Concurrent detection of absolute distance and relative movement for sensing action gestures

1. A device comprising:

a processing system; and

a radar-based gesture detection component implemented at least partially in hardware and comprising:

a two-tone radar front-end component comprising a radar-emitting element for emitting a first carrier frequency tone and a second carrier frequency tone;

an antenna for receiving incoming radio frequency (RF) signals generated by the first carrier frequency tone and the second carrier frequency tone reflecting off a target object;

a direct-conversion homodyne receiver electrically coupled to the antenna for receiving the incoming RF signals from the antenna and converting the incoming RF signals into baseband quadrature signals;

at least one analog-to-digital converter (ADC) to digitize the baseband quadrature signals to generate digital samples; and

a processing pipeline component for detecting absolute distance and relative movement information about the target object by processing the digital samples.

2. The device as recited in claim 1 , wherein the radar-emitting element comprises a Voltage Controlled Oscillator (VCO).

3. The device as recited in claim 2 , wherein the direct-conversion homodyne receiver is electrically coupled to the VCO.

4. The device as recited in claim 1 , wherein the digital samples comprise:

a first set of digital samples generated from a first set of baseband quadrature signals associated with the first carrier frequency tone;

a second set of digital samples generated from a second set of baseband quadrature signals associated the second carrier frequency tone; and

wherein detecting absolute distance and relative movement information further comprises concurrently detecting absolute distance and relative movement information by:

processing the first set of digital samples and the digital samples to extract phase difference information associated with the first set of baseband quadrature signals and the second set of baseband quadrature signals;

extracting absolute distance using the phase difference information;

processing the first set of digital samples or the second set of digital samples to extract phase offset information; and

extracting relative movement information using the phase offset information.

5. The device as recited in claim 1 , wherein first carrier frequency tone and the second carrier frequency tone have a frequency difference of 40 Megahertz (MHz).

6. The device as recited in claim 1 , wherein the radar-based gesture detection component reconfigures the radar-emitting element to alternate transmitting the first carrier frequency tone and the second carrier frequency tone.

7. The device as recited in claim 1 , wherein the processing pipeline component uses the absolute distance and the relative movement information to identify an in-the-air gesture performed by the target object from multiple gestures.

8. The device recited in claim 7 , wherein the radar-based gesture detection component utilizes a programmatic interface to send a notification that the in-the-air gesture has been detected.

9. A method comprising:

transmitting, using a radar-based gesture detection system, a first carrier frequency tone via a radar-emitting element of the radar-based gesture detection system;

demodulating, using the radar-based gesture detection system, a first return signal generated by the first carrier frequency tone reflecting off a target object to generate a first set of baseband quadrature signals;

transmitting, using the radar-based gesture detection system, a second carrier frequency tone via the radar-emitting element of the radar-based gesture detection system;

demodulating, using the radar-based gesture detection system, a second return signal generated by the second carrier frequency tone reflecting off a target object to generate a second set of baseband quadrature signals;

concurrently extracting, using the radar-based gesture detection system, absolute distance and relative movement information based, at least in part, on the first set of baseband quadrature signals and the second set of baseband quadrature signals; and

identifying a gesture performed by the target object using the absolute distance and relative movement information.

10. The method as recited in claim 9 , further comprising:

sampling the first set of baseband quadrature signals to generate a first set of digital samples;

sampling the second set of baseband quadrature signals to generate a second set of digital samples;

processing the first set of digital samples and the second set of digital samples to extract phase difference information used in the extracting the absolute distance; and

processing the first set of digital samples or the second set of digital samples to extract phase offset information used in the extracting the relative movement information.

11. The method as recited in claim 10 , wherein the sampling the first set of baseband quadrature signals or the sampling the second set of baseband quadrature signals further comprises:

utilizing a first Analog-to-Digital converter (ADC) to sample an in-phase component (I-component) of the first set of baseband quadrature signals or the second set of baseband quadrature signals; and

utilizing a second ADC synchronized to the first ADC to sample a quadrature-phase component (Q-component) of the first set of baseband quadrature signals or the second set of baseband quadrature signals.

12. The method as recited in claim 9 , wherein the demodulating the first return signal to generate the first set of baseband quadrature signals or the demodulating the second return signal to generate the second set of baseband quadrature signals further comprises:

utilizing a direct-conversion homodyne receiver to demodulate the first return signal or the second return signal.

13. The method as recited in claim 12 , further comprising:

utilizing a Voltage Controlled Oscillator (VCO) as at least part of the radar-emitting element; and

using, in the demodulating the first return signal or the demodulating the second return signal, a signal source generated by electrically coupling the VCO to the direct-conversion homodyne receiver.

14. The method as recited in claim 9 , further comprising:

receiving, at the radar-based gesture detection device, information associated with the first carrier frequency tone or the second carrier frequency tone via a programmatic interface; and

configuring the radar-emitting element based, at least in part, on the information associated with the first carrier frequency tone or the second carrier frequency tone.

15. The method as recited in claim 9 , further comprising:

selecting the first carrier frequency tone and the second carrier frequency tone based, at least in part, on a signal-to-noise ratio (SNR).

16. The method as recited in claim 9 , wherein the concurrently extracting the absolute distance and the relative movement information further comprises:

identifying a first trajectory associated with the first set of baseband quadrature signals;

identifying a second trajectory associated with the second set of baseband quadrature signals;

determining a phase difference between a first phase offset associated with a center of the first trajectory and a second phase offset associated with a center of the second trajectory; and

utilizing the phase difference to perform the extracting the absolute distance.

17. A device comprising:

a two-tone radar front-end component for:

transmitting a first carrier frequency tone;

receiving a first return signal generated by the first carrier frequency tone reflecting off a target object;

demodulating the first return signal into a first set of baseband quadrature signals;

transmitting a second carrier frequency tone;

receiving a second return signal generated by the second carrier frequency tone reflecting off the target object; and

demodulating the second return signal into a second set of baseband quadrature signals; and

a digital signal processing component for:

generating a first set of digital samples from the first set of baseband quadrature signals;

generating a second set of digital samples from the second set of baseband quadrature signals; and

concurrently extracting absolute distance and relative movement information associated with the target object by processing the first set of digital samples and the second set of digital samples.

18. The device as recited in claim 17 , wherein the two-tone radar front-end component comprises:

a direct-conversion homodyne receiver for demodulating the first return signal and the second return signal;

a radar-emitting element that is configurable to alternate transmitting the first carrier frequency tone and the second carrier frequency tone;

a first antenna electrically coupled to the radar-emitting element for transmitting the first carrier frequency tone and the second carrier frequency tone; and

a second antenna electrically coupled to the direct-conversion homodyne receiver for receiving the first return signal and the second return signal.

19. The device as recited in claim 17 , wherein the digital signal processing component comprises:

at least two synchronized Analog-to-Digital converters (ADC) for generating the first set of digital samples or the second set of digital samples as a respective set of quadrature digital samples; and

a processing pipeline component for processing the respective set of quadrature digital samples.

20. The device as recited in claim 17 , wherein the device is a system-on-chip (SoC).