CN107528638A - Wide-band microwave Direction-of-arrival method based on microwave photon filtering - Google Patents

Abstract

The invention discloses a kind of method of the wide-band microwave Direction-of-arrival based on microwave photon filtering, the invention is related to microwave technical field and technical field of photo communication, is mainly used in microwave photon signal transacting.Methods described as shown in drawings, including lasing light emitter, palarization multiplexing MZ Mach-Zehnder, polarization beam combiner, Polarization Controller, polarization beam apparatus, optical delay line and photodetector.The program utilizes palarization multiplexing MZ Mach-Zehnder, with reference to differential group delay module, constructs two-tap microwave photon filter, carries out notch filter to input electrical signal and observes result, so as to estimate wide-band microwave direction of arrival.The method of estimation is simple in construction simultaneously is easily achieved, cheap, is not influenceed by electronic bottleneck, can be worked under the conditions of incoherent, have the advantages that strong robustness.

Description

Estimation of Angle of Arrival for Broadband Microwave Signals Based on Microwave Photon Filtering

technical field

The invention relates to the technical fields of optical communication and microwave technology, and mainly relates to a method for estimating the arrival angle of broadband microwave signals based on microwave photon filtering in the optical communication technology.

Background technique

In areas such as radar systems and electronic warfare, there is a wide range of needs for angle of arrival estimation. However, limited by the electronic bottleneck, the use of existing electronic technology to achieve angle-of-arrival measurement of microwave signals with high frequency bands and large instantaneous bandwidths faces great challenges. In order to overcome the limitations of electronic bottlenecks, microwave photonics combines electronic technology and photon technology to realize the generation, transmission and processing of microwave signals in the optical domain. One of the hot spots. Among them, the broadband microwave signal measurement technology based on microwave photons has the advantages of simple structure, easy implementation, and not being affected by electronic bottlenecks, and has thus attracted the attention of research institutions in various countries.

The current basic principle of microwave photon-based angle-of-arrival estimation of microwave signals is to measure the phase shift or relative time delay between received RF signals at two separate antenna elements. According to different implementation methods, it can be mainly divided into three types: (1) The microwave signals received by two antennas and their phase delay components are loaded to two electro-optic modulators, and the phase shift obtained by measuring the optical carrier power is obtained to obtain the arrival (2) Using a parallel optical delay structure composed of a dual parallel Mach-Zehnder modulator (DP-MZM) or a dual-driver MZM, the phase delay is obtained by suppressing the optical carrier and measuring the optical sideband power, thereby obtaining the angle of arrival; (3) Based on a pair of microwave photonic downconverters, the time delay between microwave signals is obtained by measuring the time delay between corresponding intermediate frequency (IF) signals to obtain the angle of arrival.

Methods based on phase detection can only be used for pure single-tone signals, while methods based on down-conversion require further IF processing. Therefore, these methods have limited ability to process signals with large instantaneous bandwidth. Methods based on the spectral hole-burning effect in spatial spectroscopy materials can handle broadband signals but need to operate at low temperatures. The angle of arrival estimation system based on photonic microwave filtering can obtain the time delay of broadband signals by measuring the transmission notch. But it requires two laser sources operating at different wavelengths and a pair of intensity modulators, which increases the complexity of the system.

Contents of the invention

In order to solve the technical problems existing in the background technology, the present invention proposes a method for estimating the angle of arrival of broadband microwave signals based on microwave photon filtering.

The technical scheme adopted in the present invention is: the device includes a laser source, a polarization multiplexing Mach-Zehnder modulator, a polarization beam combiner, a polarization controller, a polarization beam splitter, an optical delay line, an adjustable optical attenuator, A photodetector and an electrical signal analyzer; the output port of the laser source is connected to the input port of a polarization multiplexing Mach-Zehnder modulator, and the output port of the modulator is connected to the input port of a polarization controller; the output port of the polarization controller is connected to the polarization The input port of the beam splitter is connected; the output port of the polarization beam splitter is connected with the input port of the optical delay line and the adjustable optical attenuator respectively; the output port of the optical delay line and the adjustable optical attenuator is connected with the input port of the polarization beam combiner connected; the output port of the polarization beam combiner is connected with the input port of the photodetector, and the output port of the photodetector is connected with an electrical signal analyzer for observation and testing.

The polarization multiplexing Mach-Zehnder modulator is composed of a Y splitter, two upper and lower parallel Mach-Zehnder modulators X-MZM and Y-MZM, a 90° polarization rotator, and a polarization beam combiner.

