Edward Regan

US Patent:

46034250, Jul 29, 1986

Filed:

Aug 31, 1984

Appl. No.:

6/646343

Inventors:

Allan M. Berlinsky - Randolph NJ
Edward F. Regan - Middletown RI

Assignee:

Raytheon Company - Lexington MA

International Classification:

H03K 708

US Classification:

375 22

Abstract:

A pulse duration modulated (PDM) signal is generated from a periodic digitized signal which may be produced by sampling an analog signal of frequency F. sub. s and using a digitizing frequency F where F>>F. sub. s. Linearity of the analog signal between sampling points is assumed. A computer solution of the intercept of the assumed straight line between each pair of successive sample values of the digitized signal and a reference triangular waveform of frequency F/2 provides the time interval between intercepts from which the interpolated pulse duration modulated (IPDM) waveform is generated. A method to add low frequency signals in the IPDM domain, useful for providing Class AD amplifiers with a feedback path and for summations of input signals without converting signals back to analog form, operates on the sum of the respective intercept times of each of the signals. The summed intercept times are used to provide an IPDM signal which represents the sum of the original digitized signals. Multiplication of digitized signals in the nonlinear (IPDM) domain is provided by operating on the product of the intercepts of two IPDM signals to obtain the intercepts of a new IPDM signal whose low frequency content is the product of the low frequency component of the two digitized signals.