Switched Capacitor Amplifier Filtering for Harmonic Suppression
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Solution Overview
Problem
Amplifiers face challenges in achieving high power efficiency while minimizing co-existence issues with other radio receivers due to harmonic emissions, with existing solutions like analog filtering being costly and inefficient.
Innovation Solution
A switched capacitor power amplifier with a semi-digital filter using a modulated sine wave carrier, which suppresses out-of-band spurs and spectral replicas by offsetting phases of signal components, allowing for high power efficiency and spectral purity without the need for analog filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If analog filtering is used to suppress harmonic emissions, then spectral purity is improved, but cost and integration difficulty increase
Solution Approach 1:
The patent replaces the mechanical/analog filtering system with a digital signal processing system. Multiple power amplifiers are controlled by digitally processed input signals that have been delayed and weighted, allowing spectral shaping and harmonic suppression through digital algorithms rather than physical analog filters. This substitution reduces integration difficulty while maintaining spectral purity.
Solution Approach 2:
The patent divides the single amplifier system into multiple parallel amplifiers (at least two), each processing a segmented portion of the signal spectrum. By distributing the signal processing across multiple amplifiers with different delay and weight settings, the system achieves spectral shaping without requiring complex analog filtering for each amplifier.
2Loss of energy
If switched PA topology is used to achieve high power efficiency, then power efficiency is improved, but harmonic emissions increase causing co-existence issues
Solution Approach 1:
The patent segments the power amplifier system into multiple parallel switched PAs, each operating at high efficiency. By distributing the total output power across multiple efficient switching amplifiers and using digital signal processing to shape the combined spectrum, the system maintains high power efficiency while suppressing harmonic emissions through coherent combination with appropriate delays and weights.
Solution Approach 2:
The patent converts the harmful harmonic emissions from switched PAs into a controllable parameter by using digital signal processing to deliberately shape the spectral content. The switching action that generates harmonics is transformed into a beneficial technique where the harmonics are systematically managed through delay and weight application, converting an unwanted byproduct into a design parameter.
3Object-generated harmful factors
If linear PA is used to reduce harmonic emissions, then spectral purity is improved, but power efficiency deteriorates
Solution Approach 1:
The patent merges the advantages of linear PAs (spectral purity) and switched PAs (power efficiency) by combining multiple switched PAs in parallel with digital signal processing. The system achieves linear-like spectral characteristics through digital filtering and coherent combination, while maintaining the high efficiency of switching operation in each individual amplifier.
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AI summary
Signals are processed to facilitate the mitigation and/or cancellation of undesirable components within the signal. As consistent with one or more embodiments, input/delay circuits offset an input signal in phase, as presented to respective amplifiers. The phase off set is used, upon combination of the outputs of the respective amplifiers, to cancel the undesirable components of the signal. Such an approach may, for example, involve phase offset in a digital domain, with correction upon combination of the signals as presented in an analog domain.