Numerically-controlled modulated oscillator and modulation method

A method for synthesizing a waveform having a selected type of modulation, comprising the steps of:

• (a) producing a first number representative of the change in phase of a waveform to be modulated;
• (b) producing a second number for a time interval;
• (c) producing periodically a third number which is representative of said first number, and during said time interval, an arithmetic combination of said first number and said second number;
• (d) producing periodically a fourth number, each consecutive fourth number being the sum of the next preceding fourth number and the current said third number;
• and
• (e) selectively varying said time interval so as to determine the type of said modulation.

An apparatus for synthesizing a waveform having a selected type of modulation, comprising:

• (a) first means, having a first input for receiving a first number representative of a change in phase of a waveform to be modulated and a second input for receiving a second number representative of a change in phase of said waveform to be modulated in response to a modulation signal, for producing periodically a third number representative of an arithmetic combination of said first number and said second number;
• (b) second means, responsive to said third number, for producing periodically a fourth number, each consecutive fourth number being the sum of the next preceding fourth number and the current said third number;
• and
• third means, responsive to a fifth number and a modulation timing signal, for producing as said second number, for a selected time interval, said fifth number, upon the occurrence of a predetermined state of said modulation timing signal, said third means including means responsive to a select control signal, for causing said third means to continue to produce said second number beyond said selected time interval when said select control signal is in a predetermined state.

An apparatus for synthesizing a waveform having a selected type of modulation, comprising:

• (a) first means, having a first input for receiving a first number representative of a change in phase of a waveform to be modulated and a second input for receiving a second number representative of a change in phase of said waveform to be modulated in response to a modulation signal, for producing periodically a third number representative of an arithmetic combination of said first number and said second number;
• (b) second means, responsive to said third number, for producing periodically a fourth number, each consecutive fourth number being the sum of the next preceding fourth number and the current said third number;
• (c) third means, responsive to a fifth number and a modulation timing signal, for producing as said second number, for a selected time interval, said fifth number, upon the occurrence of a predetermined state of said modulation timing signal;
• and
• (d) processor means for producing said second number, whereby said second number is equal to a number representative of a desired change in phase of said waveform to be modulated relative to said first number less the sum of all previous second numbers that have been produced since a predetermined point in time.

a method for synthesizing a waveform having a selected type of modulation, comprising the steps of:

• (a) producing a first number representative of the change in phase of a waveform to be modulated;
• (b) producing for a selected time interval a second number;
• (c) producing periodically a third number which is representative of said first number, and during said selected time interval, an arithmetic combination of said first number and said second number;
• (d) producing periodically a fourth number, each consecutive fourth number being the sum of the next preceding fourth number and the current said third number;
• and
• (e) computing said second number so that it is equal to a desired change in the phase of said waveform to be modulated less the sum of all previous second numbers that have been produced since a predetermined point in time.