WO2023019649A1

WO2023019649A1 - Monopulse antenna tracking and phase correction method

Info

Publication number: WO2023019649A1
Application number: PCT/CN2021/116335
Authority: WO
Inventors: 王举思; 路波; 屈会鹏; 杨文洁
Original assignee: 王举思; 路波
Priority date: 2021-08-19
Filing date: 2021-09-03
Publication date: 2023-02-23
Also published as: CN113629400B; CN113629400A

Abstract

The present invention relates to the field of sum-difference dual-channel or single-channel monopulse tracking antennas. Disclosed is a phase correction method for a monopulse antenna using a novel TE21 mode signal combiner and a receiver. In the present invention, a novel T21 mode signal combiner is used, so that during phase correction, an azimuth error signal and a pitch error signal can be isolated, cross-coupling is avoided, and phase correction can be performed on a tracking target rapidly in real time; after an antenna finds the target at a waiting point, a receiver detects sum and difference signal levels, and identifies, according to sum and difference pattern data of the antenna, whether the target enters a main beam of the antenna; after the target enters the main beam of the antenna, a phase correction program is started, and in the process of phase correction, whether the difference signal level meets a phase correction requirement is identified; in the process of tracking the target by the antenna, a monopulse tracking state is determined according to normalized null depth data and difference signal level change of the antenna, alarm information is output when the monopulse tracking is abnormal, and an output of angle error data is set to zero.

Description

A Tracking and Phasing Method of Monopulse Antenna

technical field

The invention belongs to the field of sum-difference dual-channel or single-channel single-pulse tracking antennas, and in particular relates to a tracking phase correction method for a single-pulse antenna.

Background technique

Monopulse tracking technology has been applied since the 1950s. When a large-aperture parabolic antenna tracks a dynamic target, in order to achieve the specified tracking accuracy, the sum-difference ratio-amplitude monopulse tracking is generally used. Early monopulse tracking used multiple horn feeds, and then output the sum and difference signals through a synthesis network. With the development of microwave technology, circular waveguide multi-mode self-tracking feeds have replaced multi-horn feeds and are widely used in monopulse tracking antennas. Since the transmission paths of the sum signal and the difference signal are different, and the phase delay is different, it is necessary to shift the phase of the reference signal of the angle pointing error voltage demodulator to offset the phase delay difference of the sum and difference channel, so that the angle pointing of the antenna tracking target can be accurately demodulated error voltage. The calculation process of the reference signal phase-shift value of the angle point error voltage demodulator is referred to as tracking phase correction.

The first is the classic phasing method. The antenna points to the calibration source (including calibration towers, radio sources, geostationary satellites, etc.), and deviates from a specific angle in the azimuth or elevation axis to excite the difference channel signal. The phase of the reference signal of the receiver is shifted step by step, and the azimuth or pitch error voltage is read, and then the phase shift value of the reference signal is calculated by curve fitting. The antenna points to the calibration source signal, and the phase calibration accuracy is high, which can be applied to various frequency bands. The disadvantage of this phasing method is that it depends on the calibration source, and it needs to store the combined phase shift values of multiple devices for recall, which takes a long time for preparation and low efficiency.

The second is the fast phase correction method. The antenna is guided by the orbit forecast data to track the target, and then a specific angle offset is set to record the change value of the output voltage of the angle difference demodulator when the phase shift is 90 degrees, 180 degrees, and 270 degrees. , and then use the curve fitting to solve the phase delay difference of the sum difference channel to complete the tracking phase correction. The method does not rely on the calibration source, and the tracking target is phased in real time, and the phase calibration accuracy meets the requirements of antenna tracking. This fast phase correction method is better applied in S-band and C-band, but there are no cases of successful application in X, Ku, Ka and other frequency bands. The precondition of this fast phase correction method is that the difference slope linearity of the difference signal pattern in the main beam of the antenna is good. In the millimeter-wave high-frequency band, the beam main lobe is narrower. Due to the influence of factors such as the surface accuracy error of the antenna panel and the gravity deformation of the large-aperture antenna, the paraxial characteristics of the antenna difference pattern deteriorate, and the difference slope has obvious nonlinear fluctuations. The fitting calculation The deviation of the phase shift value is large, and the phase correction result cannot meet the requirements of antenna tracking.

