Efficient minimum pulse spread spectrum modulation for...

Details Efficient minimum pulse spread spectrum modulation for... Efficient minimum pulse spread spectrum modulation for...

2005-01-25

2005-01-25

Nguyen, Khanh V. (Department: 2817)

Amplifiers

Modulator-demodulator-type amplifier

C330S251000

Reexamination Certificate

active

06847257

ABSTRACT:
Method and apparatus to enable the use of class D amplifiers without the need for an output filter, while maintaining both a high efficiency and a high audio fidelity. Using the classic differential Pulse Width Modulation scheme, the high frequency carrier is first suppressed to achieve a ternary modulation, and then re-introduced as a common mode pulse whose width is modulated to provide the necessary output voltage, but whose width never decreases below a well-defined threshold. The frequency of the modulator waveform (ramp or triangle) may itself be modulated on a sample-by-sample basis, so that the EMI spectrum of the output waveforms can be made white at high frequencies. The combination of the modulation scheme and spread spectrum high frequency behavior allows the user to eliminate the external filter. Various embodiments are disclosed.

REFERENCES:
patent: 4968948 (1990-11-01), Tokumo et al.
patent: 5077539 (1991-12-01), Howatt
patent: 5767740 (1998-06-01), Fogg
patent: 6211728 (2001-04-01), Chen et al.
patent: 6614297 (2003-09-01), Score et al.

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