RF Front End Feed-Forward Cancellation for TX-RX Isolation
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Solution Overview
Problem
Existing radio frequency front ends for wireless communication face challenges in providing adequate isolation between transmit and receive paths without bulky elements like circulators or transmit/receive switches, and they fail to effectively cancel portions of the transmit signal reflected by the antenna, leading to performance degradation in both full-duplex and half-duplex operations.
Innovation Solution
A radio frequency front end utilizing a modified quadrature balanced power amplifier with intentionally unbalanced power amplifiers to create a feed-forward signal that cancels the reflected transmit signal, eliminating the need for bulky elements and achieving isolation through phase differences in signal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a transmit/receive switch is used to isolate transmit and receive paths, then isolation between paths is improved, but the switch becomes bulky with high power loss and high cost
Solution Approach 1:
The power amplifier is segmented into two separate power amplifiers, each handling a different signal path. This segmentation eliminates the need for a bulky transmit/receive switch while maintaining isolation between transmit and receive paths, as each amplifier independently drives its designated path without requiring physical switching.
Solution Approach 2:
The radio frequency front end is designed to support both full-duplex and half-duplex operation modes using the same antenna and simplified circuit topology. The system achieves multi-functionality without requiring mode-specific switching components, reducing overall device complexity and bulkiness while maintaining adequate isolation in both operation modes.
2Productivity
If a circulator is used for full-duplex operation, then simultaneous transmit and receive is enabled, but the leaking portion of transmit signal still reaches receive path input causing interference
Solution Approach 1:
A feed-forward signal is generated that is equal in magnitude but opposite in phase to the expected self-interference signal. This anti-action signal is injected into the receive path beforehand to cancel out the harmful reflected transmit signal, enabling clean simultaneous transmit and receive operation without requiring complex circulator-based isolation.
Solution Approach 2:
The patent converts the harmful reflected transmit signal into a useful cancellation mechanism. By deliberately generating and injecting an equal-and-opposite feed-forward signal, the system transforms the potential interference problem into an active cancellation solution, improving full-duplex performance while simplifying the overall architecture.
3Power
If signal switch connects antenna to transmit path output, then full transmit signal is supplied to antenna, but the switch must be rated for maximum transmit power making it expensive
Solution Approach 1:
The single high-power transmit path is segmented into two parallel power amplifier paths. Each amplifier operates at a lower power level, eliminating the need for an expensive high-power-rated switch. The segmented architecture maintains full transmit power delivery capability while using more affordable, lower-rated components.
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
The solution provides significant isolation between transmit and receive paths, cancels reflected transmit signals, and maintains low insertion loss, enabling dual-mode operation with improved performance compared to prior art designs, reducing the need for additional circuitry and bulky components.
Implementation Method 1
a magnitude and/or a phase of their amplification factors differ from each other
Implementation Method 2
create a feed-forward signal that cancels the reflected transmit signal
Data Source
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AI summary
A radio frequency front end for wireless communication, comprises an antenna port, a receive path comprising a receive signal input configured to receive a receive signal, and a transmit path comprising a modified quadrature balanced power amplifier that comprises a transmit signal input port for receiving a transmit input signal, at least a first transmit signal path for amplifying a first portion of the transmit input signal and a second transmit signal path for amplifying a second portion of the transmit input signal, a transmit signal output port for supplying a transmit signal generated from the amplified first portion and the amplified second portion to the antenna port, and an output isolated port connected to the receive signal input. The first transmit signal path and/or the second transmit signal path are configured or configurable so that a magnitude and/or a phase of their amplification factors differ from each other.