KR101527772B1

KR101527772B1 - METHOD FOR DETECTING TARGET OF FMCW(frequency-modulated continuous wave) RADAR AND FMCW RADAR FOR DETECTING TARGET

Info

Publication number: KR101527772B1
Application number: KR1020140034683A
Authority: KR
Inventors: 김현국
Original assignee: 주식회사 에스원
Priority date: 2014-03-25
Filing date: 2014-03-25
Publication date: 2015-06-10

Abstract

There is disclosed an FMCW radar that performs a target search method and a target search of an FMCW radar. A search method based on a frequency modulation continuous wave (FMCW) radar includes determining a first search range of an FMCW radar, determining a first band pass filter for a first search range and a first band pass sampling frequency And a first filtering and sampling step of filtering the received first signal based on the first band pass filter and sampling the filtered first signal based on the first band pass sampling frequency to generate a second signal can do.

Description

METHOD FOR DETECTING TARGET OF FMCW RADAR AND FMCW RADAR FOR DETECTING TARGET [Technical Field] The present invention relates to an FMCW radar,

The present invention relates to a radar, and more particularly to a frequency-modulated continuous wave (FMCW) radar.

Recently, radar technology, which was used for military purposes, is being promoted as a private technology, and many studies are being carried out for civilian security and automobile navigation. Radar technology, which is widely used in civilian areas, is a pulse type and a continuous wave type.

The pulse scheme uses very low power, but it can have a distance resolution of up to a few centimeters because of the advantage of using a very wide frequency bandwidth. On the other hand, the transmission output is too low, so that it can be used only within about 10m. The continuous wave method has a disadvantage in that it can not use the distance information because it can use a relatively high transmission power and can be used for a long distance but simply extracts the Doppler frequency to detect the target.

In the continuous wave method, the radar technique used to obtain the coarse distance information is Frequency Modulated Continuous Waveform (FMCW). The FMCW method has the advantage that the target can be detected to a long distance because the distance resolution is lower than the pulse method but the high output can be used.

However, the FMCW method still has a disadvantage that the distance resolution is very low compared to the pulse method. Generally, FMCW radar technology requires a large frequency bandwidth and a very large FFT (Fast Fourier Transform) in order to obtain a high distance resolution. However, in the case of a large frequency bandwidth, There is a problem that requires a very high calculation amount and power consumption.

A first object of the present invention is to provide a method for searching a target of an FMCW radar.

A second object of the present invention is to provide an FMCW radar that performs a target search.

According to one aspect of the present invention, there is provided a search method based on a frequency modulation continuous wave (FMCW) radar, comprising the steps of: determining a first search range of an FMCW radar; Determining a first band pass filter and a first band pass sampling frequency for a search range; filtering the received first signal based on the first band pass filter; And a first filtering and sampling step of sampling based on the band-pass sampling frequency to generate a second signal. A FMCW radar-based search method includes determining a second search range of the FMCW radar, determining a second band-pass filter and a second band-pass sampling frequency for the second search range, Further comprising a second filtering and sampling step of filtering the received third signal based on the band pass filter and sampling the filtered third signal based on the second band pass sampling frequency to generate a fourth signal Wherein the first filtering and sampling step and the second filtering and sampling step are performed in parallel. The FMCW radar-based search method may further include searching for the search range based on a signal obtained by FFT (fast fourier transform) of the second signal and a signal obtained by FFT of the fourth signal have. The first band pass sampling frequency and the second band pass frequency may be determined based on the following equation.

&Lt; Equation &

The filtering frequency band of the first band-pass filter is determined based on the mapping table, and the mapping table may include information on a filtering frequency band mapped according to the search distance range.

According to an aspect of the present invention, there is provided a frequency modulation continuous wave (FMCW) radar for performing a search for a target, the FMCW radar including a processor, Determining a first search range of the FMCW radar, determining a first band pass filter and a first band pass sampling frequency for the first search range, and determining a first signal range based on the first signal And perform first filtering and sampling to generate a second signal by sampling the filtered first signal based on the first band pass sampling frequency. Wherein the processor is further configured to determine a second search range of the FMCW radar, determine a second band pass filter and a second band pass sampling frequency for the second search range, And to perform a second filtering and sampling to generate a fourth signal by sampling the filtered third signal based on the second band pass sampling frequency. The processor may be configured to perform a search for the search range based on a signal obtained by FFT (Fast Fourier Transform) of the second signal and a signal obtained by FFT of the fourth signal. The first band pass sampling frequency and the second band pass frequency may be determined based on the following equation.