The third method is the data comparison and correction method. Under the condition that the calibration source is available, the tracking phase calibration is completed and stored, and then the signal is injected into the tracking link through the directional coupler, and the phase difference of the injected signal is tested and stored. When no calibration source is available, test the change of the phase difference of the injected signal and correct the phase value stored earlier. The accuracy of phase correction is not high by this method, and additional equipment and workload are added.

Aiming at the shortcomings of the above three phase correction methods, the patent of the present invention proposes a novel monopulse tracking phase correction technology. Use the new T21 analog signal synthesizer to isolate the azimuth error signal or pitch error signal during phasing, avoiding cross-coupling, and can quickly phasing the tracking target in real time. During the antenna tracking target process, the monopulse tracking state is judged according to the normalized zero-depth data of the antenna and the level change of the difference signal.

Contents of the invention

Aiming at the above-mentioned technical problems existing in the prior art, the present invention proposes a novel monopulse antenna tracking phase correction method, which is reasonably designed, overcomes the deficiencies of the prior art, and has good effects.

In order to achieve the above object, the present invention adopts the following technical solutions:

A monopulse antenna tracking phase correction method, using a T21 mode signal synthesizer with a built-in microwave switch, and realizing fast phase correction of monopulse tracking through phase difference measurement technology, specifically includes the following steps:

Step 1: Wait for the target;

Step 2: capture the target signal through the receiver;

Step 3: Identify the target to enter the main beam;

Step 4: Start the phase tracking program;

Step 5: Disconnect the pitch difference signal, and check whether the level of the azimuth difference signal meets the phase correction requirements;

If: the azimuth difference signal level satisfies the phase correction requirements, then perform step 6;

Or if the azimuth difference signal level does not meet the requirements for phase correction, go to step 8;

Step 6: Carry out azimuth tracking and phase calibration;

Step 7: Determine whether the pitch calibration is completed;

If: the pitch calibration has been completed, go to step 11;

Or if the pitch calibration is not completed, go to step 8;

Step 8: Disconnect the azimuth difference signal, and check whether the level of the pitch difference signal meets the phase correction requirements;

If: the pitch difference signal level meets the phase correction requirements, then perform step 9;

Or if the pitch difference signal level does not meet the phase correction requirements, go to step 5;

Step 9: Perform pitch tracking and phasing;

Step 10: Judging whether the azimuth tracking phase correction is completed;

If: the azimuth tracking phase correction has been completed, then perform step 11;

Or if azimuth tracking and calibration is not completed, go to step 5;

Step 11: Tracking and calibration is over.

Preferably, a microwave switch is arranged inside the T21 mode signal synthesizer, and the azimuth difference signal or the pitch difference signal is isolated through the microwave switch, so as to avoid the cross-coupling of the two.

Preferably, in step 3, the receiver detects the sum and difference signal levels, and identifies whether the target enters the main beam of the antenna according to the antenna sum and difference pattern data.

Preferably, in step 6, when doing azimuth tracking and phase correction, the receiver controls the microwave switch in the T21 analog signal synthesizer to isolate the pitch difference signal, so that the phase difference of the measured sum difference signal is equal to the phase delay difference of the sum difference channel , complete azimuth tracking calibration.

Preferably, in step 9, when doing pitch tracking phase correction, the receiver controls the microwave switch in the T21 analog signal synthesizer to isolate the azimuth difference signal, so that the phase difference of the sum difference signal is equal to the phase delay difference of the sum difference channel , to complete pitch tracking calibration.

Preferably, when the antenna is in the monopulse tracking state, the receiver detects the sum signal and the difference signal level, and judges the monopulse tracking state according to the antenna normalized zero-depth data and the difference signal level change, and when the monopulse tracking is abnormal Output alarm information, and set the angular error data output to zero to avoid overshoot or obvious oscillation of the antenna drive.

