阅读说明：本技术 一种单脉冲天线跟踪校相方法 (Monopulse antenna tracking and phase correcting method ) 是由 王举思 路波 屈会鹏 杨文洁 于 2021-08-19 设计创作，主要内容包括：本发明公开了一种单脉冲天线新型TE21模信号合成器和接收机校相方法,属于和差双通道或单通道单脉冲跟踪天线领域。本发明使用新型T21模信号合成器,在校相时可以隔离方位误差信号或俯仰误差信号,避免了交叉耦合,可以对跟踪目标实时快速校相；天线在等待点发现目标后,接收机检测和、差信号电平,依据天线和、差方向图数据,识别目标是否进入天线主波束；当目标进入天线主波束后,启动校相程序,在校相过程中,识别差信号电平是否满足校相要求；在天线跟踪目标过程中,依据天线归一化零深数据以及差信号电平变化,判断单脉冲跟踪状态,在单脉冲跟踪异常时输出告警信息,角误差数据输出置零。(The invention discloses a novel TE21 mode signal synthesizer of a monopulse antenna and a receiver phase calibration method, belonging to the field of sum-difference dual-channel or single-channel monopulse tracking antennas. The novel T21 mode signal synthesizer is used, the azimuth error signal or the pitching error signal can be isolated during phase calibration, cross coupling is avoided, and the phase of a tracking target can be calibrated quickly in real time; after the antenna finds a target at a waiting point, the receiver detects the sum and difference signal levels and identifies whether the target enters the antenna main beam or not according to the antenna sum and difference directional diagram data; when the target enters the antenna main wave beam, starting a phase calibration program, and identifying whether the difference signal level meets the phase calibration requirement in the phase calibration process; in the process of tracking the target by the antenna, judging the single-pulse tracking state according to the normalized zero-depth data of the antenna and the level change of the difference signal, outputting alarm information when the single-pulse tracking is abnormal, and setting the output of the angle error data to zero.)

1. A monopulse antenna tracking and phase correcting method is characterized in that: a T21 mode signal synthesizer with a built-in microwave switch is adopted, and the single pulse tracking and rapid phase correction are realized through a phase difference measurement technology, and the method specifically comprises the following steps:

step 1: waiting for the target;

step 2: capturing a target signal by a receiver;

and step 3: identifying that a target enters a main beam;

and 4, step 4: starting a tracking phase correction program;

and 5: disconnecting the pitching difference signal, and detecting whether the level of the azimuth difference signal meets the phase correction requirement;

if: if the azimuth difference signal level meets the phase correction requirement, executing step 6;

or the azimuth difference signal level does not meet the phase correction requirement, executing the step 8;

step 6: carrying out azimuth tracking and phase correction;

and 7: judging whether the pitching phase correction is finished or not;

if: if the pitching phase correction is finished, executing step 11;

or the pitching phase correction is not completed, executing the step 8;

and 8: disconnecting the azimuth difference signal, and detecting whether the level of the pitching difference signal meets the phase correction requirement;

if: if the level of the pitching difference signal meets the phase correction requirement, executing the step 9;

or the pitching difference signal level does not meet the phase correction requirement, executing the step 5;

and step 9: carrying out pitching tracking phase correction;

step 10: judging whether the azimuth tracking phase correction is finished or not;

if: if the azimuth tracking phase correction is finished, executing step 11;

or the azimuth tracking phase calibration is not completed, executing the step 5;

step 11: and finishing tracking and phase correction.

2. The monopulse antenna tracking phase calibration method as claimed in claim 1, wherein: a microwave switch is arranged in the T21 mode signal synthesizer, and the azimuth difference signal or the pitch difference signal is isolated through the microwave switch, so that cross coupling of the azimuth difference signal and the pitch difference signal is avoided.

3. The monopulse antenna tracking phase calibration method as claimed in claim 1, wherein: in step 3, the receiver detects the sum and difference signal levels and identifies whether the target enters the antenna main beam according to the sum and difference directional diagram data of the antenna.

