WO2020085656A1

WO2020085656A1 - Antenna for radar

Info

Publication number: WO2020085656A1
Application number: PCT/KR2019/012186
Authority: WO
Inventors: 최수호; 양희진
Original assignee: (주)디지탈엣지
Priority date: 2018-10-25
Filing date: 2019-09-20
Publication date: 2020-04-30
Also published as: KR101963384B1

Abstract

The present invention relates to an antenna for radar, comprising: a first array for radiating a signal in one direction; a second array for radiating a signal in the opposite direction as the first array; and a feed part for supplying a signal to the first array and the second array, wherein the first array and the second array comprise a plurality of first emitters and second emitters alternately provided to radiate a signal in a direction opposite to each other, and, in a direction in which the first and second emitters do not radiate, a parasitic element for broadening a band by resonating at a frequency near the first and second emitters is disposed, so that a wide bandwidth of 4 ㎓ exists at the center frequency of 79 ㎓, and a range resolution can be improved.

Description

Radar Antenna

The present invention relates to an antenna for a radar, and more particularly, to a radar antenna for transmitting a radar signal and receiving a radar signal reflected from a surrounding obstacle.

The radar sensor is a sensing means that transmits radio waves using microwaves and receives distance, velocity, and angle information by receiving some reflection signals reflected from the target.

These radar sensors include Pulsed Doppler Radar, Frequency Modulated Continuous Wave (hereinafter referred to as 'FMCW'), and Stepped-Frequency Continuous Wave (hereinafter referred to as 'SFCW'), frequency Target information is measured using various radar waveforms such as shift shift keying (hereinafter referred to as 'FSK').

The present applicant has registered and applied for a patent by initiating a radar sensor technology in a number of patent documents 1 and 2 below.

Meanwhile, the vehicle radar is classified into a long-range radar device (Long Range Radar, LRR) and a medium-range radar device (Middle Range Radar, MRR) and a short-range radar device (Short Range Radar (SRR) or Blind Spot Detection (BSD)). Can be.

Among them, the LRR and MRR for detecting the front of a vehicle mainly use a frequency of 77 ㎓ band, and the SRR or BSD for detecting the rear side of a vehicle uses a frequency of 24 ㎓ band.

The antenna applied to the vehicle radar sensor is used to obtain special characteristics, and when complex structures such as chebyshov, binomial, and taylor are applied to the array antenna, for the feeding of each radiating element, Complex feeding circuits are required. Therefore, there is a disadvantage in that the development period of designing and optimizing the performance of an array antenna having a complicated power supply circuit is prolonged.

Therefore, the patch array antenna for the 24㎓ or 77㎓ band is designed to uniformly input the magnitude and phase of the current to each patch in order to solve the above problems due to design complexity.

However, since the array antenna having a uniform size and phase of the current input to the patch shows a high side lobe level characteristic, there is a problem in that the sensing area is very non-uniform.

In addition, when the detection area of the radar detector is very narrow, the side lobe level of the beam generated from the array antenna is high, and thus it is difficult to generate a narrow and uniform width beam using only the radar algorithm.

Accordingly, the applicant has filed and registered a patent application for a radar antenna technology having high gain and low side lobe level characteristics in Patent Document 3 below.

However, in recent years, the frequency of the 79 kHz band, which replaces the 24 kHz frequency band, is mainly used in SRR or BSD.

Since the 79 ㎓ band has a bandwidth of 4 넓은 wider than the 24 ㎓ band having a bandwidth of 250 MHz, it has excellent distance resolution (or range resolution) performance, and enables precise target detection at a short distance.

And in the case of SRR using the 79㎓ band, it has a wide-angle characteristic by detecting a wide range in the azimuth direction at a short distance.

The SRR using the 79㎓ band with such a wide beam width is used as a radar for the front and rear of the vehicle, and can detect short-range targets in a wide range when driving at intersections, and has high distance resolution due to the use of a wide bandwidth. There are characteristics.

The distance resolution refers to a minimum distance difference that can be identified even when two targets in the same direction are approached from the radar.

The distance resolution can be calculated by Equation 1.

[Equation 1]

Where ΔR is the distance resolution and BW is the bandwidth.

As can be seen from Equation 1, as the bandwidth increases, the distance resolution decreases, thereby enabling precise distance measurement.

On the other hand, Figure 1 is a graph showing a radiation pattern of a radar antenna according to the prior art using a frequency band of 79 kHz.

When using the 79 kHz frequency band having a wide bandwidth of 4 kHz, as shown in FIG. 1, as the center frequency is changed from 77 kHz to 81 kHz, the elevation beam characteristic of the antenna beam is at 0 degrees. There was a problem in that a deviation occurred while shaking in the left and right directions without being fixed.

