KR20100053834A - Method and device for calibrating doppler frequency, system for testing radar set using the same - Google Patents

Abstract

PURPOSE: A method and a device for measuring Doppler frequency and a system for testing a radar set using the same are provided to precisely measure the error in the RF frequency of a measurement unit based on the RF transmission frequency of a radar set by performing an automatic Doppler frequency calibration. CONSTITUTION: A signal generator(40) generates continuous wave RF signal with a specific frequency. A pulse generator(20) delays pulsed repetition frequency(PRF) signal from a radar set and generates delayed PRF. A pulse modulator(30) performs a pulse modulation operation for the delayed PRF and the continuous wave RF signal. A Doppler frequency measurement unit(100) samples and holds image signal from the radar set based on the PRF signal.

Description

Method and device for calibrating Doppler frequency, System for testing radar set using the same

The present invention relates to a method and apparatus for measuring Doppler frequency and a test system for a radar set using the same. More specifically, the Doppler frequency measurement unit can be configured by using a sample hold circuit, so that a Doppler frequency 1 Hz calibration can be performed. It is possible to measure the error of the RF frequency emitted from the generator, and to accurately sample the level of the video signal in the sample hold circuit part by delaying the PRF signal by a predetermined interval and adjusting the pulse width using an FPGA. The present invention relates to a Doppler frequency measuring method and apparatus for amplifying an image signal of a radar to facilitate a sampling operation in a sample hold circuit, and a test system for a radar set using the same.

Radar (RADAR) is an abbreviation of Radio Detecting And Ranging, and emits electromagnetic waves of microwaves (microwave, 10cm ~ 100cm wavelength) to an object to receive electromagnetic waves reflected from the object, and then distance to the object. It is a wireless monitoring device that finds direction, altitude, etc.

Since microwaves have a short wavelength and have a straightness like light and are not reflected from the ionosphere, the radio waves emitted from the directional antenna travel in a straight line to the target and then return. By measuring the time of the reflected electromagnetic waves, the distance, direction, and altitude of the target can be determined. Through this information, the location, topography, and cloud formation of the aircraft can be determined.

Radar is divided into continuous wave radar and pulse radar according to the propagation type. Continuous wave radar includes Doppler radar and FMCW radar. Pulse radar includes pulse Doppler radar and pulse compression radar.

The pulsed Doppler radar allows the signal output from the transmitter to be received by the receiver as a transitioned signal compared to the transmit frequency by the Doppler Effect caused by the target when the target moves at a speed along the radar line of sight. will be. A pulsed Doppler radar is composed of a transmitter, a transmitting antenna, and a receiving antenna, a receiver, and an indicator, which receive a reflected wave from a target. Therefore, pulse-modulated transmit radio waves reach the target and re-radiate in all directions, and out of these re-radiated radio waves are received toward the receiving antenna, so that the detection of the presence of the target and the measurement of the distance and the function of the receiver, depending on the radar and target Relative velocity, relative speed, etc. can be measured.

During the test of the radar set, an instrument (signal generator) converts an RF signal of a specific frequency into a virtual target signal and supplies it to the radar set. In this case, a frequency difference occurs between the signal transmitted by the radar set as a signal of a specific frequency and the received virtual target signal. This is because an error exists in the transmission RF frequency of the radar set itself, and an error also exists in the frequency of the RF signal emitted from the measuring instrument (signal generator). Therefore, in the radar moving target detection mode, it is necessary to operate a measuring instrument (signal generator) based on the RF transmission frequency of the radar set to match the transmission frequency of the radar set. This process is called "Doppler Frequency 1Hz" calibration.

Doppler frequency 1 Hz calibration is essential for testing radar sets.

Conventionally, the sweep frequency of an instrument (signal generator) is adjusted so that the Doppler frequency is 1 Hz while visually confirming using an analog oscilloscope. According to this method, the test should be performed manually by an experienced operator (tester) because the Doppler frequency of 1 Hz must be relyed on visual measurements while manually operating the oscilloscope each time. Therefore, the beginner has a problem that takes a long test time.

