Doppler Compensated Digital Non-Linear Waveform Generator Apparatus.
DEPARTMENT OF THE AIR FORCE WASHINGTON DC
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THE PRESENT INVENTION UTILIZES A DIGITAL WAVEFORM GENERATOR FOR Doppler compensation of waveforms to correct for dispersion due to target velocity. The apparatus utilizes a modified binary rate multiplier to produce an accurate clock signal that is related to target velocity. This variable or Doppler clock is used to drive a digital waveform generator to produce a signal for transmission that is predistorted in an opposite sense from the distortion or dispersion that is due to the target velocity. As a result, the return signal from the target has a zero Doppler appearance, which enhances signal processing. The present apparatus also includes a digital method of generating non-linear chirp waveforms. An advantage of using a non-linear chirp in radar is that pulse compression can be performed without incurring the 1 to 1.5 dB loss associated with weighting a linear FM pulse. However, non-linear chirp waveforms are limited to situations where target Doppler is small andor the transmitted pulse length is short, or where compensation for target motion can be employed. The present method of Doppler compensation is applicable to all types of digital waveform generation, including linear and non-linear chirp waveforms.
- Active and Passive Radar Detection and Equipment
- Radiofrequency Wave Propagation