CN114518558B - Uniform circular array correlation interferometer direction finding method based on microwave photon phase discriminator - Google Patents
Uniform circular array correlation interferometer direction finding method based on microwave photon phase discriminator Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
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- G01S3/143—Systems for determining direction or deviation from predetermined direction by vectorial combination of signals derived from differently oriented antennae
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Abstract
The application relates to a direction finding method of a uniform circular array correlation interferometer based on a microwave photon phase discriminator. The method comprises the following steps: optical domain interference of two paths of radio frequency signals is realized through a double parallel Mach-Zehnder modulator in a microwave photon phase discriminator, optical signals output by the double parallel Mach-Zehnder modulator are subjected to carrier suppression through an optical notch filter, the optical power value of the optical signals output by the optical notch filter is measured through an optical power meter, and a phase difference measurement value of the two paths of signals is obtained through a signal processing unit; the direction finding module of the correlation interferometer aims at maximizing the correlation function based on the trigonometric function, and the direction of the incoming wave signal is determined according to the measured value of the phase difference. The application combines the electric domain and the optical domain based on the microwave photonics and the related interferometer direction finding technology to realize the direction finding of the microwave signals, the system can realize the accurate measurement of the 0-360 DEG phase, the system can adapt to the direction finding of the high-frequency band and large-bandwidth microwave signals, and the performance requirement of the related interferometer direction finding system is met.
Description
Technical Field
The application relates to the fields of microwave photonics and radio direction finding, in particular to a direction finding method and a direction finding system of a uniform circular array correlation interferometer based on a microwave photon phase discriminator.
Background
The direction of arrival refers to the direction of incoming waves of radio signals, and is an important technical parameter focused in the fields of electromagnetic spectrum monitoring, radio positioning, signal detection and the like. The direction finding technology is to accurately acquire the information of the incoming wave direction of a signal by taking certain measures and means, and is widely applied to the fields of broadband mobile communication, radar, electronic warfare and the like. Currently, spatial spectrum estimation and interferometry are two measurement regimes of major interest in the industry. The spatial spectrum technology is a super-resolution direction finding technology, and can realize high-precision measurement of a plurality of signals, but the technology needs each channel to have amplitude-phase consistency, has complex algorithm and large calculation amount, thus leading to higher complexity of a direction finding system, higher realization difficulty and limitation of wide application of the system. Interferometer direction finding is divided into two technical systems of phase interferometers and related interferometers. The phase interferometer has simple principle and low complexity, but the algorithm needs the receiver to have phase consistency, the hardware requirement is high, and the phase ambiguity problem exists in high-frequency measurement. The correlation interferometer direction finding technology has the advantages of simple calculation, high precision, no restriction of antenna aperture, wavefront distortion resistance and the like, and is widely applied to the fields of radio positioning, frequency spectrum monitoring, electronic countermeasure and the like. In addition, the uniform circular array direction finding has the advantages of consistency of all directions, capability of measuring azimuth angle and pitch angle simultaneously, compact array and the like, and is suitable for various direction finding systems.
The traditional electric domain direction-finding system has the defects of low working frequency, small bandwidth, large influence by electromagnetic interference and the like under the influence of 'electronic bottleneck'. At present, with the increasing complexity of electromagnetic environment and the shortage of frequency spectrum resources, the forward high-frequency band of various fields such as broadband mobile communication, radar, electronic warfare and the like is exploited. Consequently, direction finding of high-band, large-bandwidth signals has become one of the major challenges facing electrical domain direction finding systems. The microwave photonics has the advantages of high working frequency band, large bandwidth, small volume, light weight, low loss, electromagnetic interference resistance and the like, so that research and development of a microwave direction finding system based on photonics are becoming one of important research directions. At present, the main scheme adopted by the microwave photon direction finding is to measure the incoming wave direction by measuring the phase difference or the relative time delay. The photon direction finding system based on time delay is limited by time delay equipment, the measuring range is narrow, the system needs a high-speed photoelectric detector, and the application range is limited. The phase difference-based measurement is to measure the phase difference of two paths of signals by using a photon interferometer so as to realize the measurement of the incoming wave direction, which is the main research direction in the current photon direction finding field. Most of the prior art schemes are based on an optical interferometer structure, and utilize the mapping relation between the optical power and the phase difference of an output optical signal or a radio frequency signal to realize signal direction finding by measuring the phase difference, but only one mapping relation is utilized when the schemes perform single measurement, for example, part of schemes utilize the optical interferometer structure to map the phase difference and the output power into cosine functions, but the 1-degree phase difference power change in part of measurement areas is only 0.0003dB, so that the resolution of the output power is low, the algorithm has larger measurement error and the measurement range is limited.
