WO2011056047A2

WO2011056047A2 - Broadband polarization twister and polarization twisting dual-reflector antenna using same

Info

Publication number: WO2011056047A2
Application number: PCT/KR2010/007877
Authority: WO
Inventors: 황금철
Original assignee: 동국대학교 산학협력단
Priority date: 2009-11-09
Filing date: 2010-11-09
Publication date: 2011-05-12
Also published as: KR100953601B1; WO2011056047A3

Abstract

Disclosed is a broadband polarization twisting technique. According to one embodiment of the present invention, the broadband polarization twister comprises a conducting plate that performs a polarization twisting process, wherein meander grooves are formed on a reflecting surface of the conducting plate. Thus, the invention improves broadband polarization twisting performance, and minimizes polarization twisting loss.

Description

Broadband Polarized Converter and Polarized Reflective Dual Reflector Antenna Using the Same

The present invention relates to a polarization conversion technology, and more particularly, to a polarization converter and a polarization conversion dual reflector antenna using the same to improve the wideband polarization conversion performance and to minimize the polarization conversion loss.

Recently, as an antenna for satellite communication, radar systems, etc., an antenna composed of a double reflector including a main reflector and a sub-reflector, such as a cassgrain reflector antenna, is widely used. It is used.

Such a dual reflector antenna has a short focal length compared to a general single reflector antenna, thereby greatly reducing the antenna width and having a high gain. However, in the case of such a dual reflector antenna, a problem arises in that the antenna gain and the side lobe characteristics are relatively degraded due to the blockage effect caused by the sub reflector present in the radiation plane.

In order to solve this problem, a polarization twisting dual-reflector antenna, such as a caseingrain antenna, which reduces the occlusion effect by using a polarization transformation, has been proposed. The polarization converting dual reflector antenna includes a polarization converter in the main reflector and a polarization filter function in the subreflector to remove the blinding effect of the subreflector.

As such, the polarization converter corresponds to an essential component for implementing the polarization conversion dual reflector antenna.

On the other hand, the existing technology uses a periodic metal-strip or a corrugated conducting surface formed with a right angle groove to implement a polarization conversion reflector. However, when using such periodic metal strips or corrugated conductor surfaces, polarization conversion can be performed only in a narrow frequency band.

In addition, the existing technology uses a layered structure of the polarization converter to obtain the broadband characteristics of the polarization conversion. However, in the case of using such a laminated structured polarization converter, high polarization conversion loss is caused due to a polarization conversion film, a spacing layer, etc. included in the laminated structure.

Therefore, there is an urgent need for a new concept of wideband polarization conversion technology capable of polarization conversion in a wide frequency band and minimizing polarization conversion loss.

Embodiments of the present invention, by using a meander-shaped groove plate for polarization conversion to improve the broadband polarization conversion performance, as well as to minimize the polarization conversion loss.

The broadband polarization converter according to an embodiment of the present invention includes a conductor plate for performing a polarization twist, and a meander-shaped groove is formed on a reflective surface of the conductor plate.

A polarization twisting dual-reflector antenna according to an embodiment of the present invention performs polarization conversion by using a broadband polarization converter according to embodiments of the present invention.

Embodiments of the present invention can improve the wideband polarization conversion performance by performing a polarization conversion by using a meander-shaped groove plate.

In addition, by implementing a single layer polarization converter using a meander shaped grooved plate, it is possible to minimize the polarization conversion loss due to the polarization conversion film, the separation layer, etc. generated in the conventional laminated structure.

Furthermore, the polarization converter according to the embodiments of the present invention can be effectively applied to a polarization conversion dual reflector antenna that requires wideband polarization conversion performance.

1 is a diagram illustrating a wideband polarization converter according to an embodiment of the present invention.

2 to 4 are meander shaped grooves formed in the conductor plate of the broadband polarization converter according to an embodiment of the present invention.

5 is a graph showing a global optimization price change with respect to the number of iterations of a GSO in the optimization design of a broadband polarization converter according to an embodiment of the present invention.

6 is a photograph showing a performance test scene in an RF anechoic chamber for a broadband polarization converter manufactured according to an embodiment of the present invention.

FIG. 7 is a graph illustrating a phase difference measurement result between reflected orthogonal components with respect to a general incident wave having an incident angle θ = 0 ° in the experiment of FIG. 6.

8 is a graph showing the cross-polarization suppression level of a broadband polarization converter according to an embodiment of the present invention.

9 is a graph showing the polarization conversion loss of a wideband polarization converter according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to clarify a solution of the technical problem of the present invention. However, in describing the present invention, when it is determined that the description of the related known technology may make the gist of the present invention unclear, the description thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users, operators, and the like. Therefore, the definition should be made based on the contents throughout the specification.

1 illustrates a wideband polarization converter according to an embodiment of the present invention.

As shown in FIG. 1, the wideband polarization converter 100 includes a conducting plane 110 that performs a polarization twist. In addition, a meander-shaped groove 120 is formed on the reflective surface of the conductor plate 110 that reflects radio waves. The meander shaped grooves 120 are formed on the reflective surface of the conductor plate 110 periodically and repeatedly.

