Multichannel minimum distance chirp echo detection
One implementation of a sensing method includes: correlating a receive signal with a first channel waveform template to obtain a first channel correlation signal in which first channel echoes would be represented as peaks; correlating the receive signal with a second channel waveform template to obtain a second channel correlation signal in which second channel echoes would be represented as peaks; and varying the first channel waveform template and the second channel waveform template based on time elapsed from a measurement start time. A sensor array implementation includes: multiple acoustic transducers that operate concurrently to send acoustic bursts in different frequency channels, each of the multiple acoustic transducers configured to use the foregoing method.
1. An integrated circuit controller for a multichannel sensor, the controller comprising:
a transmitter to drive a piezoelectric transducer to generate acoustic bursts;
a receiver to obtain a receive signal from the piezoelectric transducer after each acoustic burst is generated; and
a processing circuit coupled to the transmitter and to the receiver, the processing circuit configured to apply echo-detection processing to said receive signal, said processing including:
correlating a receive signal with a first channel waveform template to obtain a first channel correlation signal in which first channel echoes would be represented as peaks;
correlating the receive signal with a second channel waveform template to obtain a second channel correlation signal in which second channel echoes would be represented as peaks; and
varying the first channel waveform template and the second channel waveform template based on time elapsed from a measurement start time.
2. The integrated circuit controller of claim 1 , wherein the processing further comprises scaling at least one of the first and second channel correlation signals based on time elapsed from the measurement start time to balance the first and second channel correlation signals.
3. The integrated circuit controller of claim 2 , wherein the processing further comprises, after said scaling, determining a first channel time of flight associated with any detected peak in the first channel correlation signal and second channel time of flight associated with any detected peak in the second channel correlation signal.
4. The integrated circuit controller of claim 1 , wherein varying the first channel waveform template and the second channel waveform template includes decreasing bandwidths of the templates based on time elapsed from the measurement start time.
5. The controller of claim 4 , wherein the processing further comprises scaling at least one of the first and second channel correlation signals to compensate for a difference between piezoelectric transducer responses to tails of the acoustic bursts received after transducer reverberation ends.
6. The controller of claim 4 , wherein the first channel waveform template represents an up-chirp in a lower sideband of a piezoelectric transducer and the second channel waveform template represents an up-chirp in an upper sideband of the piezoelectric transducer.
7. The controller of claim 4 , wherein the first channel waveform template represents a down-chirp in a lower sideband of a piezoelectric transducer and the second channel waveform template represents a down-chirp in an upper sideband of the piezoelectric transducer.
8. A method that comprises:
correlating a receive signal with a first channel waveform template to obtain a first channel correlation signal in which first channel echoes would be represented as peaks;
correlating the receive signal with a second channel waveform template to obtain a second channel correlation signal in which second channel echoes would be represented as peaks; and
varying the first channel waveform template and the second channel waveform template based on time elapsed from a measurement start time.
9. The method of claim 8 , further comprising: determining a first channel time of flight associated with any detected peak in the first channel correlation signal and second channel time of flight associated with any detected peak in the second channel correlation signal.
10. The method of claim 9 , further comprising, before said determining, scaling at least one of the first and second channel correlation signals based on time elapsed from the measurement start time to balance the first and second channel correlation signals.
11. The method of claim 8 , wherein varying the first channel waveform template and the second channel waveform template includes varying bandwidths of the templates from wide to narrow.
12. The method of claim 11 , further comprising, before said determining, scaling at least one of the first and second channel correlation signals to compensate for a difference between transducer responses to portions of the acoustic bursts received after transducer reverberation ends.
13. The method of claim 11 , wherein the first channel waveform template represents an up-chirp in a lower sideband of a piezoelectric transducer and the second channel waveform template represents an up-chirp in an upper sideband of the piezoelectric transducer.
14. The method of claim 11 , wherein the first channel waveform template represents a down-chirp in a lower sideband of a piezoelectric transducer and the second channel waveform template represents a down-chirp in an upper sideband of the piezoelectric transducer.
15. The method of claim 8 , wherein the measurement start time is a debounce interval after a detected end of reverberation.
16. The method of claim 8 , further comprising downconverting the receive signal to zero intermediate frequency (ZIF) before said correlating with the first and second channel waveforms.
17. A sensor array comprising:
multiple acoustic transducers that operate concurrently to send acoustic bursts in different frequency channels, each of the multiple acoustic transducers configured to correlate their receive signals with multiple channel waveform templates that vary based on time elapsed from a measurement start time to provide, for each of the different frequency channels, a correlation signal in which acoustic burst echoes in the associated frequency channel are represented as peaks; and
an electronic control unit configured to determine a time of flight for any detected peak in each of the different frequency channels.
18. The sensor array of claim 17 , wherein each of the multiple acoustic transducers is configured to scale at least one of the correlation signals based on time elapsed from the measurement start time to balance the correlation signals for each of the different frequency channels.
19. The sensor array of claim 17 , wherein the multiple channel waveform templates are varied by reducing bandwidths of the templated based on the time elapsed from the measurement start time.
20. The sensor array of claim 17 , wherein a first of the multiple channel waveform templates represents an up-chirp or a down-chirp in a lower sideband of each of the multiple acoustic transducers and a second of the multiple channel waveform templates represents an up-chirp or a down-chirp in an upper sideband of each of the multiple acoustic transducers.