US 4,068,178 A · Variable frequency waveform synthesizer

Abstract

A variable frequency waveform synthesizer includes a programmable counter coupled to count cycles of a single reference clock signal and recycle at an intermediate frequency determined by a count number selected in response to frequency selection signals. Because of the need to select an integral count number, a count number that is exactly required for a desired frequency must be rounded off to the nearest integral number and the higher the number the lower the percent round off error. Thus, the percentage frequency error for a plurality of different waveforms that are synthesized as a sequence of discrete steps derived from a common reference clock signal is reduced by dividing the reference frequency to obtain an intermediate frequency signal and dividing each period of the intermediate frequency signal into a plurality of not necessarily equal steps to obtain a stepping signal commanding step changes in the synthesized waveform. The stepping signal is thus exactly periodic at the intermediate frequency and approximately periodic at the higher stepping frequency while the resulting synthesized waveform has a reduced percentage frequency error and only a small harmonic distortion.

Claims18

Dependent claims

A digital waveform synthesizer repetitively generating a waveform at a desired frequency with each cycle of the waveform being generated as N discrete steps, the synthesizer comprising:

a clock generator generating a reference signal at a known frequency;
a frequency divider circuit coupled to repetitively cycle by counting M cycles of the reference signal where M is an integral number that remains constant for a given desired frequency;
a decoder coupled to define discrete parts by dividing each cycle of the frequency divider into an integral number of discrete parts and generate a step increment signal for each discrete part, each discrete part corresponding to one of N steps of the synthesized waveform with at least one of the discrete parts having a time duration different than at least one other discrete part during each cycle of the frequency divider;
and
a waveform generator providing a sequence of N discrete waveform signals defining the synthesized waveform;
the waveform generator being coupled to be incremented in response to the step increment signal for each discrete part provided by the decoder.

3 more elements

A digital waveform synthesizer comprising:

a clock generator connected to generate a reference signal at a known frequency;
a frequency divider connected to receive the reference signal and provide in response thereto a step increment signal that is periodic at an intermediate frequency greater than the frequency of a synthesized output waveform and having a period extending over a plurality of cycles of the step increment signal with at leat two cycles of different duration of the step increment signal occurring during each period of the step increment signal for at least one of the intermediate frequencies;
a waveform signal generator coupled to generate a synthesized output waveform as a sequence of discrete steps which are advanced in synchronism with the cycles of the step increment signal.

Dependencies are inferred from the claim text.

Variable frequency waveform synthesizer

Life of this patent

Variable frequency waveform synthesizer

Life of this patent

Abstract

Claims18