KR101135982B1 - Synchronization method of radar systems for the rejection of interference in FMCW radars - Google Patents

Abstract

The present invention relates to a system-to-system synchronization method for interference cancellation in a frequency modulated continuous wave (FMCW) radar. (A) When two radars are operated simultaneously, the cell average-constant error alarm probability Using the CA-CFAR) algorithm, when a synchronization command is generated from the radar to synchronize with the reference radar, the signal is converted into a continuous wave-linear frequency modulation (CW-LFM) waveform, and the radar signal is acquired to convert the received signal to the radar. Determining the presence of interference using time domain CA-CFAR; (b) synchronizing between radar systems when interference occurs in a continuous wave (CW) section; (c) synchronizing between radar systems when interference occurs in a frequency modulation (LFM) section; (d) if no occurrence of interference is detected; And (e) when the same type radar synchronization is completed, controlling the waveform generator to return to the original waveform. The present invention recognizes an interference signal in a radar using a frequency modulated continuous wave (FMCW) signal, calculates and corrects an asynchronous time between devices through forced time delay and frequency hopping, synchronizes radar equipment, and powers up when synchronization is completed. Eliminates interfering signals between radars until turned off, increasing equipment co-operation.

Description

Synchronization method of radar systems for the rejection of interference in FMCW radars

The present invention relates to a system-to-system synchronization method for interference cancellation in a frequency modulated continuous wave (FMCW) radar, and more particularly, when two or more radars are operated simultaneously, a frequency modulated continuous wave (FMCW) signal is generated. For interference cancellation in frequency modulated continuous wave radar that recognizes interference signals in the used radar and synchronizes radar equipment by eliminating and calibrating asynchronous time between devices through forced time delay and frequency hopping. It relates to a system-to-system synchronization method.

Radar's principle proved the existence of radio waves in the experiments of German physicist Heinrich Hertz, and demonstrated that light has a similar property of reflecting off a mirror.

Applicability in detecting objects by the reflection of radio waves by the object was investigated by Italian engineer Guhhelmo Marconi in 1922 on this principle, and later by Naval Research Laboratory using Marconi's proposal to send transmitters and receivers. Continuous wave (CW) was used to detect ships passing through.

A radar is a device that measures the direction and distance to an airplane by firing microwaves from an antenna at a radio wave launch point and reaching an airplane within a certain distance, receiving a radio wave reflected by a target through an antenna, processing a signal, and displaying the signal on a screen. . The radar can accurately measure the plane's exact distance and the target's relative speed to the point of view.

Radar devices usually operate by emitting electromagnetic waves of microwaves to a target and receiving electromagnetic waves reflected from the target. The nature of the received electromagnetic waves, or echo, is amplified and analyzed using a signal processor. Information about the target (distance, direction, altitude) is usually displayed on the cathode ray tube's screen, which also maps the area where the radar beam is being scanned, such as the Plan Position Indicator (PPI).

Radar systems come in several varieties: pulsed radar, continuous wave (CW) radar, and light radar, which use different types of signals for the radar transmitter, and different properties in the received direction. Currently, the most widely used radar is pulse radar.

The radar is first triggered by a trigger oscillator to induce a pulsed voltage to the modulator and generates it repeatedly at regular intervals.The modulator and the oscillator oscillate powerful microwaves to the magnetron and launch them into the air through the wave guide. The number of firings of this pulse is equal to the pulse repetition frequency of the trigger oscillator and is fired continuously.

When the reflected wave returns, the radar receives the aerial signal, amplifies the reflected wave, transmits it to the Cathode Ray Tube (CRT), and the current of the saw tooth wave driven by the deflection trigger oscillator flows through the CRT deflection coil. The position of the mesh is displayed according to the distance and direction, and the point is displayed on the screen.

CW (Continous Wave) radar is a radar that transmits and receives a sine wave without using pulse modulation (PM) using a duplexer that uses the same antenna as a transmitter and a receiver at the same time. Because of their lack of capability, they often apply frequency modulation repeatedly. This method is called Frequency Modulation Continous Wave (FMCW) radar.

A frequency modulated continuous wave (FMCW) radar measures the distance between the target and the radar by launching electromagnetic waves onto the target and then measuring the bit frequency by mixing a reflected echo from the target with a portion of the transmit frequency. FMCW radars are commonly used in tide gauges, water gauges, and the like in altimeter tanks in aircrafts. In this case, the FMCW radar continuously transmits the frequency of the transmission signal continuously from the antenna, and the frequency of the received echo has a value different from the frequency of the wave emitted by the transmitter at that time. If the FMCW radar knows the rate at which the frequency changes over time, it measures the distance to the target by the difference in frequency during transmission and reception.

