Method and system for non-contact motion-based user authentication
View Patent ↗Methods and systems are provided for authenticating an individual using a motion of a physiological structure. For example, an individual may be authenticated using their cardiac motion. A first radiofrequency (“RF”) signal is transmitted towards the physiological structure of the individual. A first RF return signal is received, where the first RF return signal corresponds to the transmitted first RF signal. The first RF signal and first RF return signal are processed to obtain a motion signal. One or more values are determined for each fiducial point of a set of pre-determined fiducial points in the motion signal. The set of pre-determined fiducial points corresponds to physical movements of the physiological structure. The individual is authenticated based on the values of one or more fiducial points.
1 . A method for authenticating an individual using a motion of a physiological structure of the individual, comprising:
transmitting, by a radar sensor, a first radiofrequency (“RF”) signal towards the physiological structure of the individual;
receiving, by the radar sensor, a first RF return signal corresponding to the transmitted first RF signal interacting with the physical structure of the individual;
processing, by a processor, the first RF signal and first RF return signal to obtain a motion signal of the physical structure;
determining, by the processor, one or more values for each fiducial point of a set of pre-determined fiducial points in the motion signal, wherein the set of pre-determined fiducial points corresponds to physical movements of the physiological structure; and
wherein the set of pre-determined fiducial points of the motion signal comprises one or more of a cycle start (ST), a first maximum amplitude of movement (AFP), a second maximum amplitude of movement (VFP), a local minimum amplitude between AFP and VFP (ASP), and a cycle end (ED);
authenticating, by the processor, the individual based on the one or more values for each fiducial point of the set of pre-determined fiducial points.
2 . The method of claim 1 , wherein the physiological structure is a heart of the individual.
3 . The method of claim 1 , wherein the receiving the first RF return signal comprises sampling, by the processor, the first RF return signal at a sampling frequency.
4 . The method of claim 1 , wherein the one or more values for each fiducial point correspond to an amplitude difference and/or a time difference between one or more of ST and AFP, AFP and ASP, ASP and VFP, and VFP and ED.
5 . The method of claim 1 , wherein the authenticating the individual further comprises calculating, by the processor, derivative values based on the one or more values of the set of pre-determined fiducial points.
6 . The method of claim 1 , wherein the processing the first RF signal and the first RF return signal further comprises noise reduction and applying phase demodulation.
7 . The method of claim 6 , wherein the noise reduction includes applying a Butterworth bandpass filter and/or applying a normalized least mean square adaptive filter to the first RF return signal.
8 . The method of claim 6 , wherein the phase demodulation includes:
phase demodulating the first RF return signal using an arctangent demodulation;
computing a derivative to the arctangent-demodulated phase information as w (t) according to:
ω
(
t
)
=
d
d
t
[
arctan
Q
(
t
)
I
(
t
)
]
=
I
(
t
)
Q
.
(
t
)
-
I
.
(
t
)
Q
(
t
)
I
(
t
)
2
+
Q
(
t
)
2
,
where ω(t) is related to the velocity function of the cardiac motion, and {dot over (Q)}(t) and İ(t) denote the time derivative of Q(t) and I(t), respectively;
integrating ω(t) to obtain signal phase Φ θ [n]; and
obtaining motion x[n] based on the signal phase Φ θ [n].
9 . The method of claim 6 , wherein the phase demodulation includes:
obtaining DC component offsets of the in-phase and quadrature channels of the first RF return signal; and
phase demodulating the first RF return signal using the DC component offsets to obtain a displacement signal x(t).