Disclosure of Invention
Based on the above, it is necessary to provide a direction finding method, device, computer equipment and storage medium for a uniform circular array correlation interferometer based on a microwave photon phase detector, which has high working frequency band, large bandwidth and electromagnetic interference resistance.
A method for direction finding by a uniform circular array correlation interferometer based on a microwave photon phase detector, the method comprising:
After receiving the incoming wave signals, the antenna array receives two paths of radio frequency signals through the radio frequency front end and the antenna selection unit, and the two paths of radio frequency signals are input into the microwave photon phase discriminator; the microwave photon phase discriminator comprises a laser, a double parallel Mach-Zehnder modulator, an optical notch filter, an optical power meter and a signal processing unit; the double parallel Mach-Zehnder modulator comprises an upper and lower branch MZM modulator and a main MZM modulator;
The method comprises the steps that an optical carrier signal sent by a laser is input into the double parallel Mach-Zehnder modulators, two paths of radio frequency signals are respectively input into the upper and lower branch MZM modulators, the upper and lower branch MZM modulators work at a minimum transmission point by adjusting direct current bias voltages of the upper and lower branch MZM modulators, phase difference bias is set by adjusting direct current bias voltages of the main MZM modulators, and optical domain interference of two paths of radio frequency signals is realized by the double parallel Mach-Zehnder modulators;
Performing carrier suppression on the optical signals output by the double parallel Mach-Zehnder modulators through the optical notch filter, measuring the optical power value of the optical signals output by the optical notch filter through the optical power meter, and obtaining a phase difference measurement value of two paths of radio frequency signals according to the optical power value by the signal processing unit;
In the direction-finding module of the correlation interferometer, the maximization of the correlation function based on the trigonometric function is taken as a target, the direction of the incoming wave signal is determined according to the measured value of the phase difference, and the result is displayed in a digital and graphical mode at the display control terminal.
In one embodiment, the method further comprises: and setting a phase difference bias by adjusting the direct current bias voltage of the main MZM modulator to enable the phase difference bias to be 0 DEG or 180 deg.
In one embodiment, the method further comprises: the higher order sidebands can be further filtered out by a filter.
In one embodiment, the method further comprises: setting the phase difference bias to be 0 degree and 180 degrees, and respectively obtaining a first optical power value and a second optical power value corresponding to the two conditions;
According to the first optical power value and the second power value, a power ratio phase difference measurement function is established as follows:
Wherein P out (θ=0°) is a first optical power value measured by an optical power meter when the phase difference offset is 0 °, P out (θ=180°) is a second optical power value measured by an optical power meter when the phase difference offset is 180 °, and T (Φ) is a ratio of the first optical power value to the second power value;
And obtaining a phase difference measurement value of the two paths of radio frequency signals by the signal processing unit according to the ratio T (phi) of the first optical power value and the second power value.
A uniform circular array correlation interferometer direction finding system based on a microwave photon phase detector, the system comprising: the system comprises an antenna array, a radio frequency front end, an antenna selection unit, a microwave photon phase discriminator and a related interferometer direction finding module;
The antenna array is used for receiving incoming wave signals;
The radio frequency front end and the antenna selection unit are used for realizing signal receiving and front end processing and realizing the combination of different baselines;
The microwave photon phase discriminator comprises a double parallel Mach-Zehnder modulator, is used for realizing optical domain interference of two paths of radio frequency signals and is used for obtaining phase difference measurement values of the two paths of radio frequency signals;
The correlation interferometer direction finding module is used for determining the direction of an incoming wave signal according to the phase difference measured value.