Beneficial technical effects brought by the present invention:

1. Without relying on the calibration source, the receiver can identify the target and enter the main beam of the antenna after capturing the target signal, and quickly complete the tracking and phase calibration;

2. According to the different characteristics of the tracking target, different phase difference measurement technologies can be selected to improve the accuracy of fast phase correction;

3. During the single-pulse tracking process of the antenna, real-time monitoring and differential signal level changes are used as early warnings for abnormal single-pulse tracking.

Description of drawings

Figure 1 is a block diagram of a single circular polarization monopulse tracking link;

Figure 2 is a combined diagram of a dual polarization tracking mode coupler;

Wherein, figure (a) is a schematic diagram of coupler A; figure (b) is a schematic diagram of coupler B; figure (c) is a schematic diagram of a combined coupler;

Fig. 3 is a schematic diagram of a dual polarization difference (Δ) channel signal synthesis network;

Figure 4 is a block diagram of a dual-polarization dual-channel single-pulse tracking link device using the new TE21 mode synthesizer;

Figure 5 is a block diagram of the dual-polarization single-channel single-pulse tracking device using the new TE21 mode synthesizer;

Figure 6 is a flow chart of digital receiver phase correction.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

1. Single polarization feed and (Σ) channel signal and difference (Δ) channel signal phase correlation analysis

The monopulse tracking antenna usually uses a circular waveguide multi-mode feed, and the TE21 mode tracking coupler (TE21 MODE COUPLER) is the source of the difference signal. Monopulse tracking antenna adopts circular polarization to track circularly polarized targets, which is the most commonly used mode. This application first discusses the phase transmission change of sum and difference two-channel signals and the principle of tracking phase correction in a single polarization mode.

TE21 mode tracking coupler is a circular four-port directional coupler located in the focal plane of the antenna feed, also known as the antenna feed receiving beam angle sensor. The phase of the TE21 mode signal at the coupling output port has a stable correlation with the phase of the feed and channel signals. The phase difference of the signals output by the two coupled ports of the azimuth TE21 mode is 180 degrees, and the output signals of the two ports are synthesized into an azimuth difference (Δ-XEL) signal; similarly, the phase difference of the signals output by the two coupled ports of the pitch TE21 mode is also 180 degrees, the output signals of the two ports are combined to form a pitch difference (Δ-EL) signal. The phase difference between the azimuth difference signal and the pitch difference signal is 90 degrees, and the two signals are synthesized into one difference (Δ-channel) signal. Fig. 1 is a block diagram of a single circular polarization monopulse tracking link device. Trk-D/C is a tracking down converter, Dual-CH DT is a dual-channel digital receiver, ACU is an antenna control unit, and SERVO is an antenna drive servo device.

Taking the single carrier (CW) signal as an example, it mainly demonstrates the phase relationship between the sum signal and the difference signal. Before the combination of azimuth difference signal and pitch difference signal, the azimuth difference signal is set as:

U _Δxel (t)=U _Δxel Sin(ω ₀ t), ω ₀ is the radio frequency angular frequency, U _Δxel =γθ _Δxel , γ is the difference slope.

Then the pitch difference signal is:

U _Δel (t)=U _Δel Cos(ω ₀ t), ω ₀ is the radio frequency angular frequency, U _ΔEL =γθ _ΔEL , γ is the difference slope.

According to the auxiliary angle formula, the combined difference signal is:

where auxiliary angle

The azimuth difference signal and the pitch difference signal are orthogonally synthesized into a difference channel (Δ-Channel) signal, which is fed to a low-noise amplifier (Δ-LNA). The sum channel (Σ-Channel) signal is output through the low noise amplifier, and is output through the coupled port of the directional coupler at the output port. Both the difference channel radio frequency (Δ-RF) signal and the sum channel radio frequency (Σ-RF) signal are connected to the tracking down converter (Trk-D/C), and the sum and difference channel RF signals share the local oscillator source, and the frequency conversion is two Channel intermediate frequency (IF) 70MHz signal. The sum and difference intermediate frequency 70MHz signals are connected to the dual-channel receiver (Dual-CH DTR), and the intermediate frequency signal of the sum channel is correlated with the phase of the reference signal (10.7MHz) through a frequency conversion phase-locked loop. The differential intermediate frequency signal is converted into a differential 10.7MHz signal with the same frequency as the reference signal in the receiver, and the phase of the differential signal has a stable correlation with the phase of the reference signal. The gain of the differential intermediate frequency signal amplifier is controlled by the AGC level of the sum intermediate frequency signal at the same time, and the amplitude normalization of the sum and difference signals is completed.