As such, when using a wide bandwidth, the elevation antenna pattern error should be small. In addition, the antenna design for a radar having a wide wide-angle characteristic should be designed with a wide left and right beam width, and a left-right symmetric characteristic based on 0 degrees as an azimuth axis.

However, a wide-angle antenna using a frequency of 77 kHz is commercially available, but the frequency bandwidth is only a maximum of 1 kHz, and no antenna considering the above-mentioned 77 kHz to 81 kHz broadband characteristics exists.

As a result, among the advanced driver assistance systems (ADAS) applied to autonomous vehicles, the 77 ㎓ band SRR radar sensor applied for the front and rear sides detects a wide area in all directions around the vehicle. In order to do this, up to eight vehicles must be installed.

[Advanced technical literature]

(Patent Document 1) Korean Patent Registration No. 10-1513878 (announced on April 22, 2015)

(Patent Document 2) Korean Patent Registration No. 10-1505044 (announced on March 24, 2015)

(Patent Document 3) Korean Patent Registration No. 10-1841685 (announced on March 27, 2018)

An object of the present invention is to solve the above problems, to provide a radar antenna having a wide bandwidth of 4 kHz in the frequency band of the central frequency 79 kHz, and can improve the distance resolution.

Another object of the present invention is to provide an antenna for a radar capable of preventing the occurrence of left and right deviations of elevation beamwidth due to a change in the center frequency in order to use a wide band in a radar antenna using a center frequency band of 79 GHz. will be.

Another object of the present invention is to provide an antenna for a radar capable of maintaining symmetrical left and right when a wide azimuth beam width is designed to expand a radar detection area.

Another object of the present invention is to provide an antenna for a radar capable of minimizing the number of radars installed in a vehicle.

In order to achieve the above object, the antenna for radar according to the present invention includes a first array that radiates a signal in one direction, a second array that radiates a signal in a direction opposite to the first array, and the first and It includes a power supply for supplying a signal to the second array, the first array and the second array each includes a plurality of first radiators and second radiators that are cross-installed to radiate signals toward opposite directions, respectively. In the non-radiating directions of the first and second radiators, parasitic elements resonating at frequencies adjacent to the first and second radiators are arranged to implement broadband.

As described above, according to the radar antenna according to the present invention, the effect of having a wide bandwidth of 4 kHz in the frequency band of the central frequency of 79 kHz and improving the distance resolution is obtained.

In addition, according to the present invention, a multi-array antenna is designed in a radar antenna using a center frequency band of 79 kHz, and an effect that a high angle beam width can be minimized is obtained.

In addition, according to the present invention, the effect of preventing the occurrence of left and right deviations of the high angle beam width according to the change in the center frequency for using the broadband can be obtained.

In addition, according to the present invention, when designing a wide azimuth beam width to expand the radar detection area, an effect that the symmetry can be maintained can be obtained.

As a result, according to the present invention, by designing a wide-band and wide-angle antenna, it is possible to detect a target for an omnidirectional (360-degree) area of a vehicle using a small number of radars, thereby minimizing the number of radars installed in the vehicle. The effect that can be obtained.

1 is a graph showing a radiation pattern of a radar antenna according to the prior art,

2 is a plan view of a radar antenna according to a preferred embodiment of the present invention,

3 is a partially enlarged view of the antenna for radar shown in FIG. 2,

4 to 7 is a graph showing the radiation pattern of the radar antenna shown in Figure 2,

8 is a graph showing the return loss of the radar antenna.

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

2 is a plan view of a radar antenna according to a preferred embodiment of the present invention, and FIG. 3 is a partially enlarged view of the radar antenna shown in FIG. 2.

Hereinafter, terms indicating directions such as 'left', 'right', 'front', 'rear', 'upper' and 'downward' are defined to indicate each direction based on the state illustrated in each drawing. do.

Radar antenna 10 according to a preferred embodiment of the present invention, as shown in Figure 2, the first array 20 that radiates a signal in one direction, the first array 20 and the signal toward the opposite direction It includes a second array 30 to radiate and a power supply unit 40 to supply signals to the first and

second arrays

20 and 30.

The first array 20 and the second array 30 each include a plurality of first radiators 21 and second radiators 31, and the first and

second radiators

21 and 31 are in opposite directions to each other. It can be cross-installed along a row to emit a signal towards.

In detail, the first array 20 includes a plurality of first radiators 21 disposed on one straight line, and the second array 30 is disposed between the plurality of first radiators 21. It includes a plurality of second radiators (31).

Here, the first radiator 21 and the second radiator 31 may be symmetrically arranged to radiate signals toward opposite directions, respectively.

In addition, a second radiator 31 is disposed between each of the first radiators 21, and the first and

second radiators

21 and 31 may be provided in the same number, respectively.

