Time-based circuits and systems for wideband spatial signal processing
An N-element baseband (BB) time-domain spatial signal processor system and methodology for large modulated bandwidth multi-antenna receivers are provided. Such a processor generally includes a pipeline converter configured as an asynchronous time-to-digital converter, wherein the asynchronous time-to-digital converter arrangement generates a residue value and an asynchronous pulse and is further arranged to amplify the residue value so as to result in an amplified residue value; and a 2-bit flash time-to-digital-converter configured to quantize the amplified residue value. Thus, a true-time delay spatial signal processing system and technique in the time-domain that enables beamforming, beam-nulling and multiple independent interference cancellation after time-alignment of signals using cascaded voltage-to-time converters and quantization using relaxed pipeline time-to-digital converters is presented.
1. A multiple element (N-element) baseband (BB) time-domain spatial signal processor, comprising:
a plurality of in series voltage-to-time converters integral to the N-element baseband (BB) time-domain spatial signal processor and configured to time-align and combine one or more received continuous-time baseband signals to result in one or more interference free intended signals; and
a pipeline converter integral to the N-element baseband (BB) time-domain spatial signal processor and configured to quantize the intended signals received from the plurality of voltage-to-time converters.
2. The N-element baseband (BB) time-domain spatial signal processor of claim 1 , wherein the plurality of in series voltage-to-time converters are configured to relate the one or more received continuous-time baseband signals to one or more time-domain output pulses, wherein the one or more time-domain output pulses include a time delay proportional to an amplitude value of the one or more received continuous-time baseband signals.
3. The N-element baseband (BB) time-domain spatial signal processor of claim 1 , wherein the plurality of in series voltage-to-time converters combine constructively a time-aligned one or more received continuous-time baseband signals for beamforming so as to increase a signal-to-noise ratio of the combined received signal.
4. The N-element baseband (BB) time-domain spatial signal processor of claim 1 , wherein the plurality of in series voltage-to-time converters combine destructively a time-aligned one or more received baseband interference signals for a beam-nulling so as to cancel one or more received baseband interference signals.
5. The N-element baseband (BB) time-domain spatial signal processor of claim 1 , wherein the processor utilizes a Kronecker decomposition to find an array of delay compensating values and filter one or more independent interference signals.
6. The N-element baseband (BB) time-domain spatial signal processor of claim 1 , wherein the pipeline converter is configured as an asynchronous time-to-digital converter, wherein the asynchronous time-to-digital converter further comprises:
a plurality of residue stages configured to extract raw bits with a Most Significant Bit value from the one or more time-domain output pulses to generate one or more residue values and an asynchronous pulse;
a plurality of time amplifiers configured to amplify the one or more residue values to a one or more amplified residue values; and
a 2-bit flash time-to-digital-converter configured to quantize the one or more amplified residue values.
7. The N-element baseband (BB) time-domain spatial signal processor of claim 6 , wherein an asynchronous pulse generated at the output of the plurality of residue stages is configured to enable a coherent synchronized output of the plurality of time amplifiers.
8. The N-element baseband (BB) time-domain spatial signal processor of claim 6 , wherein each of the plurality of residue stages further comprise a plurality of time-comparators configured to compare the one or more time-domain pulses to generate a residue value in a limited range so as to enhance linearity of the plurality of time amplifiers.
9. The N-element baseband (BB) time-domain spatial signal processor of claim 8 , wherein the one or more interference free and quantized signals have a signal-to-noise-distortion ratio of at least 6.4 dB.
10. The N-element baseband (BB) time-domain spatial signal processor of claim 6 , wherein the time-to-digital converter further comprises a Digital Error Correction block configured to combine the raw bits extracted from the plurality of the residue stages and the 2-bit flash time-to-digital converter.
11. The N-element baseband (BB) time-domain spatial signal processor of claim 6 , wherein a particle swarm optimization is configured to calibrate the plurality of time amplifiers.
12. The N-element baseband (BB) time-domain spatial signal processor of claim 10 , wherein one of the sub-time amplifiers from the pair of sub-time amplifiers are configured as one or more NOT gates to achieve a companding input-output characteristic.
13. The N-element baseband (BB) time-domain spatial signal processor of claim 10 , wherein one of the sub-time amplifiers from the pair of sub-time amplifiers are configured as one or more cross-coupled NAND gates to achieve an expanding input-output characteristic.
14. The N-element baseband (BB) time-domain spatial signal processor of claim 6 , wherein a statistical time-to-digital converter calibration is provided, wherein a pilot signal is applied to the time-to-digital converter for calibration.
15. The N-element baseband (BB) time-domain spatial signal processor of claim 6 , wherein each of the plurality of time amplifiers further comprise a pair of sub-time amplifiers further configured as a companding-expanding architecture to enhance the linearity of the plurality of time amplifiers.
16. A time-domain spatial signal processing method, comprising: time-aligning and combining constructively one or more received continuous-time baseband signals in the beam-forming mode;
time-aligning and combining destructively one or more received interference signals in the beam-nulling mode, wherein a plurality of in series of voltage-to-time converters perform the time-aligning and combining of the constructively and destructively one or more received continuous-time baseband signals; and
applying a Kronecker decomposition of array vectors to one or more received interference signals in the multiple independent interference filtering mode, wherein the Kronecker decomposition of array vectors cancels one or more independent interference signals.
17. The time-domain spatial signal processing method of claim 16 , wherein the time-aligning and adding destructively step further comprises: subtracting a first half of a plurality of interference signals with a second half of a plurality of interference signals.
18. The time-domain spatial signal processing method of claim 16 , wherein the time-domain spatial signal processing method further includes quantizing the time-aligned and combined one or more received continuous-time baseband signals.
19. The time-domain spatial signal processing method of claim 18 , wherein quantizing the time-aligned and combined one or more received continuous-time baseband signals step further comprises: extracting raw bits with a Most Significant Bit, generating residue values and generating an asynchronous pulse utilizing a plurality of residue stages.
20. The time-domain spatial signal processing method of claim 18 , wherein quantizing the time-aligned and combined one or more received continuous-time baseband signals step further comprises: extracting raw bits with a Least Significant Bit and generating an asynchronous pulse utilizing a 2-bit flash time-to-digital converter.
21. The time-domain spatial signal processing method of claim 18 , wherein quantizing the time-aligned and combined one or more received continuous-time baseband signals step further comprises: amplifying residue values utilizing a plurality of time-amplifiers.