As will be described again below, when the polarization converter is implemented using the conductor plate 110 having the meander groove 120, wideband polarization conversion is possible, and further, the optimization design further improves the broadband polarization conversion characteristics. You can do it.

In addition, when the polarization converter is implemented using the polarization converter using the conductor plate 110 having the meander groove 120 formed therein, the film includes a polarization conversion film and a spacing layer. The polarization converter can be implemented in a single layer structure rather than a layered structure, thereby minimizing the polarization conversion loss caused by loss tangent of the polarization conversion film or the separation layer. do.

2 to 4 illustrate a meander shaped groove 120 formed in the conductor plate 110 of the wideband polarization converter 100 according to an embodiment of the present invention.

As shown in FIG. 2, the meander shaped groove 120 may be configured of a groove in a horizontal direction and a groove in a vertical direction perpendicular to each other.

In addition, as shown in FIG. 3, the meander shaped groove 120 may be viewed as a periodic combination of unit cells. Accordingly, the geometric shape of the meander shaped groove 120 may be defined using the shape parameters of the unit cell, and the wideband of the wideband polarization converter 100 may be optimized through the design of the shape parameters of the unit cell. Polarization conversion characteristics can be further improved.

As shown in FIG. 4, shape parameters of the unit cell may be defined as follows. That is, the widths of the vertical and horizontal grooves may be defined as w ₁ and w ₂ , the depth d, the thickness of the horizontal bulkhead b, the thickness of the vertical bulkhead g, and the distance between the vertical grooves a. have. Then, each meander shaped groove 120 physically has a vertical period of 2 ( b + w 2), a horizontal period of a + 2 ( g + w 1), and the width of the vertical and horizontal grooves w 1, respectively. And w 2 and the depth of the groove can be defined as a.

Considering a plane wave as an electric field vector polarized at an angle of 45 ° with respect to the axes of the meander shaped groove 120, the incident electric field is two orthogonal components, i.e., horizontal components, as shown in FIG.

And vertical components

Can be divided into An electric field having an incident angle θ acts on the reflecting surface of the conductor plate 110 on which the meander shaped groove 120 is formed.

When the plane wave is incident on the reflecting surface on which the meander shaped groove 120 is formed, the two electrically orthogonal components are in phase. However, while the plane wave passes through the reflection path, a horizontal component

The phase of is preceded by the meander shaped grooves 120 formed periodically. In contrast, vertical components

The phase of is delayed.

therefore,

And

When the phase difference of 180 degrees occurs, the polarization vector of the reflected wave can be converted to 90 degrees with respect to the incident polarization. The wideband polarization converter 100 according to the embodiments of the present invention determines the optimized dimension of the meander shaped groove 120 for the polarization conversion by selecting the optimized dimension in a wide frequency range.

And

A phase difference of 180 degrees can be generated in the liver.

Hereinafter, an optimization design process of a broadband polarization converter according to embodiments of the present invention will be described, and its performance will be verified.

For the optimization design of the meander shaped groove 120, as a probabilistic optimization technique, a GSO (Genetical Swarm Optimization) technique, which improves convergence speed by combining Particle Swarm Optimization (PSO) and Genetic Algorithm (GA), can be used. have. In addition, the CST MicroWave Studio (MWS), which is a three-dimensional finite integral time domain solver, may be used to calculate the reflected wave generated by the conductor plate 110 having the meander groove 120. In this case, simulation results by the CST MWS are passed to the GSO code to evaluate the cost function. Based on the price estimate, the GSO algorithm determines and updates geometric parameters of the meander shaped groove 120.

More specifically, the broadband polarization converter 100 has a finite number of meander grooves formed on the reflecting surface of the conductor plate 110, but the structure is considered to be an infinite periodic structure. Can be. This is because the number of unit cells is very large. Therefore, the operation of the overall structure of the wideband polarization converter 100 may be calculated from the response of the unit cell calculated by applying the periodic boundary condition used in the CST MWS.

Meanwhile, in order to implement the GSO algorithm, a damping boundary condtion with a damping factor of 0.5 may be applied in the PSO process. In this case, GA may be implemented through a roulette wheel selection method and a uniform crossover of the probability P _cross = 0.8. It can also allow for random mutation of probability P _mut = 0.15. In addition, the PSO and GA may be combined with a hybridization coefficient hc = 0.2. This means that in each iteration step, 20% of the population total evolves via GA, and the remaining population evolves via PSO.

The population used in the GSO process is 20. The cost function for designing a broadband polarization converter can be defined as in Equation 1.

Equation 1

In Equation 1, TL ( f _n ) is a co-polarization twist loss at the test frequency f _n , and TL _obj is an objective twist loss. The TL ( f _n ) may be defined as in Equation 2.

Equation 2

The price function may target 0.1 dB polarization conversion loss at 15.5 GHz ≤ f _n ≤ 17.5 GHz. Through the GSO algorithm, the meander shaped grooves 120 start from any type of population and evolve into an optimized form of minimum price.

FIG. 5 is a graph illustrating a global optimization price change with respect to the number of iterations of a GSO in an optimization design of a broadband polarization converter according to an embodiment of the present invention.

