QBPA RF Front End With Pre-PA Self-Interference Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional RF front ends for wireless communications suffer from power efficiency loss and signal-to-noise ratio degradation due to the implementation of Transmit-Receive Self Interference Cancellation (SIC) mechanisms post-power amplifier, which complicates the design and limits wide-band signal isolation.
Innovation Solution
A multi-mode RF front end with a Quadrature Balanced Power Amplifier (QBPA) configuration that generates and amplifies SIC signals pre-power amplifier, reusing the QBPA power amplifiers to improve efficiency and minimize signal-to-noise losses, while allowing for flexible adaptation to different leakage mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If SIC is implemented at the PA output (post-PA), then transmit-receive isolation is improved, but power efficiency is degraded and signal-to-noise ratio is reduced
Solution Approach 1:
The patent implements SIC at the input of the power amplifier (pre-PA) rather than at the output. The cancellation signal is generated and applied before the PA stage, allowing the PA to amplify both the transmit signal and the cancellation signal together. This preliminary action avoids the need for a separate post-PA cancellation path, thereby improving power efficiency while maintaining transmit-receive isolation.
Solution Approach 2:
The patent merges the transmit signal path and the cancellation signal path by feeding both signals into the same power amplifier. The PA amplifies both signals simultaneously, and their combined output provides both the transmitted signal and the cancelled signal through the antenna. This merging eliminates redundant amplification stages and improves overall power efficiency.
2Object-affected harmful factors
If SIC is implemented at the PA output (post-PA), then transmit-receive isolation is improved, but signal-to-noise ratio is degraded
Solution Approach 1:
By implementing SIC pre-PA, the cancellation signal is combined with the transmit signal before amplification. This allows the PA to process both signals together through its inherent noise floor, avoiding the introduction of additional noise from separate post-PA cancellation circuitry. The signal-to-noise ratio is preserved because the cancellation occurs in the high-signal regime before the PA's noise is added.
3Object-affected harmful factors
If unequal PA paths are used to enable feed-forward cancellation, then transmit-receive isolation is improved, but device complexity increases due to amplitude and phase control requirements
Solution Approach 1:
The cancellation signal is generated and combined with the transmit signal before the power amplifier stage. This preliminary combination simplifies the control requirements because the PA's inherent linearity and symmetry can be exploited, reducing the need for complex post-PA amplitude and phase adjustment circuitry.
Solution Approach 2:
The patent uses identical PA paths for both transmit and cancellation signals, making the PA system universal for both functions. This approach reduces complexity by eliminating the need for separate, specially tuned unequal PA paths, while still achieving effective cancellation through the combined signal approach.
4Object-affected harmful factors
If conventional SIC implementation is used, then transmit-receive isolation is improved, but the system loads both TX and RX channels creating power efficiency loss
Solution Approach 1:
The patent merges the TX and cancellation signal paths by feeding both into the same PA. This combining allows the PA to amplify both signals simultaneously using its full power capability, rather than having separate amplification paths that would both be partially loaded. The result is improved power efficiency while maintaining isolation.
Solution Approach 2:
The PA is made universal by using it for both transmit signal amplification and cancellation signal amplification. This multi-functionality eliminates the need for dedicated cancellation amplification hardware, reducing overall system power consumption while maintaining effective SIC performance.
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
This approach enhances power efficiency and reduces signal-to-noise degradation, enabling improved transmit-receive isolation and supporting wide-band signal processing with reduced complexity and power consumption.
Implementation Method 1
a first power amplifier (PA A) configured to amplify the transmit input signal and a second power amplifier (PA B) configured to amplify the cancellation input signal
Implementation Method 2
a hybrid coupler configured to divide a combined signal into a first part and a second part, with a phase difference of 90° between the first part and the second part
Implementation Method 3
combine the amplified first and second parts of the input signal to form a first output signal at a second port and a second output signal at a third port
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present relates to a Radio Frequency (RF) front end for wireless communications, in particular for use in a Half Duplex, Full Duplex and/or Frequency Division Duplex transceiver. The RF front end of the invention is especially based on a Quadrature Balanced Power Amplifier (QBPA). The RF front end comprises an antenna port for outputting a transmit signal to and receiving a receive signal from an antenna, and a receive port for outputting the receive signal to a signal processing section. Further, it comprises a cancellation input signal generator for generating a cancellation input signal and outputting the cancellation input signal to the QBPA, and comprises the QBPA, which is configured to: receive a transmit input signal at a first port or a fourth port, receive a cancellation input signal from the cancellation input signal generator, and receive the receive signal at a second port connected to the antenna port.