4. The monopulse antenna tracking phase calibration method as claimed in claim 1, wherein: in step 6, when the azimuth tracking phase calibration is carried out, the receiver controls a microwave switch in a T21 mode signal synthesizer to isolate the pitching 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, and the azimuth tracking phase calibration is completed.

5. The monopulse antenna tracking phase calibration method as claimed in claim 1, wherein: in step 9, when the pitching tracking phase calibration is performed, the receiver controls a microwave switch in a T21 mode signal synthesizer to isolate the azimuth difference signal, so that the phase difference of the measured sum and difference signal is equal to the phase delay difference of the sum and difference channel, and the pitching tracking phase calibration is completed.

6. The monopulse antenna tracking phase calibration method as claimed in claim 1, wherein: when the antenna is in a single-pulse tracking state, the receiver detects the sum signal level and the difference signal level, judges the single-pulse tracking state according to the normalized zero-depth data of the antenna and the level change of the difference signal level, outputs alarm information when the single-pulse tracking is abnormal, and sets the output of the angular error data to zero to avoid causing overshoot or obvious oscillation of the antenna driving.

Technical Field

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

Background

Monopulse tracking technology began to be used in the 50's of the 20 th century. When a large-aperture parabolic antenna tracks a dynamic target, sum-difference amplitude-comparison single-pulse tracking is generally adopted in order to achieve specified tracking accuracy. The early monopulse tracking adopts a multi-horn feed source and outputs sum signals and difference signals through a synthesis network. With the development of microwave technology, a circular waveguide multimode self-tracking feed source replaces a multi-horn feed source and is widely used in a single-pulse tracking antenna. Because the transmission paths of the sum signal and the difference signal are different and the phase delay is different, the phase of the reference signal of the angle pointing error voltage demodulator needs to be shifted, and the phase delay difference value of the sum channel and the difference channel needs to be cancelled, so that the angle pointing error voltage of the antenna tracking target can be accurately demodulated. The reference signal phase shift value solving process of the angle pointing error voltage demodulator is called tracking phase correction for short.

The first is the classical phase correction method, where the antenna is pointed at a calibration source (including calibration towers, radio sources, geostationary satellites, etc.) at a specific angle off the azimuth or elevation axis to excite the difference channel signal. The phase of the reference signal of the receiver is shifted in a stepping mode, the azimuth or pitching error voltage is read, and then the phase shift value of the reference signal is calculated through curve fitting. The antenna points to the calibration source signal, the calibration phase precision is high, and the method is suitable for various frequency bands. The phase correction method has the disadvantages of long preparation time and low efficiency because the phase correction method depends on a calibration source, and a plurality of equipment combined phase shift values need to be stored for calling.

The second is a rapid phase correction method, which guides an antenna to track a target by track forecast data, sets a specific angle offset, records the change values of the output voltage of an angle difference demodulator when the phase is shifted by 90 degrees, 180 degrees and 270 degrees respectively, and then solves the sum and difference channel phase delay difference value by curve fitting to finish tracking phase correction. The method does not depend on a calibration source, and performs real-time phase calibration on the tracking target, wherein the phase calibration precision meets the antenna tracking requirement. The rapid phase calibration method is better applied to S frequency bands and C frequency bands, and has no case of successful application in X, Ku, Ka and other frequency bands. The precondition of the rapid phase correction method is that the linearity of the difference slope of the difference signal directional diagram in the main beam of the antenna is good. In a millimeter wave high frequency band, a wave beam main lobe is narrower, the paraxial characteristics of an antenna difference directional diagram are poor due to the influence of factors such as surface precision error of an antenna panel and gravity deformation of a large-caliber antenna, the difference slope has obvious nonlinear fluctuation, the deviation of a fitting calculation phase shift value is large, and the antenna tracking requirement cannot be met by a phase correction result.

The third method is a data comparison correction method, which completes tracking correction and storage under the condition that a calibration source is available, injects signals into a tracking link through a directional coupler, and tests the phase difference of the injected signals and stores the phase difference. And when no calibration source is available, testing the change of the phase difference of the injection signals and correcting the phase value stored in the early stage. The method has low phase correction precision and additionally increases equipment and workload.

