A six-port self-injection-locked (SIL) radar includes an oscillation element, an antenna element, a six-port frequency demodulation element and a signal processing element. Because of a coupler and a phase shifter of the six-port frequency demodulation element, the signal processing element can extract vibration information of subject by using only two demodulated signals output from the six-port frequency demodulation element. As a result, the operation frequency of the six-port SIL radar is not limited by hardware architecture, and the hardware costs and the power consumption are also reduced.

FIELD OF THE INVENTION

This invention generally relates to a self-injection-locked (SIL) radar, and more particularly to a six-port SIL radar.

BACKGROUND OF THE INVENTION

Conventional SIL radar includes a SIL oscillator, an antenna and a frequency demodulator, the antenna is electrically connected to the SIL oscillator in order to receive an oscillation signal output from the SIL oscillator. The antenna transmits the oscillation signal to a subject as a transmitted signal and receives a reflected signal from the subject as a received signal. The movement of the subject relative to the antenna may cause the Doppler Effect in the transmitted signal to allow the reflected signal and the received signal to contain the Doppler phase shift resulted from the movement of the subject. The received signal with the Doppler phase shifts is delivered and injected into the SIL oscillator to shift the oscillation frequency of the SIL oscillator. Hence, the frequency demodulator can receive and demodulate the oscillation signal output from the SIL oscillator to acquire the movement information of the subject.

Generally, a delay line frequency discriminator is used as the frequency demodulator for the conventional SIL radar. Frequency mixing is unavailable in the delay line frequency discriminator when the SIL oscillator is operated in a high frequency, for this reason, operation frequency and sensitivity to tiny vibration is restricted in the conventional SIL radar.

SUMMARY

The object of the present invention is to utilize a six-port frequency demodulation element as a frequency demodulator of a SIL radar such that the operation frequency of the SIL radar is not restricted by the hardware architecture of the general frequency demodulator. Additionally, a coupler and a phase shifter are provided in the SIL radar to allow a signal processing element to extract vibration information of subject by using only two demodulated signals output from the six-port frequency demodulation element. As a result, the required hardware costs of the SIL radar can be reduced.

A six-port SIL radar of the present invention includes an oscillation element, an antenna element, a six-port frequency demodulation element and a signal processing element. The oscillation element is configured to output an oscillation signal. The antenna element coupled to the oscillation element for receiving the oscillation signal is configured to transmit the oscillation signal to a subject as a transmitted signal and receive a reflected signal from the subject as a received signal. The received signal is injected into the oscillation element to allow the oscillation element to operate in a SIL state. The six-port frequency demodulation element includes a coupler, a phase shifter, a delay line and a six-port demodulation circuit. The coupler is coupled to the oscillation element and configured to receive and divide the oscillation signal into a first coupling signal and a second coupling signal. The phase shifter is electrically connected to the coupler and configured to shift a phase of the first or second coupling signal. The delay line is electrically connected to the coupler and configured to delay the second coupling signal. The first coupling signal is delivered to the six-port demodulation circuit as a local oscillation signal, and the second coupling signal is delivered to the six-port demodulation circuit as a radio frequency signal. The six-port demodulation circuit is configured to demodulate the local oscillation signal and the radio frequency signal to output two demodulated signals. The signal processing element includes two power detectors and a processor. The two power detectors are electrically connected to the six-port demodulation circuit for receiving the two demodulated signals and configured to detect the power of the two demodulated signals and then output two power signals. The processor is coupled to the two power detectors for receiving the two power signals and configured to compute a baseband signal of the subject according to the two power signals.

The six-port frequency demodulation element of the present invention is configured as frequency discriminator to allow the six-port SIL radar to be not restricted by hardware architecture, accordingly, the six-port SIL radar is able to be operated at higher frequency and be highly sensitive. Besides, the signal processing element is able to obtain the vibration information of the subject according to demodulated signals of only two paths with the configuration of the coupler and the phase shifter of the six-port frequency demodulation element. This architecture is benefits to reduce the hardware costs and the power consumption of the six-port SIL radar.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIG.1, a six-port SIL radar100in accordance with one embodiment of the present invention includes an oscillation element110, an antenna element120, a six-port frequency demodulation element130and a signal processing element140. The oscillation element110outputs an oscillation signal SO, the antenna element120is coupled to the oscillation element110in order to receive the oscillation signal SO. The antenna element120transmits the oscillation signal SOtoward a subject O as a transmitted signal STand receives a reflected signal SRfrom the subject O as a received signal Sr. The received signal Srreceived by the antenna element120is delivered and injected into the oscillation element110to operate the oscillation element110in a SIL state. The six-port frequency demodulation element130, that is coupled to the oscillation element110for receiving the oscillation signal SO, demodulates the oscillation signal SOin frequency and then outputs two demodulated signals Sde1and Sde2. The signal processing element140coupled to the six-port frequency demodulation element130receives the two demodulated signals Sde1and Sde2and computes a baseband signal SBBaccording to the two demodulated signals Sde1and Sde2.