Let the quadrature reference signals be Sin(ω ₁ t) and Cos(ω ₁ t) respectively, and the differential 10.7MHz signal is expressed by formula (2).

Parameter in formula (2): G is normalization gain, ω ₁ intermediate frequency PLL reference signal angular frequency,

is the phase difference between the difference signal and the reference signal.

In order to accurately decompose and restore the amplitude of the azimuth difference signal and the amplitude of the pitch difference signal (linear ratio), the demodulated signal amplitudes are required to be:

The reference signal is phase-shifted by δ, and the trigonometric function expression of the coherent demodulation multiplier is as follows:

After low-pass filtering, the 2nd harmonic is filtered out, and the DC output is:

According to the previous discussion, when

, the amplitude of the azimuth difference signal and the amplitude of the pitch difference signal can be accurately decomposed. Can make

It is defined as the phase delay difference of the sum and difference channel, so the definition is clear. The phase difference between the sum signal and the difference signal is linearly superimposed by two phase values, one of which is the auxiliary angle synthesized by the orthogonal synthesis of the azimuth difference signal and the pitch difference signal , and the other is the phase delay difference between the phase of the sum channel and the phase of the difference channel.

It can be seen from the above formulas (7) and (8) that only when

, the demodulator can accurately decompose the amplitude of the azimuth difference signal and the amplitude of the pitch difference signal. when

When , the decomposition of the amplitude of the azimuth difference signal and the amplitude of the pitch difference signal is inaccurate, which is also called cross-coupling. solve

When the corresponding reference signal phase shift value δ is tracking phase correction.

Due to the different transmission paths between the T21 mode directional coupling output port of the corrugated horn and the synthesizer, the orthogonality between the azimuth difference signal and the elevation difference signal may be deteriorated, and the phase shift value of the reference signal of the azimuth difference amplitude-dependent demodulator is related to the elevation value. The phase shift value of the reference signal of the differential amplitude correlation demodulator is not necessarily 90 degrees different, so it needs to be solved separately.

2. Phase correlation analysis of dual-polarization feed and (Σ) channel signal and difference (Δ) channel signal

Monopulse tracking antennas are generally required to be able to track target signals with different polarizations. The output of the feed Σ channel is a dual-linear polarization port/dual circular polarization port, and the linear polarization/circular polarization mode can be switched. The feed Δ channel is the right Switch between circular polarization (RHCP) and left-handed circular polarization (LHCP). Monopulse tracking requires the polarization matching of the Σ channel and the Δ channel, and the receiver demodulates the azimuth angle error and the pitch angle error from the Δ channel signal, which requires the Σ channel signal as a reference.

At the focal plane of the circular waveguide corrugated horn feed, two staggered differential mode couplers are arranged. One is a vertically polarized T21 mode coupler (TE21 MODE COUPLER), and the other is a horizontally polarized T21 mode coupler. Figure 2 is a combination diagram of a dual-polarized tracking mode coupler.

These two mutually orthogonal T21 mode couplers are respectively connected to two 4-in-1 combiners (4:1 Combiner). The vertical polarization T21 mode signal synthesizer is connected to the four ports of the vertical polarization (V-POL) T21 mode coupler, and the horizontal polarization is connected to the four ports of the horizontal polarization (H-POL) T21 mode coupler T21 analog signal synthesizer. The output ports of these two differently polarized T21 mode combiners are connected to the microwave hybrid joint combination (Hybird Junction) to output two channels, one for right-handed circularly polarized waves (RHCP), and the other for left-handed circularly polarized waves ( LHCP). If a linearly polarized beam is received, the microwave hybrid joint decomposes it into right-handed circularly polarized waves (RHCP) and left-handed circularly polarized waves (LHCP) of equal amplitude. If the elliptical polarization beam is received, since the elliptical polarization can be decomposed into RHCP components and LHCP components, the microwave hybrid joint decomposes it into right-handed circularly polarized waves (RHCP) and left-handed circularly polarized waves (RHCP) and left-handed circularly Polarized waves (LHCP).

