Multi-tone continuous wave detection and ranging
View Patent ↗Various examples for multi-tone continuous wave detection and ranging are disclosed herein. In some embodiments, an initial signal is generated using initial radio frequency (RF) tones, and is emitted as a multi-tone continuous wave signal. The initial signal is reflected from a target and received as a reflected signal. Resultant RF tones, including a frequency, a phase and a power, are determined from the reflected signal in a frequency domain. A frequency-domain sinusoidal wave is fitted to the resultant RF tones in the frequency domain, and a distance to the target is determined using a modulation of the frequency-domain sinusoidal wave. A phase processing algorithm is applied to generate the target distance and speed by triangulating the range information encoded in the backscattered RF tones.
1. A range detection and velocimetry apparatus ( 1000 ) comprising:
a. a transmitter ( 1002 ) capable of producing a multi-tone signal comprising a plurality of simultaneous radiofrequency (RF) tones ( 1001 ) and a plurality of corresponding simultaneous RF frequencies, wherein the plurality of RF tones ( 1001 ) comprises a sum of multiple single side band modulation or double side band modulation;
b. a transmit antenna or optics ( 1003 ) operatively coupled to the transmitter ( 1002 ) capable of generating a transmitted signal ( 1004 ) modulated with the plurality of RF tones ( 1001 ) to a target ( 1005 );
c. a receiver antenna or optics ( 1007 ) capable of receiving a reflected signal ( 1006 ) from the target ( 1005 ) based on the transmitted signal ( 1004 );
d. a local oscillator ( 1008 ) capable of generating a reference signal ( 1009 );
e. a beam combiner ( 1010 ) capable of receiving the reflected signal ( 1006 ) from the receiver antenna ( 1007 ) and the reference signal ( 1009 ) from the local oscillator ( 1008 ) to generate a superposition signal ( 1011 );
f. a photodetector ( 1012 ) capable of receiving the superposition signal ( 1011 ) to be converted into an electrical current; and
g. an electronic processing unit ( 1013 ) comprising a processor capable of executing computer-readable instructions and a memory component comprising a plurality of computer-readable instructions comprising:
i. accepting the reflected signal and the reference signal;
ii. generating a superposition ( 1011 ) of the reflected signal and the reference signal, wherein generating the superposition ( 1011 ) generates beating tones;
iii. determining, by a plurality of phases of the beating tones or relative amplitude variations of tones, a broad range to a target ( 1005 );
iv. identifying a Doppler shift of the superposition signal ( 1011 );
v. estimating, by the Doppler shift and the plurality of beating tones, a velocity of the target ( 1005 ); and
vi. determining, based on the phase, frequency and amplitude of plurality of beating tones and the broad range to the target ( 1005 ), a precise range to the target ( 1005 ).
2. The apparatus ( 1000 ) of claim 1 , wherein the plurality of RF tones ( 1001 ) comprise a sum of multiple RF frequency tones such that the plurality of RF tones ( 1001 ) are non-harmonic, harmonic of a first common RF signal, subharmonic of a second common RF signal, phase-locked, or a combination thereof.
3. The apparatus ( 1000 ) of claim 1 , wherein the plurality of RF tones ( 1001 ) comprise a broadband RF signal such as subcarrier modulation signals with distinguishable frequency characteristics that are suitable for phase, frequency, and amplitude measurement at a selected part of the spectrum of the apparatus ( 1000 ).
4. The apparatus ( 1000 ) of claim 1 , wherein the transmitter ( 1002 ) comprises a CW or quasi CW electromagnetic signal generator selected from a group comprising laser, an RF generator, a TeraHertz (THz) generator, or a source operating at any frequency of the electromagnetic spectrum with direct modulation or external modulation capability to encode the plurality of RF tones ( 1001 ).
5. The apparatus ( 1000 ) of claim 1 , wherein the local oscillator ( 1008 ) comprises a fraction of the transmitter ( 1002 ) before or after RF modulation.
6. The apparatus ( 1000 ) of claim 1 further comprising a frequency shifter capable of generating the reference signal to compensate for at least a portion of the Doppler shift.
7. The apparatus ( 1000 ) of claim 1 , wherein the reference signal comprises a fixed frequency and a fixed phase difference from the transmitter ( 1002 ) to compensate for at least a portion of the Doppler shift.
8. The apparatus ( 1000 ) of claim 1 , wherein the reference signal comprises an independent unmodulated CW or quasi-CW signal.
9. The apparatus ( 1000 ) of claim 1 , wherein the electronic processing unit ( 1013 ) further comprise a data acquisition system, an analog filter, a digital filter, a RF spectrum analyzer, a frequency counter, a phase detector, and an amplitude detector.