In one embodiment, the microwave photon phase detector further comprises: the device comprises a laser, an optical notch filter, an optical power meter and a signal processing unit;
the laser is used for generating an optical carrier signal;
The optical notch filter is used for carrying out carrier suppression on the optical signals output by the double parallel Mach-Zehnder modulators;
The optical power meter is used for measuring the optical power value of the optical signal output by the optical notch filter;
And the signal processing unit is used for obtaining a phase difference measurement value of the two paths of radio frequency signals according to the optical power value output by the optical power meter.
In one embodiment, the dual parallel mach-zehnder modulator comprises: an upper and lower arm MZM modulator and a main MZM modulator;
the carrier double-sideband modulation is inhibited by adjusting the direct-current bias voltage value in the upper and lower branch MZM modulators;
and setting phase difference bias is realized by adjusting the direct current bias voltage value of the main MZM modulator.
In one embodiment, the system further comprises: a display control terminal;
And the display control terminal is used for digital and graphical display of the direction finding result.
According to the direction finding method and system of the uniform circular array correlation interferometer based on the microwave photon phase discriminator, optical domain interference of two paths of radio frequency signals is achieved through the double parallel Mach-Zehnder modulators in the microwave photon phase discriminator, carrier suppression is carried out on optical signals output by the double parallel Mach-Zehnder modulators through the optical notch filter, optical power values of the optical signals output by the optical notch filter are measured through the optical power meter, and phase difference measurement values of the two paths of radio frequency signals are obtained through the signal processing unit according to the optical power values; the direction of the incoming wave signal is determined in the correlation interferometer direction finding module according to the measurement value of the phase difference, with the maximization of the correlation function based on the trigonometric function as a target. The invention combines the electric domain and the optical domain based on the microwave photonics and the related interferometer direction finding technology to realize the direction finding of the microwave signals, the system can adapt to the direction finding of the high-frequency band and large-bandwidth microwave signals, the accurate measurement of 0-360 DEG phase can be realized, and the performance requirement of the related interferometer direction finding system is met. The invention has wide application value in various fields such as communication, navigation, radar, electromagnetic spectrum monitoring and the like.
Drawings
FIG. 1 is a flow chart of a method for direction finding by a uniform circular array correlation interferometer based on a microwave photon phase detector in one embodiment;
FIG. 2 is a schematic diagram of a microwave photon phase detector in one embodiment;
FIG. 3 is a schematic diagram of a uniform circular array in one embodiment;
FIG. 4 is a graph of normalized power versus phase difference for a first order sideband in one embodiment;
FIG. 5 is a graph of a power ratio phase difference measurement function in one embodiment;
FIG. 6 is a schematic diagram of a uniform circular array correlation interferometer direction finding system based on a microwave photon phase detector in one embodiment;
fig. 7 is a block diagram of a direction finding system of a uniform circular array correlation interferometer based on a microwave photon phase detector in another embodiment.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In one embodiment, as shown in fig. 1, a method for measuring direction by using a uniform circular array correlation interferometer based on a microwave photon phase detector is provided, which comprises the following steps:
Step 102, after receiving the incoming wave signal by the antenna array, receiving two paths of radio frequency signals through the radio frequency front end and the antenna selection unit, and inputting the two paths of radio frequency signals into the microwave photon phase discriminator.
The schematic diagram of the microwave photon phase discriminator is shown in fig. 2, and comprises a laser, a double parallel Mach-Zehnder modulator, an optical notch filter, an optical power meter and a signal processing unit; the dual parallel mach-zehnder modulator includes upper and lower arm MZM modulators and a main MZM modulator.
The implementation principle of the scheme provided by the invention is that the phase difference caused by the path difference of plane wave signals on different antenna array elements has a corresponding relation with the incoming wave direction, and the measurement of the incoming wave direction is realized by calculating the correlation between the measured value and the theoretical value. After receiving the incoming wave signals, the antenna array receives the incoming wave signals of different antenna array elements through the radio frequency front end and the antenna selection unit. Because the designed microwave photon phase discriminator needs to receive two paths of radio frequency signals simultaneously, the proposal is suitable for a double-channel or multi-channel receiver. And then, inputting radio frequency signals of different paths received by a receiver into a microwave photon phase discriminator unit, thereby measuring and calculating phase differences among the signals of different paths, finally, calculating an incoming wave direction value through a correlation interferometer direction finding unit, and outputting the incoming wave direction value to a display control terminal for result display.
