Noncontact self-injection-locked sensor

Abstract

In a noncontact self-injection-locked sensor, a self-injection-locked oscillating integrated antenna is designed to radiate a signal to a subject and be injection-locked by a reflect signal reflected from the subject. Owing to the reflect signal is phase-modulated by vital signs of the subject, a demodulator is provided to demodulate an injection-locked signal of the self-injection-locked oscillating integrated antenna to obtain a vital signal of the subject.

Claims

1. A noncontact self-injection-locked sensor comprising: a self-injection-locked oscillating integrated antenna including an antenna and an active element which are electrically connected to each other, the antenna is configured for oscillation with the active element to generate an oscillation signal and configured for frequency selection, and the antenna is further configured to radiate the oscillation signal to a subject and receive a reflect signal reflected from the subject to bring the self-injection-locked oscillating integrated antenna to a self-injection-locked state, wherein the oscillation signal is modulated by the vital sign of the subject to become a frequency- and amplitude-modulated signal; and a demodulator including a differentiator and an envelope detector, the differentiator is electrically connected to the self-injection-locked oscillating integrated antenna and configured to receive and differentiate the frequency- and amplitude-modulated signal into an amplitude-modulated signal, the envelope detector is electrically connected to the differentiator and is configured to demodulate the amplitude-modulated signal in amplitude to obtain a vital signal of the subject.

2. The noncontact self-injection-locked sensor in accordance with claim 1, wherein the differentiator is a microstrip differentiator, and an operation frequency of the differentiator is substantially the same as a frequency of the frequency- and amplitude-modulated signal.

3. The noncontact self-injection-locked sensor in accordance with claim 2, wherein the frequency of the frequency- and amplitude-modulated signal and the operation frequency of the differentiator are higher than or equal to 300 MHz.

4. The noncontact self-injection-locked sensor in accordance with claim 1, wherein the antenna is a plane printed antenna.

5. The noncontact self-injection-locked sensor in accordance with claim 4, wherein the self-injection-locked oscillating integrated antenna further includes an adjustable capacitance, one end of the adjustable capacitance is electrically connected to the antenna and the other end of the adjustable capacitance is connected to ground.

6. The noncontact self-injection-locked sensor in accordance with claim 4, wherein the active element is a solid-state amplifier, and the active element has an input port and an output port which are both electrically connected to the antenna.

7. The noncontact self-injection-locked sensor in accordance with claim 4, wherein the active element is a solid-state element, a drain of the active element is coupled to the antenna, a gate of the active element is connected to ground via a first reactance element and a source of the active element is connected to ground via a second reactance element.

8. The noncontact self-injection-locked sensor in accordance with claim 2, wherein the antenna is a plane printed antenna.

9. The noncontact self-injection-locked sensor in accordance with claim 8, wherein the self-injection-locked oscillating integrated antenna further includes an adjustable capacitance, one end of the adjustable capacitance is electrically connected to the antenna and the other end of the adjustable capacitance is connected to ground.

10. The noncontact self-injection-locked sensor in accordance with claim 8, wherein the active element is a solid-state amplifier, and the active element has an input port and an output port which are both electrically connected to the antenna.

11. The noncontact self-injection-locked sensor in accordance with claim 8, wherein the active element is a solid-state element, a drain of the active element is coupled to the antenna, a gate of the active element is connected to ground via a first reactance element and a source of the active element is connected to ground via a second reactance element.

12. The noncontact self-injection-locked sensor in accordance with claim 3, wherein the antenna is a plane printed antenna.

13. The noncontact self-injection-locked sensor in accordance with claim 12, wherein the self-injection-locked oscillating integrated antenna further includes an adjustable capacitance, one end of the adjustable capacitance is electrically connected to the antenna and the other end of the adjustable capacitance is connected to ground.

14. The noncontact self-injection-locked sensor in accordance with claim 12, wherein the active element is a solid-state amplifier, and the active element has an input port and an output port which are both electrically connected to the antenna.

15. The noncontact self-injection-locked sensor in accordance with claim 12, wherein the active element is a solid-state element, a drain of the active element is coupled to the antenna, a gate of the active element is connected to ground via a first reactance element and a source of the active element is connected to ground via a second reactance element.

16. The noncontact self-injection-locked sensor in accordance with claim 1 further comprising a baseband amplifier, wherein the baseband amplifier is electrically connected to the demodulator and configured to receive and amplify the vital signal.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a circuit diagram illustrating a noncontact SIL sensor in accordance with a first embodiment of the present invention.

(2) FIG. 2 is a circuit diagram illustrating a noncontact SIL sensor in accordance with a second embodiment of the present invention.

(3) FIG. 3 is a circuit diagram illustrating a noncontact SIL sensor in accordance with a third embodiment of the present invention.

(4) FIG. 4 is a circuit diagram illustrating a noncontact SIL sensor in accordance with a fourth embodiment of the present invention.

