking them down into manageable single-channel segments that can be processed individually and then recombined
Solution Approach 2:
The patent creates a universal PIM cancellation apparatus that can function across both single-channel and multi-channel systems. By designing the cancellation mechanism to work with channel combiners and multiple transmission/reception paths, the system achieves multi-functionality that adapts to different network configurations while maintaining effective PIM cancellation performance
2Productivity
If channel combiners in bridge or V network structures are used to combine multiple transmission channels, then system capacity is increased, but PIM interference signals cannot be cancelled due to channel inconsistencies
Solution Approach 1:
The patent changes the approach from attempting to eliminate channel inconsistencies to adapting the cancellation process to account for them. By adjusting the digital signal processing parameters to match the specific channel characteristics introduced by bridge or V network combiners, the system maintains PIM cancellation effectiveness despite the presence of channel inconsistencies that result from using these combiner structures
3Measurement precision
If digital domain non-linear modeling is performed on PIM interference signals, then cancellation accuracy is improved, but the system cannot handle multi-transmission and multi-reception scenarios with combiners
Solution Approach 1:
The patent applies segmentation by dividing the multi-channel digital domain processing into separate single-channel modeling and cancellation stages. Each channel undergoes independent non-linear modeling to maintain accuracy, while the segmented approach enables the system to scale to multi-transmission and multi-reception scenarios that would be intractable as a unified complex system
Solution Approach 2:
The patent introduces an intermediary processing stage that bridges single-channel cancellation accuracy with multi-channel system compatibility. This intermediary layer handles the channel combining and separation operations, allowing high-precision digital domain non-linear modeling to be applied effectively in each channel while maintaining overall system adaptability to various multi-channel configurations
Data Source
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AI summary
The present invention discloses a multichannel PIM digital cancellation circuit, including a first frequency-shift variable rate module, a second frequency-shift variable rate module, a first conversion circuit, a second conversion circuit, a duplexer, a second transmission duplexer, a channel combiner, a third conversion circuit, a cascaded filter circuit, a PIM canceller, a feedback circuit, and a first adder. The cascaded filter circuit compensates for channel responses such as a delay difference or a phase difference generated after a transmit signal passes through a digital domain downlink, a digital-to-analog converter, and an analog domain downlink; the cascaded filter circuit simulates a group delay unevenness characteristic of the duplexer in the multichannel PIM digital cancellation circuit; a cascaded filter fits an S parameter of the channel combiner in the multichannel PIM digital cancellation circuit, and precisely fits a combining process of the channel combiner in a digital domain, so that a signal capable of canceling a PIM interference signal of a multi-transmission and multi-reception inter-mediate radio frequency system that includes the channel combiner is finally generated in the present invention.