The present invention comprises the following steps when working:

(1) Light waves emitted from a narrow-linewidth laser are injected into a polarization-multiplexed Mach-Zehnder modulator;

(2) The optical signal incident on the polarization division multiplexing Mach-Zehnder modulator enters the X-MZM and Y-MZM respectively through the splitter. The signals received by the antenna are respectively input to the radio frequency ports of X-MZM and Y-MZM after passing through the electric amplifier. The output signal of Y-MZM passes through the 90° polarization rotator, and the output signal of X-MZM is input to the polarization beam combiner, and then the polarization state is orthogonal to realize polarization multiplexing;

(3) Polarization multiplexing The output signal of the Mach-Zehnder modulator is injected into the polarization beam splitter through the polarization controller. By adjusting the polarization controller, the polarization multiplexed optical signal can be precisely polarization demultiplexed. One output of the polarization beam splitter passes through the optical delay line to introduce a relative time delay; the other passes through the variable optical attenuator to minimize the power difference between the two branches;

(4) The two optical signals are input to the photodetector through the polarization beam combiner for photoelectric conversion, and the output electrical signal spectrum is observed and tested by the electrical signal analyzer;

The present invention proposes a method for estimating the angle of arrival of broadband microwave signals based on microwave photon filtering. The scheme uses a polarization division multiplexing Mach-Zehnder modulator, combined with an optical delay line and an optical adjustable attenuator, to construct a double-tap microwave photon filter. For incoming waves at different angles, the response of the filter changes with the difference of the two-way delay. By notch filtering the input electrical signal, observing and recording the measurement results of the notch position, and then calculating the direction of the incoming wave, the broadband microwave Estimate the angle of arrival of the signal.

In this scheme, a double-tap microwave photonic filter is constructed, which eliminates the limitation of laser source coherence through orthogonal polarization. The proposed scheme only needs one laser source and one modulator, which can improve the stability of the system and reduce the system cost.

The microwave photon filtering of the present invention is directly carried out in the optical domain, and the purpose of microwave signal filtering is achieved by processing the optical signal, which overcomes the bandwidth limitation and electromagnetic interference of traditional microwave phase shifting, so the performance of the system is greatly improved improve.

Description of drawings

Fig. 1 is the schematic diagram of the method for the angle of arrival estimation of broadband microwave signal based on microwave photon filtering of the present invention; Fig. 2, Fig. 3, Fig. 4 are experimental test result figures, and Fig. 2 (a) is the spectrum of the broadband signal without filtering , Figure 2(b) is the spectrum of the filtered broadband signal, Figure 3 is the measured frequency offset value versus relative time delay, and Figure 4 is the measured relative time delay (points) and the corresponding measurement error (vertical bars).

detailed description

The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings: this embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following The described embodiment:

FIG. 1 is a schematic diagram of a method for estimating the angle of arrival of a broadband microwave signal based on microwave photon filtering according to the present invention. The polarization multiplexed Mach-Zehnder modulator modulates the microwave signal to generate a polarization multiplexed signal; the polarization multiplexed Mach-Zehnder modulator consists of a Y splitter, an upper and lower parallel Mach-Zehnder modulator X- Composed of MZM and Y-MZM, 90° polarization rotator, and polarization beam combiner; the polarization controller is controlled to demultiplex the polarization multiplexed signal into two paths through the polarization beam splitter, and one path uses an optical delay line to introduce a relative time delay. The other uses a variable optical attenuator to minimize the power difference between the two branches; uses a polarization beam combiner to combine the two signals and outputs them to the photodetector; after the photodetector beats, the filtered signal can be obtained microwave signal. The output port of the laser source is connected to the input port of the polarization multiplexing Mach-Zehnder modulator, and the output port of the modulator is connected to the input port of the polarization controller; the output port of the polarization controller is connected to the input port of the polarization beam splitter; The output port of the beam splitter is connected with the input port of the optical delay line and the adjustable optical attenuator respectively; the output port of the optical delay line and the adjustable optical attenuator is connected with the input port of the polarization beam combiner; the output port of the polarization beam combiner is connected with the The input ports of the photodetectors are connected; the photodetectors output electric signals.

In this example, the specific implementation steps of the method are:

Step 1: The laser source generates a continuous light wave with a wavelength of 1552nm and a power of 12dBm, and the continuous light wave is input into a polarization multiplexing Mach-Zehnder modulator with a half-wave voltage of 3.5V and an insertion loss of 6dB. The 1.6Gbps non-return-to-zero signal generated by the arbitrary waveform generator is mixed with the 18GHz local oscillator generated by the microwave signal generator, as shown in Figure 2(a). The mixed signal is divided into two channels and input to the RF ports of X-MZM and Y-MZM respectively.