In addition, microwave remote sensing is mainly used as a sensor for measuring the scattering coefficient of various objects installed on the ground. However, when using this as a scattering meter, scattering from a target body must be measured simultaneously with distance measurement.

Multi-functional radars used in the surface-to-air guided weapons business must be capable of performing functional target detection, tracking and engagement, and precisely generated waveforms to minimize distance and speed errors. For this purpose, the waveform generator of the multi-function radar must have precise waveform generation and accurate diagnosis of the generated waveform. Waveforms generated by the waveform generator of the multifunction radar include Linear Frequency Modulation (LFM), Phase Code Modulation (PCM), Pulse Train (PT), Frequency Shift Keying (FSK), and Linear Frequency Modulation-Pulse Train (LFM-PT). have. Multi-function radar has the function to diagnose each generated waveform to ensure the precision of waveform generation.

When two or more radars are operated simultaneously, the radars are powered on at the same time and if all the synchronization is not synchronized, the asynchronous phenomenon occurs between the devices.

In the existing two or more radars, the interference cancellation methods use an adaptive interference signal removal device that excludes an interference signal in the time domain or controls the antenna beam steering in the direction in which the interference enters. However, the prior art has a problem in that it is not possible to completely remove the inter-radar interference signal resulting in degradation of the target recognition ability.

The present invention has been proposed to solve the problems of the prior art, and an object of the present invention is to recognize an interference signal in a radar using a frequency modulated continuous wave (FMCW) signal when two or more radars are operated simultaneously, and a forced time delay. Frequency modulated continuous wave radar that calculates and corrects asynchronous time between devices through frequency hopping (upward hopping, downward hopping) to synchronize radar devices, eliminate radar interference signals, and improve concurrent operation of FMCW radar equipment. To provide a system-to-system synchronization method for interference elimination.

In order to achieve the object of the present invention, the inter-system synchronization method for interference cancellation in a frequency modulated continuous wave (FMCW) radar, (a) a cell average in the time domain to determine the presence of interference when two radars are operated simultaneously Using the Cell Averaging-Constant False Alarm Rate (CA-CFAR) algorithm, when a synchronization command is issued from the radar to synchronize to the reference radar, it is changed to a CW-LFM waveform. Acquiring a radar signal and determining whether the signal received by the radar has interference using a time-domain cell average-constant alarm probability (CA-CFAR); (b) synchronizing between radar systems when interference occurs in a continuous wave (CW) section; (c) synchronizing between radar systems when interference occurs in a linear frequency modulation (LFM) section; (d) if no occurrence of interference is detected; And (e) when the same type radar synchronization is completed, controlling the waveform generator to return to the original waveform.

In addition, in order to achieve another object of the present invention, when three or more frequency modulated continuous wave (FMCW) radar is operated at the same time, the synchronization method for interference cancellation, (a) the power of the radar only the reference radar high frequency device When the radio wave is turned on, the reference radar is set for synchronization to remove the interference, and the waveforms 101, 102, and 103 of the radars I, II, and III to synchronize are generated in the continuous wave (CW) section. Synchronizing with a reference radar using a synchronization method when interference occurs in a synchronization method or a frequency modulation (LFM) section; (b) When the radar I is synchronized with the reference radar, the power of the high frequency devices of the radars II and III is turned off, and when the interference occurs in the frequency modulation (LFM) section, two synchronization algorithms are used. Eliminating interference through radar synchronization, turning off high frequency devices of the synchronized radar, and turning on high frequency devices of other non-synchronized radars in the same manner to synchronize the reference radar; (c) When the radar II is synchronized with the reference radar, the high frequency devices of the radars I and III are turned off, and when the interference occurs in the continuous wave (CW) section, the two radars are synchronized with each other using a synchronization algorithm. Removing interference through synchronization; And (d) during synchronization of the radar III to synchronize the reference radar with the reference radar, the power of the high frequency devices of the radars I and II is turned off, and the interference 109 generated in the continuous wave (CW) section is a continuous wave ( CW) when the interval interference occurs using a synchronization algorithm to remove the interference through the synchronization between the two radar.

According to the present invention, a system-to-system synchronization method for interference cancellation in a frequency modulated continuous wave (FMCW) radar recognizes an interference signal in a radar using a frequency modulated continuous wave (FMCW) signal when two or more radars are operated simultaneously. It also calculates and corrects asynchronous time between devices through forced time delay and frequency hopping (upward and downward hopping) to synchronize radar equipment, eliminate radar interference signals, and improve radar equipment's simultaneous operation. It works.