The present invention has been made to solve the above problems, especially for experienced workers, even beginners can easily measure the error of the RF frequency emitted from the instrument (signal generator) based on the RF transmission frequency of the radar set. It is an object of the present invention to provide a Doppler frequency measuring method and apparatus for accurately sampling the level of an image signal in a sample hold circuit and a radar set test system using the same.

In order to achieve the above object, a test system of a radar set according to the present invention includes a signal generator for generating a continuous wave RF signal having a specific frequency; A pulse generator for delaying a Pulse Repetition Frequency (PRF) signal input from the radar set to generate a delayed PRF; A pulse modulator for receiving a delayed PRF signal from the pulse generator and receiving a continuous wave RF signal from the signal generator to perform pulse modulation; And a Doppler frequency measuring unit configured to sample and hold the image signal input from the radar set based on the delayed PRF signal input from the pulse generator.

The pulse modulator may also input a pulse modulated RF signal to the radar set.

In addition, the test system of the radar set may further include a frequency counter for receiving the output signal of the Doppler frequency measuring unit to count the frequency.

The radar set test system may further include an oscilloscope configured to receive an image signal and a PRF signal from the radar set to check a Doppler frequency waveform.

The Doppler frequency measuring unit may further include an image amplifier configured to amplify an image signal input from the radar set; A field programmable gate array (FPGA) for adjusting delay and pulse width with respect to the delayed PRF signal input from the pulse generator; A sample hold circuit unit may perform a sample hold function on the output signal of the image amplifier based on the output signal of the FPGA.

The image amplifier may include an amplifier for amplifying the image signal, and a filter unit for filtering the output signal of the amplifier.

The Doppler frequency measurer may further include a low pass filter for removing components other than the Doppler frequency from the output signal of the sample hold circuit.

The Doppler frequency measuring apparatus according to the present invention is a Doppler frequency measuring apparatus for inputting an image signal from a radar set and receiving a delayed PRF signal from a pulse generator to perform a Doppler frequency 1 Hz calibration, which is input from the radar set. A video amplifier for amplifying the video signal; A field programmable gate array (FPGA) for adjusting delay and pulse width with respect to the delayed PRF signal input from the pulse generator; And a sample hold circuit unit performing a sample hold function on the output signal of the image amplifier based on the output signal of the FPGA.

The image amplifier may include an amplifier for amplifying the image signal, and a filter unit for filtering the output signal of the amplifier.

The apparatus may further include a low pass filter for removing components other than the Doppler frequency from the output signal of the sample hold circuit.

Doppler frequency measuring method according to the present invention comprises the steps of (a) amplifying the video signal input from the radar set; (b) adjusting delay and pulse width of the PRF signal input from the signal processor of the radar set; (c) sampling and holding the output signal of step (a) based on the output signal of step (b); And (d) removing components other than the Doppler frequency from the output signal of step (c).

In addition, the Doppler frequency measuring method may further comprise the step of (e) counting the frequency of the output signal of the step (d).

In addition, the method may further include performing a Doppler frequency 1 Hz calibration by checking the counted frequency through step (e) and adjusting the frequency of the signal generator.

According to the present invention, the Doppler frequency measurement unit is configured by using a sample hold circuit, so that the Doppler frequency 1 Hz calibration can be automatically performed, so that a skilled worker as well as a beginner can easily refer to the RF transmission frequency of the radar set. There is an effect that can measure the error of the RF frequency emitted from the instrument (signal generator).

In addition, according to the present invention, by using an FPGA, the PRF signal is delayed by a predetermined interval and the pulse width is adjusted to accurately sample the level of the image signal in the sample hold circuit.

In addition, according to the present invention, the image signal of the radar is amplified by the image amplifier to facilitate the sampling operation in the sample hold circuit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible, even if shown on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the following will describe a preferred embodiment of the present invention, but the technical idea of the present invention is not limited thereto and may be variously modified and modified by those skilled in the art.

1 is a block diagram of a radar set test system according to a preferred embodiment of the present invention.

1, a radar set test system according to a preferred embodiment of the present invention, a radar set 10, a pulse generator 20, a pulse modulator 30, a signal generator 40, and a Doppler frequency measurement unit ( 100), frequency counter 50, and oscilloscope 60.

The radar set 10 is a radar set to be tested for normal operation, and a pulsed Doppler radar is applied. The radar set 10 includes a power amplifier (not shown), a transmitter (not shown), a receiver (not shown), a power supply (not shown), a transmission / reception front end 12, and a signal processor 14.