Meanwhile, the plurality of first and

second radiators

21 and 31 form a radiation pattern of the radar antenna 10.

As the plurality of first and

second radiators

21 and 31 are arranged along the first and

second feeding lines

41 and 42 of the feeding part 40 to be described below, the first and second feeding lines Signals are supplied from (41,42) to each radiator (21,31).

Here, the plurality of emitters may be made of a conductive material including at least one of silver (Ag), palladium (Pd), platinum (Pt), copper (Gu), gold (Au), and nickel (Ni).

On the other hand, between the first and

second radiators

21 and 31, as shown in Figs. 2 and 3, for widebanding the antenna 10 for radar, parasitic in the non-radiating slot direction, that is, above and below, respectively. Element 50 may be installed.

The parasitic element 50 is formed in an approximately square pattern in the space between the first radiator 21 and the second radiator 31, and resonates at frequencies adjacent to the first and

second radiators

21 and 31 to widen the band. It functions to implement.

However, when parasitic elements are installed in each non-radiative slot direction, the length of the radar antenna is unnecessarily long, and manufacturing cost increases.

Therefore, in this embodiment, only one parasitic element 50 is disposed between the first and

second radiators

21 and 31, as shown in FIG. 3.

Therefore, the first and

second radiators

21 and 31 share one parasitic element 50 disposed therebetween.

For this reason, the present invention can arrange one parasitic element between the first and second radiators and share them with each other, thereby minimizing the length of the radar antenna and reducing manufacturing cost.

As described above, according to the present invention, as the parasitic elements disposed between the first and second radiators are arranged in a shared manner, the limited space for designing the radar antenna can be effectively utilized to minimize the overall length of the antenna.

The antenna 10 for the radar is preferably set to 79 kHz as the performance deviation or performance deterioration occurs in a high frequency band.

On the other hand, in general, the width of the main radiator and the parasitic element is designed to be smaller than the length of each element.

In this embodiment, the widths of the first and

second emitters

21 and 31 are smaller than the lengths of the first and

second emitters

21 and 31, but designed as wide as possible, as shown in FIG. 3 to implement wide-angle characteristics. Can be.

Further, the width of the parasitic element 50 may be designed to be slightly larger than the length of the parasitic element 50.

In addition, the first and second radiators (21,31) and the resonant frequencies of the parasitic element (50) are designed to be located in the vicinity for realizing broadband characteristics, and the first and second radiators (21,31) fed directly. The length of the parasitic element 50 to which electromagnetic coupling (coupling) is fed can all be designed to be about 0.5λ.

In addition, in order to separate the resonant frequencies of the two elements, it is designed to give a difference to the lengths of the two elements.

In general, the resonant length of the patch is 0.5λ, and the lengths of the two elements can be designed in the range of 0.4λ to 0.6λ.

In FIG. 2 again, the power supply unit 40 includes a plurality of first power supply lines 41 and second arrays 30 that supply signals to a plurality of first radiators 21 provided in the first array 20. The first and

second feeding lines

41 and 42 are connected to one end of the second feeding line 42 and the first and

second feeding lines

41 and 42 for supplying a signal to the second radiator 31. It may include a feed point 43 for supplying a signal.

The first feed line 41 is disposed on one side of the first array 20, as shown in FIG. 1, and each first radiator 21 of the first array 20 is a first connection line 44, respectively. It can be connected to the first feed line 41 through.

The second feed line 42 is disposed on one side of the second array 30, as shown in FIG. 1, and each second radiator 31 of the second array 30 is respectively a second connection line 45. It can be connected to the second feed line 42 through.

On the other hand, in the radar antenna 10 according to the present embodiment, as the first and

second radiators

21 and 31 are alternately disposed, the radiation pattern in the wide-angle direction, that is, the azimuth direction, of the single antenna is asymmetric.

That is, when a feed line is arranged on one side based on the first and

second radiators

21 and 31, asymmetry occurs based on the azimuth beam width of 0 degrees.

So, in this embodiment, the first and

second feeding lines

41 and 42 are arranged on both sides of the first and

second radiators

21 and 31, and the zigzag is provided through the first and second connecting

lines

44 and 45. Implement the power supply circuit.

As described above, the present invention can eliminate the asymmetry of the beam pattern in the radial direction by applying the structures feeding from the left and right sides of the first and second arrays having asymmetric structures.

In addition, first and

second stubs

46 and 47 may be formed to extend upward at the upper ends of the first feed line 41 and the second feed line 42, respectively.

The first and

second stubs

46 and 47 may provide an effect of suppressing side lobes by reducing power supplied to the first and

second arrays

20 and 30.

Along with this, the first and

second stubs

46, 47 can help regulate the power ratio supplied to the first and second arrays 2, 30.