&Lt; Equation &

As described above, by using the FMCW radar that performs the target searching method and the target searching of the FMCW radar according to the embodiment of the present invention, there is no loss of the signal-to-noise ratio of the processed signal with high distance resolution regardless of the distance .

1 is a graph showing a method of detecting an object using an FMCW radar.
2 is a graph showing a method of detecting an object using an FMCW radar.
3 shows a graph of a bit signal sampled based on DFT.
4 shows a receiver structure of a conventional FMCW radar.
5 is a conceptual diagram showing an existing FMCW radar.
6 is a conceptual diagram showing an existing FMCW radar.
7 is a conceptual diagram showing an FMCW radar according to an embodiment of the present invention.
FIG. 8 is a flowchart showing the operation of the FMCW radar according to the embodiment of the present invention.
FIG. 9 is a flowchart showing the operation of the FMCW radar according to the embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals will be used for the same constituent elements in the drawings, and redundant explanations for the same constituent elements will be omitted.

1 to 3, a general FMCW radar sensing operation will be described.

1 is a graph showing a method of detecting an object using an FMCW radar.

The FWCW radar can measure the distance and velocity of the target by transmitting a frequency modulated continuous signal to the target.

For a typical CW (continuous wave) radar, the speed of a moving object can be measured, but the distance can not be measured due to the relatively narrow bandwidth. Therefore, the FMCW radar modulates the amplitude, frequency, or phase of the transmitted wave to broaden the bandwidth to perform distance measurement and velocity measurement.

Referring to FIG. 1, it is assumed that an object distant from the radar by a distance R is stopped, and the frequency waveform is expressed with time. First, when a linearly frequency modulated signal is transmitted as in the first waveform, it is reflected on an object at a distance R and is received by a radar after a time delay of 2R / c. At this time, if the transmitted signal and the received signal are mixed with each other, the difference frequency can be obtained. The frequency is expressed by Equation 1 below.

&Quot; (1) "

Based on the difference frequency information calculated in Equation (1), the distance R can be determined by substituting into Equation (2) below.

&Quot; (2) "

2 is a graph showing a method of detecting an object using an FMCW radar.

It is assumed that an object at a distance R from the radar is moving at a relative speed Vr.

The FMCW radar can transmit a frequency modulated continuous signal to measure the speed and distance of the target.

In this case, a frequency shift as shown in Equation (3), which is caused by the time delay of 2R / c and the Doppler effect, occurs.

&Quot; (3) "

When the transmitted signal and the received signal are mixed, the sum and the difference of the frequency change fr due to the time-delay and the frequency change fv due to the Doppler effect can be obtained as shown in the lower part of FIG. 2, Distance and velocity information can be obtained as shown in Equation 4.

&Quot; (4) "

The bit frequency and the Doppler frequency can be obtained by signal processing.

The bit frequency may represent the difference between the transmitted signal and the received signal. The bit frequency is expressed by fbu when it is the provider pf, and the frequency when it is down-pfed can be expressed by fbd.

The frequency spectrum of the bit signal sampled at the frequency fs can be obtained by performing a discrete fourier transform (DFT) of Ns points in each chirp cycle. Based on the frequency spectrum of the bit signal determined in the FMCW radar, the surrounding environment can be sensed to detect objects in the surroundings. The FMCW radar can still transmit the sensing signal of the FMCW radar while the signal receiver of the FMCW radar receives the signal reflected from the target. The FMCW radar can mix the waveform of the received signal and the transmitted sensing signal to generate a bit signal. If there is more than one target, the output of the mixer may be a bit signal having one or more different frequency bands.

3 shows a graph of a bit signal sampled based on DFT.

Referring to FIG. 3, it is a spectrum of a bit signal sampled at a frequency fs by performing DFT of Ns points in each chirp cycle.

Delta-f is the frequency step and Ns is the number of data samples in the chirp period T.

In the case of the FMCW radar, the target information is generated by pairing the frequency peak information extracted from the up chirp and the down chirp, respectively.

The bit frequencies detected in the up chirp, which is the frequency rising period and the down chirp, which is the frequency falling period, are fbu = fr-fd and fbd = fr + fd. That is, fbu and fbd are values shifted symmetrically with respect to fr as a + -fd value. Therefore, when the combination is found, the distance and speed can be obtained. This method is called a pairing algorithm.

In performing the pairing algorithm, more than target can be detected when there are two targets, and these targets are called ghost targets. When such a ghost target exists, it is difficult to accurately sense the object in the FMCW radar.