1 is a view showing a frequency allocation scheme for simultaneous operation of a frequency modulated continuous wave (FMCW) radar.
FIG. 2 is a diagram illustrating an interference phenomenon when a frequency-modulated continuous wave radar is asynchronous when two radars are operated simultaneously.
FIG. 3 is a flowchart illustrating an interference determination procedure using a time-domain cell averaging-constant false alarm rate (CA-CFAR).
FIG. 4 is a flowchart illustrating a synchronization procedure when interference occurs (1 in FIG. 2) in a continuous wave (CW) section.
FIG. 5 is a flowchart illustrating a synchronization procedure when interference occurs (Line 2 in FIG. 2) in a linear frequency modulation (LFM) section.
FIG. 6 is a flowchart of a synchronization procedure when no interference is detected (3 in FIG. 2 and 4 in FIG. 2).
FIG. 7 is a diagram illustrating a synchronization algorithm of two radars when interference occurs in the continuous wave (CW) section of FIG. 4.
FIG. 8 is a diagram illustrating a synchronization algorithm when interference occurs in the linear frequency modulation (LFM) section of FIG. 5.
9 is a diagram illustrating a synchronization algorithm when the occurrence of interference of FIG. 6 is not detected.
10 is a diagram illustrating a synchronization scheme for interference cancellation when three or more radars are operated simultaneously.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

The inter-system synchronization method for interference cancellation in a frequency modulated continuous wave (FMCW) radar according to the present invention includes (a) a cell average-constant error alarm probability (CA) in the time domain to determine whether or not two radars are operated simultaneously. Continuous Wave-Linear Frequency Modulation (CW-LFM) waveforms when synchronization commands are generated from the radar to synchronize with the reference radar using the CFAR: Cell Averaging-Constant False Alarm Rate (CFAR) algorithm. Acquiring the radar signal and determining whether the signal received by the radar is interference using a time-domain cell average-constant alarm probability (CA-CFAR) algorithm; (b) synchronizing between radar systems when interference occurs in a continuous wave (CW) section; (c) synchronizing between radar systems when interference occurs in a linear frequency modulation (LFM) section; And (d) if no occurrence of interference is detected.

1 is a diagram illustrating a frequency allocation scheme for simultaneous operation of a linear frequency modulated continuous wave radar.

Two or more radars change the waveform as shown in FIG. 1 through the control of the waveform generator to remove the interference signal from the frequency modulated continuous wave (FMCW) radar. A continuous wave (CW) signal having one frequency is transmitted during the modulation time T, and a signal in which the frequency is continuously modulated by the modulation width BW during the next modulation time T is transmitted. Once the final synchronization is complete, control the waveform generator to return to the original waveform.

The present invention is applied to a radar system in which the center frequency between the radars is designed to be spaced apart by Δf to increase the simultaneous operability of the frequency modulated continuous wave (FMCW) radar. The Δf value is designed to be at least twice by analyzing the information spectrum of the target received by the radar. The radar is operated by selecting one of the n frequencies shown in FIG. 1, and the maximum number of radars n that can be operated simultaneously in the available frequency band is calculated as in Equation 1 below.

Here, BW denotes a modulation width during modulation time T, n (n is a natural number of 1 or more), and Δf denotes a maximum frequency deviation from a carrier frequency of the carrier of the radar.

If two or more radars are operated simultaneously, the radar will be asynchronous due to asynchronous operation if the radars are turned on at the same time and not synchronized.

FIG. 2 is a diagram for explaining cases of interference generated when a frequency-modulated continuous wave (FMCW) radar is asynchronous when two radars are operated simultaneously. 2 is a continuous wave-linear frequency modulation (CW-LFM) signal of a radar to be synchronized, and (22) is a continuous wave (CW: Continuous) of a radar to be synchronized. Wave) represents the interference region in the time-frequency domain occurring in the interval. Case 1 is when interference occurs in a continuous wave (CW) section of a radar to be synchronized, and occurs when the center frequency is higher than the center frequency of the reference radar.

2 is a continuous wave-linear frequency modulation (CW-LFM) signal of the radar to be synchronized, and (24) is a time-frequency domain occurring in the frequency modulation (LFM) section of the radar to be synchronized. Represents the interference region. Case 2 is a case where interference occurs in a linear frequency modulation (LFM) section of a radar to be synchronized, and occurs when the center frequency is lower than the center frequency of the reference radar.

(25) and (27) of FIG. 2 are continuous wave linear frequency modulation (CW-LFM) signals of the radar to be synchronized, and (26) and (28) are time-frequency generated from the radar to be synchronized. It represents the interference region in the time-frequency domain.

Cases 3 and 4 are cases in which the linear frequency modulation (LFM) section signal of the reference radar enters the information spectrum band of the radar to be synchronized, and may not recognize the actual target because it is recognized as a strong signal target.