As shown in FIG. 5, the price value decreases from 2500.87 to 0 during 150 iterations through the GSO. The optimization design of the meander shaped groove 120 may be obtained after 102 iterations.

The shape parameters of the meander shaped groove 120 optimized through the GSO may be shown in Table 1 below.

Table 1

In the actual optimization design and performance experiments, it took 26 seconds on an Intel Xeon Quad 3.0 GHz PC to perform one polarization transducer analysis. Therefore, the total CPU time for 150 iterations took 21.67 hours (26s x 20 objects x 150 times). Finally, an optimized 53 × 45 × 2 cm ³ wideband polarized transducer was fabricated using CNC milling equipment.

FIG. 6 is a photograph showing a performance test scene in an RF anechoic chamber for a broadband polarization converter actually manufactured according to an embodiment of the present invention.

As shown in FIG. 6, a Ku-band dual-polarized Ku-band circular horn antenna was used to obtain a reflection operation by the wideband polarization converter. In addition, the time-gating method of the Agilent N5230A network analyzer was used to eliminate multi-path interference caused by the measurement environment.

FIG. 7 shows a reflected quadrature component of a general incident wave having an incident angle θ = 0 ° in the experiment of FIG.

And

Phase difference between

-∠

Measurement results are shown graphically.

As shown in FIG. 7, it can be seen that the simulation value and the actually measured value almost match. The slight difference between the simulated value and the measured value is due to a curved line having a radius of 1 mm for the convenience of the meander groove in the actual manufacturing process of the wideband polarization converter. Also, the

And

It can be observed that the measured phase difference between the phases is in the range of 161 ° to 192 ° in the 15.5 GHz to 17.5 GHz band.

8 is a graph illustrating a crosspolarization suppression level of a wideband polarization converter according to an embodiment of the present invention.

As shown in FIG. 8, it can be seen that the cross polarization suppression rate is 17 dB or more in the 12.5% frequency bandwidth (15.48 GHz to 17.55 GHz).

9 is a graph illustrating copolarization twist loss of a wideband polarization converter according to an embodiment of the present invention.

As shown in FIG. 9, it can be seen that the positive polarization conversion loss is 0.2 dB or less in the 15.35 GHz to 17.6 GHz band, which means that more than 95.5% of the incident power is polarized in the wide frequency bandwidth of 13.6% or more. That is, it can be seen that the bandwidth performance level of the broadband polarization converter according to the embodiments of the present invention is superior to the structure using a periodic strip or grating of the conventional technology. In addition, the broadband polarization converter according to the embodiments of the present invention can minimize the polarization conversion loss because it does not need to use a high-loss dielectric such as an adhesive layer or a spacing layer used in the conventional broadband design. have.

Meanwhile, the broadband polarization converter according to the embodiments of the present invention includes a polarization twisting dual-reflector antenna that requires wideband polarization conversion performance, for example, a polarization converter in the main reflector and a polarization filter in the secondary reflector. It can be efficiently applied to a case-grain antenna and the like having a function to minimize the blinding effect by the secondary reflector.

That is, the polarization conversion dual reflector antenna may perform wideband polarization conversion by including the wideband polarization converter according to the embodiments of the present invention in the main reflector. In this case, most of the vertical polarization components radiated from the feed antenna of the polarization conversion dual reflector antenna are reflected in the direction of the main reflector by the polarization filter provided in the secondary reflector of the polarization conversion dual reflector antenna, and the reflected vertical polarization is reflected. The component is polarized in the 90 ° direction by the wideband polarization converter provided in the main reflector and converted into horizontal polarization. The polarization filter of the secondary reflector reflects only vertical polarization components, so that the horizontal polarization can be radiated without being affected by the secondary reflector.

As described above, when the wideband polarization converter according to the embodiments of the present invention is applied to a polarization conversion dual antenna, it is possible to remove the electric blinding effect on the antenna radiation even though the sub-reflector is physically present in the radiation plane. As a result, the wideband polarization conversion performance can be greatly improved and the loss in the polarization conversion can be minimized.

So far, the present invention has been described with reference to embodiments. However, one of ordinary skill in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential technical spirit of the present invention. Therefore, the above-described embodiments should be considered in descriptive sense only and not for purposes of limitation. That is, the true technical scope of the present invention is shown in the appended claims, and all differences within the equivalent scope will be construed as being included in the present invention.

Claims

A conductor plate performing a polarization twist,

And a meander-shaped groove formed on the reflecting surface of the conductor plate.
The method of claim 1,

The conductor plate is a broadband polarization converter, characterized in that formed in a single layer structure (single layer structure).
The method of claim 1,

The meander shaped groove is a broadband polarization converter, characterized in that consisting of a groove in the horizontal direction and a vertical direction perpendicular to each other.
The method of claim 3,

And the meander shaped groove is formed repeatedly on the entire reflective surface of the conductor plate.
A conductor plate of a single layer structure that performs a polarization twist,

And a meander-shaped groove formed on the reflecting surface of the conductor plate.
A polarization twisting dual-reflector antenna for performing polarization conversion using the wideband polarization converter according to any one of claims 1 to 5.