When the pairing algorithm is executed, as the number of targets is increased, a lot of ghost targets are generated. Various techniques are used to prevent the ghost target from being generated. However, as the frequency peak extracted from the upchip / downchuck increases, the probability of occurrence of the ghost target increases. In the case where a structure is spread over a road such as a tunnel or a guard rail, there may occur a situation where the radar is difficult to be sensed further. In such a case, detection of the radar and control stability may be threatened by the occurrence of the ghost target .

Such an FMCW radar can detect an object through a beam generated based on a frequency modulation scheme within a conventional wide frequency bandwidth. In FMCW radar, most antennas can be operated with high gain for long detection distances. The high gain array antennas have narrow radiation pattern characteristics. Due to the narrow radiation pattern characteristic, a method of spatially radiating a radiation beam of an FMCW radar electrically or mechanically must be used in order to detect a space based on a two-dimensional space detection radar. However, in this case, the increase of material cost and development cost in the implementation of FMCW radar causes an increase in the overall radar development unit price. Also, due to the complexity of the design, there is a limit to mass production of FMCW radar. Therefore, there is a need in the radar market for a method of scanning a radiation beam in addition to a method of adjusting the radiation beam using an active element or scanning a beam using a mechanical motor.

In the present invention, an FMCW radar using a metamaterial leak-spectrum antenna is applied to solve the problem, and a FMCW radar using the antenna array is described. Hereinafter, an FMCW radar according to an embodiment of the present invention will be referred to as a space detection scanning FMCW radar.

In the conventional FMCW radar technology, sampling is performed only on a desired band based on a bandpass filter for a specific frequency band without using a frequency mixer which is a cause of nonlinear problems in the receiver of the FMCW radar After that, we proposed a signal processing system. Using this method has the advantage of not requiring a frequency mixer, but it requires a high sampling frequency and has no improvement in distance resolution.

In addition, in the conventional FMCW radar technology, a method of increasing the distance resolution of a vehicle FMCW radar system has been proposed. We have published a method with a low distance resolution in a long distance and a high distance resolution in order to obtain precise distance information at a close distance. However, such a technique has not been used in a system requiring a high distance resolution even in a real distance. In addition, since the FFT is performed after the decimation, the distance resolution can be improved. However, the loss of the signal-to-noise ratio due to decimation is reduced by decimation It can have a disadvantage that it can not be done at the same time.

4 shows a receiver structure of a conventional FMCW radar.

In the conventional FMCW radar disclosed in FIG. 4, a signal received through an antenna may pass through a VCO (Voltage Controlled Oscillator) 410 and a frequency mixer (400). The signal passed through the VCO 410 and the frequency mixer 400 may be lowpass filtered through the low-pass filter 420. The low-pass filtered signal is amplified by passing through an intermediate frequency amplifier 430. The signal that has passed through the intermediate frequency amplifier 430 is sampled and then a fast Fourier transform (FFT) Lt; / RTI > This conventional FMCW radar has the disadvantage that the distance resolution is much lower than that of the pulse type radar.

5 is a conceptual diagram showing an existing FMCW radar.

In the conventional FMCW radar published in Fig. 5, selective bandpass filtering can be performed on the signal.

Referring to FIG. 5, the signal received by the antenna may be subjected to a selective bandpass filtering (510) after passing through a wideband amplifier 500. After performing the selective bandpass filtering on the signal, it may perform sampling 520 and perform signal processing 530.

The existing FMCW radar disclosed in FIG. 5 may not use a frequency mixer which causes a non-linear problem in the receiver, unlike the FMCW radar shown in FIG. It is possible to perform filtering on a specific frequency band through selective band pass filtering to perform sampling only on a desired band, and then process the signal. When using the method disclosed in FIG. 5, there is an advantage that a frequency mixer is unnecessary compared with the FMCW radar shown in FIG. However, it has a disadvantage in that a high sampling frequency is required and there is no improvement in distance resolution.

6 is a conceptual diagram showing an existing FMCW radar.

In the case of the FMCW radar disclosed in FIG. 6, the operation to the intermediate frequency signal extracting part may be the same as the operation of the FMCW radar disclosed in FIG. 4 and FIG. A long-range, a middle-range, and a short-range can be sensed based on a signal obtained by extracting an intermediate frequency signal.

Referring to FIG. 6, an FFT 600 is performed on the original distance to obtain a low range resolution for a long distance. N / 2 decimation 610 (where N is the FFT size) is performed for the intermediate distance and then zero padding is performed followed by the FFT 620 to obtain the intermediate distance resolution .

For short distances, N / 4 decimation 650 may be performed and zero padding may be performed followed by FFT 660 to obtain high range resolution at near.