The present invention proposed a synchronization method between radars to remove interference when several radars are operated at the same time. Initially, the radar is turned on and only the reference radar is turned on to transmit the radio wave, and the radar to be synchronized is synchronized with the reference radar using the following method while the radio is turned on and operated. After the synchronization is completed, the radar is turned off and the high frequency device of the unsynchronized radar is turned on in the same way to synchronize the reference radar with the reference method. When the synchronization is completed in the time domain of the radar, the inter-radar interference signal is removed until the power is turned off.

Hereinafter, a synchronization scheme using an interference signal in two or more radars will be described.

3 to 6 show flowcharts illustrating a synchronization method for interference cancellation when two radars are operated simultaneously. To determine the radar interference, two or more radars used CA-CFAR (Cell Averaging-Constant False Alarm Rate) in the time domain.

FIG. 3 is a flowchart illustrating an interference determination procedure using a time-domain cell averaging-constant false alarm rate (CA-CFAR).

As shown in FIG. 3, when two radars are operated simultaneously, the radar uses a cell average-constant false alarm rate (CA-CFAR) in the time domain to determine the presence of interference. (S11), when a synchronization command is generated from the radar to synchronize with the reference radar (S12), it is changed into a continuous wave-linear frequency modulation (CW-LFM) waveform as shown in FIG. 1 (S13), and a radar signal is obtained ( S14) Signals received by the radar through time-domain cell averaging-constant false alarm rate (CA-CFAR) algorithm (S15) presence or absence of interference in the continuous wave (CW) section, linear frequency modulation In the (LFM) section, it is determined whether or not interference is detected or not (S16) and the algorithm is applied according to each case.

When the interference occurs in the continuous wave (CW) section, when the interference occurs in the linear frequency modulation (LFM) section, when the interference is not detected, when the radar synchronization is complete according to each algorithm (S45) In step S46, the waveform generator is controlled to return to the original waveform.

The adaptive cell averaging-constant false alarm rate (CA-CFAR) algorithm in step S15 is an envelope signal for the radar echo to effectively suppress and eliminate the radar clutter signal. Although the amplitude of is varied according to the Rayleigh distribution, if the parameter of the amplitude distribution of the clutter is changed and the distribution shape is changed, the false alarm probability is sufficiently changed. It is suppressed by a low constant value to maintain a constant false alarm rate (CFAR).

The adaptive constant alarm probability (CFAR) algorithm is used to increase the detection probability while maintaining a constant false alarm rate in a clutter background environment, especially in a nonuniform clutter environment with large spatial correlation and size deviation. In order to improve performance, an adaptive filtering scheme is required. Two-dimensional block interpolation (TBI) adaptive CFAR algorithm obtains representative estimates by dividing regions in two dimensions for clutter background estimation and final estimation using interpolation filter. Determine the value. This method eliminates irregular interference signals by selecting the median histogram distribution of the partial region as the region estimation value, and outputs the final estimation value for each cell using the double block node estimation value.

The radar's CA-CFAR processing block receives an input signal and passes it through a square-law detector, followed by two blocks (1 to M / 2, M / 2 + 1). Representative estimates are calculated by ˜M), the final estimate is determined using an interpolation filter, and the threshold value is calculated by multiplying the average value of the data of M (M is one or more natural numbers) around the cell by a magnification α, A comparator compares the current cell, which is the median value of the histogram distribution, to determine whether the threshold is exceeded. The magnification α is determined according to the false alarm rate and the M value.

FIG. 4 is a flowchart illustrating a synchronization procedure when interference occurs in a continuous wave (CW) section (1 in FIG. 2).

4 is a diagram illustrating a synchronization method when interference occurs in a continuous wave (CW) section after the interference determination procedure of FIG. 3, and FIG. 7 is a diagram illustrating a synchronization algorithm in the continuous wave (CW) section of FIG. 4.

When interference occurs in the continuous wave (CW) section, the synchronization method is to adjust the center frequency (f _c ) of the radar to be synchronized with the reference radar in the time domain as shown in equation (2) f _H Downward jump as much as (S18), and perform the time-domain cell averaging-constant false alarm rate (CA-CFAR) algorithm (S19) to the downward until no interference in the continuous wave (CW) section The number of jumps i is increased by 1 and repeated. When interference occurs in the continuous wave (CW) section as shown in (72) of FIG. 7, the center frequency of the radar 71 to be synchronized as shown in (a) of FIG. 7 is higher than the center frequency of the reference radar. Occurs when.

As shown in (b) of FIG. 7, the radar to synchronize after downlinking once using Equation (2) becomes (71) to (73). Interference occurs as shown in (75). In addition, after hopping down the center frequency of the radar to be synchronized with the reference radar once again, the radar to be synchronized is from 73 to 74, and it is determined whether or not the interference is present (S20). If not, stop the frequency hopping.

