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.

Abstract: A digital sound synthesizer produces a variable spectral line width to synthesize tones by accumulating phase quanta sequentially for each of a set of tone samples. The rate of accumulation of phase for each tone is randomly altered with preset values of phase increment to broaden the spectral line. The broadened spectral lines provide a display with a spectral presentation of sounds more closely resembling naturally occurring sounds. The embodiment shows how one-hundred non-harmonic frequencies can be generated (using integrator 64), each of which can be independently amplitude controlled and band-width modulation controlled using random deviation of a sine wave.

Abstract: A divider/combiner amplifier circuit divides input power through a sectored coaxial line to a plurality of longitudinal parallel channels spaced around the circumference of a cylinder; the power in each channel is amplified by a semiconductor device; and the amplified power is combined in another sectored coaxial line. A microwave waveguide connected to the input and output of each amplifying device confines the microwave energy of the operating mode to the longitudinal channel formed by said waveguide. Each waveguide extends longitudinally along the cylinder and each is circumferentially spaced from its neighboring waveguide by a space which forms a cut-off waveguide to the operating mode.