The implementation principle of the microwave photon phase detector is analyzed in theory as follows.
First, assume that the optical carrier signal output by the laser is:
E(t)＝E0exp(jω0t) (1)
Where E 0 denotes the amplitude of the optical signal, ω 0 denotes the angular frequency of the optical carrier signal.
The optical carrier signal is divided into two paths and is respectively input into an upper branch and a lower branch of a double parallel Mach-Zehnder modulator (DPMZM), and the direct current bias voltages of the upper branch MZM modulator (MZM 1) and the lower branch MZM modulator (MZM 2) are adjusted to enable the two branch MZM modulators to work at a minimum transmission point. Two paths of radio frequency signals with phase difference are respectively input into the MZM1 and the MZM2 to realize CS-DSB modulation. For convenience of description, the two radio frequency signals may be expressed as:
E1m(t)＝Emexp(jωmt+jφ) (2)
E2m(t)＝Emexp(jωmt) (3)
Wherein E m and omega m respectively represent the amplitude and the angular frequency of the radio frequency signal, and phi is the phase difference of the two paths of signals.
When modulating with a small signal, the Gao Jiedi Bessel function is almost zero, and ignoring the second and above side bands, the output signal of the MZM1 can be expressed as:
where m=pi E m/Vπ denotes the modulation index, V π is the half-wave voltage of MZM 1.
Similarly, the output signal of the lower-arm MZM2 can be expressed as:
Assuming that the phase bias angle of the main MZM modulator (MZM 3) in the DPMZM is θ, the output signal of the DPMZM can be expressed as:
therefore, the optical signal powers of the upper and lower sidebands are respectively:
As can be seen from the above equation, the output power of the DPMZM is related to the phase difference, and the estimated value of the phase difference can be obtained by measuring the optical power value. In general, the power of the upper and lower sidebands is not uniform, subject to the bias angle θ. In order to achieve the measurement of the power of the upper and lower sidebands, the upper and lower sidebands need to be decomposed in advance by an optical demultiplexer or a filter. In order to avoid this process, P +1＝P-1, i.e., θ=0° or θ=180°, where the upper and lower sidebands have the same trend, and the phase difference can be measured by directly measuring the optical power of the output signal.
And 104, transmitting an optical carrier signal by a laser to be input into the double parallel Mach-Zehnder modulators, respectively inputting two paths of radio frequency signals into the upper and lower branch MZM modulators, enabling the upper and lower branch MZM modulators to work at a minimum transmission point by adjusting the direct current bias voltage of the upper and lower branch MZM modulators, setting phase difference bias by adjusting the direct current bias voltage of the main MZM modulator, and realizing optical domain interference of the two paths of radio frequency signals by the double parallel Mach-Zehnder modulators.
And 106, performing carrier suppression on the optical signals output by the double parallel Mach-Zehnder modulators through the optical notch filter, measuring the optical power value of the optical signals output by the optical notch filter through the optical power meter, and obtaining the phase difference measurement value of the two paths of radio frequency signals according to the optical power value through the signal processing unit.
The Optical Notch Filter (ONF) is used to filter out the optical carrier signal, so as to avoid the optical carrier signal from affecting the power measurement of the output optical signal and improve the resolution of the power measurement.
And step 108, in the direction-finding module of the correlation interferometer, the direction of the incoming wave signal is determined according to the measured value of the phase difference with the aim of maximizing the correlation function based on the trigonometric function, which is constructed in advance, and the result is displayed in a digital and graphical mode at the display control terminal.
In the conventional correlation interferometer direction-finding algorithm, if the antenna array is a uniform circular array, the incoming wave direction of the signal is assumed to be (alpha, beta), wherein alpha is an azimuth angle, and beta represents a pitch angle. The circle center O of the N-element uniform circular array is made to be a phase reference point, and the connecting line of the circle center and the first antenna is made to be a reference direction (0, 0). At this time, as shown in fig. 3, the phase of the nth antenna element is:
wherein r is the radius of the circular array, lambda is the wavelength of the incoming wave signal, r/lambda is the radius-wavelength ratio, and θ=2pi/N is the included angle between adjacent antenna elements.
