Digital-to-bandpass converter

Claim 1

A signal conversion system for generating a desired bandpass, higher frequency waveform from a relatively lower frequency, bandlimited original waveform, said system comprising: a digital sample generator operative to provide a series of digital signals representative of analog samples taken from said original waveform at a predetermined sampling frequency f s characterized by predetermined intervals; a digital to analog convert and hold circuit, responsive to said series of digital signals, to provide a stairstep waveform signal, each level of which is representative of one of said analog samples and persists for one of said intervals; a gating function generator operative to provide gating pulses at said predetermined sampling frequency and having a pulse width less than the intervals between samples; an analog switch, connected to be responsive to said stairstep waveform signal and to said gating pulses, and operative to provide a train of weighted pulses, said weighted pulses being characterized by having substantially the same widths as said gating pulses, and the same amplitudes as the corresponding levels of said stairstep waveform; and a bandpass filter, connected to receive said weighted pulse train, and responsive thereto to provide said higher frequency waveform.