JPH03236614A - Corrugated horn antenna - Google Patents

Abstract

PURPOSE:To obtain excellent radiation characteristic whose major polarized wave component is in rotation symmetry over a wide band by constituting the inner diameter of three circular waveguide constituting a high-order mode generating section so as to satisfy a specific condition. CONSTITUTION:A corrugated horn antenna is constituted by connecting a corrugated conical horn 1, a high-order mode generating section 3 and a feeding waveguide 6 sequentially from an opening side. Three circular waveguides 4a, 4b, 4c with a different inner diameter and three taper waveguides 5a, 5b, 5c constitute the generating section 3. Then the inner diameter Da of the waveguide 4a is selected within the range of 1.22 to 1.7 times the wavelength of the used highest operating frequency and the inner diameter Db of the waveguide 4b is selected within the range of a multiple of 1.7 to 2.2 times of the wavelength of the used highest operating frequency. Since the cross polarized wave component in plural frequency bands is decreased and the quantity of generation at a desired high-order mode capable of correction of E and H planes of the major component is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a corrugated horn antenna used as a primary horn of a reflector antenna.

[Conventional technology]

Figure 2 shows, for example, the Institute of Electronics, Information and Communication Engineers Antenna Propagation Study Group Material A-PO2-22, 1), 17 (1989-6-
16), which is a configuration explanatory diagram of a conventional corrugated horn antenna, 1 is a corrugated conical horn in which a large number of fins are arranged periodically along the tube axis inside the conical horn, and 2a.

2b is a feeding waveguide for low frequency band, 3 is a circular waveguide 4
a, 4b and tapered waveguides 5a, 5b.
6 is a feeding waveguide for high frequency bands.

In the corrugated horn antenna configured in this way, radio waves in the low frequency band are fed from the feeding waveguides 2a and 2b, and then converted into a corrugated mode having good radiation characteristics in the corrugated conical horn 1, and then transmitted from the aperture. radiated. Since the inner diameter of the waveguide at the position where the feeding waveguides 'la and 'lb are set is determined by the value of the low frequency, the inner diameter is sufficiently small in the vicinity of the high frequency feeding waveguide 6. It is difficult to provide fins up to that point. Therefore,
A part of the radio waves in the high frequency band fed from the feeding waveguide 6 is converted into an unnecessary higher-order mode at the part where it enters the corrugated conical horn 1. Therefore, a higher-order mode generating section 3 is provided to offset this unnecessary higher-order mode. The higher-order mode generated in the portion incident on the corrugated conical horn 1 is mainly the HE + t mode, and this mode corresponds to the T M + + mode of the circular waveguide. Therefore, by generating a desired amount of T M l r modes in the higher-order mode generating section 3, unnecessary HE modes can be canceled out. Further, the higher-order mode generating section 3 has a structure that combines two circular waveguides and two tapered waveguides with different inner diameters in order to obtain good radiation characteristics at two high frequencies, T at two frequencies
A desired amount of occurrence of M r + mode can be obtained.

[Problem to be solved by the invention]

As shown in Fig. 2, the conventional corrugated horn antenna is constructed as described above, so that two frequencies ft and fz in the high frequency band that require good radiation characteristics are used.
If (rz > r,) are far apart, the frequency f,
When the TM mode is generated at the frequency ft, the TE mode is generated in addition to the TM mode.

Therefore, at frequency f2, in addition to the desired TM and mode, an unnecessary TE+z mode is generated, resulting in a problem that the reflection pattern of the corrugated horn antenna is degraded.

Furthermore, at frequency f, it is difficult to control both the amount of TM mode generation and the amount of TEIz mode generation due to the degree of freedom of design parameters, so it is difficult to effectively utilize these two higher-order modes. There was a problem in that it was difficult to obtain a good reflection pattern in a corrugated horn antenna.

This invention was made to solve the above-mentioned problems, and even in many frequency bands and widely separated frequencies, the cross-polarized wave component is small and the main polarized wave component has a desired shape. The purpose is to obtain a corrugated horn antenna with good radiation characteristics.

[Means to solve the problem]

The corrugated horn antenna according to the present invention includes three circular waveguides (A, B, and C from the feeding waveguide side) having different inner diameters, each of the circular waveguides and the feeding waveguide. It consists of three tapered waveguides connecting the tubes, and the inner diameter of the circular waveguide B is 1.22 of the wavelength of the highest frequency.
The value is within the range of 1.7 times to 1.7 times, and the inner diameter of the circular waveguide A is 1.7 to 2.2 times the wavelength of the highest frequency used.
The value is within the range of 3 times.

[Operation] In this invention, two frequencies in a high frequency band that require good radiation characteristics are expressed as f,,ft (f,>f,)
In this case, the frequency f Ii? In order to obtain a desired amount of TM++ mode generation, the length of the circular waveguide C and the opening angle of the tapered waveguide connected to this circular waveguide C can be designed.