The phase vector is constructed by using the result as follows:
At this time, a phase difference vector is obtained as:
Wherein B F∈RL×N represents a base line selection matrix, the elements of which consist of 1, -1 and 0 for antenna base line selection. The dimension of the phase difference vector is L.
Assume that the measured value of the phase difference vector is:
The correlation value can be calculated using the following formula:
at this time, the estimated value of the direction angle is obtained as:
the direction-finding algorithm of the traditional correlation interferometer is used for calculating the correlation value between the measured value and the theoretical value, and judging and comparing the correlation value and the theoretical value, wherein the direction angle corresponding to the maximum correlation value is the estimated value of the incoming wave direction. However, as can be seen from the formula, the molecular denominator can simultaneously cancel cos beta when the correlation value is calculated, the correlation value is irrelevant to the pitch angle, namely the pitch angle cannot be distinguished by the algorithm, and the problem of boundary phase jump exists in the algorithm. To overcome these two disadvantages, the present invention uses a cosine function to construct a correlation function as:
Wherein phi i is the theoretical value of phase difference, Is a phase difference measurement.
Similarly, the determination of the incoming wave direction is achieved by determining the maximum value of the correlation function, namely:
In the direction finding method of the uniform circular array correlation interferometer based on the microwave photon phase discriminator, optical domain interference of two paths of radio frequency signals is realized through the double parallel Mach-Zehnder modulators in the microwave photon phase discriminator, carrier suppression is carried out on the optical signals output by the double parallel Mach-Zehnder modulators through the optical notch filter, the optical power value of the optical signals output by the optical notch filter is measured through the optical power meter, and phase difference measurement values of the two paths of radio frequency signals are obtained through the signal processing unit according to the optical power value; the direction of the incoming wave signal is determined in the correlation interferometer direction finding module according to the measurement value of the phase difference, with the maximization of the correlation function based on the trigonometric function as a target. The invention combines the electric domain and the optical domain based on the microwave photonics and the related interferometer direction finding technology to realize the direction finding of the microwave signals, the system can adapt to the direction finding of the high-frequency band and large-bandwidth microwave signals, the accurate measurement of 0-360 DEG phase can be realized, and the performance requirement of the related interferometer direction finding system is met. The invention has wide application value in various fields such as communication, navigation, radar, electromagnetic spectrum monitoring and the like.
The uniform circular array is a common array configuration, as shown in fig. 3, when the number of antenna array elements is equal to or greater than or equal to 5, the omnidirectional unambiguous direction finding can be realized, and the uniform circular array can simultaneously measure azimuth angle and pitch angle, so that the two-dimensional direction finding can be realized.
In one embodiment, the method further comprises: the phase difference bias is set by adjusting the DC bias voltage of the main MZM modulator to be 0 DEG or 180 deg.
The purpose of setting the phase difference bias to 0 or 180 is to make the upper and lower sideband optical signal power of the DPMZM output consistent.
In one embodiment, the method further comprises: the higher order sidebands can be further filtered out by a filter.
In one embodiment, the method further comprises: setting the phase difference bias to be 0 degree and 180 degrees, and respectively obtaining a first optical power value and a second optical power value corresponding to the two conditions;
According to the first optical power value and the second power value, a power ratio phase difference measurement function is established as follows:
Wherein P out (θ=0°) is a first optical power value measured by the optical power meter when the phase difference offset is 0 °, P out (θ=180°) is a second optical power value measured by the optical power meter when the phase difference offset is 180 °, and T (Φ) is a ratio of the first optical power value to the second power value;
And obtaining a phase difference measurement value of the two paths of radio frequency signals by the signal processing unit according to the ratio T (phi) of the first optical power value and the second power value.
As is clear from the equations (7) and (8), the functional relationship between the output optical power and the phase difference is a cosine function. As shown in fig. 4, the minimum power difference for the 1 ° phase difference was only 0.0003dB, and the minimum power difference for the 5 ° phase difference was only 0.008dB. In practice, the better commercial optical power meter can reach 0.01dB resolution, and is influenced by laser power fluctuation, modulator bias voltage drift, system noise and the like, and the optical power output by the system can have certain fluctuation. Under the influence of the two aspects, only the power of the upper sideband and the lower sideband is used for measurement and judgment, or larger measurement errors are caused.
