Switching Amplifier Pulse Timing for Low RF Interference
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Solution Overview
Problem
Conventional switching amplifiers generate excessive electromagnetic radio frequency (RF) interference while attempting to minimize signal distortion, often increasing RF interference by increasing the number of switching transistors or introducing distortion through varying switching times.
Innovation Solution
A switching amplifier system that applies periodic pulses to output terminals, modulating pulse widths based on input signal magnitude and varying the timing of unmodulated pulses to minimize RF interference without introducing significant distortion, ensuring constant sampling times for the input signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of switching transistors is increased to minimize signal distortion through balanced operation, then signal distortion is reduced, but RF interference increases
Solution Approach 1:
The patent applies periodic action by using asynchronous pulse sequences with specific duty cycles to drive the switching transistors. The first pulse sequence has a first duty cycle and the second pulse sequence has a second duty cycle, creating periodic switching patterns that minimize distortion while controlling RF interference through the asynchronous timing relationship between the two sequences.
Solution Approach 2:
The patent employs asymmetry by using asynchronous pulse sequences where the switching times of the first and second pulse sequences are deliberately misaligned. This asymmetric timing arrangement allows the amplifier to achieve balanced operation for distortion reduction without requiring symmetric switching patterns that would increase RF interference.
2Object-generated harmful factors
If switching times are varied to minimize RF interference frequency, then RF interference frequency is reduced, but output signal distortion increases
Solution Approach 1:
The patent uses periodic action by maintaining regular, periodic pulse sequences with fixed duty cycles rather than varying the switching times irregularly. The first pulse sequence repeats with a specific period and the second pulse sequence repeats with another specific period, ensuring that sampling occurs at regular intervals to avoid distortion while still managing RF interference through the asynchronous relationship between the two sequences.
3Measurement precision
If pulse widths are modulated based on input signal magnitude, then output signal accuracy is improved, but RF interference magnitude increases
Solution Approach 1:
The patent applies periodic action by using asynchronous pulse sequences with specific duty cycles to drive the switching transistors. The first pulse sequence has a first duty cycle and the second pulse sequence has a second duty cycle, creating periodic switching patterns that minimize distortion while controlling RF interference through the asynchronous timing relationship between the two sequences.
Data Source
AI summary
A switching amplifier includes first and second output terminals that may be connected to a load. A pulse-width modulator receiving an input signal to obtain respective positive and negative values of the input signal. The modulator is connected to first and second switching circuits. The first switching circuit applies a plurality of pulses to the first output terminal that, in response to the positive samples, have a constant frequency and are pulse-width modulated, and, in response to the negative samples, have a varying frequency and a constant width. Similarly, the second switching circuit applies a plurality of pulses to the second output terminal that, in response to the negative samples, have a constant frequency and are pulse-width modulated, and, in response to the positive samples, have a varying frequency and a constant width. The varying phase of the constant width pulses disperses RF interference across a wider spectrum.