Here, i is a natural number when the interference existing in the continuous wave (CW) period disappears, Δf is a maximum frequency deviation from the carrier frequency of the carrier of the radar, f _c is the initial The center frequency, f _c 'is the center frequency after the jump, F _min is the lowest frequency available band, F _max is the highest frequency available band.

)은 수학식 3을 사용하여 계산된다(S21).The radar that wants to synchronize with the reference radar may calculate the center frequency separation between two radars as shown in Equation 3 by moving down the center frequency. As shown in (b) of FIG. 7, when interference occurs when i = 1, but does not occur when i = 2, the center frequency interval between two radars (

) Is calculated using Equation 3 (S21).

Where Δf _B : center frequency interval between two radars, k is the number of downward jumps when interference existing in the continuous wave (CW) period disappears i, Δf: maximum frequency from the carrier frequency of the carrier of the radar It represents the maximum frequency deviation.

After hopping to synchronize with the reference radar, the center frequency f _c ′ of the radar is hopped upward by -f _H to return to the original center frequency f _c of the radar to be synchronized (S22).

As shown in (c) of FIG. 7, time-domain cell average-constant alarm probability (CA-CFAR) is performed (S23) to calculate the time t _Int at the point where the recognized interference occurs (S24). The asynchronous time t _sync is calculated (S25). 7 shows the noise level when executing the time-domain cell average-constant error alarm probability (CA-CFAR). The signal obtained in the time domain and the CA-CFAR noise level calculated using the same are compared to determine that the interference occurs when the noise level is exceeded. In addition, the time (the time at which the interference occurs) at the point where the signal having the maximum magnitude is received among the time points at which the interference occurs is defined as t _Int .

Where T is the modulation time, BW is the bandwidth, and Δf _B is the center frequency interval between the two radars.

As shown in FIG. 7D, the waveform of the radar to be synchronized to move the time domain of the radar to be synchronized with the reference radar to the previous time point by asynchronous time t _sync is 71 to 77. By controlling to remove the interference (S26).

FIG. 5 is a flowchart illustrating a synchronization procedure when interference occurs in case of linear frequency modulation (LFM) (2 in FIG. 2).

5 is a diagram illustrating a synchronization method when interference occurs in the linear frequency modulation (LFM) section of FIG. 3, and FIG. 8 is a schematic diagram of FIG. 5.

In case of interference in the linear frequency modulation (LFM) section, the synchronization method in the LFM section hops up the center frequency (f _c ) of the radar to synchronize with the reference radar by f _H as shown in Equation 5 (S27) The time domain CFAR is executed (S28), and the number of upward hops i is repeatedly increased by 1 until there is no interference in the linear frequency modulation (LFM) section. When interference occurs in a linear frequency modulation (LFM) section as shown in (82) of FIG. 8, when the center frequency of the radar 81 to be synchronized as shown in (a) of FIG. 8 is lower than the center frequency of the reference radar Occurs. As shown in (b) of FIG. 8, the radar to be synchronized after the first upward leap becomes (81) to (83), and the interference occurs as shown in (85) in the continuous wave (CW) section by determining the presence or absence of interference. After another uplift, the radar to be synchronized is from 83 to 84, and in step S29 it is determined whether the LFM interval interference (S29) and if the interference does not exist, the frequency hopping stops. The radar to be synchronized is in the state of 84, where the center frequency separation from the reference radar is always 0.5 * Δf.

Here, i is a natural number when the interference existing in the continuous wave (CW) period disappears, Δf is a maximum frequency deviation from the carrier frequency of the carrier of the radar, f _c is the initial The center frequency, f _c 'is the center frequency after the jump, F _min is the lowest frequency available band, F _max is the highest frequency available band.

In FIG. 8C, the radar to be synchronized is forced by a time delay T / 2 through waveform control (S30). The radar to be synchronized through one time delay is from 84 to 86, and the time-domain cell average-constant alarm probability (CA-CFAR) algorithm is executed (S31) to check for continuous wave (CW) interval interference. If it is determined (S32) that there is no interference, the number of times (i) is increased by one and a time delay of one T / 2 is executed.

The radar to be synchronized is from 86 to 87, and if interference occurs in the continuous wave (CW) section as shown in (88) (S32), the time forced delay through the waveform control is stopped. The forced time delay can be executed up to three times and four times (T / 2 * 4 times = 2T) will return to the original waveform.