For this purpose, the phase bias of MZM3 can be set to 0 ° and 180 °, respectively, and the optical power values output in both cases can be measured, respectively. Then, a phase difference measurement function is established by using the ratio of the two output powers, namely:
As is evident from the phase difference measurement function shown in fig. 5, the function has a large slope, which is advantageous for increasing the resolution of the measurement and improving the measurement accuracy. From the calculation result, the minimum measured value difference corresponding to the 1 ° phase difference was 0.1516dB, and the minimum measured value difference corresponding to the 5 ° phase difference was 0.759dB, using the above phase difference measurement function. In addition, as can be seen from the formula (17), the provided power ratio measurement function is irrelevant to the actual power value, and can effectively overcome the measurement error caused by power fluctuation or equipment devices by only using the ratio of two output powers. Therefore, the resolution of power measurement can be greatly improved by using the measurement function, and the accuracy of phase difference measurement can be effectively improved.
In another embodiment, the bias voltage of the main MZM in the dual parallel mach-zehnder modulator may be set at other values, so that the upper and lower sideband powers of the output optical signal are inconsistent, and the phase difference measurement ambiguity problem can be solved by comparing.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be performed in other orders. Moreover, at least some of the steps in fig. 1 may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, or the order in which the sub-steps or stages are performed is not necessarily sequential, but may be performed in rotation or alternatively with at least a portion of the sub-steps or stages of other steps or steps.
In one embodiment, as shown in fig. 6, a uniform circular array correlation interferometer direction finding system based on a microwave photon phase detector, the system comprises: an antenna array 602, a radio frequency front end and antenna selection unit 604, a microwave photon phase detector 606 and an associated interferometer direction finding module 608;
The antenna array 602 is used for receiving incoming wave signals;
the radio frequency front end and antenna selection unit 604 is used for realizing the receiving and front end processing of signals and realizing the combination of different baselines;
The microwave photon phase discriminator 606 comprises a double parallel Mach-Zehnder modulator, which is used for realizing optical domain interference of two paths of radio frequency signals, and the microwave photon phase discriminator 606 is used for obtaining a phase difference measurement value of the two paths of radio frequency signals;
The correlation interferometer direction finding module 608 is used for determining the direction of the incoming wave signal according to the phase difference measurement value.
In one embodiment, the microwave photon phase detector 606 further includes: the device comprises a laser, an optical notch filter, an optical power meter and a signal processing unit; the laser is used for generating an optical carrier signal; the optical notch filter is used for carrying out carrier suppression on the optical signals output by the double parallel Mach-Zehnder modulators; the optical power meter is used for measuring the optical power value of the optical signal output by the optical notch filter; the signal processing unit is used for obtaining a phase difference measurement value of the two paths of radio frequency signals according to the optical power value output by the optical power meter.
In one embodiment, the dual parallel mach-zehnder modulator comprises: an upper and lower arm MZM modulator and a main MZM modulator; the direct-current bias voltage value in the upper and lower branch MZM modulators is adjusted to realize the suppression of carrier double-sideband modulation; by adjusting the DC bias voltage value of the main MZM modulator, the setting of the phase difference bias is realized.
In one embodiment, as shown in fig. 7, the system further comprises: a display control terminal; the display control terminal is used for digital and graphical display of the direction finding result.