Aiming at the defects of the three phase calibration methods, the invention provides a novel single-pulse tracking phase calibration technology. By using the novel T21 mode signal synthesizer, the azimuth error signal or the pitch error signal is isolated during phase calibration, cross coupling is avoided, and the phase of the tracked target can be calibrated quickly in real time. And in the process of tracking the target by the antenna, judging the single-pulse tracking state according to the normalized zero-depth data of the antenna and the level change of the difference signal.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides a novel monopulse antenna tracking and phase correcting method which is reasonable in design, overcomes the defects of the prior art and has a good effect.

In order to achieve the purpose, the invention adopts the following technical scheme:

a monopulse antenna tracking phase calibration method adopts a T21 mode signal synthesizer with a built-in microwave switch to realize monopulse tracking rapid phase calibration through a phase difference measurement technology, and specifically comprises the following steps:

step 1: waiting for the target;

step 2: capturing a target signal by a receiver;

and step 3: identifying that a target enters a main beam;

and 4, step 4: starting a tracking phase correction program;

and 5: disconnecting the pitching difference signal, and detecting whether the level of the azimuth difference signal meets the phase correction requirement;

if: if the azimuth difference signal level meets the phase correction requirement, executing step 6;

or the azimuth difference signal level does not meet the phase correction requirement, executing the step 8;

step 6: carrying out azimuth tracking and phase correction;

and 7: judging whether the pitching phase correction is finished or not;

if: if the pitching phase correction is finished, executing step 11;

or the pitching phase correction is not completed, executing the step 8;

and 8: disconnecting the azimuth difference signal, and detecting whether the level of the pitching difference signal meets the phase correction requirement;

if: if the level of the pitching difference signal meets the phase correction requirement, executing the step 9;

or the pitching difference signal level does not meet the phase correction requirement, executing the step 5;

and step 9: carrying out pitching tracking phase correction;

step 10: judging whether the azimuth tracking phase correction is finished or not;

if: if the azimuth tracking phase correction is finished, executing step 11;

or the azimuth tracking phase calibration is not completed, executing the step 5;

step 11: and finishing tracking and phase correction.

Preferably, 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, so that cross coupling of the azimuth difference signal and the pitch difference signal is avoided.

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

Preferably, in step 6, when performing azimuth tracking phase calibration, the receiver controls a microwave switch in the T21 mode signal synthesizer to isolate the pitch difference signal, so that the measured sum and difference signal phase difference is equal to the sum and difference channel phase delay difference, and the azimuth tracking phase calibration is completed.

Preferably, in step 9, when the pitch tracking phase calibration is performed, the receiver controls a microwave switch in the T21 mode signal synthesizer to isolate the azimuth difference signal, so that the phase difference of the measured sum and difference signals is equal to the phase delay difference of the sum and difference channels, and the pitch tracking phase calibration is completed.

Preferably, when the antenna is in a single-pulse tracking state, the receiver detects the sum signal level and the difference signal level, judges the single-pulse tracking state according to the normalized zero-depth data of the antenna and the level change of the difference signal level, outputs alarm information when the single-pulse tracking is abnormal, and sets the angle error data output to zero to avoid causing overshoot or obvious oscillation of the antenna driving.

The invention has the following beneficial technical effects:

1. the receiver can identify that a target enters an antenna main beam after capturing a target signal without depending on a calibration source, and tracking and phase calibration are completed quickly;

2. different phase difference measurement technologies can be selected according to different tracking target characteristics, and the rapid phase correction precision is improved;

3. and in the single-pulse tracking process of the antenna, the level change of the sum and difference two paths of signals is monitored in real time, and the single-pulse tracking abnormity is early warned.

Drawings

FIG. 1 is a block diagram of a single circularly polarized monopulse tracking link;

FIG. 2 is a diagram of a dual polarization tracking mode coupler assembly;

wherein, figure (a) is a schematic diagram of coupler A; FIG. B is a schematic view of coupler B; FIG. (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;

FIG. 4 is a block diagram of a dual-polarized dual-channel single-pulse tracking link device using a novel TE21 model synthesizer;

FIG. 5 is a block diagram of a dual-polarized single-channel single-pulse tracking device using a novel TE21 model synthesizer;

fig. 6 is a flow chart of a digital receiver phase calibration.

