KR101841685B1 - Antenna for radar - Google Patents

Abstract

The present invention relates to an antenna for a radar, comprising an array antenna including at least one radiating unit including a plurality of radiating elements and a feeder line for connecting the plurality of radiating elements in series. The plurality of radiating elements are formed with a patch of an isosceles trapezoidal shape with both ends with different lengths which are radiating slots to radiate energy, respectively. Accordingly high gain and low side lobe level characteristics of the antenna for a radar can be obtained by minimizing a loss due to the feeder line by applying a serial feeding microstrip patch of the isosceles trapezoidal shape.

Description

ANTENNA FOR RADAR "

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

A radar sensor is a sensing means for measuring the distance, velocity, and angle information by transmitting a radio wave using a microwave and receiving a reflection signal reflected from the target.

The radar sensor may be a pulse radar, a frequency modulated continuous wave (FMCW), a stepped-frequency continuous wave (SFCW) And a frequency shift keying (FSK) radar. The radar waveform is used to measure target information.

The applicant of the present invention has disclosed a radar sensor technology to many of the following Patent Documents 1 and 2 and has been patented and registered.

Meanwhile, a patch array antenna in the form of a printed microstrip is mainly used for radar detectors for 24GHz Industrial, Scientific and Medical (ISM) bands.

The radar sensors for automobiles mainly use the 24GHz band or the 77GHz band.

It is necessary to give special characteristics of the antenna such as an antenna gain or an increase in the side lobe level (SLL), as in a vehicle radar sensor.

Thus, in order to obtain special characteristics of an antenna, when a complex structure such as a chebyshov, binomial, or taylor is applied to an array antenna, a complicated feeding circuit . Therefore, it takes a long time to design and optimize the performance of the array antenna having a complex power supply circuit.

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

However, the array antenna having a uniform magnitude and phase of a current input through the patch has a high side lobe level, which results in a problem that the sensing area is very uneven.

Further, when the detection area of the radar detector is very narrow, there is a problem that it is difficult to generate a narrow and uniformly wide beam only by the radar algorithm because the level of the side lobes generated by the array antenna is high.

The following patent document 3 discloses an array antenna technology having high gain and low side-leaf level characteristics.

Korean Patent Registration No. 10-1513878 (issued on April 22, 2015) Korean Patent Registration No. 10-1505044 (issued on March 24, 2015) Korean Patent Registration No. 10-1935782 (issued on May 15, 2017)

The array antenna according to the related art has a problem that the feed line loss increases as the feed line between patches becomes longer.

Particularly, since the loss in the millimeter wave band is further increased, improvement of the feed line is required.

For example, FIG. 1 is a configuration diagram of a conventional serial feed microstrip patch array antenna using a rectangular structure patch according to the related art.

In the rectangular microstrip patches (# 1 to # 4) in the array antenna shown in Fig. 1, both longitudinal ends are radial slots through which energy is radiated.

Here, since the rectangles are equal in length in both longitudinal ends, that is, the lengths of the two radiation slots, the same energy is emitted.

For this reason, in the array antenna to which the rectangular structure patch is applied, the radiation levels are distributed in a step-like manner for each slot (see the dotted line in FIG. 3).

Therefore, it is required to develop an array antenna having high gain and low side level characteristics by modifying the patch structure so as to minimize the loss caused by the feed line.

SUMMARY OF THE INVENTION An object of the present invention is to provide a radar antenna capable of minimizing loss due to a feed line by applying a series feed microstrip patch.

Another object of the present invention is to provide a radar antenna having a high gain and a low sidelobe level characteristic by minimizing loss caused by a feed line.

According to an aspect of the present invention, there is provided a radar antenna comprising: an array antenna including at least one radiating element including a plurality of radiating elements and a feed line for connecting the plurality of radiating elements in series, And the plurality of radiating elements are each provided with an isosceles trapezoidal patch having a length different from that of a radiating slot at which both ends are radiated to emit energy.

The present invention may further include a power feeder for delivering power to be supplied to the plurality of radiation units and the plurality of radiation units and a power distribution unit for distributing power supplied through the power feeder, Of the antenna array.

The plurality of radiating elements are arranged in series along the longitudinal direction of the radiating portion,

Among the plurality of radiating elements, the size of the radiating element located at the center is the largest, the size of the radiating element decreases from the center to both ends, and the size of the patch is changed according to the application of the array antenna design theory to the number of patches .

And each patch provided by the plurality of radiating elements has a symmetrical structure in the entire structure of the array antenna.

When determining the current ratio of each patch, the array antenna calculates the value of each patch * 2 conductance (G) in consideration of the width of two radiation slots of each patch, and uses the array antenna design theory based on the calculated conductance value And determining the current ratio of each patch.

The array antenna is characterized in that the gradient is reduced to gradually increase or decrease the radiation level for each slot to which the isosceles trapezoidal structure patch is applied, and the array antenna is distributed in a more gentle manner than the radiation level type when the rectangular structure patch is applied.

