KR100222665B1 - Mode converter - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Mode converter

2. Technical problem to be solved by the invention

The mode loss due to the mode change is small and the coupling energy transmitted from the rectangular waveguide to the circular waveguide is transmitted without reflection.

3. Summary of the Solution of the Invention

Mode converter that converts TE ₁₀ mode, the basic mode of rectangular waveguide, to TE ₁₁ mode, the basic mode of circular waveguide.

4. Important uses of the invention

C-Band Dual Polarization Feeding System for Satellite Communications Base Stations

Description

Mode converter {MODE CONVERTER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mode converter, and more particularly, to a mode converter for converting a mode of a signal transmitted through a circular waveguide for signal connection and outputting it externally through an output rectangular waveguide.

In general, a mode converter which converts TE ₁₁ mode, which is the basic mode of the intrinsic waveguide, into TE ₁₀ mode, which is the basic mode of the spherical waveguide, and combines different waveguides is mainly used in combination with a polarizer. It should be designed to transmit the coupling energy transmitted from the waveguide to the circular waveguide without reflection. Schelkunoff introduces a complete set of the most suitable orthogonal functions according to the geometry of the waveguide, and expands the electromagnetic field in the waveguide to the series of orthogonal functions. By applying the mode conversion method, which is considered to be the highest telegraphist and ignores the higher-order mode, it is easy to apply to waveguides or coupled transmission lines with complex boundary conditions. In addition, three-dimensional problems can be reduced to one-dimensional problems to solve the problem of curve coordinates that cannot be separated.

However, the method proposed by Shelknov is a result of the series expansion and Volterra integral equations, so that the number of matrices is increased and the equation expansion is complicated to obtain an accurate solution. And the production technology is far behind the foreign advanced technology, so domestic technology development and localization of equipment is urgent.

Here, referring to the waveguide taper, which has been used in the past, it is a device that connects two waveguides (circular-circular and spherical-spherical) having the same shape but different sizes. This is to minimize the return loss of incident energy.

In addition, the conventional mode converter is a device for reducing the mode loss due to the mode change caused by the modes of the rectangular waveguide and the circular waveguide are not the same as one another in the prior art by connecting the rectangular waveguide after grooves in the circular waveguide. There is a method of causing a mode change in the branch part, which has to solve the branching part based on the exact design theory, and there is a problem in that energy efficiency is not good because branching signal power is very small.

Accordingly, the present invention has been made to solve the above problems, the waveguide by converting the waveguide discontinuous interface into a smooth continuous interface in order to transmit the coupling energy transmitted between the circular waveguide for signal connection and the spherical waveguide for output without reflection. It is an object of the present invention to provide a mode converter capable of transmitting energy without reflection at the coupling portion.

1 is a perspective view of an embodiment of a mode converter according to the present invention;

2 is an illustrative example of a method of designing a mode converter according to the present invention;

3 and 4 are characteristic diagrams for measuring performance of a mode converter according to the present invention;

* Explanation of symbols for main parts of the drawings

10: circular waveguide 20: spherical waveguide

30: mode converter

The present invention for achieving the above object, in the mode converter through the output rectangular waveguide by converting the mode of the signal input through the circular waveguide for signal connection, the circular for signal connection to be coupled with the circular waveguide for signal connection A first flange having the same size and shape as the flange of the waveguide; A second flange having the same size and shape as the flange of the output spherical waveguide so as to be coupled to the output spherical waveguide; And a Fourier transform taper function formed integrally with both ends of the first and second flanges, and for converting the discontinuous interface between the signal connection circular waveguide and the output spherical waveguide into a smooth continuous interface. And a waveguide taper configured to convert coordinate systems of different structures of the signal connection waveguide and the output waveguide into coordinate systems having the same structure and correspond to each other according to angles.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 is a perspective view of an embodiment of a mode converter according to the present invention.

2 is an exemplary view illustrating a method of designing a mode converter according to the present invention.

As shown in Fig. 1, the mode converter of the present invention includes flanges 31 and 32 and a waveguide taper 33. Here, the mode converter 30 is connected to the circular waveguide 10 for signal connection by the flange 31, and is coupled to the flange 32 to the output spherical waveguide 20 connected to the transmitter or receiver.

The circular waveguide 10 for signal connection performs an input port function for connecting a signal transmitted from the outside to the mode converter 30, and the spherical waveguide 20 for output has a mode changed by the mode converter 30. Output port function to transfer the converted signal to the outside.

The function of the mode converter 30 converts the TE ₁₁ mode, which is the basic mode induced in the circular waveguide 10, into the TE ₁₀ mode from the transmission signal when the rectangular waveguide 20 is connected to the receiver, and transmits the TE ₁₁ mode to the rectangular waveguide 20. When the spherical waveguide 20 is connected to the transmitter, it converts the TE ₁₀ mode induced in the spherical waveguide 20 into the TE ₁₁ mode and functions as an interface for transferring the circular waveguide 10 to the circular waveguide 10.

In the case where the circular waveguide 10 coupled to the mode converter 30 is a polarization converter having a dielectric plate inserted therein, the positional change of the circular waveguide 10 due to the linear-circular polarization transformation is a flange that is a circular waveguide connection surface of the mode converter 30. (flange) can be selectively engaged by screw holes located 45 degrees apart. In the design of the mode converter 30, an appropriate taper function is selected in order to achieve a mode conversion without loss of mode by forming a smooth curve between the circular waveguide 10 and the rectangular waveguide 20 and having a smooth reflection coefficient characteristic. Should be.

In order to design waveguide taper, the minimum reflection coefficient should be obtained from the input reflection coefficient of tapered transmission line with different characteristic impedance. To find the minimum value, we need to replace the normalized impedance derivative with an appropriate taper function. Here, the taper function uses Fourier transform taper function and the taper function and the reflection coefficient equation are as follows.