Step 2: The polarization multiplexed signal is demultiplexed by a polarization controller and a polarization beam splitter and then divided into two paths, one of which is input to the optical delay line, and the angle of arrival is simulated by changing the time delay introduced by the optical delay line Variety. Simultaneously, the notch frequencies corresponding to different relative time delays were recorded, and two sets of measurements were performed. To determine the initial time delay between the two branches, the measurement is first used for calibration. The measured frequency offset and the corresponding time delay are shown in Figure 3. The larger the slope, the greater the measurement error of the fixed frequency will lead to a larger measurement error of the time delay. The slope of the theoretical curve is calculated as -21.2ps/GHz.

Step 3: After calibration, measure the filtered frequency offset by an electrical signal analyzer, and calculate the relative time delay. Figure 4 shows the measurement results, which correspond to a measurement error of less than ±0.35ps. Assuming that the antenna spacing is λ/2, the measurement error of the angle of arrival is less than 0.72°. The time delay ranges from -14ps to 16ps, and the corresponding arrival angle ranges from -30.26° to 35.17°.

To sum up, the present invention utilizes polarization multiplexing Mach-Zehnder modulator, differential group delay module, etc. to realize the estimation of angle of arrival of broadband microwave signal based on microwave photon filtering. It works under non-coherent conditions, which makes the system more robust.

In a word, the embodiments described above are only examples of the present invention, and are not only used to limit the protection scope of the present invention. Several equivalent deformations and replacements can be made. If the microwave photonic filter adopts different differential group delay values, the measurement capabilities will be different. These equivalent deformations and replacements as well as the adjustment of the frequency range should also be regarded as the protection scope of the present invention.

Claims (4)

1. a kind of wide-band microwave Direction-of-arrival method based on microwave photon filtering, including lasing light emitter, palarization multiplexing horse Conspicuous-Zeng Deer modulators, polarization beam combiner, Polarization Controller, polarization beam apparatus, optical delay line and photodetector, its feature It is：The output port of lasing light emitter is connected with palarization multiplexing Mach-Zehnder modulators input, the output end of the modulator with Polarization Controller input port is connected；The output port of Polarization Controller is connected with the input port of polarization beam apparatus；Polarization point Input port of the output port of beam device respectively with optical delay line and adjustable optical attenuator is connected；Optical delay line and variable optical attenuation The output port of device is connected with polarization beam combiner input port；The input port of polarization beam combiner output port and photodetector It is connected, the output port connection electric signal analyzer of photodetector carries out observation test.

The palarization multiplexing Mach-Zehnder modulators are by the parallel Mach of Y shunts, upper and lower two-way-increasing Dare modulator X- MZM and Y-MZM and polarization rotator, polarization beam combiner are formed.Incident optical signal is divided into two-way power phase by the Y shunts Deng optical signal, respectively enter in X-MZM and Y-MZM.Radiofrequency signal is separately input to X-MZM and Y-MZM prevention at radio-frequency port.Y- The signal of MZM outputs is input to polarization beam combiner after 90 ° of polarization rotators, with X-MZM output signal, and to retrodeviate polarization state orthogonal, Realize polarization state multiplexing.

A differential group delay module is connected after the palarization multiplexing Mach-Zehnder modulators.The module is to two polarization states Relative time-delay is introduced, after photodetector, whole system can be equivalent to the microwave photon filtering of two taps Device.

The change of arrival bearing will produce tuning effect to above-mentioned microwave photon filter, by the trap frequency for measuring microwave signal Rate, it is estimated that the arrival bearing of microwave signal.

2. the wide-band microwave Direction-of-arrival method according to claim 1 based on microwave photon filtering, its feature It is：Polarization point multiplexing Mach-Zehnder modulators combination differential group delay module can realize that two-tap microwave photon trap is filtered Ripple device.

3. the wide-band microwave Direction-of-arrival method according to claim 1 based on microwave photon filtering, its feature It is：Pass through the relative time for measuring transmission trap to obtain between two signals received at the antenna element of two separation Delay, is calculated time delay so as to obtain the estimation to wide-band microwave direction of arrival.

4. the wide-band microwave Direction-of-arrival method according to claim 1 based on microwave photon filtering, its feature It is：Measurement range can be further improved by selecting larger differential group delay value.