| 摘要 |
A digital synthesizer is disclosed for generating complex waveforms of selected multiple frequencies and selected phases in the time domain. A plurality of independent frequency sources each produces square waves at its selected fundamental frequency and at frequencies which are integral multiples, such as twice, four times and eight times, that of the fundamental. A sampling clock whose frequency is at least the highest frequency produced by any frequency source, multiplied by the number of fundamentals used, provides a signal to a binary counter whose output is connected to a line decoder or multiplexer which multiplexes each frequency source's signals on a time-share basis via a system of AND and OR gates. The signal produced by the OR gates is provided to address a memory device which contains a predetermined waveform in a look-up table. The signal produced by the memory device is therefore the multiplexed combination of the signals that would have been produced therefrom had each frequency source alone been applied to address the memory. The complex waveform produced by the memory is provided to a plurality of serial in-parallel out shift registers whose outputs are applied to a plurality of digital-to-analog converters each producing identical waveforms time-delayed with respect to each other.
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