CN114545384A - Integration method and system applied to runway foreign matter detection - Google Patents

Abstract

The invention discloses an integration method and system applied to runway foreign matter detection, wherein the method comprises the following steps: collecting a plurality of continuous pulse echoes, carrying out coherent demodulation on the plurality of continuous pulse echoes to generate a plurality of baseband data, and forming a two-dimensional data matrix by the plurality of baseband data; preprocessing the two-dimensional data matrix to obtain frequency mixing signal data; extracting the mixing signal data for filtering; extracting and filtering, matching the filtering and compressing the pulse, wherein the pulse compression is to compress the wide pulse with frequency in the pulse or the pulse with increased bandwidth after phase modulation into a narrow pulse; and carrying out high-pass filtering on the fast time or slow time data matrix along the slow time dimension to obtain a new data matrix, and judging whether the target exists. The invention can determine the existence, the position and the speed of the target and eliminate the influence of common noise and interference on the final data.

Description

Integration method and system applied to runway foreign matter detection

Technical Field

The invention relates to the technical field of foreign matter detection radars, in particular to an integration method and system applied to runway foreign matter detection.

Background

The run-up foreign matter detection radar is used for automatically monitoring and identifying foreign matters on the runway, accurately positioning, automatically alarming and timely removing the foreign matters. The detection system mainly detects the foreign matters on the runway by combining a radar detection technology and a video image recognition technology, the refreshing frequency is calculated in tens of seconds, and the size of the discovered foreign matters can be as small as 2-3 centimeters. The radar has various types, and is classified according to radar signal forms, such as pulse radar, continuous wave radar, pulse compression radar, frequency agility radar and the like; the method is classified according to an angle tracking mode, and comprises a monopulse radar, a cone scanning radar, a hidden cone scanning radar and the like; according to the parameter classification of target measurement, there are height measuring radar, two-coordinate radar, three-coordinate radar, friend-foe radar, multi-station radar, etc.

Pulse radars are a type of sensing system that use high power pulse signals reflected by objects to determine their distance from the radar antenna. The basic operating principle of pulse radar is that a pulse modulator generates a short pulse, which is then amplified. The amplified pulse then passes through a duplexer or a switching circuit to a pulse radar antenna. The pulse then propagates in air until it hits an object that is capable of reflecting radio frequency energy. Some of the reflections produced on the reflecting object interact with the radar antenna to produce an electrical signal. The signal is conducted through a duplexer or switch to the receiver portion of the pulse radar, switching its direction immediately after the transmitted pulse passes through the duplexer/switch. The received signal is amplified with a low noise amplifier because the radar received signal is often weak. The amplified Radio Frequency (RF) signal is then typically mixed to an Intermediate Frequency (IF) signal, which is then sent to a detector that measures the time difference between the arrival of the original pulse transmitted and received signals. The time difference between transmission and reception determines the time of flight of the pulse and thus how far the object is from the radar.

In a common pulse radar applied to runway foreign matter detection, noise and various interferences are always mixed in echo signals received in the using process, and the noise, the various interferences and normal echoes are converted into corresponding electric signals by a receiving device in the radar. Therefore, the normal judgment of the pulse radar is influenced, the phenomenon of false alarm of the radar occurs, and the normal monitoring is influenced.

Disclosure of Invention

The invention aims to provide an integration method and system applied to runway foreign matter detection, which solve the following technical problems:

noise and various interferences are always mixed in the echo signals, so that normal monitoring is influenced.

The purpose of the invention can be realized by the following technical scheme:

as shown in fig. 1, an integrated method applied to runway foreign object detection includes the following steps:

collecting a plurality of continuous pulse echoes, carrying out coherent demodulation on the plurality of continuous pulse echoes to generate a plurality of baseband data, and forming a two-dimensional data matrix by the plurality of baseband data;

preprocessing the two-dimensional data matrix to obtain frequency mixing signal data;

extracting the mixing signal data for filtering;

extracting and filtering, matching the filtering and compressing the pulse, wherein the pulse compression is to compress the wide pulse with frequency in the pulse or the pulse with increased bandwidth after phase modulation into a narrow pulse;

and carrying out high-pass filtering on the fast time or slow time data matrix along the slow time dimension to obtain a new data matrix, and judging whether the target exists.

As a further scheme of the invention: the preprocessing is digital down-conversion processing, and the digital down-conversion processing is to mix an intermediate frequency A/D sampling signal with a local digital intermediate frequency carrier signal generated by a digital control oscillator in a DDC, so that the intermediate frequency A/D sampling signal and the local digital intermediate frequency carrier signal are down-converted to a baseband signal.

