Switching Amplifier PWM Sampling Split for Lower RF Interference
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Solution Overview
Problem
Switching amplifiers generate excessive electromagnetic RF interference, which can distort output signals and limit bandwidth, and existing methods to reduce this interference often result in increased distortion or high costs.
Innovation Solution
A system and method for a switching amplifier that uses two sets of switching devices with different sampling rates to control voltages, where the sampling rate of the coarse high voltage pulses is reduced while maintaining the sampling rate of the fine low voltage pulses, thereby reducing RF interference without causing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the sampling rate of a single PWM stream is reduced to attenuate RF interference, then RF interference is reduced, but significant distortion is introduced to the output signal
Solution Approach 1:
The invention segments the PWM stream into multiple parallel streams (first PWM stream and second PWM stream), each operating at different sampling rates. The first stream operates at a lower sampling rate to reduce RF interference, while the second stream operates at a higher sampling rate to maintain signal accuracy and prevent distortion. This segmentation allows each stream to be optimized for its specific function.
Solution Approach 2:
The invention applies local quality by assigning different sampling rates to different PWM streams based on their specific requirements. The first PWM stream uses a lower sampling rate where RF interference is the primary concern, while the second PWM stream uses a higher sampling rate where signal fidelity is critical. This localized optimization resolves the contradiction between RF interference reduction and distortion prevention.
2Object-generated harmful factors
If the sampling rate is reduced to reduce RF interference, then RF interference is attenuated, but the bandwidth and frequency range of the amplified signal is limited
Solution Approach 1:
The invention segments the bandwidth requirements across multiple PWM streams. The first stream handles lower frequency components with reduced sampling rate, while the second stream handles higher frequency components with increased sampling rate. This segmentation preserves the overall bandwidth of the amplified signal while reducing RF interference in the aggregate output.
Solution Approach 2:
The invention adds the dimension of multiple parallel PWM streams with different sampling rates, transforming the single-dimension problem of sampling rate selection into a multi-dimensional solution space. This allows simultaneous optimization for both RF interference reduction and bandwidth preservation by operating in the dimension of parallel processing streams.
3Object-generated harmful factors
If conventional filtering methods are used to attenuate RF interference, then some RF interference is reduced, but expensive output filters are required and distortion remains
Solution Approach 1:
The invention extracts the RF interference reduction function from the output filter and relocates it to the PWM generation stage. By implementing differential sampling rates at the source (PWM streams), the system eliminates the need for expensive output filters while maintaining RF interference attenuation. This extraction moves the interference mitigation function upstream in the signal chain.
Solution Approach 2:
The PWM streams self-regulate RF interference through their differential sampling rates, eliminating the need for external filtering components. The system serves its own RF interference reduction needs through the inherent properties of the multi-stream PWM architecture, reducing device complexity and cost.
Data Source
AI summary
The present invention is directed toward providing a system and method of reducing RF interference in switching amplifiers without degrading performance. In one embodiment, the sampling rate of coarse high voltage modulated pulsewidths are decreased relative to the sampling rate of fine lower voltage modulated pulsewidths. This reduction in the sampling rate of coarse high voltage modulated pulsewidths results in a reduction in EMI. In addition, the higher sampling rate of the fine lower voltage modulated pulsewidths mitigates the distortion caused by the reduced sampling rate of the coarse pulsewidths.