Dual-Reference Switching Amplifier Sampling for Lower RF Interference
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Solution Overview
Problem
Switching amplifiers generate excessive electromagnetic radio frequency (RF) interference, which interferes with the amplifier and other electronic devices, and existing methods to attenuate this interference either limit bandwidth or compromise the output signal dynamic range.
Innovation Solution
A dual-reference switching amplifier system with separate sets of switching devices and output filters, where the sampling rates of the coarse high voltage and fine low voltage PWM streams are adjusted to optimize RF interference attenuation without degrading the output signal dynamic range, by increasing the sampling rate of the coarse high voltage pulses and maintaining the sampling rate of the fine low voltage pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the sampling rate is increased to allow the filter to provide better attenuation of the RF interference, then the RF interference attenuation is improved, but the available dynamic range of the output signal is reduced
Solution Approach 1:
The patent divides the single PWM stream into two separate PWM streams: a coarse high-voltage PWM stream and a fine low-voltage PWM stream. Each stream operates at different sampling rates, allowing independent optimization. The coarse stream uses a higher sampling rate for better RF attenuation, while the fine stream maintains a lower sampling rate to preserve dynamic range, thus resolving the contradiction between RF interference attenuation and output signal dynamic range.
Solution Approach 2:
The patent changes the sampling rate parameter differently for the two PWM streams. The coarse high-voltage PWM stream operates at a first sampling rate that is higher than the second sampling rate of the fine low-voltage PWM stream. This parameter differentiation allows the system to achieve better RF interference attenuation in the coarse stream while maintaining adequate dynamic range through the fine stream.
2Object-affected harmful factors
If the cutoff frequency is decreased to better attenuate the RF interference, then the RF interference attenuation is improved, but the bandwidth of the switching amplifier is limited
Solution Approach 1:
The patent segments the filtering function across two separate output filters, each associated with a different PWM stream. The first output filter processes the coarse high-voltage PWM stream at a higher sampling rate, allowing the filter to operate effectively at a higher cutoff frequency that preserves bandwidth. The second output filter processes the fine low-voltage PWM stream, providing additional RF attenuation. This segmentation allows the system to achieve better overall RF attenuation without unnecessarily limiting the bandwidth.
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
Effectively reduces RF interference by up to 12 dB while maintaining the output signal dynamic range, as higher frequency coarse high voltage pulses are better attenuated by second-order filters without affecting the output signal performance.
Implementation Method 1
higher frequency coarse high voltage pulses are better attenuated by second-order filters
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 increased relative to the sampling rate of fine lower voltage modulated pulsewidths. This increase in the sampling rate of coarse high voltage modulated pulsewidths results in a reduction in EMI.