Detailed Description

The invention is described in further detail below with reference to the following figures and detailed description:

phase correlation analysis of single polarization feed source sum (sigma) channel signal and difference (delta) channel signal

The single pulse tracking antenna usually adopts a circular waveguide multimode feed source, and a TE21 MODE tracking COUPLER (TE21 MODE COUPLER) is the source of a difference signal. The single pulse tracking antenna is the most common mode for tracking circularly polarized targets in a circular polarization manner. The application first discusses the phase transmission change and tracking phase correction principle of the sum-difference two-channel communication signal in a single polarization mode.

The TE21 mode tracking coupler is a ring four port directional coupler located at the antenna feed focal plane, also known as an antenna feed receive beam angle sensor. The phase of the TE21 mode signal of the coupled output port is stably related to the phase of the feed source and the path signal. The phase difference of signals output by two coupled ports of the orientation TE21 mode is 180 degrees, and the output signals of the two ports are synthesized into an orientation difference (delta-XEL) signal; similarly, the phase difference of the signals output by the two coupled ports of the pitch TE21 mode is also 180 degrees, and the output signals of the two ports are combined into 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 combined into a path of difference (delta-channel) signal. FIG. 1 is a block diagram of a single circular polarization single pulse 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 antenna driving SERVO equipment.

Taking a single Carrier (CW) signal as an example, the phase relationship between the sum signal and the difference signal is mainly demonstrated. Before the azimuth difference signal and the pitch difference signal are synthesized, the azimuth difference signal is set as follows:

U_Δxel(t)＝U_ΔxelSin(ω₀t)，ω₀at radio frequency angular frequency, U_Δxel＝γθ_ΔxelAnd γ is the difference slope.

The pitch difference signal is then:

U_Δel(t)＝U_ΔelCos(ω₀t)，ω₀at radio frequency angular frequency, U_ΔEL＝γθ_ΔELAnd γ is the difference slope.

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

wherein the auxiliary angle

The azimuth difference signal and the pitch difference signal are orthogonally synthesized into a difference Channel (delta-Channel) signal, and the difference Channel signal is fed to a low noise amplifier (delta-LNA). And the sum Channel (sigma-Channel) signal passes through the low noise amplifier to be output, and is output through the coupling port of the directional coupler at the output port. The difference channel radio frequency (delta-RF) signal and the sum channel radio frequency (sigma-RF) signal are both connected to a tracking down converter (Trk-D/C), the sum channel radio frequency signal and the difference channel radio frequency signal share a local vibration source, and the frequency is converted into two channels of Intermediate Frequency (IF)70MHz signals. And the sum and difference two paths of intermediate frequency 70MHz signals are connected to a Dual-channel receiver (Dual-CH DTR), and the sum path intermediate frequency signals are correlated with the phase of a reference signal (10.7MHz) through a frequency conversion phase-locked loop. The difference circuit intermediate frequency signal is converted into a difference circuit 10.7MHz signal with the same frequency as the reference signal in the receiver, and the phase of the difference signal has a stable correlation with the phase of the reference signal. And the AGC level of the sum intermediate frequency signal controls the gain of the difference intermediate frequency signal amplifier at the same time to finish the amplitude normalization of the sum and difference signals.

Let the orthogonal reference signals be Sin (omega)₁t)、Cos(ω₁t), the difference 10.7MHz signal is expressed by equation (2).

The parameter in formula (2) is G is normalized gain, omega₁The intermediate frequency phase-locked loop is referenced to the signal angular frequency,is the phase difference of the difference signal and the reference signal.

