RF Cancellation Circuit for Power Amplifier Impedance Mismatch
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Solution Overview
Problem
RF power amplifiers in wireless communications face challenges in maintaining constant load impedance due to antenna impedance mismatches, leading to signal reflections that reduce output power.
Innovation Solution
An RF cancellation circuit is introduced between the power amplifier and the antenna, using directional couplers to extract and phase-shift reflected signals, creating a cancellation signal that eliminates the balance of the reflected signal, thus presenting a stable load impedance to the power amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the load impedance is allowed to vary due to antenna conditions, then the device complexity is reduced, but the output power of the PA decreases due to signal reflections
Solution Approach 1:
The invention captures the harmful reflected signal that would normally be lost and converts it into a useful cancellation signal. The directional coupler extracts the reflected signal, which is then phase-shifted by 180 degrees and amplified to create an anti-phase signal that cancels the reflection, thereby converting the harmful reflection into a beneficial cancellation mechanism that maintains constant load impedance and maximizes output power
Solution Approach 2:
The invention introduces an intermediary cancellation signal path between the reflected signal and the main signal path. The directional coupler, phase shifter, and amplifier form an intermediary system that processes the reflected signal and injects a cancellation signal into the main path, mediating between the variable antenna impedance and the power amplifier to maintain constant load conditions
2Power
If a cancellation circuit is added to eliminate reflected signals, then the output power is optimized, but the device complexity increases
Solution Approach 1:
The invention segments the reflected signal processing into distinct functional blocks: the directional coupler extracts the reflected signal, the phase shifter applies 180-degree phase shift, and the amplifier amplifies the phase-shifted signal. This segmentation allows each component to perform a specific function efficiently, making the overall cancellation system manageable and implementable with standard RF components
Solution Approach 2:
The invention implements a feedback mechanism where the reflected signal is continuously monitored by the directional coupler, processed through phase shifting and amplification, and the resulting cancellation signal is fed back into the main signal path. This closed-loop feedback system automatically adapts to varying antenna conditions and maintains optimal power output without requiring external control
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 solution effectively cancels reflected signals, ensuring a constant load impedance and optimizing total radiated power across varying antenna conditions, enhancing compliance with TRP specifications.
Implementation Method 1
Directional circuitry is used to process the reflected signals without interfering with normal transmitted signals
Implementation Method 2
phase-shifts by 180 degrees and amplifies the extracted portion of the reflected signal
Implementation Method 3
amplifies the extracted portion of the reflected signal to create a cancellation signal
Implementation Method 4
combines the cancellation signal with the balance of the reflected signal to cancel both signals
Data Source
AI summary
The present invention is an RF cancellation circuit located between the output of a power amplifier and downstream circuitry, such as a transmitting antenna. The RF cancellation circuit cancels reflections resulting from antenna impedance mismatches, thereby presenting a constant load impedance to the output of the power amplifier. The RF cancellation circuit extracts a portion of the reflected signal, phase-shifts by 180 degrees and amplifies the extracted portion of the reflected signal to create a cancellation signal, and then cancels the balance of the reflected signal by adding in the cancellation signal. Directional circuitry is used to process the reflected signals without interfering with normal transmitted signals. Presenting a constant load impedance to the output of the power amplifier helps facilitate compliance with total radiated power into load mismatch specifications.