The phase delay of the microwave hybrid joint to the transmission signal is determined by the polarization characteristics of the receiving beam, which is a relatively stable value. The phase delay of the Δ channel signal passing through the microwave hybrid connector is a part of the phase delay difference between the sum and difference channels. After tracking and correcting the phase shift and offsetting, it will not affect the auxiliary angle

value.

Fig. 3 is a schematic diagram of a dual polarization difference (Δ) channel signal synthesis network.

3. New monopulse tracking phase correction technology

From the previous analysis and formulas (7) and (8), it can be seen that the phase difference of the sum and difference signals consists of two parts, one is the auxiliary angle synthesized by the orthogonal synthesis of the azimuth difference signal and the pitch difference signal

The other is the sum and difference channel phase delay difference

Because of the auxiliary angle

In the presence of , the phase difference of the sum and difference signal is different from the phase delay difference of the sum and difference channel.

The invention adopts a novel T21-mode signal synthesizer, and a microwave switch is arranged in the synthesizer, so that the azimuth difference signal and the pitch difference signal can be separated and combined. When doing azimuth tracking and phase correction, the receiver controls the microwave switch in the synthesizer, which isolates the pitch difference signal and avoids the auxiliary angle

In this way, the phase difference of the sum-difference signal is equal to the phase delay difference of the sum-difference channel, and the azimuth tracking phase correction is completed. In the same way, when doing pitch tracking and phasing, the receiver controls the microwave switch in the synthesizer, which isolates the azimuth difference signal and avoids the auxiliary angle

In this way, the phase difference of the measured sum and difference signal is equal to the difference of the phase delay of the sum and difference channel, and the pitch tracking phase correction is completed. After the tracking and phase correction is completed, the receiver controls the microwave switch in the synthesizer, the azimuth difference signal and the pitch difference signal are connected, and the quadrature synthesis becomes the difference channel signal, and the receiver can demodulate and output the azimuth error voltage and the pitch error voltage to the Antenna Control Unit (ACU). Figure 4 is a block diagram of dual-channel single-pulse tracking equipment for dual-polarized feed antennas. Eight TE21-mode coupling output ports are connected to two 4:1 combiner input ports with phase-stable cables of equal length.

Single-channel single-pulse tracking system, the RF signal of the difference channel undergoes four-phase modulation (QPSK) in the tracking down-conversion, and then synthesizes a RF signal with the RF signal of the sum channel, and the single-channel RF signal is sent to the receiver after a frequency conversion to the L frequency band , which simplifies tracking links. The phasing method is the same as that of the dual-channel monopulse tracking system. Figure 5 is a block diagram of the dual-polarization feed antenna single-channel monopulse tracking device.

Using this new type of monopulse tracking and phase correction technology, it does not need the assistance of a calibration source, and can quickly track and correct the target in real time. The antenna is at the holding point or guided by orbital data, and the receiver acquires the target signal. In order to ensure the accuracy of phase correction, the receiver collects and analyzes the signal levels of the sum and difference channels, and judges whether the target enters the main lobe beam of the antenna according to the change trend of the sum signal receiving pattern and the difference signal receiving pattern of the antenna. When the identified target enters the main lobe beam of the antenna, the tracking phase correction process is started. Figure 6 is a flow chart of digital receiver phase calibration.

Since the difference signal and the sum signal have the same source, the frequency conversion is a common local oscillator, and the phase difference measurement can use digital quadrature correlation integration method or fast Fourier transform (FFT) method. The phase correction algorithm of the digital receiver can be set according to the dynamic size of the target and the strength of the signal.

When the tracking target has a large dynamic carrier-to-noise ratio, the digital quadrature correlation integration method is used to measure the phase difference of the sum and difference signals. When the carrier noise spectral density is 46dBHz, the integration time is 1ms, and the phase measurement error is less than 6 degrees, which meets the requirements of single pulse tracking.