As a further scheme of the invention: the method further comprises the following steps:

FFT processing is carried out on the same distance units of the echo signals of different pulse groups, and the average calculation is carried out on the result, so that one-dimensional discrete waveform points are obtained;

executing cognitive constant false alarm detection, and acquiring a maximum peak value, wherein the maximum peak value corresponds to the position information of a target;

and obtaining the Doppler value of the target through the position information, thereby distinguishing the clutter from the target through the Doppler frequency.

As a further scheme of the invention: in the digital down-conversion process, an input signal contains an intermediate frequency carrier, and the input signal is frequency-shifted according to a carrier frequency to obtain a band-limited signal, and the input signal is sampled by using bandwidth sampling.

As a further scheme of the invention: in the sampling process, the frequency spectrums of any two sample signals cannot be mixed.

As a further scheme of the invention: the specific steps of the pulse compression are as follows:

extracting pulse echoes;

setting pulse width, and splitting the pulse echo into a plurality of sub-pulses according to the set pulse width, wherein the widths of the sub-pulses are equal, and the phases of the sub-pulses are transmitted after being coded.

As a further scheme of the invention: the bandwidth sampling is to set a sampling bandwidth and acquire one sample data every other sampling bandwidth.

An integrated system for runway foreign object detection, comprising:

the acquisition end acquires a plurality of continuous pulse echoes, performs coherent demodulation on the plurality of continuous pulse echoes to generate a plurality of baseband data, and the plurality of baseband data form a two-dimensional data matrix;

the processing end is used for preprocessing the pulse echo, filtering the frequency mixing signal data obtained by preprocessing and compressing the pulse;

and the output end carries out high-pass filtering on the fast time or slow time data matrix along the slow time dimension to obtain a new data matrix and judge whether the target exists.

The invention has the beneficial effects that: by acquiring continuous pulse echoes and performing coherent demodulation on the basis of collected basic data, original pulse echo data is converted into baseband data and a two-bit data matrix consisting of the baseband data, the I and Q components or IQ signals in the two-bit data matrix are processed by digital down-conversion to realize the change from the intermediate frequency signal to the baseband signal, and the subsequent pulse compression is to split the wide wave pulse with large time width and bandwidth into a plurality of narrow wave pulses, realize the emission of wide coded pulses and process echoes to obtain the narrow pulses, not only keep the high-distance resolution of the narrow pulses, but also obtain the strong detection capability of the wide pulses, determine the existence, the position and the speed of a target by corresponding high-pass filtering, FFT processing and the like again aiming at the obtained narrow wave data, and eliminate the influence of common noise and interference on the final data.

Drawings

The invention will be further described with reference to the accompanying drawings.

Fig. 1 is a schematic flow chart of an integrated method applied to runway foreign object detection according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, the present invention is an integrated method for runway foreign object detection, including the following steps:

collecting a plurality of continuous pulse echoes, carrying out coherent demodulation on the plurality of continuous pulse echoes to generate a plurality of baseband data, and forming a two-dimensional data matrix by the plurality of baseband data;

preprocessing the two-dimensional data matrix to obtain frequency mixing signal data;

extracting the mixing signal data for filtering;

extracting and filtering, matching the filtering and compressing the pulse, wherein the pulse compression is to compress the wide pulse with frequency in the pulse or the pulse with increased bandwidth after phase modulation into a narrow pulse;

and carrying out high-pass filtering on the fast time or slow time data matrix along the slow time dimension to obtain a new data matrix, and judging whether the target exists.

The coherent demodulation is also called synchronous detection, and is suitable for demodulation of all linear modulation signals. The key to realize coherent demodulation is that the receiving end needs to recover a coherent carrier strictly synchronized with the modulated carrier. Each row of the two-dimensional data matrix represents a series of pulse measurements for the same range bin, and each column corresponds to a successive sample of the pulse echo, also called a successive range gate, in which the element of each small square is a complex number representing the I, Q component of each range bin.

The IQ signal is typically analog, but also digital, such as a square wave. The current digital radio frequency chip uses IQ signals without exception, even if the digital radio frequency chip is an RFID chip, the IQ signals are used inside, wherein I represents in-phase, Q represents quadrature, and is 90 degrees out of phase with I, and digital signals processed in a baseband are generally subjected to D/a (digital-to-analog) conversion at an outlet.

