RF Echo Cancellation Module for Simultaneous Transmit and Receive
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Solution Overview
Problem
Simultaneous transmit and receive (STR) wireless communication systems face interference due to high-power Tx signal echoes through the duplexer, which can overpower the weak Rx signal, preventing successful decoding.
Innovation Solution
An RF echo cancellation module is used to generate an analog echo cancellation signal based on delayed taps of the transmitted RF signal, with phase shifters and multipliers applying phase shifts and weights to estimate and cancel the echo, allowing for effective echo cancellation in the digital baseband domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a duplexer is used to enable simultaneous transmit and receive over the same frequency, then duplex communication capability is improved, but echo interference from high-power Tx signal leakage into the receive chain worsens
Solution Approach 1:
The patent generates an echo cancellation signal by deliberately creating a copy of the transmitted signal and processing it through simulated duplexer leakage paths, then subtracting this synthesized echo from the received signal. This converts the harmful echo effect into a useful cancellation mechanism by modeling and removing the interference mathematically
Solution Approach 2:
The patent introduces an intermediate echo cancellation signal as a mediator between the transmitted signal and the received signal. This cancellation signal, generated through tap delay lines and complex multiplication, serves as a bridging element that represents the echo component and enables its removal from the received signal
2Measurement precision
If echo cancellation signals are generated using multiple delayed taps with phase shifters and multipliers, then echo cancellation accuracy is improved, but device complexity worsens
Solution Approach 1:
The patent segments the echo cancellation process into multiple discrete delayed taps, where each tap processes a specific time-delayed version of the transmitted signal. This segmentation allows the system to model different propagation paths and echo characteristics independently, improving cancellation accuracy through parallel processing of multiple signal components
Solution Approach 2:
The patent changes the parameters of the transmitted signal by applying different time delays, phase shifts, and complex weights to create multiple versions of the signal. These parameter variations enable the system to match and cancel different echo components that arrive at the receiver at different times and with different characteristics
Data Source
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AI summary
In some demonstrative embodiments, a simultaneous transmit and receive (STR) transceiver may include a receiver; a transmitter; a Radio Frequency (RF) echo cancellation module to generate an analog echo cancellation signal to be applied to a received RF signal via the receiver based on a transmitted RF signal via the transmitter; and a digital baseband module. The RF echo cancellation module may include a plurality of tap modulators to modulate a plurality of delayed taps of the transmitted RF signal. A tap modulator may include a plurality of phase shifters to generate a plurality of phase-shifted signals by applying a plurality of phase shits to a delayed tap; and a plurality of multipliers to multiply the plurality of phase-shifted signals with a respective plurality of weights. The digital baseband module may determine the plurality of weights based on a plurality of subcarriers of a digital frequency-domain signal corresponding to the transmitted RF signal.