The radar transfers the captured speed information to the signal processor 14.

The signal processor 14 inputs a pulse repeating frequency (“PRF”) to the pulse generator 20.

The pulse generator 20 generates a delayed PRF (hereinafter referred to as "delayed PRF") by delaying the PRF input from the signal processor 14 by a predetermined amount, and inputs it to the pulse modulator 30. In addition, the pulse generator 20 inputs the delayed PRF to the oscilloscope 60 and the Doppler frequency measuring unit 100 so that the Doppler frequency can be measured.

The signal generator 40 corresponds to a measuring instrument, and generates an RF signal of continuous wave CW having a specific frequency and inputs the RF signal to the pulse modulator 30.

The pulse modulator 30 receives a delayed PRF from the pulse generator 20, receives a continuous wave RF signal from the signal generator 40, performs pulse modulation, and transmits and receives a pulse modulated RF signal of the radar set 10. Input to section 12.

The Doppler frequency measuring unit 100 receives a radar image signal from the signal processing unit 14 of the radar set 10, receives a delayed PRF from the pulse generator 20, and measures the Doppler frequency 1 Hz. The Doppler frequency measurement unit 100 will be described later.

The frequency counter 50 counters the frequency of the signal passing through the Doppler frequency measuring unit 100, whereby the operator (tester) adjusts the signal generator 40 by the frequency displayed by the frequency counter 50 to adjust the Doppler frequency 1 Hz. To do this.

The oscilloscope 60 receives the radar image signal and the PRF signal from the signal processor 14 of the radar set 10 so that an operator (tester) can visually check the image signal carrying the Doppler frequency.

FIG. 2 is a detailed configuration diagram of the Doppler frequency measuring unit in FIG. 1.

Referring to FIG. 2, the Doppler frequency measuring unit 100 according to the preferred embodiment of the present invention includes an image amplifier 110, a sample hold circuit unit 120, a low pass filter 130, and an FPGA 140. do.

The image amplifier 110 amplifies the radar image signal input from the signal processor 14 of the radar set 10. These video signals carry Doppler frequency components. The image amplifier 110 may include an amplifier 112 and a filter 114. For example, when the gain of the amplifier 112 is 10 times, when the image signal having the peak to peak voltage Vp-p is 1V is input, the image amplifier 110 outputs the image signal having the Vp-p of 5V.

The sample & hold circuit unit 120 performs a sample hold function on the image signal loaded with the Doppler.

The low pass filter 130 removes the high frequency signal of the signal passed through the sample hold circuit unit 120.

The field programmable gate array (FPGA) 140 adjusts the delay and pulse width of the PRF input from the signal processor 14 of the radar set 10, and then inputs the adjusted signal to the sample hold circuit unit 120. .

The signal from which the high frequency signal is removed through the low pass filter 130 is counted through the frequency counter 50, and the operator (tester) sees it and adjusts the frequency of the signal generator 40 by the Doppler frequency Fd = 1 to 3 kHz. Finally, the Doppler frequency Fd = 1 Hz. This result can be confirmed through the waveform shown in the oscilloscope 60.

3 is a graph illustrating a process of adjusting delay and pulse width of a PRF signal through the FPGA of FIG. 2.

In FIG. 3, the upper graph is a PRF input from the signal processor 14 and may be, for example, a signal having a pulse width of 250 ns having a frequency of 25 kHz.

In FIG. 3, the lower graph is a signal in which delay and pulse width adjustment are performed through the FPGA 140, for example, a signal having a pulse width of 100 ns having a frequency of 25 kHz, and is delayed by 10.7 us with respect to the upper graph.

As described above, adjusting the delay and the pulse width of the PRF signal through the FPGA 140 before being input to the sample hold circuit unit 120, the sample hold circuit unit 120 uses the PRF signal of the radar set 10 as an input signal. If you use this signal as a control signal of the sample hold IC, it may not be able to accurately sample the level of the video signal. Therefore, for accurate sampling, the FPGA 140 delays the PRF signal by 10.7 us and adjusts the pulse width from 250 ns to 100 ns.