The preprocessing of the two-dimensional data matrix refers to digital down-conversion processing of IQ-path signals: the core is mixing an intermediate frequency A/D (analog to Digital) sampling signal with a local Digital intermediate frequency carrier signal generated by a Numerically Controlled Oscillator (NCO) in a DDC (Direct Digital Control, commonly referred to as DDC controller, DDC for short), and down-converting the intermediate frequency signal to a baseband.

Matched filtering is also called deskewing, which is "active correlation" and is usually used to process LFM waves with very large bandwidth (if direct sampling is performed, because the frequency band is very wide, the sampling rate required at high frequency is very large, and the number of sampling points is very large, so that deskewing is performed).

It can be understood that the requirements of the ranging accuracy and the range resolution on the signal form are consistent, and mainly depend on the frequency structure of the signal, the signal is required to have a large bandwidth in order to improve the ranging accuracy and the range resolution, the speed measurement accuracy and the speed resolution depend on the time domain structure of the signal, and the signal is required to have a large time width in order to improve the speed measurement accuracy and the speed resolution. In addition, to improve the discovery capability of the radar system, the signal is required to have large energy. It follows that in order to improve the discovery, measurement accuracy and resolution of radar systems, radar signals are required to have large time widths, bandwidths and energy products. However, in the case of a system where the peak power of the transmitting and feeding equipment is limited, large signal energy can only be obtained by increasing the time width of the signal. The distance measurement precision and the distance resolution as well as the speed measurement precision, the speed resolution and the action distance have irreconcilable contradictions. Therefore, the pulse compression radar can transmit the wide coded pulse and process the echo to obtain the narrow pulse through compressing the pulse, so that the pulse compression radar not only keeps the high distance resolution of the narrow pulse, but also can obtain the strong detection capability of the wide pulse, and the specific steps are as follows:

extracting pulse echoes;

setting pulse width, and splitting the pulse echo into a plurality of sub-pulses according to the set pulse width, wherein the widths of the sub-pulses are equal, and the phases of the sub-pulses are transmitted after being coded.

The fast/slow time data matrix is high pass filtered along the slow time dimension to obtain a new data matrix in which clutter components have been attenuated, which can determine the presence of a target but cannot determine the motion of the target.

In order to judge the movement of the target, the following steps are required:

performing FFT (fast Fourier transform) processing on the same distance units of the echo signals of different pulse groups, and performing average calculation on the result to obtain one-dimensional discrete waveform points;

executing cognitive Constant False Alarm Rate (CFAR) detection, and acquiring a maximum peak value, wherein the maximum peak value corresponds to the position information of a target;

and obtaining the Doppler value of the target through the position information, thereby distinguishing the clutter from the target through the Doppler frequency.

The constant false alarm detector firstly processes the input noise and then determines a threshold, compares the threshold with the input end signal, if the input end signal exceeds the threshold, the constant false alarm detector judges that the target exists, otherwise, the constant false alarm detector judges that the target does not exist. The signal is transmitted from signal source, and is affected by various interferences in the process of propagation, and after reaching the receiver, the signal is processed and output to the detector, and then the detector makes decision on the input signal according to proper criteria. The radar interference comprises thermal noise inside the receiver, clutter interference such as ground objects, rain and snow, sea waves and the like, and active interference and passive interference released by enemies are also included sometimes. Clutter and jamming are often much stronger than the receiver internal noise level. Therefore, extracting signals in strong interference requires not only a certain signal-to-noise ratio, but also constant false alarm processing of the signals.

In this embodiment, multiple outputs can be obtained from multiple inputs, which is generally implemented by FFT, that is, FFT processing is performed on the same distance unit of echo signals of different pulse groups, N outputs are obtained from N inputs, and cognitive constant false alarm detection (CFAR detection) is to detect and determine the target | from the N outputs! If there is a target, the number of the N outputs is the largest number than that of the peak, and the number is probably the position information of the target, and the Doppler value of the moving target can be obtained according to the position information. And distinguishing between moving objects and clutter is the difference in their velocity. Since the doppler frequencies of the echo signals are not equal due to the difference in velocity, clutter can be distinguished from moving objects by the difference in doppler frequency. The clutter suppression method not only can filter out clutter, but also can distinguish targets with different motion speeds, thereby greatly improving the capability of detecting the moving target under the clutter background.

And the cognitive constant false alarm detection (CFAR detection) mainly aims to obtain a threshold value of the RD plane, and then finds the doppler frequency according to the threshold value judgment, thereby obtaining the speed of the desired target.