When using the method disclosed in Fig. 6, it can have a high distance resolution for obtaining accurate distance information at a short distance. However, in a system requiring a high range resolution even in a real distance, the FMCW radar disclosed in FIG. 6 may not be used because a longer range has a lower range resolution. In addition, the distance resolution can be improved because the FFT is performed after the decimation, but the loss of the signal-to-noise ratio due to the decimation may be disadvantageously caused by the decimation. have.

7 is a conceptual diagram showing an FMCW radar according to an embodiment of the present invention.

In the case of using the method disclosed in Fig. 7, not only a high distance resolution can be obtained even for a long distance, but there is no loss of signal-to-noise ratio because no decimation is used.

Referring to FIG. 7, up to the intermediate frequency signal extracting part may be the same as the conventional FMCW radar. The signal can be amplified through an intermediate frequency amplifier. The FMCW radar according to an embodiment of the present invention performs different filtering and different sampling on an intermediate-frequency-amplified signal through an intermediate frequency amplifier to obtain a high range resolution for a selected distance or a high range resolution for an entire range FMCW radar can be implemented.

The FMCW radar according to the embodiment of the present invention can sample the intermediate frequency amplified signal 720 and then perform the FFT 725 to extract the first signal. The first signal may have a low range resolution for the all-range.

In addition, the FMCW radar according to the embodiment of the present invention can have a high distance resolution with respect to a search distance to be sensed through a band pass filter determined for each search distance before sampling the intermediate frequency amplified signal. Band pass filtering can determine various filtering bands along the desired distance of sensing.

7, a signal that is first bandpass filtered 700 may be determined as a second signal via sampling 730 and FFT 735, and the second bandpass filtered 710 signal may be sampled 740 and And may be determined as the third signal via the FFT 745. [ That is, after performing bandpass filtering individually through at least one band-pass filter determined according to the search frost before sampling, separate band-pass sampling according to the band-pass filter can be performed. By using this method, the FMCW radar can have high range resolution for all range areas to be searched.

Each of the band pass filters according to the embodiment of the present invention can pass a sub-band obtained by dividing the entire frequency band into a plurality of bands (for example, M regions). Each of the plurality of bandpass signals having passed through each of the different bandpass filters can perform FFT after performing different bandpass sampling.

The frequency of the band-pass sampling for sampling the band-pass signal according to the embodiment of the present invention can be determined by the following equation.

&Lt; Equation &

If bandpass filtering is performed by dividing the entire frequency bandwidth into M frequency regions, the sampling frequency may be significantly lowered by fs / M, so that the sampling frequency may be significantly lowered. The size of the received data is still N, so an N-sized FFT is performed. Therefore, in the case of using the FMCW radar according to the embodiment of the present invention, the range-resolution is calculated as the existing distance resolution / M regardless of the distance, such as the distance and the near distance, Can be obtained.

Also, since no decimation is performed as in the conventional FMCW radar, there is no loss of signal-to-noise ratio. For example, assuming that an existing FMCW radar performs N / 4 decimation, a signal-to-noise ratio improvement of 6 dB can be achieved by using the FMCW radar according to the embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the FMCW radar according to the embodiment of the present invention.

In FIG. 8, the FMCW radar publishes a method for selectively searching for a specific distance range. However, as described above, the FMCW can perform bandpass filtering for various range of distances and synthesize the filtered signals for these various ranges of distances to obtain high distances for all ranges such as short, medium, and long distances Filtering with resolution may be performed.

Referring to FIG. 8, a search range is determined for an FMCW radar (Step S800).

The FMCW radar according to the embodiment of the present invention can perform band pass filtering and band pass sampling according to the search distance. Therefore, the FMCW radar can first determine for the range of distances to be searched.

A bandpass filter and a bandpass sampling frequency for the determined search distance range are determined (step S810).

The entire frequency band may be divided into a plurality of bands and the band pass sampling frequency according to the pass band and the pass band of the band pass filter may be determined for the search distance range selected by step S800. The relationship between the search distance range and the pass band of the band pass filter may be predetermined and the pass band of the band pass filter according to the search distance range may be determined based on this relationship. The band-pass sampling frequency may be determined based on the above-described equation.

A plurality of band pass filters and a band pass sampling frequency can be set according to the band that the FMCW radar is intended to sense.

The intermediate-frequency amplified signal is filtered by the determined band-pass filter, and the signal filtered by the band-pass filter is sampled based on the band-pass sampling frequency (step S820).

The intermediate frequency amplified signal may be band-pass filtered and band-pass sampled based on the band-pass filter and the band-pass sampling frequency determined in step S810 to calculate a sampling signal.