FIG.2represents the six-port SIL radar100in accordance with a first embodiment of the present invention. In the first embodiment, the oscillation element110includes a SIL oscillator111and a coupler112. The SIL oscillator111, a voltage-controlled oscillator, is controlled by a voltage (not shown) to output the oscillation signal SOfrom its output port111a. The coupler112is a hybrid coupler and electrically connected to the output port111aof the SIL oscillator111, the antenna element120and the six-port frequency demodulation element130. The coupler112receives the oscillation signal SOfrom the output port111aand couples the oscillation signal SOinto a first coupling oscillation signal SO1and a second coupling oscillation signal SO2. The first coupling oscillation signal SO1is delivered to the antenna element120, and the second coupling oscillation signal SO2is delivered to the six-port frequency demodulation element130.

With reference toFIG.2, the antenna element120transmits the first coupling oscillation signal SO1to the subject as the transmitted signal STand receives the reflected signal SRfrom the subject as the received signal Sr. The coupler112receives the received signal Srfrom the antenna element120and couples the received signal Srinto a coupling received signal Scr. The coupling received signal Scris delivered and injected into an injection port111bof the SIL oscillator111to allow the SIL oscillator111to operate in a SIL state. If the subject is moved or moving relative to the antenna element120, the reflected signal SR, the received signal Srand the coupling received signal Scrmay all contain Doppler phase shifts caused by the movement of the subject owing to the Doppler Effect in the transmitted signal ST, and the SIL oscillator111injection-locked by the coupling received signal Scrmay generate frequency shifts on the oscillation signal SO. Accordingly, the six-port frequency demodulation element130can frequency-demodulate the oscillation signal SOoutput from the SIL oscillator111to extract the vibration information of the subject.

With reference toFIG.2, the six-port frequency demodulation element130includes a coupler131, a phase shifter132, a delay line133and a six-port demodulation circuit134. In the first embodiment, the coupler131is a directional coupler and coupled to the oscillation element110via the coupler112to receive the second coupling oscillation signal SO2. The coupler131is used to divide the second coupling oscillation signal SO2into a first coupling signal SC1and a second coupling signal SC2. And in the first embodiment, the phase shifter132is electrically connected to one port of the coupler131so as to shift the phase of the first coupling signal SC1, the delay line133is electrically connected to the other port of the coupler131to delay the second coupling signal SC2. The phase-shifted first coupling signal SC1is delivered to the six-port demodulation circuit134as a local oscillation signal LO, and the delayed second coupling signal SC2is delivered to the six-port demodulation circuit134as a radio frequency signal RF. The six-port demodulation circuit134demodulates the local oscillation signal LO and the radio frequency signal RF to output the two demodulated signals Sde1and Sde2.

Through the coupler131, preferably, the power of the second coupling signal SC2is greater than a power difference of the first coupling signal SC1, and the power difference of the first coupling signal SC1is equal to a power attenuation of the delay line133. Consequently, the local oscillation signal LO and the radio frequency signal RF received by the six-port demodulation circuit134have the same amplitude, that is able to prevent too high noise level of one path from covering the Doppler phase shifts of the other path and able to improve the sensitivity of the six-port SIL radar100. In addition, because the first coupling signal SC1is phase-shifted by the phase shifter132, the phase of the first coupling signal SC1minus the phase of the second coupling signal SC2is equal to 45±(180×N) or 135±(180×N) degrees, N is a natural number. Also, the phase of the local oscillation signal LO received by the six-port demodulation circuit134minus the phase of the radio frequency signal RF received by the six-port demodulation circuit134is equal to 45±(180×N) or 135±(180×N) degrees.

