Adjacent Channel Interference Cancellation in Digital Microwave Modems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing digital microwave systems face significant challenges in effectively canceling adjacent channel interference, which leads to a decrease in signal-to-noise ratio due to limited filtering capabilities of band pass filters and residual interference signals in dual-channel bonding technology with high-order QAM modulation.
Innovation Solution
A method and modem system that utilize a cancellation signal from an adjacent channel to filter and adjust its frequency to match the interference signal, then multiply it by a gain factor to subtract from the affected channel, combined with error adjustment to minimize remaining interference, thereby improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If band pass filter and low pass filter are used to filter modulation signals before decoding, then filtering capability is provided, but adjacent channel interference signals cannot be completely eliminated and signal to noise ratio decreases
Solution Approach 1:
The patent converts the harmful adjacent channel interference signal into a useful cancellation signal. By extracting the interference signal from the adjacent channel, processing it through filtering and frequency adjustment, and then subtracting it from the affected channel, the system transforms the harmful interference into a beneficial cancellation process that improves signal quality and restores the signal to noise ratio
Solution Approach 2:
The patent introduces an intermediary cancellation signal processing mechanism between the received signal and the decoder. This intermediary process includes filtering the cancellation signal to match phase and amplitude characteristics, adjusting its frequency, and adaptively determining the gain factor. This intermediary step effectively removes adjacent channel interference before the signal reaches the decoder, preventing degradation of signal to noise ratio
2Productivity
If dual-channel bonding technology is used to transmit larger amount of data with fewer devices, then device quantity and installation cost are reduced, but adjacent channel interference occurs during signal separation
Solution Approach 1:
The patent converts the harmful adjacent channel interference signal into a useful cancellation signal. By extracting the interference signal from the adjacent channel, processing it through filtering and frequency adjustment, and then subtracting it from the affected channel, the system transforms the harmful interference into a beneficial cancellation process that improves signal quality and restores the signal to noise ratio
Solution Approach 2:
The patent implements a feedback mechanism where the cancellation signal is derived from the adjacent channel signal itself. The system continuously monitors the adjacent channel, extracts the interference component, processes it through adaptive filtering and frequency adjustment, and feeds back the processed cancellation signal to subtract from the affected channel. This closed-loop feedback approach dynamically compensates for adjacent channel interference while maintaining high data transmission capacity
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for canceling adjacent channel interference includes: receiving signal of a first channel, where an interference signal of a second channel remains in the signal of the first channel, and the second channel and the first channel are adjacent channels; receiving a cancellation signal provided by the second channel for canceling the interference signal; filtering the received cancellation signal so that phase characteristics and amplitude variation characteristics of the filtered cancellation signal are the same as phase characteristics and amplitude variation characteristics of the interference signal of the second channel that remains in the signal of the first channel; adjusting a frequency of the filtered cancellation signal, where the adjusted frequency of the cancellation signal is the same as a frequency of the interference signal; multiplying the cancellation signal with the adjusted frequency by a gain factor to obtain a signal to be cancelled; and subtracting the signal to be cancelled from the signal of the first channel, and canceling the interference signal to obtain a signal to be decoded. According to the technical solutions provided in the embodiments of the present invention, interference signals of adjacent channels are cancelled, and the signal to noise ratio is improved.