Nyquist folded bandpass sampling receivers and related methods
View Patent ↗Nyquist folded bandpass sampling receivers are disclosed that utilize wideband filters and modulated sampling clocks to identify received signals. In operation, multiple Nyquist zones are allowed to fold on top of each other during sampling. Because the RF sampling clock is modulated, separate frequency modulations can be induced within each Nyquist zone. The signals that are folded together from different Nyquist zones can then be identified and distinguished. In particular, when the Nyquist zones fold on top of each other, the different signals from different Nyquist zones can be separated and identified based on the fact that the added modulation is different for each Nyquist zone. Thus, by using one or more clock modulations to induce frequency modulations that are Nyquist zone dependent, multiple Nyquist zones can be aliased together while still allowing for signals from different Nyquist zones to be separated and identified. Other variations and implementations are also described.
1. Receive path circuitry for a bandpass sampling receiver having folded Nyquist zones, comprising:
wideband filter circuitry having a center frequency within a frequency range of interest and having a bandwidth less than or equal to the frequency range of interest and wide enough to cover multiple Nyquist zones associated with a modulated sampling clock; and
sampling circuitry configured to receive a filtered signal from the wideband filter circuitry and to receive the modulated sampling clock signal as an input, the modulated sampling clock signal being configured to provide non-uniform sampling for signals within the multiple Nyquist zones to induce frequency modulation on signals dependent on a Nyquist zone of origin.
2. The receive path circuitry of claim 1 , wherein the modulated sampling clock signal comprises a frequency modulated clock signal.
3. The receive path circuitry of claim 2 , wherein the frequency modulated clock signal comprises a linear sawtooth modulation, a sinusoidal modulation, a triangle modulation, a frequency shift key modulation, a frequency agile modulation, a communications frequency modulation, or a combination thereof.
4. The receive path circuitry of claim 1 , wherein the sampling circuitry comprises:
non-quantizing sampling circuitry;
an analog interpolation filter coupled to receive the output of the non-quantizing sampling circuitry, the analog interpolation filter having a center frequency within a Nyquist zone of operation for the non-quantizing sampling circuitry; and
analog to digital converter (ADC) circuitry configured to receive a quantization sampling clock signal and to quantize an analog signal received from the analog interpolation filter.
5. The receive path circuitry of claim 4 , wherein the modulated clock signal comprises a frequency modulated clock signal.
6. The receive path circuitry of claim 4 , wherein the wideband filter circuitry comprises a wideband filter having bandwidth of 10 GHz or more and the modulated sampling clock has a sampling rate of 1 GHz or more.
7. The receive path circuitry of claim 4 , wherein the wideband filter circuitry comprises a wideband filter having bandwidth of 20 GHz or more and the modulated sampling clock has a sampling rate of 2 GHz or more.
8. The receive path circuitry of claim 4 , wherein the analog interpolation filter comprises a tunable or switchable interpolation filter.
9. The receive path circuitry of claim 4 , wherein the modulated sampling clock comprises clock signal having a tunable frequency or an adjustable frequency modulation or both.
10. The receive path circuitry of claim 1 , wherein the wideband filter circuitry comprises a tunable bandpass filter having a tunable center frequency dependent upon a filter control signal, the center frequency being tunable across the frequency range of interest, and the tunable bandpass filter having a bandwidth less than the frequency range of interest.
11. The receive path circuitry of claim 1 , further comprising digital signal processing circuitry coupled to receive an output from the sampling circuitry and configured to identify different signals from different Nyquist zones based upon differences in frequency modulation due to the non-uniform sampling caused by the modulated sampling clock.
12. The receive path circuitry of claim 11 , wherein the digital signal processing circuitry is configured to utilize a frequency slope associated with multiple samples related to a signal to identify the signal and a Nyquist zone in which it was located.
13. The receive path circuitry of claim 11 , wherein the digital signal processing circuitry is configured to remove the induced modulation associated with the Nyquist zone in which the signal was located and to acquire the original signal.
14. The receive path circuitry of claim 1 , further comprising signal injection circuitry coupled to the wideband filter circuitry to provide an injected signal that is combined with the input signal received by the wideband filter circuitry; and digital signal processing circuitry coupled to receive an output from the sampling circuitry and configured to identify modulations to the injected signal in order to recover the modulated clock signal, the recovered modulated clock signal being further utilized to identify different signals from different Nyquist zones based upon differences in frequency modulation due to the non-uniform sampling caused by the modulated sampling clock.
15. The receive path circuitry of claim 14 , wherein the digital signal processing circuitry comprises a delay signal path and a clock recovery signal path.
16. The receive path circuitry of claim 15 , wherein the digital signal processing circuitry is configured to remove the recovered modulated clock signal from the sampled data signal and to use the recovered modulated clock signal to analyze the sampled data signal.
17. The receive path circuitry of claim 14 , wherein the wideband filter circuitry comprises a wideband filter having bandwidth of 10 GHz or more and the modulated sampling clock has a sampling rate of 1 GHz or more.
18. The receive path circuitry of claim 14 , further comprising digital signal processing circuitry coupled to receive an output from the sampling circuitry and configured to identify different signals from different Nyquist zones based upon differences in frequency modulation due to the non-uniform sampling caused by the modulated sampling clock.