In order to accurately resolve the reduced azimuth difference signal amplitude and the pitch difference signal amplitude (linear scale), that is, the demodulated signal amplitudes are required to be:

k is demodulator gain (3)

k is demodulator gain (4)

The reference signal shifts the phase delta, and the trigonometric function expression of the coherent demodulation multiplier is as follows:

after low-pass filtering, 2 harmonics are filtered out, and the direct current output is as follows:

in light of the foregoing discussion, whenIn time, the azimuth difference signal amplitude and the pitch difference signal amplitude can be accurately resolved. Can makeThe difference between the sum and difference signals is defined as the sum and difference channel phase delay difference, which is clearly defined as the sum and difference channel phase delay difference, where the phase difference between the sum and difference signals is linearly superimposed by two phase values, one of which is the auxiliary angle of the quadrature combination of the azimuth and elevation difference signals, and the other is the sum and difference channel phase delay difference.

As can be seen from the above equations (7) and (8), only ifThe demodulator can accurately resolve the azimuth difference signal amplitude and the pitch difference signal amplitude. When in useIn time, the amplitude of the azimuth difference signal and the amplitude of the pitch difference signal are not accurately resolved, which is also called cross coupling. Solving forThe phase shift value delta of the corresponding reference signal is the tracking phase correction.

Because the transmission paths between the corrugated horn T21 mode directional coupling output port and the synthesizer are different, the orthogonality of the azimuth difference signal and the pitch difference signal may be deteriorated, and the phase shift value of the reference signal of the azimuth difference amplitude-dependent demodulator and the phase shift value of the reference signal of the pitch difference amplitude-dependent demodulator are not necessarily 90 degrees different, so that separate solution is needed.

Phase correlation analysis of two-polarization feed source and (sigma) channel signal and difference (delta) channel signal

The single-pulse tracking antenna generally requires that target signals with different polarizations can be tracked, the output of the feed source sigma-loop is a dual-linear polarization port/dual-circular polarization port, the linear polarization/circular polarization mode can be switched, and the feed source delta-loop is switched by either right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP). The single-pulse tracking requires that the sigma-delta path and the delta path are polarized and matched, and the receiver demodulates the azimuth angle error and the pitch angle error from the delta path signal and needs the sigma-delta path signal as a reference.

Two staggered differential mode couplers are arranged on a focal plane of a circular waveguide corrugated horn feed source. One is a vertically polarized T21 MODE COUPLER (TE21 MODE COUPLER) and the other is a horizontally polarized T21 MODE COUPLER, fig. 2 is a combined diagram of dual-polarized tracking MODE COUPLERs.

The two orthogonal T21 mode couplers are respectively connected to two four-in-one combiners (4:1 combiners). Connected to the four ports of the vertical polarization (V-POL) T21 mode coupler is a vertical polarization T21 mode signal combiner, and connected to the four ports of the horizontal polarization (H-POL) T21 mode coupler is a horizontal polarization T21 mode signal combiner. The output ports of the two T21 mode combiner with different polarizations are connected to a microwave hybrid Junction combination (Hybird Junction) to output two paths, wherein one path is right-hand circularly polarized wave (RHCP), and the other path is left-hand circularly polarized wave (LHCP). If the linear polarized wave beam is received, the microwave hybrid joint decomposes the linear polarized wave beam into a right-hand circularly polarized wave (RHCP) and a left-hand circularly polarized wave (LHCP) with equal amplitudes. If receiving the elliptically polarized wave beam, the elliptically polarized wave can be decomposed into an RHCP component and an LHCP component, and the microwave hybrid joint decomposes the elliptically polarized wave into a right-hand circularly polarized wave (RHCP) and a left-hand circularly polarized wave (LHCP) with unequal amplitudes according to the ratio of the elliptically polarized axes.

The phase delay of the microwave hybrid coupler for the transmission signal is determined by the polarization characteristic of the receiving beam, and is a relatively stable value. The phase delay of the delta path signal passing through the microwave hybrid joint is a part of the phase delay difference value of the sum channel and the difference channel, and the phase delay is offset through tracking correction without influencing the auxiliary angleThe value is obtained.

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

Three, novel single pulse tracking phase correction technology

From the above analysis and equations (7) and (8), it can be seen that the phase difference of the sum and difference signals is composed of two parts, one is the auxiliary angle of the orthogonal synthesis of the azimuth difference signal and the pitch difference signalThe other is the sum-difference channel phase delay differenceDue to the auxiliary angleThe phase difference of the sum and difference signals is different from the phase delay difference of the sum and difference channels.

