Adaptive frequency correction for pulse compression radar
Various implementations described herein are directed to adaptive frequency correction for pulse compression radar. In one implementation, a method may include generating a first transmission signal using a first direct digital synthesizer of a pulse compression radar system based on frequency sweep coefficients. The method may also include comparing a frequency of the first transmission signal at a feedback loop of a phase locked loop circuit and a frequency of an ideal waveform signal. The method may further include generating adaptive frequency coefficients based on the comparison, where the adaptive frequency coefficients are configured to compensate for a difference between the frequency of the first transmission signal at the feedback loop and the frequency of the ideal waveform signal. The method may additionally include generating a compensated transmission signal using the pulse compression radar system based on the adaptive frequency coefficients and the frequency sweep coefficients.
1. A method, comprising:
generating a first transmission signal using a first direct digital synthesizer of a pulse compression radar system based on one or more frequency sweep coefficients, wherein the one or more frequency sweep coefficients correspond to an ideal waveform signal, and wherein the pulse compression radar system includes a phase locked loop circuit;
comparing a frequency of the first transmission signal at a feedback loop of the phase locked loop circuit and a frequency of the ideal waveform signal;
generating one or more adaptive frequency coefficients based on the comparison, wherein the one or more adaptive frequency coefficients are configured to compensate for a difference between the frequency of the first transmission signal at the feedback loop and the frequency of the ideal waveform signal; and
generating a compensated transmission signal using the pulse compression radar system based on the one or more adaptive frequency coefficients and the one or more frequency sweep coefficients.
2. The method of claim 1 , wherein the first transmission signal at the feedback loop of the phase locked loop circuit comprises a down converted output signal from a voltage controlled oscillator of the phase locked loop.
3. The method of claim 1 , wherein comparing comprises comparing the frequency of the first transmission signal at the feedback loop of the phase locked loop circuit and a frequency of an output signal of a second direct digital synthesizer, wherein the output signal is generated based on the one or more frequency sweep coefficients.
4. The method of claim 3 , wherein the one or more adaptive frequency coefficients are configured to compensate for a difference between the frequency of the first transmission signal at the feedback loop and the frequency of the output signal of the second direct digital synthesizer.
5. The method of claim 1 , wherein comparing comprises comparing a time-frequency curve of the first transmission signal at the feedback loop to a time-frequency curve of the ideal waveform signal.
6. The method of claim 1 , wherein generating the compensated transmission signal comprises:
subtracting the one or more adaptive frequency coefficients from the one or more frequency sweep coefficients; and
using the difference between the one or more adaptive frequency coefficients and the one or more frequency sweep coefficients as an input to the first direct digital synthesizer.
7. The method of claim 1 , wherein generating the compensated transmission signal comprises:
inverting the one or more adaptive frequency coefficients;
adding the inverted one or more adaptive frequency coefficients and the one or more frequency sweep coefficients to produce a sum; and
using the sum as an input to the first direct digital synthesizer.
8. The method of claim 1 , wherein generating the compensated transmission signal comprises:
expressing the one or more adaptive frequency coefficients as one or more correction ratios;
multiplying the one or more correction ratios with the one or more frequency sweep coefficients to produce a product; and
using the product as an input to the first direct digital synthesizer.
9. The method of claim 1 , further comprising continuously updating the one or more adaptive frequency coefficients.
10. The method of claim 1 , further comprising generating the one or more adaptive frequency coefficients in real-time or substantially near real-time.
11. A method, comprising:
generating a first transmission signal using a first direct digital synthesizer of a pulse compression radar system based on one or more frequency sweep coefficients, wherein the one or more frequency sweep coefficients correspond to an ideal waveform signal, and wherein the pulse compression radar system includes a phase locked loop circuit;
comparing a frequency of the first transmission signal at a feedback loop of the phase locked loop circuit and a frequency of an output signal of a second direct digital synthesizer, wherein the first transmission signal at the feedback loop of the phase locked loop circuit comprises a down converted output signal from a voltage controlled oscillator of the phase locked loop, and wherein the output signal is generated based on the one or more frequency sweep coefficients;
generating one or more adaptive frequency coefficients based on the comparison, wherein the one or more adaptive frequency coefficients are configured to compensate for a difference between the frequency of the first transmission signal at the feedback loop and the frequency of the ideal waveform signal; and
generating a compensated transmission signal using the pulse compression radar system based on the one or more adaptive frequency coefficients and the one or more frequency sweep coefficients.
12. The method of claim 11 , wherein the one or more adaptive frequency coefficients are configured to compensate for a difference between the frequency of the first transmission signal at the feedback loop and the frequency of the output signal of the second direct digital synthesizer.
13. The method of claim 11 , wherein generating the compensated transmission signal comprises:
subtracting the one or more adaptive frequency coefficients from the one or more frequency sweep coefficients; and
using the difference between the one or more adaptive frequency coefficients and the one or more frequency sweep coefficients as an input to the first direct digital synthesizer.
14. The method of claim 11 , wherein generating the compensated transmission signal comprises:
inverting the one or more adaptive frequency coefficients;
adding the inverted one or more adaptive frequency coefficients and the one or more frequency sweep coefficients to produce a sum; and
using the sum as an input to the first direct digital synthesizer.
15. The method of claim 11 , wherein generating the compensated transmission signal comprises:
expressing the one or more adaptive frequency coefficients as one or more correction ratios;
multiplying the one or more correction ratios with the one or more frequency sweep coefficients to produce a product; and
using the product as an input to the first direct digital synthesizer.
16. The method of claim 11 , further comprising continuously updating the one or more adaptive frequency coefficients.
17. The method of claim 11 , further comprising generating the one or more adaptive frequency coefficients in real-time or substantially near real-time.
18. A pulse compression radar system, comprising:
a processor;
a memory comprising a plurality of program instructions which, when executed by the processor, cause the processor to store in memory:
one or more frequency sweep coefficients, wherein the one or more frequency sweep coefficients correspond to an ideal waveform signal; and
one or more adaptive frequency coefficients;
a first direct digital synthesizer configured to generate a signal based on the one or more frequency sweep coefficients and the one or more adaptive frequency coefficients;
a phase locked loop circuit configured to convert the frequency of the signal from the first direct digital synthesizer; and
a transmitter module configured to amplify the converted signal from the phase locked loop circuit for output by an antenna;
wherein the one or more adaptive frequency coefficients are generated based on a comparison of a frequency of a transmission signal at a feedback loop of the phase locked loop circuit and a frequency of the ideal waveform signal.
19. The pulse compression radar system of claim 18 , wherein the transmission signal at the feedback loop of the phase locked loop circuit comprises a down converted output signal from a voltage controlled oscillator of the phase locked loop.
20. The pulse compression radar system of claim 18 , wherein the one or more adaptive frequency coefficients are generated based on a comparison of the frequency of the transmission signal at the feedback loop of the phase locked loop circuit and a frequency of an output signal of a second direct digital synthesizer.