10. The apparatus of claim 1 , wherein determining the precise range to the target ( 1005 ) comprising a triangulation algorithm utilizing phases of the plurality of beating tones and relative phase differences between plurality of beating tones.
11. The apparatus of claim 1 , wherein determining the precise range further comprising using time-of-arrival information of pulses of the multi-tone signal.
12. The apparatus of claim 1 , wherein determining the precise range further comprising generating, by the superposition signal ( 1011 ), a plurality of amplitude variations due to differences in phase accumulations and then fitting, by the plurality of amplitude variations, the superposition signal ( 1011 ) to a sine wave.
13. The apparatus ( 1000 ) of claim 1 , wherein the memory component further comprises instructions for:
a. mixing, by an analog or digital mixer, a selected set of the plurality of beating tones to cancel common noise terms and perform ranging of the target ( 1005 ) beyond a coherence length of the transmitter ( 1002 ).
14. A RADAR ranging and velocimetry apparatus ( 1000 ) comprising:
a. a transmitter ( 1002 ) capable of generating a multi-tone signal comprising a plurality of simultaneous radiofrequency (RF) tones in a continuous wave (CW) signal, a quasi-CW signal, or a TeraHertz signal, and a plurality of corresponding simultaneous RF frequencies;
b. a local oscillator ( 1008 ) capable of using at least a portion of the multi-tone signal from the transmitter ( 1002 ) as a reference signal; and
c. an electronic processing unit ( 1013 ) comprising a processor capable of executing computer-readable instructions and a memory component comprising a plurality of computer-readable instructions comprising:
i. accepting the multi-tone signal and the reference signal;
ii. generating a superposition ( 1011 ) of the multi-tone signal and the reference signal, wherein generating the superposition ( 1011 ) generates beating tones;
iii. determining, by a plurality of phases of the beating tones, a broad range to a target ( 1005 );
iv. identifying a Doppler shift of the superposition signal ( 1011 );
v. estimating, by the Doppler shift and the plurality of beating tones, a velocity of the target ( 1005 ); and
vi. determining, based on the plurality of beating tones and the broad range to the target ( 1005 ), a precise range to the target ( 1005 ).
15. The apparatus of claim 14 , wherein determining the precise range to the target ( 1005 ) comprising a triangulation algorithm utilizing phases of the plurality of beating tones and utilizing relative changes in phases of the plurality of beating tones.
16. The apparatus of claim 14 , wherein determining the precise range further comprising using time-of-arrival information of pulses of the multi-tone signal.
17. The apparatus ( 1000 ) of claim 14 , wherein the reference signal comprises an unmodulated CW or quasi-CW signal.
18. A global position and navigation apparatus ( 1000 ) comprising:
a. a remote transmitter ( 1002 ) capable of generating a multi-tone signal comprising a plurality of simultaneous radiofrequency tones in a continuous wave (CW) signal, a quasi-CW signal, or a TeraHertz signal, and a plurality of corresponding simultaneous RF frequencies;
b. a local receiver ( 1007 ) comprising a local oscillator ( 1008 ) capable of generating an independent unmodulated CW or quasi-CW signal as a reference signal;
c. a photodetector ( 1012 ) capable of receiving the multi-tone signal and the reference signal and generating an electrical signal, wherein a frequency difference between the local oscillator ( 1008 ) and the remote transmitter ( 1002 ) is set to be within a bandwidth of the photodetector ( 1012 ); and
d. an electronic processing unit ( 1013 ) comprising a processor capable of executing computer-readable instructions and a memory component comprising a plurality of computer-readable instructions comprising:
i. accepting the electrical signal from the photodetector ( 1012 );
ii. generating a superposition ( 1011 ) of the multi-tone signal and the reference signal, wherein generating the superposition ( 1011 ) generates beating tones;
iii. determining, by a plurality of phases of the beating tones, a broad range to a target ( 1005 );
iv. identifying a Doppler shift of the superposition signal ( 1011 );
v. estimating, by the Doppler shift and the plurality of beating tones, a velocity of the target ( 1005 );
vi. determining, based on the plurality of beating tones and the broad range to the target ( 1005 ), a precise range to the target ( 1005 ); and
vii. mixing, by an analog or digital mixer, a selected set of the plurality of beating tones to cancel common noise terms and perform ranging of the target ( 1005 ) beyond a coherence length of the transmitter ( 1002 ).
19. The apparatus of claim 18 , wherein determining the precise range to the target ( 1005 ) comprising a triangulation algorithm utilizing phases of the plurality of beating tones and utilizing the relative phase changes between tones.
20. The apparatus of claim 18 , wherein determining the precise range further comprising using time-of-arrival information of quasi CW pulses of the multi-tone signal.