The radar to be synchronized is shown in (c) to (87) of FIG. 8 due to the frequency hopping and time forced delay, and the interference point recognized by executing the time domain CA-CFAR algorithm as shown in (d) of FIG. The time t _Int is calculated (S33), and the asynchronous time t _sync is calculated by the following equation (6) (S34).

Where T is the modulation time, BW is the bandwidth, and Δf is the maximum frequency shift from the center frequency of the carrier of the radar.

As shown in FIG. 8E, the waveform of the radar to be synchronized to move to the previous time point by the asynchronous time t _Sync is controlled (from 87 to 89) to remove the interference (S35).

As shown in (f) of Figure 9, the center frequency of the radar returns to want to tune the synchronization by _H -f central downward (as in (89) (8A)) bound to the original frequency by (S36).

FIG. 6 is a flowchart of a synchronization procedure when no interference is detected (3 in FIG. 2 and 4 in FIG. 2).

FIG. 6 illustrates a synchronization method when interference is not recognized in both a continuous wave (CW) section and a linear frequency modulation (LFM) section, and FIG. 9 is a schematic diagram of FIG. 6.

If no interference occurs, it occurs when synchronization is perfectly matched and when the asynchronous time is greater than the modulation time T. It determines whether there is interference through time forced delay by T / 2 and applies algorithm according to the interval of interference occurrence. The forced execution delay is executed up to three times. If the interference is not recognized even after three times, it occurs because the center frequencies between the radars to synchronize with the reference radar are the same. Should be.

The following is a method of synchronizing the radar when the interference is not recognized.

① The radar to synchronize with the reference radar forcibly delays the time by T / 2 through the waveform control (S37).

② The radar to be synchronized is executed by the time domain CFAR (S38) to determine whether there is interference (S39), and if the interference does not occur and i <3 condition (S41), the waveform is controlled by the time forced delay T / 2. Do

If i <3 is not satisfied (S41), the radar to synchronize with the reference radar reselects and initializes the center frequency (S42).

③ If it is determined whether or not interference in the continuous wave section (S40), if the interference occurs, the synchronization algorithm is performed in the continuous wave (CW) section at the time when the interference occurs respectively according to the continuous wave (CW) section and linear frequency modulation (LFM) section interference A synchronization method when an interference occurs, and a synchronization method when an interference occurs in a linear frequency modulation (LFM) section, respectively.

9A illustrates a case where the center frequency of the radar to be synchronized is higher than the reference radar. As shown in (b) of FIG. 9, when time forced delay is performed through the waveform control of the radar to be synchronized, it becomes (91) to (92). Becomes (93). As shown in (94) of FIG. 9, since the interference occurs in a continuous wave (CW) section of the radar to be synchronized, the algorithm of FIG. 4 may be used.

9C is a case where the center frequency of the radar to be synchronized is lower than the reference radar. As shown in FIG. 9 (d), when time forced delay is performed through the waveform control of the radar to be synchronized, 94 to 95 is obtained. As shown in (96) of FIG. 9, since the interference occurs in the linear frequency modulation (LFM) section of the radar to be synchronized, the synchronization algorithm of the radar of FIG. 5 may be used.

10 illustrates a synchronization method for interference cancellation when three or more radars are operated at the same time. Once the radar is synchronized, the inter-radar interference signal is removed until the power is turned off.

When three or more radars are operated simultaneously, the synchronization method for interference elimination is (a) to turn on the radar, turn on the reference radar only to transmit radio waves, set a reference radar for synchronization Determining an interference by applying power to waveforms 101, 102, and 103 of radars I, II, and III to be synchronized with the reference radar; (b) When the radar I is synchronized with the reference radar, the power of the high frequency devices of the radars II and III is turned off, and an interference synchronization algorithm occurs in the linear frequency modulation (LFM) section. Removing interference through synchronization between the two radars, turning off the high frequency devices of the synchronized radars, and turning on the high frequency devices of the other non-synchronized radars in the same manner to synchronize the reference radars; (c) When the radar II is synchronized with the reference radar, the high frequency devices of the radar I and III are turned off, and when the interference occurs in the continuous wave (CW) section, the CW section synchronization algorithm is used. Removing interference through synchronization between two radars; And (d) in case of occurrence of linear frequency modulation (LFM) interval interference, eliminating interference through synchronization between two radars using an LFM interval synchronization algorithm.

FIG. 10 (a) shows the waveforms assigned to the radar when the initial power is applied, and the waveforms of the radars I, II, and III to determine and synchronize the reference radar for synchronization for interference cancellation. (101), (102), and (103), respectively, were arbitrarily determined.

The radars that are to be synchronized with each other are synchronized with the reference radar using the aforementioned method while operating by powering up a high frequency device.