(5) FIG. 5 is a vital-sign waveform diagram of human chest detected by the noncontact SIL sensor in accordance with the second embodiment of the present invention.

(6) FIG. 6 is a vital-sign waveform diagram of human wrist detected by the noncontact SIL sensor in accordance with the second embodiment of the present invention.

(7) FIG. 7 is a circuit diagram illustrating a noncontact SIL sensor in accordance with a fifth embodiment of the present invention.

(8) FIG. 8 is a waveform diagram of output signal and received signal when the noncontact SIL sensor in accordance with the fifth embodiment of the present invention produces a linear variation in frequency.

DETAILED DESCRIPTION OF THE INVENTION

(9) A noncontact SIL sensor 100 of a first embodiment of the present invention is shown in FIG. 1. The noncontact SIL sensor 100 includes a SIL oscillating integrated antenna 110, a demodulator 120 and a baseband amplifier 130.

(10) The SIL oscillating integrated antenna 110 includes an antenna 111 and an active element 112 electrically connected to the antenna 111. In the first embodiment, the antenna 111 is a plane printed antenna and the active element 112 is a solid-state amplifier. Furthermore, the active element 112 of the first embodiment has an input port 112a and an output port 112b which are both electrically connected to the antenna 111 to form a loop configuration.

(11) In the first embodiment, the antenna 111 is configured for oscillation with the active element 112 to generate an oscillation signal S.sub.oc and for frequency-selection. Furthermore, the antenna 111 is also employed to radiate the oscillation signal S.sub.oc to a subject B. After the oscillation signal S.sub.oc contacts the subject B, a reflect signal S.sub.re is reflected from the subject B and received by the antenna 111. The reflect signal S.sub.re injects into and locks the SIL oscillating integrated antenna 110 in a SIL state. The SIL oscillating integrated antenna 110 is not only used as a signal radiating/receiving element but also involved in oscillation. As a result, the oscillation signal S.sub.oc is modulated by a vital sign of the subject B (e.g. respiration, heartbeat and wrist pulse) in frequency and amplitude to become a frequency- and amplitude-modulated signal S.sub.FM-AM.

(12) With reference to FIG. 1, the demodulator 120 is electrically connected to the SIL oscillating integrated antenna 110 in order to receive the frequency- and amplitude-modulated signal S.sub.FM-AM. The demodulator 120 is configured to demodulate the frequency- and amplitude-modulated signal S.sub.FM-AM to obtain a vital signal S.sub.vt of the subject B. In the first embodiment, the demodulator 120 is an envelope detector 121 configured to proceed amplitude demodulation of the frequency- and amplitude-modulated signal S.sub.FM-AM. The envelope detector 121 can extract the amplitude modulation components of the frequency- and amplitude-modulated signal S.sub.FM-AM to obtain the vital signal S.sub.vt. The baseband amplifier 130 is electrically connected to the demodulator 120 to receive and amplify the vital signal S.sub.vt.

(13) Because the noncontact SIL sensor 100 of the first embodiment can acquire the vital sign S.sub.vt of the subject B through the amplitude demodulation proceeded by the envelope detector 121 only, the demodulator 120, compared with other radars, has advantages of simple architecture and low costs. Moreover, the operation frequency band of the SIL oscillating integrated antenna 110 can be increased to millimeter wave range (30-300 GHz) to improve sensitivity of sensing tiny vibration dramatically so that the noncontact SIL sensor 100 can be applied to further potential applications, not only applied to detect vital signs of large subjects with large vibration movement.

(14) With reference to FIG. 2, different to the first embodiment, the demodulator 120 in a second embodiment further includes a differentiator 122 which is added between and electrically connected to the SIL oscillating integrated antenna 110 and the envelope detector 121. The differentiator 122 is configured to receive the frequency- and amplitude-modulated signal S.sub.FM-AM from the SIL oscillating integrated antenna 110 and differentiate the frequency- and amplitude-modulated signal S.sub.FM-AM to convert the frequency modulation components into the amplitude modulation components. Consequently, the frequency- and amplitude-modulated signal S.sub.FM-AM is converted to an amplitude-modulated signal S.sub.AM to improve the sensitivity of sensing vital signs of the subject B. The envelope detector 121, electrically connected to the differentiator 122, is configured to receive and amplitude-demodulate the amplitude-modulated signal S.sub.AM for obtaining the vital signal S.sub.vt. Because the noncontact SIL sensor 100 of the second embodiment further utilize the differentiator 122 to convert frequency modulation to amplitude modulation, frequency and amplitude modulations of the oscillation signal S.sub.oc caused by vital signs of the subject B are fused to further enhance the sensitivity of the noncontact SIL sensor 100 for sensing tiny vibrations.