In another preferred embodiment of the present invention, in a digital down-conversion system, since the input signal contains an intermediate frequency carrier, the signal is frequency shifted according to the carrier frequency to obtain a band-limited signal. If the nyquist sampling theorem is still used at this time, and the sampling frequency is twice the highest frequency of the signal, the required sampling frequency will be very high, and the complexity of the receiver design will be increased. At this time, a bandwidth sampling theorem is adopted, and it is noted that the frequency spectrum of the signal cannot be aliased after sampling in the sampling process, so that the original signal can be restored in a lossless manner through a certain filtering means.

In another preferred embodiment of the present invention, the bandwidth sampling is to acquire one sample data every other sampling bandwidth by setting a sampling bandwidth.

An integrated system for runway foreign object detection, comprising:

the acquisition end acquires a plurality of continuous pulse echoes, performs coherent demodulation on the plurality of continuous pulse echoes to generate a plurality of baseband data, and the plurality of baseband data form a two-dimensional data matrix;

the processing end is used for preprocessing the pulse echo, filtering the frequency mixing signal data obtained by preprocessing and compressing the pulse;

and the output end carries out high-pass filtering on the fast time or slow time data matrix along the slow time dimension to obtain a new data matrix and judge whether the target exists.

While one embodiment of the present invention has been described in detail, the description is only a preferred embodiment of the present invention and should not be taken as limiting the scope of the invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.

Claims (8)

1. An integration method applied to runway foreign object detection is characterized by comprising the following steps:

collecting a plurality of continuous pulse echoes, and performing coherent demodulation on the plurality of continuous pulse echoes to generate a plurality of baseband data, wherein the plurality of baseband data form a two-dimensional data matrix;

preprocessing the two-dimensional data matrix to obtain frequency mixing signal data;

extracting the mixing signal data for filtering;

extracting and filtering, matching the filtering and compressing the pulse, wherein the pulse compression is to compress the wide pulse with frequency in the pulse or the pulse with increased bandwidth after phase modulation into a narrow pulse;

and carrying out high-pass filtering on the fast time or slow time data matrix along the slow time dimension to obtain a new data matrix, and judging whether the target exists.

2. An integrated method as claimed in claim 1, wherein the pre-processing is digital down-conversion processing, and the digital down-conversion processing is to mix the if a/D sampling signal with a local digital if carrier signal generated by a digital controlled oscillator in the DDC, so as to down-convert the if a/D sampling signal and the local digital if carrier signal to a baseband signal.

3. An integrated method for runway foreign object detection as defined in claim 1 and further comprising:

FFT processing is carried out on the same distance units of the echo signals of different pulse groups, and the average calculation is carried out on the result, so that one-dimensional discrete waveform points are obtained;

executing cognitive constant false alarm detection, and acquiring a maximum peak value, wherein the maximum peak value corresponds to the position information of a target;

and obtaining the Doppler value of the target through the position information, thereby distinguishing the clutter from the target through the Doppler frequency.

4. An integrated method as claimed in claim 2, wherein in the digital down-conversion process, the input signal comprises an intermediate frequency carrier, and the input signal is frequency shifted according to the carrier frequency to obtain a band-limited signal, and the input signal is sampled by using bandwidth sampling.

5. The integrated method for runway foreign object detection as claimed in claim 4, wherein the frequency spectrum of any two sample signals cannot be aliased during the sampling process.

6. The integrated method for runway foreign object detection as claimed in claim 1, wherein the pulse compression comprises the following steps:

extracting pulse echoes;

setting pulse width, and splitting the pulse echo into a plurality of sub-pulses according to the set pulse width, wherein the widths of the sub-pulses are equal, and the phases of the sub-pulses are transmitted after being coded.

7. The integrated method as claimed in claim 4, wherein the bandwidth sampling is performed by setting a sampling bandwidth, and sampling one sample data at every other sampling bandwidth.

8. An integrated system for runway foreign object detection, comprising:

the acquisition end acquires a plurality of continuous pulse echoes, performs coherent demodulation on the plurality of continuous pulse echoes to generate a plurality of baseband data, and the plurality of baseband data form a two-dimensional data matrix;

the processing end is used for preprocessing the pulse echo, filtering the frequency mixing signal data obtained by preprocessing and compressing the pulse;

and the output end carries out high-pass filtering on the fast time or slow time data matrix along the slow time dimension to obtain a new data matrix and judge whether the target exists.

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