RF Envelope Tracker Notch Filtering for Wideband PA Linearity
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Solution Overview
Problem
Existing RF front-end circuits face distortions and efficiency issues due to inherent output impedance in envelope tracking circuits, particularly at high modulation bandwidths, leading to degradation of modulated voltage and increased power dissipation.
Innovation Solution
A wide modulation bandwidth RF circuit is designed with a tracker circuit generating modulated voltage and an integrated notch circuit that filters the RF offset spectrum, reducing distortions by adjusting notch frequency and bandwidth to overlap with the RF offset spectrum, thereby improving linearity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If envelope tracking circuit is used to improve power amplifier efficiency, then power dissipation is reduced, but output impedance interacts with load current to cause modulated voltage degradation and distortions at high modulation bandwidth
Solution Approach 1:
A notch circuit is introduced as an intermediary component between the envelope tracking circuit and the power amplifier. This notch circuit selectively filters out the problematic frequency components caused by the interaction between output impedance and load current, thereby eliminating distortions while preserving the efficiency benefits of envelope tracking.
Solution Approach 2:
The notch circuit is configured with adjustable parameters including notch frequency and notch bandwidth. By dynamically adjusting these parameters to match the operating conditions and modulation bandwidth, the system optimizes distortion rejection while maintaining modulated voltage quality across different operating points.
2Productivity
If higher modulation bandwidth is used to achieve higher data rates, then wireless communication performance is improved, but output impedance interaction causes increased distortions in RF offset spectrum
Solution Approach 1:
The notch circuit serves as a mediator that specifically targets and removes distortion components in the RF offset spectrum without affecting the main signal band. This allows high modulation bandwidth operation for improved data rates while simultaneously rejecting the harmful spectral regrowth and distortions generated by impedance interactions.
3Reliability
If notch circuit is added to filter modulated voltage and reduce distortions, then linearity and efficiency of amplifier circuit are improved, but device complexity increases
Solution Approach 1:
The notch circuit employs adjustable parameters (notch frequency and bandwidth) that can be optimized for different operating conditions. This flexibility allows the circuit to achieve high linearity performance across various modulation bandwidths and power levels without requiring multiple fixed circuits, thereby managing complexity through parameter optimization rather than structural multiplication.
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 effectively reduces distortions and improves the linearity and efficiency of the amplifier circuit by filtering the RF offset spectrum, enhancing the overall performance of the RF front-end circuit.
Implementation Method 1
a notch circuit coupled between the tracker output and a ground, the notch circuit is configured to filter the modulated voltage in an RF offset spectrum adjacent to the TDD RF spectrum
Data Source
AI summary
A wide modulation bandwidth radio frequency (RF) circuit is provided. In examples discussed herein, the RF front-end circuit includes a tracker circuit configured to generate a modulated voltage at a wide modulation bandwidth. The modulated voltage can be used by an amplifier circuit(s) for amplifying an RF signal(s). Notably, the tracker circuit may have inherent frequency-dependent impedance that can interact with a load current of the amplifier circuit(s) to cause degradation in the modulated voltage, which can further lead to distortions in an RF offset spectrum. In this regard, a notch circuit is provided and configured to operate at an appropriate notch frequency and a notch bandwidth to filter the modulated voltage in the RF offset spectrum. As a result, it may be possible to reduce the distortions caused by the modulated voltage degradation in the RF offset spectrum, thus helping to improve linearity and efficiency of the amplifier circuit(s).