For example, the lengths of the first and

second stubs

46 and 47 can be designed to be 0.25λ of the center frequency.

And in this embodiment, since the feeding circuit is designed in a zigzag manner for wide-angle lateral symmetry of the radial beam width, and the phases of signals fed to each patch must be the same, the lengths of the first and

second feeding lines

41 and 42 are It can be designed in multiples of λ.

Meanwhile, the feed points 43 and the first and

second feed lines

41 and 42 may be connected by first and

second branch lines

48 and 49.

The first and

second branch lines

48 and 49 may be provided in a diagonal structure that is inclined toward the lower ends of the first and

second feed lines

41 and 42 with respect to the feed points 43, respectively.

As described above, according to the present invention, as the first and second branch lines are arranged in a diagonal structure, the horizontal area at the bottom of the feeding part is minimized, so that the center of the beam in the elevation direction, that is, the vertical direction, can be vertically aligned. The peak can be adjusted to 0 degrees and the side lobe level of the broadband signal can be minimized.

Meanwhile, when designing an antenna, a specific center frequency is selected and designed.

Therefore, in the case of a wide band such as the 79 kHz band described in this embodiment, the center frequency is selected as 79 kHz and designed, and the center frequency is varied and verified from 77 kHz to 81 kHz through simulation.

The simulation check results of the radar antenna according to the preferred embodiment of the present invention will be described with reference to FIGS. 4 to 8.

4 to 7 is a graph showing the radiation pattern of the radar antenna shown in Figure 2, Figure 8 is a graph showing the return loss of the radar antenna.

4 to 7 show antenna gain graphs according to power and angles at 77 Hz to 80 Hz, respectively.

4 to 7, the radar antenna 10 according to the present embodiment suppresses the level of the side lobe to less than -10 dB in all bands of 77 Hz to 80 Hz, thereby reducing the level of the main lobe and the side lobe. It can be seen that the difference is maintained at about 20 dB or more.

And it can be seen that the radar antenna 10 according to the present embodiment satisfies S11 = -10 dB or less in all bands of 77 ㎓ to 81 으로 due to the influence of the power supply line, as shown in FIG. 8.

Therefore, the present invention can effectively propagate a transmission signal through a transmission antenna by satisfying S11 = -10 dB or less for a wide bandwidth of 77 kHz to 81 kHz.

Through the above-described process, the present invention has a wide bandwidth of 4 kHz in the frequency band of the central frequency of 79 kHz and can improve the distance resolution.

In addition, the present invention can design a multi-array antenna in a radar antenna using a center frequency band of 79 GHz and minimize a high angle beam width.

In addition, the present invention can prevent the occurrence of left and right deviation of the elevation beam width according to the change in the center frequency for using the broadband.

In addition, the present invention can maintain left and right symmetry when a wide azimuth beam width is designed to expand a radar detection area.

As described above, according to the present invention, the number of radars installed in the vehicle can be minimized by designing a wide-band and wide-angle antenna and detecting targets in an omnidirectional (360-degree) area of the vehicle using a small number of radars. .

Although the invention made by the present inventors has been described in detail according to the above-described embodiments, the present invention is not limited to the above-described embodiments, and it is needless to say that the invention can be changed in various ways without departing from its gist.

The present invention is applied to antenna technology for radar having wide bandwidth and wide angle characteristics with a wide bandwidth.

Claims

A first array including a plurality of first radiators that emit a signal in one direction,

A second array comprising a plurality of second radiators that emit a signal in a direction opposite to the first array,

A power supply for supplying signals to the first and second arrays, and

And parasitic elements disposed in non-radiating directions of the first and second radiators,

The first and the first radiators are cross-installed along a row to radiate signals in opposite directions, respectively,

The parasitic elements resonate at frequencies adjacent to the first and second radiators to implement broadband, and are disposed one by one between the first and second radiators so that the first and second radiators are shared,

The feeding unit is a first feeding line for supplying a signal to a plurality of first radiators provided in the first array,

A second feed line for supplying signals to a plurality of second radiators provided in the second array, and

And a feeding point connected to one end of the first and second feeding lines to supply signals to the first and second feeding lines,

The first and second radiators receive signals from the first and second feeding lines through a zigzag feeding structure connected through first and second connecting lines, respectively.

Radar antenna, characterized in that the first and second stubs to reduce the power supplied to the first and second array to suppress the side lobes, respectively, are formed at the upper ends of the first and second feed lines.
According to claim 1,

The feed point and the first and second feed lines are connected by first and second branch lines,

Each of the first and second branch lines is a radar antenna, characterized in that it is provided with a diagonal structure that is inclined toward the bottom of the first and second feeder lines with respect to the feed point, respectively.