As described above, according to the antenna for a radar of the present invention, it is possible to minimize the loss due to the feeder line by applying an isosceles trapezoidal series feed microstrip patch to obtain high gain and low side level characteristics of a radar antenna Effect is obtained.

That is, according to the present invention, by applying a patch having an isosceles trapezoidal structure and adjusting the width and length of the two radiation slots of each patch, the current distribution is made more gentle as compared with the case of applying the patch of the rectangular structure, It is possible to obtain an effect that it can be effectively improved.

FIG. 1 is a schematic view of a conventional series feed microstrip patch array antenna using a rectangular structure patch according to the prior art. FIG.
2 is a configuration diagram of a radar antenna according to a preferred embodiment of the present invention,
FIG. 3 is a graph comparing signal levels radiated from the antenna shown in FIGS. 1 and 2,
4 is an exploded perspective view of a radar antenna according to another embodiment of the present invention,
5 is an equivalent circuit diagram of a rectangular patch antenna structure and a transmission line model,
6 is a view showing electric field distribution characteristics of the patch antenna shown in FIG.

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

FIG. 2 is a configuration diagram of a radar antenna according to a preferred embodiment of the present invention, and FIG. 3 is a graph comparing signal levels radiated from the antenna shown in FIG. 1 and FIG.

In FIG. 3, the signal levels radiated from the array antennas to which the rectangular structure patches are applied are shown by dotted lines, and the signal levels radiated from the array antennas using the isosceles trapezoidal structure patches are shown by solid lines.

2, a radar antenna 10 according to a preferred embodiment of the present invention includes a plurality of (N) radiating elements 21 and a plurality of radiating elements 21 connected in series to a feed line 22, And a radiation part 20 including a radiation part.

2, the radiation unit 20 is shown as one array antenna including a feed line 22 connecting a plurality of radiation elements 21 and a plurality of radiation elements 22 in series, but the present invention is not limited thereto It is not.

For example, FIG. 4 is an exploded perspective view of a radar antenna according to another embodiment of the present invention.

4, a plurality of (M) radiating parts 20 and a plurality of radiating parts 20 for distributing power supplied through a power feeding part 30 for transmitting power to be supplied to each radiating part 20 The power distributor 40 may be provided to supply power to each radiation section 20 so that it can be configured as an N * M array antenna.

The radiation portion 20, the power feeder 30, and the power distribution portion 40 may be arranged on the dielectric substrate 50 and the ground plane.

The power feeder 30 functions to supply electric power to be supplied to the respective radiation units 20 to the power distributor 40. The power feeder 30 may be a coaxial line or a coplanar waveguide ) Can be applied in various feeding modes.

The power distribution unit 40 functions to distribute the power supplied from the power feeder 30 and provide the distributed power to each radiation unit 20. [

For example, the power distributor 40 may be a uniform power distributor for evenly distributing the power provided from the power feeder 30 to a constant output power ratio, or an unequal power distributor for distributing power of different sizes to each radiator 20 And the power distributor connected directly to each radiation section 20 and supplying the distributed power can impedance match the impedance of the radiation section 20 with respect to the feed section 30. [

2 and 3, the radiating portion 20 includes a plurality of (N) radiating elements 21, and between the radiating elements 21, a feed line 22 are provided.

For example, in the present embodiment, a plurality of (N) radiating elements 21 may be provided as patches # 1 to # 4 each having an isosceles trapezoidal shape.

The plurality of radiating elements 21 are arranged in series along the longitudinal direction of the radiating element 20 and the radiating elements 21 located at the center among the plurality of radiating elements 21 are the largest in size, The size of the radiating element 21 becomes smaller.

Here, the size of each radiating element 21 can be determined according to the radiation conductance. That is, the large-size radiating element 21 can have a larger radiation conductance than the small-sized radiating element 21.

For example, as the array antenna is fabricated in a printed form on the dielectric substrate 50, each radiating element 20 can be sized in a plane having a length in the x direction (width) and a length in the y direction (length) have.

The number of radiating elements 21 may be variously changed depending on the purpose of use of the array antenna.

And the radiation conductance of the plurality of radiating elements 21 can be determined according to an array function having a low side-leaf level characteristic.

The feed line 22 can control the slope of the emitted beam by adjusting the phase of the current input to each radiating element 21. [

That is, the length of the feed line 221 connecting each radiating element 21 is approximated to the wavelength? / 2 of the signal inputted to each radiating element 21, and has a length of about? / 2, And inverts the feed phase with the feed coil 21.

The feed line 222 connecting the input and the radiating element 21 has a greater function in impedance matching.

For this purpose, the feeder line 222 connecting the input and the radiating element 21 may be adjusted in length or changed to a multi-stage impedance line for impedance matching.

In this way, when an isosceles trapezoidal patch is applied to each radiating element 21, since the radiation levels of the two radiating slots are different from each other, as shown by the solid line in Fig. 3 , It can be distributed in a more gentle manner by decreasing the slope to gradually increase or decrease the radiation level per slot.

FIG. 5 is an equivalent circuit diagram of a rectangular patch antenna structure and a transmission line model, and FIG. 6 is a view showing an electric field distribution characteristic of a patch antenna.