The specific limitation of the direction-finding device of the uniform circular array correlation interferometer based on the microwave photon phase detector can be referred to as the limitation of the direction-finding method of the uniform circular array correlation interferometer based on the microwave photon phase detector, and the description is omitted here. All or part of each module in the uniform circular array correlation interferometer direction-finding device based on the microwave photon phase discriminator can be realized by software, hardware and a combination thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that modifications and improvements can be made by those skilled in the art without departing from the spirit of the application, which falls within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (8)
1. A method for direction finding by a uniform circular array correlation interferometer based on a microwave photon phase detector, the method comprising:
After receiving the incoming wave signals, the antenna array receives two paths of radio frequency signals through the radio frequency front end and the antenna selection unit, and the two paths of radio frequency signals are input into the microwave photon phase discriminator; the microwave photon phase discriminator comprises a laser, a double parallel Mach-Zehnder modulator, an optical notch filter, an optical power meter and a signal processing unit; the double parallel Mach-Zehnder modulator comprises an upper and lower branch MZM modulator and a main MZM modulator;
The method comprises the steps that an optical carrier signal sent by a laser is input into the double parallel Mach-Zehnder modulators, two paths of radio frequency signals are respectively input into the upper and lower branch MZM modulators, the upper and lower branch MZM modulators work at a minimum transmission point by adjusting direct current bias voltages of the upper and lower branch MZM modulators, phase difference bias is set by adjusting direct current bias voltages of the main MZM modulators, and optical domain interference of the two paths of radio frequency signals is realized by the double parallel Mach-Zehnder modulators;
Performing carrier suppression on the optical signals output by the double parallel Mach-Zehnder modulators through the optical notch filter, measuring the optical power value of the optical signals output by the optical notch filter through the optical power meter, and obtaining a phase difference measurement value of two paths of radio frequency signals according to the optical power value by the signal processing unit;
In a direction-finding module of the correlation interferometer, a pre-constructed correlation function based on a trigonometric function is maximized as a target, the direction of an incoming wave signal is determined according to the measured value of the phase difference, and the direction-finding result is displayed in a digital and graphical mode at a display control terminal.
2. The method of claim 1, wherein the antenna array is a uniform circular array.
3. The method of claim 1, wherein setting the phase difference bias by adjusting a dc bias voltage of the main MZM modulator comprises:
and setting a phase difference bias by adjusting the direct current bias voltage of the main MZM modulator to enable the phase difference bias to be 0 DEG or 180 deg.
4. The method of claim 1, further comprising, after carrier-suppressing the optical signal output by the dual parallel mach-zehnder modulator by the optical notch filter:
The higher order sidebands are further filtered out by a filter.
5. The method of claim 1, wherein obtaining, by the signal processing unit, a phase difference measurement of the two radio frequency signals from the optical power value, comprises:
setting the phase difference bias to be 0 degree and 180 degrees, and respectively obtaining a first optical power value and a second optical power value corresponding to the two conditions;
According to the first optical power value and the second optical power value, a power ratio phase difference measurement function is established as follows:
；
Wherein, First optical power value measured by optical power meter when phase difference bias is 0 DEG,/>For a second optical power value measured by an optical power meter when the phase difference bias is 180 DEG,/>Is the ratio of the first optical power value to the second optical power value,/>Representing the phase difference;
The signal processing unit is used for processing the first optical power value and the second optical power value according to the ratio of the first optical power value and the second optical power value And obtaining a phase difference measurement value of the two paths of radio frequency signals.
6. A uniform circular array correlation interferometer direction finding system based on a microwave photon phase detector, the system comprising: the system comprises an antenna array, a radio frequency front end, an antenna selection unit, a microwave photon phase discriminator and a related interferometer direction finding module;
The antenna array is used for receiving incoming wave signals;
the radio frequency front end and the antenna selection unit are used for realizing signal receiving and front end processing and realizing the combination of different baselines;
The microwave photon phase discriminator comprises a double parallel Mach-Zehnder modulator, is used for realizing optical domain interference of two paths of radio frequency signals and is used for obtaining phase difference measurement values of the two paths of radio frequency signals;
the microwave photon phase discriminator further comprises: the device comprises a laser, an optical notch filter, an optical power meter and a signal processing unit; the laser is used for generating an optical carrier signal; the optical notch filter is used for carrying out carrier suppression on the optical signals output by the double parallel Mach-Zehnder modulators; the optical power meter is used for measuring the optical power value of the optical signal output by the optical notch filter; the signal processing unit is used for obtaining a phase difference measurement value of two paths of radio frequency signals according to the optical power value output by the optical power meter;
The dual parallel Mach-Zehnder modulator comprises: an upper and lower arm MZM modulator and a main MZM modulator; the direct-current bias voltage value in the upper and lower branch MZM modulators is adjusted to realize the suppression of carrier double-sideband modulation; setting of phase difference bias is achieved by adjusting a direct current bias voltage value of the main MZM modulator;
the correlation interferometer direction finding module is used for determining the direction of an incoming wave signal according to the phase difference measurement value.
7. The system of claim 6, wherein the system further comprises: a display control terminal;
And the display control terminal is used for digital and graphical display of the direction finding result.
8. The system of claim 6, wherein the antenna array is a uniform circular array.
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