The invention adopts a novel T21 mode signal synthesizer, a microwave switch is arranged in the synthesizer, and the azimuth difference signal and the pitch difference signal can be separated and combined controllably. When the azimuth tracking and phase correction are carried out, the receiver controls a microwave switch in the synthesizer, the pitching difference signal is isolated, and the auxiliary angle is avoidedSo that the measured sum and difference signal phase difference is equal to the sum and difference channel phase delay difference, and the azimuth tracking phase correction is completed. Similarly, when the pitching tracking phase calibration is carried out, the receiver controls a microwave switch in the synthesizer, so that the azimuth difference signal is isolated, and the auxiliary angle is avoidedSuch that the measured sum and difference signal phase difference is equal to the sum and difference channel phase delay difference, completing the pitch tracking phase correction. After the tracking phase calibration is finished, the receiver controls a microwave switch in the synthesizer, the azimuth difference signal and the pitch difference signal are both switched on, the azimuth difference signal and the pitch difference signal are orthogonally synthesized into a difference channel signal, and the receiver can demodulate and output an azimuth angle error voltage and a pitch angle error voltage to an Antenna Control Unit (ACU). Fig. 4 is a block diagram of dual-polarization feed antenna dual-channel single pulse tracking equipment, and eight TE21 mode coupling output ports are respectively connected to two 4:1combiner input ports by phase-stabilizing cables with equal length.

In the single-channel single-pulse tracking system, a difference channel radio-frequency signal is firstly subjected to Quadrature Phase Shift Keying (QPSK) in tracking down-conversion and then is synthesized with a sum channel radio-frequency signal to form a path of radio-frequency signal, and the single-channel radio-frequency signal is subjected to frequency conversion once to an L frequency band and then is sent to a receiver, so that a tracking link is simplified. The phase calibration method is the same as that of a dual-channel single-pulse tracking system, and fig. 5 is a block diagram of the dual-polarized feed source antenna single-channel single-pulse tracking device.

By adopting the novel single-pulse tracking and phase correcting technology, the target can be quickly tracked and corrected in real time without the assistance of a calibration source. The receiver captures the target signal with the antenna at a stand-by point or under the guidance of the orbit data. In order to ensure the phase calibration precision, the receiver collects and analyzes the signal levels of the sum channel and the difference channel, and judges whether a target enters an antenna main lobe beam or not according to the variation trend of a sum signal receiving directional diagram and a difference signal receiving directional diagram of the antenna. And when the identified target enters the antenna main lobe beam, starting tracking and phase correction processing. Fig. 6 is a flow chart of a digital receiver phase calibration.

Since the difference signal and the sum signal are homologous, the frequency transformation is common to the local oscillator, and the phase difference measurement can adopt a digital orthogonal correlation integration method or a 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.

And when the dynamic large-load noise ratio of the tracked target is high, measuring the phase difference of the sum signal and the difference signal by adopting a digital orthogonal correlation integration method. When the carrier noise spectral density is 46dBHz, the integration time is 1ms, the phase measurement error is less than 6 degrees, and the single-pulse tracking requirement is met.

And when the dynamic small carrier-to-noise ratio of the tracked target is low, the sum and difference signal phase difference is measured by adopting an FFT method. At a carrier noise spectral density of 35dBHz, N is selected to be 2 because the target dynamics is small¹⁵And the phase measurement error is less than 8 degrees, so that the single-pulse tracking requirement is met.

The angular error voltage directional sensitivity of the digital receiver is calibrated, different coefficients can be set according to the difference slope of an antenna tracking link and the dynamic size of a target, ACU angular offset increment and corresponding angular error voltage increment are collected, and the ACU angular offset increment and the corresponding angular error voltage increment are calculated and given through data fitting.

When the antenna is in the single-pulse tracking state, the receiver detects the sum signal level and the difference signal level, and judges the single-pulse tracking state according to the normalized zero-depth data of the antenna and the level change of the difference signal. When the monopulse tracking is abnormal, alarm information is output, the angle error data output is set to zero, and the phenomenon that the antenna drive overshoots or vibrates obviously is avoided.

It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.