4A is a graph illustrating a process of detecting from a video signal carrying a Doppler frequency at regular intervals, and FIG. 4B is a waveform of observing an video signal through an oscilloscope.

The radar set 10 using the pulsed Doppler radar method cannot measure the frequency of an image signal of which amplitude changes as shown in FIG. 4B using a frequency counter. The frequency can be measured.

FIG. 4B shows the image signal waveform 1Vp-p before amplification, and the image-hold amplifier 110 including the amplifier 112 and the filter 114 is used in the sample hold circuit 120 without using the image signal as it is. Take it through. This facilitates the sampling operation in the sample hold circuit unit 120. For example, when the maximum input level of the sample hold circuit unit 120 is ± 2.5V, the amplification is performed such that the input signal is applied at 5Vp-p, thereby preventing the case where the level is low and not being detected.

5 is a graph illustrating a Doppler signal waveform passing through a sample hold circuit.

The Doppler signal waveform of FIG. 5 performs a sample hold operation using the PRF signal adjusted through the FPGA 140 as a control signal. In Fig. 4, the sawtooth waveform of the hold portion shows that a high frequency signal of 25 kHz is mixed.

Fig. 6 is a graph showing the Doppler signal waveform (one periodic waveform) passing through the low pass filter.

When the signal passing through the sample hold circuit unit 120 passes through the low pass filter 130, high frequency components other than the Doppler frequency are removed. By setting the cutoff frequency of the low pass filter 130, unwanted high frequency components are removed. For example, the low-pass filter 130 has a secondary butter Worth (2 ^nd order Butterworth) method can be applied. The cutoff frequency can be set at approximately 17 kHz to remove the frequency component of 25 kHz. On the other hand, the Butterworth characteristic has a slightly gentler slope in the stop band, so a three-stage structure may be applied to compensate for this.

FIG. 7 is a graph showing the Doppler signal waveform passing through the low pass filter in a specific section, and FIG. 8 is a graph showing the Doppler signal waveform after a Doppler frequency 1 Hz operation by operating a signal generator in a specific section. 9 is a waveform of a Doppler frequency 1 Hz signal measured through an oscilloscope. For example, the specific period in FIGS. 7 and 8 is a half cycle of 1 Hz, that is, 500 ms.

FIG. 7 illustrates a 2.77 kHz signal in which a high frequency component is removed through a low pass filter in a 500 ms interval. The signal is input to a frequency counter having a measurement range of 1 to 300 kHz and the frequency is measured. The operator (tester) sees the frequency measured through the frequency counter, adjusts the signal generator by the displayed frequency, and performs the Doppler frequency 1 Hz adjustment.

Comparing the case where the 2.77 kHz signal is viewed for a specific time (500 ms) (Figure 7) and the 1 Hz signal for half a cycle (Figure 8), the Doppler frequency 1 Hz signal is relatively close to the direct current (DC) signal. see. When a signal that looks relatively close to a direct current is detected at every pulse repetition interval (PR) period of the radar set, the oscilloscope confirms the signal as shown in FIG. 9. It can be seen that the waveform of Figure 9 slightly shakes with time.

10 is a flowchart of a Doppler frequency measuring method according to a preferred embodiment of the present invention.

Step S10 is amplifying the video signal input from the radar set. The video signal is input from the signal processor of the radar set, and the Doppler frequency component is reflected. In operation S10, amplification may be performed to facilitate sampling of the image signal, and filtering may be performed through a low pass filter.

Step S20 is a step of adjusting the delay and the pulse width with respect to the PRF signal input from the signal processor of the radar set. Delay and pulse width adjustments enable accurate sampling of the level of the video signal.

Step S30 is a step of sampling and holding the output signal of step S10 based on the output signal of step S20.

Step S40 is a step of removing components other than the Doppler frequency from the output signal of step S30. A low pass filter is used to eliminate unnecessary high frequency signals.

Step S50 is a step of countering the frequency of the output signal of step S40.

Step S60 is a step of performing a Doppler frequency 1 Hz calibration by checking the frequency counted through step S50 and adjusting the frequency of the signal generator. Doppler frequency 1 Hz calibration results can be confirmed using an oscilloscope or the like.

