Microwave photonic system and method for cancelling leakage interference of phased array antennas
An apparatus and method for cancelling leakage interference of phased array antenna based on microwave photonic. The apparatus consists of a signal generation unit, a splitter, a beaming unit, a transmitting antenna, a receiving antenna, a microwave photonic channel construction array, a control unit, a combiner array, and a signal receiving unit. The receiving antennas are divided into several receiving subarrays, and the microwave photonic channel construction unit corresponds to each receiving subarray, respectively. For each receiving subarray, a reference channel is constructed by adjusting the array of amplitude adjustment unit, the array of time delay adjustment unit, and the array of phase adjustment unit in the microwave photonic channel construction array. Thus, the reference channel has the matched delay, equal amplitude response, and opposite phase response relative to the leakage interference channel, based on which the leakage interference of phased array antenna is cancelled.
1 . A system for cancelling leakage interference in phased array antenna based on microwave photonic, wherein the system consists of a signal generation unit, a splitter, a beamforming unit, a transmitting phased array antenna, a receiving phased array antenna, a microwave photonic channel construction array, a control unit, a combiner array, and a signal receiving unit;
the signal generation unit, the splitter, the beamforming unit, and the transmitting phased array antenna are sequentially connected by cables or microstrip lines;
the signal generation unit is used to generate a microwave signal, which transmits to the splitter;
the splitter divides the microwave signal generated by the signal generation unit into two parts, which transmit to the beamforming unit as transmitting signal and to the microwave photonic channel construction array as a reference signal for cancelling leakage interference;
the beamforming unit adjusts the amplitude and phase of the transmitting signal of each antenna element, thereby achieving function of beamforming;
the control unit controls an array of amplitude adjustment unit, an array of optical delay adjustment unit, and an array of phase adjustment unit in the microwave photonic channel construction array to generate a matched reference signal, according to a leakage interference channel response of a receiving subarray;
each combiner in the combiner array includes two input ports and one output port; the input ports are connected to a receiving antenna subarray and the microwave photonic channel construction array respectively; the output port is connected to the signal receiving unit;
the signal receiving unit samples and quantizes received signal, analyses target information, and provides feedback to the control unit to achieve closed-loop feedback control;
a multi-wavelength laser source is a multi-wavelength laser array or an optical frequency comb, which generates multiple optical carriers with a certain wavelength interval;
an electro-optic conversion unit, consists of an electro-optic modulator and a driving control circuit; the electro-optic conversion unit modulates the reference signal from the splitter onto multi-wavelength optical carriers to achieve electro-optic conversion;
a wavelength division demultiplexing unit is a wavelength decomposer or a multi-channel optical filter, which is used to separate an optically carried microwave signals according to its wavelengths to subchannels of a microwave photonic channel construction unit; the optically carried microwave signals sequentially pass through the array of amplitude adjustment unit, the array of optical delay adjustment unit, and the array of phase adjustment unit in each subchannel;
the array of amplitude adjustment unit consisting of M-path adjustable optical attenuators, which have the function of adjusting the amplitude of the optically carried microwave signals;
the array of optical delay adjustment unit consisting of M-path adjustable optical delay lines, which have the function of adjusting the delay of the optically carried microwave signal;
the array of phase adjustment unit array consisting of M-channel adjustable phase shifters based on microwave photonic, which have the function of adjusting the phase of optically carried microwave signals;
a wavelength division multiplexer unit is a wavelength multiplexer or a coupler, which is used to combine the optically carried microwave signals and transmit them to an opto-electric conversion unit;
the opto-electric conversion unit is a photodetector having opto-electric conversion function.
2 . A system for cancelling leakage interference in phased array antenna based on microwave photonic according to claim 1 , wherein the microwave photonic channel construction array corresponds one-to-one with each receiving subarray in receiving antenna; the microwave photonic channel construction array consists of N microwave photonic channel construction units; the microwave photonic channel construction unit consists of a multi wavelength laser source, an electro-optical conversion unit, a wavelength division demultiplexing unit, an array of amplitude adjustment unit, an array of optical delay adjustment unit, an array of phase adjustment unit, a wavelength division multiplexer unit, and an opto-electronic conversion unit; they are connected in sequence by optical fibers or integrated optical waveguides; for each receiving subarray, the microwave photonic channel construction unit constructs a reference channel with the matched delay, equal amplitude, and opposite phase relative to the leakage interference.
3 . A system for cancelling leakage interference in phased array antenna based on microwave photonic, wherein the implementation steps are as follows:
feeding a signal output from the signal generation unit to the input of a splitter; one of the outputs of the splitter is fed to the input of the beamforming unit as transmitting signal, and the other of the outputs of the splitter is fed to the microwave photonic channel construction array as reference signal; the beamforming unit adjust the amplitude and relative phase of transmitting signal according to command of a control unit; then the transmitting signal is sent out through a transmitting antenna; at the same time, a self-interference signal with high power leaks into a receiving antenna;
dividing the receiving antenna into several receiving subarrays; the receiving subarray is used as the basic unit to process received signals;
feeding the reference signal from the output of splitter to a microwave photonic channel construction array; in microwave photonic channel construction unit- 1 , the reference signal is modulated on a multi-wavelength optical carrier via an electro-optic conversion unit; a optically carried microwave signals is fed to wavelength division demultiplexing unit, and separated according to wavelength; the optically carried microwave signals with different wavelengths are fed to an array of amplitude adjustment units, an array of delay adjustment unit and an array of phase adjustment units sequentially; after through a wavelength division multiplexing unit, the optically carried microwave signals are fed to opto-electric conversion unit, a multi-tap reference signal is output from opto-electric conversion unit; microwave photonic channel construction unit- 2 , microwave photonic channel construction unit- 3 , and microwave photonic channel construction unit-N have the same structure and function as microwave photonic channel construction unit- 1 ;
according to the signal received by the subarray, the control unit adaptively controls the array of amplitude adjustment units, the array of optical delay adjustment units and the array of phase adjustment units in the microwave photonic channel construction array; thus, the reference signal from the microwave photonic channel construction unit- 1 has the matched time delay, the same amplitude, and the opposite phase relative to multipath interference signal;
the multi-tap reference signal generated by the microwave photonic channel construction unit- 2 , the microwave photonic channel construction unit- 3 , and the microwave photonic channel construction unit-N are combined with the signals received by each subarray, respectively; the delay, amplitude, and phase of the multi-tap reference signals are controlled by the control unit to satisfy the condition for cancelling multi-path leakage interference signals received from the respective subarrays;
cancelling out the leakage interference received by each subarray using each multi-tap reference signal in array of combiners; thus, an echo signal is recovered to a signal receiving unit, wherein the signal is processed and analyzed to provide target information; a detection function of the target is completed.