When the tracking target has a low dynamic carrier-to-noise ratio, the FFT method is used to measure the phase difference of the sum and difference signals. When the carrier noise spectral density is 35dBHz, because the target dynamic is small, choose N=2 ¹⁵ , the phase measurement error is less than 8 degrees, which meets the requirement of monopulse tracking.

The angle error voltage orientation sensitivity calibration of the digital receiver can comprehensively analyze the difference slope of the antenna tracking link and the target dynamic size, set different coefficients, collect the ACU angle offset increment and the corresponding angle error voltage increment, and then pass Data fitting calculations are given.

When the antenna is in the monopulse tracking state, the receiver detects the sum signal and the difference signal level, and judges the monopulse tracking state according to the normalized zero-depth data of the antenna and the change of the difference signal level. When the single pulse tracking is abnormal, the alarm information is output, and the angle error data output is set to zero, so as to avoid overshoot or obvious oscillation of the antenna drive.

Of course, the above descriptions are not intended to limit the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or replacements made by those skilled in the art within the scope of the present invention shall also belong to the present invention. protection scope of the invention.

Claims

A monopulse antenna tracking phase correction method is characterized in that: a T21 mode signal synthesizer with a built-in microwave switch is used to realize fast phase correction of monopulse tracking through phase difference measurement technology, specifically comprising the following steps:

Step 1: Wait for the target;

Step 2: capture the target signal through the receiver;

Step 3: Identify the target to enter the main beam;

Step 4: Start the phase tracking program;

Step 5: Disconnect the pitch difference signal, and check whether the level of the azimuth difference signal meets the phase correction requirements;

If: the azimuth difference signal level satisfies the phase correction requirements, then perform step 6;

Or if the azimuth difference signal level does not meet the requirements for phase calibration, go to step 8;

Step 6: Carry out azimuth tracking and phase calibration;

Step 7: Determine whether the pitch calibration is completed;

If: the pitch calibration has been completed, go to step 11;

Or if the pitch calibration is not completed, go to step 8;

Step 8: Disconnect the azimuth difference signal, and check whether the level of the pitch difference signal meets the phase correction requirements;

If: the pitch difference signal level meets the phase correction requirements, then perform step 9;

Or if the pitch difference signal level does not meet the phase correction requirements, go to step 5;

Step 9: Perform pitch tracking and phasing;

Step 10: Judging whether the azimuth tracking phase correction is completed;

If: the azimuth tracking phase correction has been completed, then perform step 11;

Or if azimuth tracking and calibration is not completed, go to step 5;

Step 11: Tracking and calibration is over.
The monopulse antenna tracking phase correction method according to claim 1, characterized in that: a microwave switch is arranged inside the T21 mode signal synthesizer, and the azimuth difference signal or the pitch difference signal is isolated by the microwave switch, thereby avoiding the cross-coupling of the two .
The monopulse antenna tracking phase correction method according to claim 1, characterized in that: in step 3, the receiver detects the sum and difference signal levels, and identifies whether the target enters the main antenna according to the sum and difference pattern data of the antenna. beam.
The monopulse antenna tracking phase correction method according to claim 1, characterized in that: in step 6, when doing azimuth tracking phase correction, the receiver controls the microwave switch in the T21 mode signal synthesizer to isolate the pitch difference signal In this way, the phase difference of the sum difference signal is equal to the phase delay difference of the sum difference channel, and the azimuth tracking phase correction is completed.
The monopulse antenna tracking phase calibration method according to claim 1, characterized in that: in step 9, when doing pitch tracking phase calibration, the receiver controls the microwave switch in the T21 mode signal synthesizer to isolate the azimuth difference signal In this way, the phase difference of the sum and difference signal is equal to the difference of the phase delay of the sum and difference channel, and the pitch tracking phase correction is completed.
The monopulse antenna tracking and phase correction method according to claim 1, characterized in that: when the antenna is in the monopulse tracking state, the receiver detects the sum signal and the difference signal level, and normalizes the zero-depth data and the difference signal according to the antenna When the level changes, the monopulse tracking status is judged, and the alarm information is output when the monopulse tracking is abnormal, and the angle error data output is set to zero, so as to avoid overshoot or obvious oscillation of the antenna drive.