(15) In the second embodiment, the differentiator 122 is a microstrip differentiator, and the operation frequency of the differentiator 122 is substantially the same as the frequency of the frequency- and amplitude-modulated signal S.sub.FM-AM. Particularly, the noncontact SIL sensor 100 of the second embodiment has better sensitivity when the frequency of the frequency- and amplitude-modulated signal S.sub.FM-AM and the operation frequency of the differentiator 122 are higher than or equal to 300 MHz.

(16) FIGS. 3 and 4 represent third and fourth embodiments of the present invention. The active element 112 in the third and fourth embodiments is a solid-state transistor having a gate, a source and a drain, different to the solid-state amplifier in the first and second embodiments. The drain of the active element 112 is coupled to the antenna 111, the gate of the active element 112 is connected to ground via a first reactance element 112c, and the source of the active element 112 is connected to ground via a second reactance element 112d such that the antenna 111 and the active element 112 constitute a reflect type configuration. The first reactance element 112c and the second reactance element 112d may be transmission lines capable of be operated under high frequency conditions. Identical to the first and second embodiments, the antenna 111 and the active element 112 in the third and fourth embodiments are employed for oscillation and the oscillation signal S.sub.oc generation. The antenna 111 is configured to radiate the oscillation signal S.sub.oc to the subject B and receive the reflect signal S.sub.re reflected from the subject B. The reflect signal S.sub.re brings the SIL oscillating integrated antenna 110 into the SIL state to output the frequency- and amplitude-modulated signal S.sub.FM-AM. The demodulator 120 is configured to demodulate the frequency- and amplitude-modulated signal S.sub.FM-AM to acquire the vital signal S.sub.vt.

(17) With reference to FIGS. 3 and 4, in the reflect type configuration, the demodulator 120 of the third embodiment only uses the envelope detector 121 to perform the amplitude demodulate process of the frequency- and amplitude-modulated signal S.sub.FM-AM to obtain the vital signal S.sub.vt, and the demodulator 120 of the fourth embodiment uses the differentiator 122 to convert the frequency modulation components to the amplitude modulation components and then uses the envelope detector 121 to amplitude-demodulate the amplitude-modulated signal S.sub.AM to obtain the vital signal S.sub.vt.

(18) FIG. 5 is a test result of the vital signal S.sub.vt using the noncontact SIL sensor 100 of the second embodiment. The SIL sensor is wore on a human chest with a separated distance due to clothes. Two clear spectrum peaks of the vital signal S.sub.vt represent respiration and heartbeat rates, and the measured heartbeat rate agrees the human heartbeat rate (the data shown on upper right corner of FIG. 5) acquired by a finger pulse oximeter well. FIG. 6 is a test result of the vital signal S.sub.vt by placing the noncontact SIL sensor 100 of the second embodiment on the human wrist. The spectrum peak of wrist pulse is identified, and there is no spectrum peak representing respiration in the vital signal S.sub.vt because the SIL sensor located on the human wrist cannot detect respiration. The measured wrist pulse rate agrees the human heartbeat rate (the data shown on upper right corner of FIG. 6) detected by the finger pulse oximeter well. The test results demonstrate the noncontact SIL sensor 100 of the present invention can sense human vital signs precisely by way of contactless.

(19) FIG. 7 shows a fifth embodiment of the present invention. The difference to the second embodiment is the SIL oscillating integrated antenna 110 further includes an adjustable capacitance 113. One end of the adjustable capacitance 113 is electrically connected to the antenna 111 and the other end of the adjustable capacitance 113 is connected to ground. The capacitance value of the adjustable capacitance 113 can influence the frequency selection of the antenna 111 to adjust the frequency of the SIL oscillating integrated antenna 110. With reference to FIG. 8, when the SIL oscillating integrated antenna 110 produces a linear variation in frequency because of the adjustable capacitance 113, the SIL oscillating integrated antenna 110 is configured as a frequency-modulated continuous-wave radar (FMCW) which can demodulate the received signals by the demodulator 120 and perform a fast-Fourier transform (FFT) to calculate the distance between the SIL oscillating integrated antenna 110 and the subject B.

(20) In the present invention, the SIL oscillating integrated antenna 110 is provided for oscillating, radiating and receiving signals such that it can acquire the amplitude and frequency modulation components in signals caused by vital signs of the subject B in the SIL state and demodulate the signals to detect the vital signs of the subject B precisely. Furthermore, owing to the architecture of the demodulator 120 used for demodulation is simple, the noncontact SIL sensor 100 can operate in extremely high frequency conditions and is highly sensitive to tiny vibration. For these reasons, the noncontact SIL sensor 100 of the present invention can be applied to further potential applications.

(21) While this invention has been particularly illustrated and described in detail with respect to the preferred embodiments thereof it will be clearly understood by those skilled in the art that is not limited to the specific features shown and described and various modified and changed in form and details may be made without departing from the spirit and scope of this invention.