10 (b) shows a synchronization process of the radar I to synchronize with the reference radar. At this time, the power of the high-frequency devices of the radar II, III proceeds to the off state, the interference 105 generated in the linear frequency modulation (LFM) section using a synchronization algorithm when the interference occurs in the linear frequency modulation (LFM) section of FIG. Synchronization between the two radars eliminates interference.

Once the synchronization is complete, the radar is powered off.

In the same way, the high frequency components of the remaining unsynchronized radars are turned on to synchronize the reference radars.

10 (c) shows the synchronization process of the radar II to synchronize to the reference radar. At this time, the power of the high-frequency devices of the radar I, III is turned off, and the interference 107 generated in the continuous wave (CW) section is synchronized between the two radars using the synchronization algorithm when the continuous wave (CW) section interference occurs in FIG. Remove interference.

10 (d) shows a synchronization process of radar III to synchronize with a reference radar. At this time, the power of the high-frequency devices of the radar I, II proceeds to the off state, the interference 109 generated in the continuous wave section by the synchronization algorithm when the interference occurs in the continuous wave (CW) section of FIG. Remove

When all the radars that you want to synchronize are synchronized, you can turn on and operate all of the radar's high-frequency devices.

The frequency modulated continuous wave (FMCW) radar, which attempts to synchronize three or more with respect to the reference radar, returns to the original waveform by controlling the waveform generator when the final synchronization is completed to remove the interference signal.

As described above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited thereto, and various changes and applications may be made without departing from the technical spirit of the present invention. Self-explanatory Accordingly, the true scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of the same should be construed as being included in the scope of the present invention.

CW: Continuous Wave
LFM: Linear Frequency Modulation
t _sync : asynchronous time
t _Int : Interference point occurrence time (time at which the maximum size signal is received among the interference occurrence points)

Claims (9)

In the system-to-system synchronization method for interference cancellation in a frequency modulated continuous wave (FMCW) radar,
(a) To synchronize the reference radar using the Cell Averaging-Constant False Alarm Rate (CA-CFAR) in the time domain to determine if two radars are operating simultaneously. When a synchronization command is generated from the radar, the signal is changed to a continuous wave-linear frequency modulation (CW-LFM) waveform, and the radar signal is acquired to detect the interference of the received signal through the time domain CFAR. Determining;
(b) synchronizing between radar systems when interference occurs in a continuous wave (CW) section;
(c) synchronizing between radar systems when interference occurs in a linear frequency modulation (LFM) section;
(d) if the occurrence of interference has not been detected, synchronizing; And
(e) when the same type of radar synchronization is completed, controlling the waveform generator to return to the original waveform;
Inter-system synchronization method for interference cancellation in a frequency modulated continuous wave radar comprising a. The method of claim 1,
The step (b)
(b1) The center frequency f _c of the radar to be synchronized is set to f _H =-(i + 0.5) * Δf (where i is a downward jump when the interference existing in the continuous wave (CW) period disappears). F, delta f: the maximum frequency shift from the carrier frequency of the radar, and the time domain CFAR is executed repeatedly until there is no interference in the continuous wave (CW) section, and the presence or absence of interference in the continuous wave (CW) section Determining;
(b2) When the center frequency of the radar to be synchronized is higher than the center frequency of the reference radar, if interference occurs in the continuous wave (CW) section, between the two radars through the frequency up leap of the radar to be synchronized Center frequency spacing (

(k is a number equal to the number of down hops i when the interference existing in the continuous wave section disappears, Δf: a predetermined frequency interval between radars);
(b3) after the hopping of the radar to be synchronized, the center frequency f _c ′ is hopped upward by -f _H to return to the original center frequency;
(b4) time-domain cell average - calculating a certain false alarm probability (CA-CFAR) by executing the algorithm generated the interference point generated in a continuous period of time (with a full-size signal of the time the interference at the receiving point of time) t _Int And the asynchronous time (t _sync )

Calculating by the formula (where T: modulation time, BW: bandwidth, Δf _B : center frequency interval between two radars); And
(b5) removing interference by controlling a waveform of the radar to be synchronized so as to move to a previous time point by an asynchronous time (t _sync ) in the time domain of the radar to be synchronized;
Inter-system synchronization method for interference cancellation in a frequency modulated continuous wave radar comprising a. The method of claim 1,
In step (c), when interference occurs in a linear frequency modulation (LFM) section,
(c1) The center frequency f _c of the radar to be synchronized is f _H = (i + 0.5) * Δf (i is the number of upward hops when the interference existing in the linear frequency modulation (LFM) period disappears) The upward hopping is performed, and the time-domain cell average-constant error alarm probability (CA-CFAR) Executing the algorithm repeatedly increasing the number of upward hops i by 1 until there is no interference in the linear frequency modulation (LFM) interval;
(c2) If there is no interference in the linear frequency modulation (LFM) section, when interference occurs in the continuous wave (CW) section when the center frequency of the radar to be synchronized is lower than the center frequency of the reference radar, By controlling the waveform of the radar to be synchronized, a time delay (T / 2) is forcibly executed until there is no interference, and time domain CFAR is executed to determine whether CW section interference exists, and if no interference exists. Executing a time delay T / 2 by the number of times i;
(c3) The radar to be synchronized is calculated using the time-domain cell average-constant alarm probability (CA-CFAR) algorithm with frequency hopping and time forced delay to calculate the time point at which the interference occurs (t _Int ), t _sync )