The above description is merely illustrative of the technical idea of the present invention, and various modifications, changes, and substitutions may be made by those skilled in the art without departing from the essential characteristics of the present invention. will be. Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

The present invention is a device for facilitating the Doppler frequency 1 Hz calibration in the test of the radar set, and can be particularly widely applied to the test of the radar set of the pulse Doppler method.

1 is a block diagram of a radar set test system according to a preferred embodiment of the present invention,

FIG. 2 is a detailed configuration diagram of the Doppler frequency measuring unit in FIG. 1;

3 is a graph illustrating a process of adjusting delay and pulse width of a PRF signal through the FPGA of FIG. 2;

4A is a graph illustrating a process of detecting a Doppler signal at regular intervals from a radar image signal;

4b is a waveform of observing an image signal through an oscilloscope,

5 is a graph showing a Doppler signal waveform passing through a sample hold circuit;

6 is a graph showing a Doppler signal waveform (one period waveform) passing through a low pass filter;

7 is a graph showing a Doppler signal waveform passing through a low pass filter in a specific section;

8 is a graph showing a Doppler signal waveform after a Doppler frequency 1 Hz operation by operating a signal generator in a specific section;

9 is a graph of a waveform of a Doppler frequency 1 Hz signal measured with an oscilloscope,

10 is a flowchart of a Doppler frequency measuring method according to a preferred embodiment of the present invention.

Claims (13)

In the test system of the radar set, A signal generator for generating a continuous wave RF signal having a specific frequency; A pulse generator for delaying a Pulse Repetition Frequency (PRF) signal input from the radar set to generate a delayed PRF; A pulse modulator for receiving a delayed PRF signal from the pulse generator and receiving a continuous wave RF signal from the signal generator to perform pulse modulation; Doppler frequency measurement unit for performing sample & hold on the image signal input from the radar set on the basis of the PRF signal input from the signal processor of the radar set Radar set test system comprising a. The method of claim 1, And said pulse modulator inputs a pulse modulated RF signal to said radar set. The method of claim 1, And a frequency counter for receiving the output signal of the Doppler frequency measuring unit and counting the frequency. The method of claim 1, And an oscilloscope configured to receive a radar image signal and a PRF signal from the radar set to check a Doppler frequency waveform. The method of claim 1, wherein the Doppler frequency measuring unit An image amplifier for amplifying the image signal input from the radar set; A field programmable gate array (FPGA) for adjusting delay and pulse width with respect to the PRF signal input from the signal processor of the radar set; A sample hold circuit unit performing a sample hold function on the output signal of the image amplifier based on the output signal of the FPGA Radar set test system comprising a. The method of claim 5, The image amplifier includes amplification unit for amplifying the image signal, and the radar set test system, characterized in that it comprises a filter for filtering the output signal of the amplifier. The method of claim 5, And a low pass filter for removing components other than the Doppler frequency from the output signal of the sample hold circuit portion. In the Doppler frequency measuring apparatus for receiving the Doppler frequency 1 Hz calibration (Crystal) by receiving the image signal and the PRF signal from the radar set, An image amplifier for amplifying the image signal input from the radar set; A field programmable gate array (FPGA) for adjusting delay and pulse width with respect to the PRF signal input from the signal processor of the radar set; And A sample hold circuit unit performing a sample hold function on the output signal of the image amplifier based on the output signal of the FPGA Doppler frequency measurement apparatus comprising a. The method of claim 8, The image amplifier includes an amplifying unit for amplifying the image signal, and a Doppler frequency measuring device, characterized in that for filtering the output signal of the amplifying unit. The method of claim 8, And a low pass filter for removing components other than the Doppler frequency from the output signal of the sample hold circuit. (a) amplifying the video signal input from the radar set; (b) adjusting delay and pulse width of the PRF signal input from the signal processor of the radar set; (c) sampling and holding the output signal of step (a) based on the output signal of step (b); And (d) removing components other than the Doppler frequency from the output signal of step (c). Doppler frequency measurement method comprising a. The method of claim 11, (e) counting the frequency of the output signal of step (d) Doppler frequency measurement method further comprising. The method of claim 12, (f) performing Doppler frequency 1 Hz calibration by checking the counted frequency in step (e) and adjusting the frequency of the signal generator Doppler frequency measurement method further comprising.

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