With reference toFIGS.2and3, the six-port demodulation circuit134of the first embodiment is composed of a power splitter134aand three branch-line couplers134b,134cand134d. The power splitter134ais electrically connected to the phase shifter132so as to receive and divide the local oscillation signal LO into two paths, the local oscillation signal LO of two paths are delivered to the branch-line coupler134band the branch-line coupler134d, respectively. The branch-line coupler134cis electrically connected to the delay line133via one end and electrically connected to a resistor via the other end. The radio frequency signal RF is received and divided into two paths by the branch-line coupler134c, one path is delivered to the branch-line coupler134band the other path is delivered to the branch-line coupler134d. After the coupling, the branch-line coupler134boutput the demodulated signals Sde1and Sde2, and the branch-line coupler134doutput two demodulated signals Sde3and Sde4.

When the phase of the local oscillation signal LO received by the six-port demodulation circuit134minus the phase of the radio frequency signal RF received by the six-port demodulation circuit134is equal to 45±(180×N) degrees, back-end circuit can demodulate them to obtain an in-phase signal (I signal) and a quadrature signal (Q signal) carrying the same DC components and opposite AC components. In contrast, when the phase of the local oscillation signal LO received by the six-port demodulation circuit134minus the phase of the radio frequency signal RF received by the six-port demodulation circuit134is equal to 135±(180×N) degrees, the I signal and the Q signal, that are obtained by the demodulation of the local oscillation signal LO and the radio frequency signal RF, have opposite DC components and identical AC components such that the Q signal can be derived from the I signal. Accordingly, back-end circuit can extract the vibration information of the subject from the demodulated signals Sde1and Sde2or from the demodulated signals Sde3and Sde4with the assistance of the phase shifter132. This architecture can reduce hardware costs and power consumption substantially.

If the demodulated signals Sde1and Sde2are utilized for further processing in the back-end circuit, the two output ports of the six-port demodulation circuit134used to output the demodulated signals Sde3and Sde4have to be grounded via two resistors (not shown), respectively, to prevent impedance mismatch. Reversely, while the demodulated signals Sde3and Sde4are selected for further processing in the back-end circuit, the two output ports of the six-port demodulation circuit134configured to output the demodulated signals Sde1and Sde2have to be grounded via the two resistors, respectively, for impedance matching.

With reference toFIG.2, the signal processing element140includes two power detectors141, two analog-to-digital converters (ADCs)142and a processor143. In the first embodiment, the two power detectors141are electrically connected to the six-port demodulation circuit134to receive the two demodulated signals Sde1and Sde2and provided to detect the powers of the two demodulated signals Sde1and Sde2to output two power signals SP1and SP2. The two ADCs142are electrically connected to the two power detectors141, respectively, to convert the two power signals SP1and SP2into digital signals. The processor143is electrically connected to the two power detectors141for receiving the two converted power signals SP1and SP2and computes the baseband signal SBBof the subject based on the two power signals SP1and SP2to obtain the vibration information. In other embodiments, the baseband signal SBBof the subject can be obtained by using the two demodulated signals Sde3and Sde4.

While the phase of the local oscillation signal LO minus the phase of the radio frequency signal RF leaves 45±(180×N) degrees, the I signal and the Q signal contain the same DC components and opposite AC components. Through the processor143, the I signal is obtained by subtraction of the two power signals SP1and SP2, and the I signal is filtered to get a DC component and an AC component. The Q signal is obtained by inverting the AC component of the I signal and applying a DC offset to the inverted AC component according to the DC component. Finally, the arctangent demodulation of the I signal and the Q signal is used to get the baseband signal SBBthat represents the vibration information of the subject relative to the six-port SIL radar100.

There are opposite DC components and identical AC components in the I signal and the Q signal when the phase of the local oscillation signal LO minus the phase of the radio frequency signal RF equals to 135±(180×N) degrees. By using the processor143, the I signal can be obtained by a subtraction of the two power signals SP1and SP2, and the I signal is filtered to get a DC component and an AC component. A DC offset is applied to the AC component of the I signal two times based on the DC component to obtain the Q signal. And also, the baseband signal SBBhaving the vibration information of the subject relative to the six-port SIL radar100can be obtained by the arctangent demodulation of the I signal and the Q signal.

Because of the phase shifter132of the six-port frequency demodulation element130, the phase of the local oscillation signal LO minus that of the radio frequency signal RF can be equal to 45±(180×N) or 135±(180×N) degrees in the first embodiment. As a result, the signal processing element140only requires the two power detectors141and the two ADCs142to extract the vibration information of the subject O, this kind of configuration is able to substantially reduce hardware costs and power consumption.