Calculating by the formula (where T: modulation time, BW: bandwidth, Δf: maximum frequency shift from the center frequency of the carrier of the radar);
(c4) removing interference by controlling a waveform of the radar to be synchronized so as to move to an advantage time point by the asynchronous time (t _Sync ); And
(c5) hopping downward of the center frequency of the radar to be synchronized by -f _H to return to the original center frequency f _c ;
Inter-system synchronization method for interference cancellation in a frequency modulated continuous wave radar comprising a. The method of claim 1,
In step (d), if no interference is detected,
(d1) causing the interference by time forced delay (T / 2) by the waveform control of the radar to be synchronized;
(d2) time-domain cell average-scheduled false alarm probability (CA-CFAR) algorithm is executed to determine whether or not interference occurs, and if no interference occurs and i <3 condition, waveform control by time forced delay T / 2 is executed. Making; And
(d3) It is determined whether or not interference occurs in the continuous wave section (CW), and if interference occurs, the continuous wave (CW) section at the time when interference occurs, respectively, according to the continuous wave (CW) section interference and linear frequency modulation (LFM) section interference. Using a synchronization method when interference occurs in and using a synchronization method when interference occurs in the linear frequency modulation (LFM) section;
Inter-system synchronization method for interference cancellation in a frequency modulated continuous wave radar comprising a. The method of claim 1,
In the step (d2),
If the condition is not i <3, the radar to be synchronized, the inter-system synchronization method for the interference cancellation in the frequency modulated continuous wave radar, characterized in that for reselecting and initializing the center frequency. The method of claim 1,
Step (e),
In the two or more frequency modulated continuous wave (FMCW) radars, the waveform is changed through the control of a waveform generator to remove the interference signal, and a continuous wave signal having one frequency is transmitted during the modulation time T, and the modulation width during the next modulation time T. (BW) A signal in which the frequency is continuously modulated is transmitted, and when the final synchronization is completed, the method of the inter-system synchronization for interference cancellation in the frequency modulated continuous wave radar, characterized in that to control the waveform generator to return to the original waveform. The method according to claim 2 or 3,
In order to improve the simultaneous operability of the frequency modulated continuous wave (FMCW) radar, the radar center frequency is applied to the radar system designed to be spaced apart by the maximum frequency deviation (Δf) of the center frequency of the carrier of the radar, and the Δf value is received by the radar. An inter-system synchronization method for interference cancellation in a frequency modulated continuous wave radar characterized in that it is designed to be at least two times by analyzing the information spectrum of the target to be. In the three or more frequency modulated continuous wave (FMCW) radar operating simultaneously, in the synchronization method for interference cancellation,
(a) Waveforms of radars I, II, and III to turn on the radar and turn on only the reference radar to transmit radio waves, determine the reference radar for synchronization to eliminate interference, and synchronize the reference radar Determining the interference by applying power to each of (101, 102, 103) one by one;
(b) When the radar I is synchronized with the reference radar, the power of the high frequency devices of the radars II and III is turned off, and when the interference occurs in the linear frequency modulation (LFM) section, the synchronization algorithm is used. Eliminating interference by synchronizing between the two radars, turning off the high frequency devices of the synchronized radar, and turning on the high frequency devices of the other non-synchronized radar in the same manner to synchronize the reference radar;
(c) When the radar II is synchronized with the reference radar, the high frequency devices of the radar I and III are turned off, and when the interference occurs in the continuous wave (CW) section, the CW section synchronization algorithm is used. Removing interference through synchronization between two radars; And
(d) when linear frequency modulation (LFM) interval interference occurs, eliminating interference by synchronizing between two radars using an LFM interval synchronization algorithm;
Inter-system synchronization method for interference cancellation in a frequency modulated continuous wave radar comprising a. The method of claim 8,
When the three or more frequency-modulated continuous wave (FMCW) radars, respectively, with respect to the reference radar are finally synchronized to remove the interference signal, controlling the waveform generator to return to the original waveform. How to sync between systems for removal.

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