| 摘要 |
A shape modulation transmit loop with digital frequency control permits spectral shaping of a digital pulse stream (12) by controlling the slew rate of the transition signal (16) between successive pulses. The loop is formed when the digital data stream is fed into an up/down counter (152) whose output is coupled to a programmable memory means (154), such as RAM, EEPROM, flash memory or similar electronic storage means. The output (108) of the programmable memory (154) forms a first input to an adder (112) which drives an accumulator (52) with specified steps. Values corresponding to the desired waveform (70) are stored in a lookup table (60) which is coupled to a digital-to-analog conversion circuit (64) which uses the values in the lookup table (60) to construct a sine wave output signal (70) corresponding to the frequency set by the current specified step of the up/down counter (152).
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