As shown in Figure 5, the microstrip patch may be a model for analyzing a transmission line, the feed line admittance of the surface which is connected to the Y ₁ equivalent admittance Y ₂ of the longitudinal section opposite the screen.

When the patch length L is about lambda / 2, the admittance of the two radiation slots is the same as the conductance of the real number, but the susceptance of the imaginary number is canceled by the same size and opposite sign.

This can be expressed as Equation (1).

[Equation 1]

2, the patches # 1 to # 4 are not symmetrical with respect to each other as shown in FIG. 5. However, in the entire structure of the array antenna, It has a symmetrical structure.

That is, the transmission line 222 of the input stage is excluded, and the structure is such that the patches # 1 and #N, the patches # 2 and # (N-1) are symmetrically arranged in the order of the patches.

Therefore, the admittance of each of the patches # 1 to # 4 shown in FIG. 2 can be expressed by the following equation (2).

&Quot; (2) "

Therefore, the total input admittance (Y _IN ) becomes the real component of the conductance without the imaginary component, as shown in Equation (3).

&Quot; (3) "

The patch width for the conductance is determined by the following equation (4).

&Quot; (4) "

Thus, the width (W) of the two radiating slots of the isosceles trapezoid patch is determined, and the length L of the patch causes the electric fields of the two radiating slots to be formed in opposite directions as shown in FIG.

Next, a method of designing the array antenna with the number of patches N = 10 will be described.

When a patch having a rectangular structure is applied as shown in FIG. 1, the current ratio of each patch is determined, and the patch width can be calculated through this.

For example, Table 1 is a table that derives the current ratio (an) of each patch using a chebyshov equation having a side edge of 26 dB.

N Current ratio (an) Normalization a1 5.7732 1.0000 a2 5.670 0.8950 a3 4.1023 0.7106 a4 2.8256 0.4894 a5 2.0846 0.3611

 On the other hand, in the case of applying the patch of the isosceles trapezoidal structure shown in FIG. 2, since the width of the two radiation slots of each patch must be considered in the process of determining the current ratio of the patches # 1 to # 5, The device value should be obtained.

Table 2 shows the results of deriving the current ratios (an) of each patch using the Chebyshev equation with side dips of 26 dB as in Table 1. [

N Current ratio (an) Normalization a1 2.8216 1.0000 a2 2.7502 0.9747 a3 2.6115 0.9255 a4 2.4138 0.8554 a5 2.1682 0.7684 a6 1.8886 0.6693 a7 1.5898 0.5634 a8 1.2872 0.4562 a9 0.9950 0.3526 a10 1.4266 0.5056

As shown in the solid line in FIG. 4, the current distribution in the case of applying the patch of an isosceles trapezoidal shape in Table 2 becomes gentler than the current distribution (dotted line) in the case of applying the rectangular structure, It is possible to confirm that it is more useful.

Through the above-mentioned process, the present invention can obtain the high gain and low side level characteristics of the radar antenna by minimizing the loss due to the feeder line by applying the isosceles trapezoidal series feed microstrip patch.

Although the invention made by the present inventors has been described concretely with reference to the above embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

That is, in the above-described embodiment, the array antenna is designed by deriving the current ratio of each patch by using the Chebyshev equation. However, the present invention is not limited thereto, and the present invention is not limited to the Chebyshev equation, , Taylor (taylor) can be changed to apply various types of array antenna design theory.

The present invention is applied to an antenna technology for radar which obtains high gain and low side level characteristics of a radar antenna by minimizing loss caused by a feeding line by applying an isosceles trapezoidal series feeding micro strip patch.

10: Antenna for radar
20:
21: radiating element
22,221,222:
30: Feeding part
40: Power distributor
50: dielectric substrate

Claims (6)

And at least one radiating part including a plurality of radiating elements and a feeder line for connecting the plurality of radiating elements in series,
Wherein the plurality of radiating elements are each provided with an isosceles trapezoidal patch having a length different from each other,
Wherein the array antenna reduces inclination to gradually increase or decrease the radiation level of each slot to which the isosceles trapezoidal structure patch is applied,
Wherein each patch provided by the plurality of radiating elements has a symmetrical structure in the entire structure of the array antenna,
The plurality of radiating elements are arranged in series along the longitudinal direction of the radiating portion,
Among the plurality of radiating elements, the size of the radiating element located at the center is the largest, the size of the radiating element is decreased from the center to both ends,
Wherein a length of a feed line connecting each radiating element is approximated to a wavelength / 2 of a signal input to each radiating element. The method according to claim 1,
The plurality of radiation parts
A power feeding part for transmitting electric power to be supplied to the plurality of radiation parts;
And a power distributor for distributing power supplied through the power feeder
And an array antenna having a plurality of columns for supplying electric power to each radiation part. delete delete The method according to claim 1,
When determining the current ratio of each patch, the array antenna calculates the value of each patch * 2 conductance (G) in consideration of the width of two radiation slots of each patch,
And the current ratio of each patch is determined by using the array antenna design theory based on the calculated conductance (G) value. delete

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