The calculated sampling signal is FFT-processed and the search is performed based on the calculated signal (step S830).

The calculated sampling signal is FFT-processed to search for the selected search range based on the calculated signal.

9 is a flowchart showing the operation of the FMCW radar according to the embodiment of the present invention.

In FIG. 9, an FMCW radar is selectively searched for a specific distance range. The FMCW radar includes a search distance determination unit 900, a band pass filter determination unit 910, a band pass sampling frequency determination unit 920, a band pass filtering unit 930, a band pass sampling unit 940, an FFT unit 950 And a processor 980. The components included in the FMCW radar shown in FIG. 9 are used to illustrate the present invention, and components of another FMCW radar, an antenna, an intermediate frequency amplifier, and the like are not shown. Also, the configuration unit shown in FIG. 9 is divided to express the operation of the FMCW radar functionally, and one configuration unit may be implemented as a plurality of configuration units, or a plurality of configuration units may be implemented as one configuration unit.

The search distance determination unit 900 may be implemented to determine the search distance to be searched by the FMCW radar.

The band pass filter determination unit 910 can be implemented to determine a band pass filter to perform band pass filtering according to the distance determined by the search distance determination unit 900.

The band-pass sampling frequency determiner 920 may be implemented to determine a sampling frequency for a signal that has undergone band-pass filtering according to the distance determined by the search distance determiner 900. The band-pass sampling frequency determiner 920 can determine a sampling frequency for a signal that has undergone band-pass filtering based on the above-described equation.

The bandpass filtering unit 930 may be implemented to filter the intermediate frequency amplified signal with a determined bandpass filter.

The band-pass sampling unit 940 may be implemented to sample the signal filtered by the band-pass filter based on the band-pass sampling frequency.

The FFT unit 950 may be implemented to FFT the band-pass sampled signal.

The processor 980 includes a search distance determiner 900, a bandpass filter determiner 910, a bandpass sampling frequency determiner 920, a bandpass filter 930, a bandpass sampler 940, Lt; RTI ID = 0.0 > 950 < / RTI >

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims

In a frequency modulation continuous wave (FMCW) radar-based search method,
Determining a first search range of the FMCW radar;
Determining a first bandpass filter and a first bandpass sampling frequency for the first search range; And
A first filtering and sampling step of filtering a first signal received based on the first bandpass filter and sampling the filtered first signal based on the first bandpass sampling frequency to generate a second signal, FMCW radar based navigation method that includes.

The method according to claim 1,
Determining a second search range of the FMCW radar;
Determining a second bandpass filter and a second bandpass sampling frequency for the second search range;
A second filtering and sampling step of filtering a third signal received based on the second band pass filter and sampling the filtered third signal based on the second band pass sampling frequency to generate a fourth signal, Further included,
Wherein the first filtering and sampling step and the second filtering and sampling step are performed in parallel.

3. The method of claim 2,
Further comprising performing a search on the search range based on a signal obtained by performing an FFT (Fast Fourier Transform) of the second signal and a signal obtained by FFT of the fourth signal.

The method of claim 3,
Wherein the first band-pass sampling frequency and the second band-pass sampling frequency are determined based on the following equation:
&Lt; Equation &

FMCW radar based navigation method.

5. The method of claim 4,
Wherein the passband of the first band-pass filter is predetermined for each search distance.

1. A frequency modulation continuous wave (FMCW) radar for performing a search on a target, the FMCW radar comprising a processor,
Wherein the processor determines a first search range of the FMCW radar,
Determining a first bandpass filter and a first bandpass sampling frequency for the first search range,
Performing first filtering and sampling to filter a first signal received based on the first band pass filter and to generate a second signal by sampling the filtered first signal based on the first band pass sampling frequency FMCW radar implemented to be

The method according to claim 6,
Wherein the processor determines a second search range of the FMCW radar,
Determine a second bandpass filter and a second bandpass sampling frequency for the second search range,
Performing second filtering and sampling to filter a third signal received based on the second band pass filter and to generate a fourth signal by sampling the filtered third signal based on the second band pass sampling frequency FMCW radar implemented to be

8. The method of claim 7,
Wherein the processor is configured to perform a search for the search distance range based on a signal obtained by FFT (Fast Fourier Transform) of the second signal and a signal obtained by FFT of the fourth signal.

9. The method of claim 8,
Wherein the first band-pass sampling frequency and the second band-pass sampling frequency are determined based on the following equation:
&Lt; Equation &

FMCW radar.

10. The method of claim 9,
Wherein the passband of the first band-pass filter is predetermined for each search distance.