FIG.4is a circuit diagram showing the six-port SIL radar100of a second embodiment of the present invention. Different to the first embodiment, the phase shifter132of the second embodiment is provided to shift the phase of the second coupling signal SC2. The phase of the first coupling signal SC1minus the phase of the second coupling signal SC2is equal to 45±(180×N) or 135±(180×N) degrees such that the phase of the local oscillation signal LO minus the phase of the radio frequency signal RF is also equal to 45±(180×N) or 135±(180×N) degrees. The vibration information of the subject O is also extracted from the only two demodulated signal Sde1and Sde2by using the signal processing element140.

With reference toFIG.5, the six-port SIL radar100of a third embodiment of the present invention is shown. In the third embodiment, different to the first or second embodiment, the coupler112is a directional coupler and the antenna element120includes a transmitting antenna121and a receiving antenna122. The SIL oscillator111output the oscillation signal SOfrom the output port111a. The coupler112, that is electrically connected to the SIL oscillator111, the antenna element120and the six-port frequency demodulation element130, receives the oscillation signal SOfrom the SIL oscillator111. The oscillation signal SOis coupled into the first coupling oscillation signal SO1and the second coupling oscillation signal SO2by the coupler112. The first coupling oscillation signal SO1is delivered to the transmitting antenna121and the second coupling oscillation signal SO2is delivered to the six-port frequency demodulation element130. The transmitting antenna121transmits the oscillation signal SOas the transmitted signal ST, the receiving antenna122receives the reflected signal SRas the received signal Srand injects the received signal Srinto the SIL oscillator111via the injection port111b. The architecture of the third embodiment also allows the SIL oscillator111to operate in a SIL state and has high sensitivity to tiny vibration. In the third embodiment, the configurations of the six-port frequency demodulation element130and the signal processing element140are as same as those of the first or second embodiment.

Different to the first or second embodiment, in a fourth embodiment of the present invention as shown inFIG.6, the antenna element120includes a transmitting antenna121and the receiving antenna122, and the SIL oscillator111includes a first output port111cand a second output port111d. The SIL oscillator111outputs a first oscillation signal SO_1to the transmitting antenna121from the first output port111c, and the transmitting antenna121transmits the first oscillation signal SO_1as the transmitted signal ST. The receiving antenna122receives the reflected signal SRas the received signal Srand delivers the received signal Srinto the SIL oscillator111via the injection port111bto allow the SIL oscillator111to operate in a SIL state. The SIL oscillator111output a second oscillation signal SO_2to the six-port frequency demodulation element130from the second output port111d. The architecture of the fourth embodiment also can make the SIL oscillator111to operate in a SIL state and be highly sensitivity to tiny vibration. The configurations of the six-port frequency demodulation element130and the signal processing element140of the fourth embodiment are as same as those of the first or second embodiment.

As shown inFIG.7, the six-port SIL radar100of a fifth embodiment of the present invention is different to that of the first or second embodiment. In the fifth embodiment, the oscillation element110further includes a circulator113, the coupler112is a directional coupler, and the antenna element120includes a transmitting antenna121and a receiving antenna122. The oscillation signal SOis output from the SIL oscillator111to a first port113aof the circulator113and then delivered from a second port113bof the circulator113to the coupler112. The coupler112divides the oscillation signal SOinto the first coupling oscillation signal SO1and the second coupling oscillation signal SO2, the first coupling oscillation signal SO1is delivered to the transmitting antenna121, and the second coupling oscillation signal SO1is delivered to the six-port frequency demodulation element130. The transmitting antenna121transmits the first coupling oscillation signal SO1as the transmitted signal ST, and the receiving antenna122receives the reflected signal SRas the received signal Sr. The received signal Sris delivered to a third port113cof the circulator113and output from the first port113aof the circulator113into the SIL oscillator111. In the fifth embodiment, the SIL oscillator111can also enter a SIL state with high sensitivity to tiny vibration, and the six-port frequency demodulation element130and the signal processing element140have the same configuration as those of the first or second embodiment.

The six-port frequency demodulation element130of the present invention is utilized as frequency discriminator so that the six-port SIL radar100is available for higher frequency and sensitivity without restrictions of hardware architecture. And the vibration information of the subject O can be extracted from the demodulated signals of two paths by using the signal processing element140result from the coupler131and the phase shifter132in the six-port frequency demodulation element130. As a result, the hardware costs and the power consumption of the six-port SIL radar100can be reduced.

The scope of the present invention is only limited by the following claims. Any alternation and modification without departing from the scope and spirit of the present invention will become apparent to those skilled in the art.