Direct digital synthesis radar timing system
OwnerThomas McEwaninventor
Life of this patent
Estimating the term…
Abstract
A direct digital synthesizer (DDS) drives a receive sampling gate at a frequency that is offset from a transmit pulse frequency to produce an expanded time sampled echo signal. The frequency offset generates a smoothly slipping phase between realtime received echoes and the sampling gate that stroboscopically expands the apparent time of the sampled echoes with an exemplary factor of 1-million and a range accuracy of 1-centimeter. The flexibility and repeatability of the digitally synthesized timing system is a quantum leap over analog prior art. The rock solid stability of the DDS allows further accuracy improvement via an error correction table.
Claims9
A Direct Digital Synthesizer (DDS) timing system for expanded time radar systems, comprising:
- a frequency source for providing a transmit clock signal at a transmit dock frequency and for providing a DDS clock signal,
- a transmitter triggered by the transmit clock signal for producing one or more transmit pulses at the transmit clock frequency,
- a DDS responsive to the DDS clock signal for producing a DDS output signal at an offset frequency from the transmit clock frequency,
- a filter for attenuating spurious frequencies in the DDS output signal and for producing a receive clock signal;
- and
- a receiver responsive to the receive dock signal for sampling echoes of the transmit pulses, wherein sampling echoes produces an expanded time output signal.
A method for time expanding radar signals, comprising:
- generating a transmit clock signal at a transmit clock frequency,
- transmitting radar pulses at the transmit clock frequency,
- clocking a DDS at a multiple of the transmit clock frequency,
- applying a tuning word to the DDS to produce a DDS output having a frequency that is offset from the transmit dock frequency,
- filtering the DDS output to attenuate spurious signals and to produce a receive clock signal at a receive clock frequency;
- and
- sampling echoes of the transmitted pulses at the receive clock frequency to produce an expanded time output signal.
Dependencies are inferred from the claim text.