19. The receive path circuitry of claim 14 , wherein the injected signal comprises a known continuous wave signal.
20. The receive path circuitry of claim 14 , wherein the injected signal comprises a known arbitrary waveform signal.
21. The receive path circuitry of claim 1 , wherein the wideband filter circuitry comprises a tunable bandpass filter circuitry having a tunable center frequency within a frequency range of interest and having a bandwidth greater than a single Nyquist zone associated with a modulated sampling clock.
22. The receive path circuitry of claim 21 , further comprising clock generation circuitry coupled to provide the modulated sampling clock signal to the sampling circuitry, the clock generation circuitry being configured to generate at least two selectable modulated sampling clock signals, each sampling clock signal being configured to correspond to a different frequency.
23. The receive path circuitry of claim 22 , wherein the clock generation circuitry is configured to allow selection of the modulated sampling clock signal through tuning of the modulated sampling clock signal.
24. The receive path circuitry of claim 22 , wherein the clock generation circuitry is configured to generate a plurality of modulated clock signals and configured to allow selection of one of these modulated clock signals as an output.
25. A method for bandpass sampling of signals using folded Nyquist zones, comprising:
utilizing wideband filter circuitry to filter a signal within a frequency range of interest, the bandpass filter having a bandwidth less or equal to than the frequency range of interest and wide enough to cover multiple Nyquist zones associated with a modulated sampling clock;
generating a modulated sampling clock configured to provide non-uniform sampling for signals within the multiple Nyquist zones; and
bandpass sampling a filtered signal from the wideband filter circuitry covering multiple Nyquist zones using the modulated sampling clock.
26. The method of claim 25 , wherein the generating step comprises generating a frequency modulated clock signal for the modulated sampling clock signal.
27. The method of claim 26 , further comprising modulating the chirp frequency modulated clock signal with a linear sawtooth modulation, a sinusoidal modulation, a triangle modulation, a frequency shift key modulation, a frequency agile modulation, a communications frequency modulation, or a combination thereof.
28. The method of claim 25 , wherein the bandpass sampling step comprises:
bandpass sampling a filtered signal from the wideband filter circuitry covering multiple Nyquist zones without quantizing the signal;
filtering the sampled signal with an analog interpolation filter having a center frequency within a Nyquist zone; and
quantizing a signal received from the analog interpolation filter.
29. The method of claim 28 , wherein the generating step comprises generating a frequency modulated clock signal for the modulated sampling clock signal.
30. The method of claim 28 , wherein the utilizing step comprises utilizing wideband filter circuitry having a bandwidth of 10 GHz or more and wherein the generating step comprises generating a modulated sampling clock signal having a sampling rate of 1 GHz or more.
31. The method of claim 28 , wherein the utilizing step comprises utilizing wideband filter circuitry having a bandwidth of 20 GHz or more and wherein the generating step comprises generating a modulated sampling clock signal having a sampling rate of 2 GHz or more.
32. The method of claim 28 , further comprising utilizing a tunable or switchable analog interpolation filter having two or more filter paths.
33. The method of claim 28 , wherein the generating step comprises generating a frequency modulated sampling clock and further tuning a center frequency for the frequency modulated sampling clock or adjusting a modulation for the frequency modulated sampling clock or both.
34. The method of claim 25 , wherein the utilizing step comprises utilizing a tunable bandpass filter and further comprising tuning the center frequency of the tunable bandpass filter within the frequency range of interest.
35. The method of claim 25 , further comprising processing sampled signals to identify different signals from different Nyquist zones based upon differences in frequency modulation due to the non-uniform sampling caused by the modulated sampling clock.
36. The method of claim 35 , wherein the processing step utilizes a slope associated with multiple samples related to a signal to identify the signal and a Nyquist zone in which it was located.
37. The method of claim 35 , wherein the processing step comprises utilizing the Nyquist zone in which the signal was located, removing an induced modulation for that Nyquist zone, and acquiring the original signal.
38. The method of claim 25 , further comprising injecting a known signal combined with the input signal; recovering the modulated clock signal utilizing the injected known signal; and utilizing the recovered modulated clock signal to identify signals within the input signal.
39. The method of claim 38 , wherein the recovering step comprises generating a delayed signal path and generating a clock recovery signal path.
40. The method of claim 38 , wherein the utilizing step comprises utilizing wideband filter circuitry having a bandwidth of 10 GHz or more and wherein the generating step comprises generating a modulated sampling clock signal having a sampling rate of 1 GHz or more.
41. The method of claim 38 , wherein the injecting step comprises injecting a known continuous wave signal.
42. The method of claim 38 , wherein the injecting step comprises injecting a known arbitrary waveform signal.
43. The method of claim 25 , wherein the utilizing step comprises utilizing a tunable bandpass filter circuitry to filter a signal within a frequency range of interest, the bandpass filter having a bandwidth greater than a single Nyquist zone associated with a modulated sampling clock.
44. The method of claim 43 , wherein the generating step comprises generating at least two selectable modulated sampling clock signals, each sampling clock signal being configured to correspond to a different frequency.