First, applying the Telegraphist equation, which is the mode conversion theory of Shelknov, to the waveguide taper, the reflection coefficient equation as shown in [Equation 1] can be obtained.

는 정규화 임피던스이고, L 은 도파관 길이이다. 테이퍼가 완만할 경우 상기 [수학식 1]의 beta `` 에 대한 적분항을 선형함수로 바꾸어 서로 다른 특성 임피던스를 갖는 테이퍼된 전송선로의 입력 반사계수식으로 변환하면 다음과 같다.here,

Is the normalized impedance and L is the waveguide length. When the taper is smooth, the integral term for beta `` in Equation 1 is converted into a linear function and converted into an input reflection coefficient of a tapered transmission line having different characteristic impedances as follows.

In order to obtain the minimum reflection coefficient in Equation 2, a Fourier transform function is used which is easy to design while reducing the reflection coefficient value to replace the normalized impedance derivative with an appropriate taper function. When the taper function to be found is calculated by inversely transforming Equation 2, Equation 3 is obtained.

When the characteristic curve function of the reflection coefficient is determined as a specific function in Equation 3, the taper function can be easily found.

In order to simplify the calculation process, a specific function is defined as shown in Equations 4 and 5 below.

The Fourier inverse transform of Equation 4 can convert the taper function into a reflection coefficient function, and the equation is expressed as a complex Fourier series to obtain a final reflection coefficient equation as shown in Equation 6 below (see FIG. 2).

Where p is equal to the following Equation 7 and u is equal to the following Equation 8.

The following describes the mode converter design.

A waveguide mode converter is designed to connect the spherical and circular waveguides using the Fourier transform function taper.

The mode conversion problem of the spherical-circular waveguide has not only different waveguide sizes but also different coordinate systems. Therefore, they are converted into coordinate systems having the same structure, and the two waveguides are corresponded according to the following Equations 9 to 12 according to the angle θ as shown in FIG.

, 2π-θ_1 ≤ θ≤θ_1

, 2π-θ_1 ≤ θ≤θ_1

, θ_1 ＜ θ≤π-θ_1

, θ_1 <θ≤π-θ_1

, π-θ_1 ＜ θ≤π+θ_1

, π-θ_1 <θ≤π + θ_1

, π+θ_1 ＜ θ≤2π-θ_1

, π + θ_1 <θ≤2π-θ_1

Although the rectangular waveguide has a different waveguide width as the angle θ changes, the waveguide width of the circular waveguide is constant regardless of the angle θ. Therefore, the rectangular waveguide is divided into 1 to 4 sections and the circular waveguide is designed to correspond to this section.

When the angle of the rectangular waveguide is a specific value θ, the width ratio value between the rectangular waveguide and the circular waveguide is expressed as a normalized load impedance value, and then substituted into a Fourier transform taper function to set the design length with the smallest reflection coefficient. By applying to Equation 4] and [Equation 6], the design value of the mode converter can be obtained by calculating the x and y values of each point depending on the taper length z.

3 and 4 are characteristic diagrams for measuring the performance of the mode converter according to the present invention. FIG. 3 shows the transmission coefficient as a result of measuring the principal component of the electric field, with a constant transmission coefficient of almost 0 dB, and a reflection coefficient of -18 dB or less. 4 is a result of measuring the cross component of the electric field, and the transmission coefficient is about -20 to -30 dB compared to the main component electric field.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not.

As described above, the present invention converts the waveguide discontinuous interface into a smooth continuous interface and transfers energy without reflection from the waveguide coupling unit, thereby reducing the mode loss due to the mode change when the circular waveguide and the rectangular waveguide are connected in the satellite communication feeding system. It can be used to feed a circular horn antenna from a rectangular waveguide, and can be usefully used in waveguide transformer, impedance matching device and horn antenna design to which this design method is applied.

Claims (5)

(correction) In the mode converter through the output rectangular waveguide by converting the mode of the signal input through the circular waveguide for signal connection, A first flange having the same size and shape as a flange of the circular waveguide for signal connection to be coupled to the circular waveguide for signal connection; A second flange having the same size and shape as the flange of the output spherical waveguide so as to be coupled to the output spherical waveguide; And The first and second flanges are integrally formed at both ends, and a Fourier transform taper function is used to convert the discontinuous interface between the signal connection circular waveguide and the output rectangular waveguide into a smooth continuous interface. However, a waveguide taper configured by converting coordinate systems of different structures of the signal connection waveguide and the output waveguide into coordinate systems having the same structure and corresponding to each other according to angles. Mode converter comprising a. (correction) The method of claim 1, The waveguide taper is, Coordinate systems of different structures of the signal connection waveguide and the output waveguide are converted into coordinate systems of the same structure and corresponded to each other according to angles, and are divided into four sections according to angles formed by the diagonals of the output waveguide on the same structure. The mode converter which divided | segmented and comprised respectively, and comprised. (correction) The method of claim 1, The Fourier transform taper function is a load impedance normalized as shown in the following equation to obtain a minimum reflection coefficient value from an input reflection coefficient of a tapered transmission line having different characteristic impedances.

And the derivative term is taken as the taper function g (p).

(only,

Where L is waveguide length and z is taper length) (correction) The method of claim 3, And the waveguide taper has a reflection coefficient that is substantially close to zero. (correction) The method of claim 4, wherein The waveguide taper is, At a specific angle, the width ratio value between the output waveguide and the signal connection waveguide is expressed by a predetermined normalized load impedance value, and then substituted into the Fourier transform taper function to set a design length having a minimum reflection coefficient, and And calculating the x-axis and y-axis coordinate values of each point depending on the length of the waveguide taper.

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