In this case, at the frequency f, TM, mode and T E + t mode occur at the discontinuities at both ends of the circular waveguide C, and then at the frequency f2, the TE, ! After considering the mode, TE1! A desired amount of mode generation is determined, and the length of the circular waveguide B and the opening angle of the tapered waveguide connected to the circular waveguide B are designed so as to realize this amount of generation. Therefore, considering the T E s z mode that occurs at the discontinuities at both ends of the circular waveguide C and at both ends of the circular waveguide B,
The amount of generation can be controlled. Specifically, the amount of generation can be set to zero. Next, since TM and modes are also generated at these discontinuities, after considering this amount of generation, the desired amount of TMl and modes to be generated is determined, and the length of the circular waveguide A is adjusted to achieve this amount of generation. Design the opening angle of the tapered waveguide connected to Satoko's circular waveguide A. The inner diameter of this circular waveguide A is TEI! Since it is specified that the mode does not propagate, TE,! No mode is generated, and design can be performed by focusing only on the TM and mode.

From the above, it is possible to obtain the desired amount of generation of TM mode at frequency f, and to obtain the desired amount of generation of both TM + + mode and TE mode at frequency f. Therefore, good radiation characteristics can be obtained at both frequencies.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the bottom of a corrugated horn antenna according to an embodiment of the present invention. In the figure, 1 is a corrugated conical horn, 2a and 2b are feeding waveguides that feed radio waves in a low frequency band f0, 4c.

5C is a frequency f in a frequency band higher than frequency f0.

circular waveguide and tapered waveguide, 4b and 5b are frequency f
o and f, for frequency f2 in the higher frequency band, TEL
! A circular waveguide and a tapered waveguide for controlling the amount of mode generation, 4a and 5a are for frequency ft, and are a circular waveguide and a tapered waveguide for controlling the amount of TM and mode generation. Here, the inner diameter DC of the circular waveguide 4c is T E at the frequency f.
+ The inner diameter Db of the zero-order circular waveguide 4b is such that the TM mode does not propagate at frequency f1, and the TM1 mode does not propagate at frequency f2. ZuniTEI! This is the dimension in which the mode propagates. Furthermore, the inner diameter of the circular waveguide 4a.

is TE at frequency f2, the mode does not propagate and T
Let M r + be the dimension in which the mode propagates. From the above, the inner diameter of each circular waveguide is given by the following equation.

However, in equations (11 to (3)), C is the speed of light, Kt
□1 (=3.83) is TM, mode cutoff wave number, K.

1□ (=5.33) is TE, cutoff wave number of t mode, Kr
N1t (=7.02) indicates the cutoff wave number of the TM mode. Furthermore, the wavelength of each frequency,f,,f,is,λ,.

If λ2, equations (11 to (3)) are 1.22λI
<I)c<1.70λ+ −(4)1.70λz
<Db <(smaller of 2,23λ8 or 1.22λ) −(5) 1.22λm <[)a<1.70λffi −(
6).

In a corrugated horn antenna with such a structure,
The frequency f fed from the feeding waveguide 6 for high frequency bands,
The radio waves of f2 and f2 are generated by unnecessary higher-order modes, mainly HE, at the fin on the feeding side of the corrugated conical horn 1. In order to offset the unnecessary higher-order modes, it is necessary to generate a predetermined amount of TM and I modes in the higher-order mode generating section 3.

As mentioned above, since the inner diameter of the circular waveguide that forms the bottom of the higher-order mode generating section 3 is determined as shown above, at the frequency f, the TM mode in the circular waveguide 4C is propagates,
At the frequency ft, the TMII mode and the TE mode propagate in the circular waveguides 4b and 4C, and the T mode propagates in the circular waveguide 4a.
The M r + mode propagates. Therefore, the circular waveguide 4
By setting the length of C and the opening angle of the tapered waveguide 5C to predetermined values, it is possible to obtain the desired amount of TM mode generation at the frequency f.At the zero-order frequency ft, the circular waveguide TE occurring at both ends of 4C,! After considering the amount of modes generated, TEL! The length of the circular waveguide 4b and the opening angle of the tapered waveguide 5b are set so as to obtain the desired amount of mode generation. Furthermore, at frequency f8, TM generated at both ends of the circular waveguides 4b and 4C
, the length of the circular waveguide 4a and the opening angle of the tapered waveguide 5a are set so as to obtain the desired amount of TM and mode generation. Therefore, the frequency f
In No. 2, a desired amount of generation can be obtained for each higher-order mode of TM, mode, and TE+z mode.

In this embodiment, cross-polarization components can be canceled in each of a plurality of frequency bands, so cross-polarization components can be reduced in each frequency band, and the E-plane and H-plane of the main polarization component can be reduced. Since it is possible to obtain a desired amount of generated higher-order modes that can be corrected, it is possible to obtain good radiation characteristics in which the main polarized wave component is rotationally symmetrical over a wide band.

〔Effect of the invention〕

As described above, according to the present invention, the higher-order mode generating section is connected to three circular waveguides A, B, and C from the feeding waveguide side having different inner diameters, each circular waveguide, and the feeding waveguide described above. The inner diameter of the circular waveguide B is within the range of 1.22 times to 1.7 times the wavelength of the highest frequency used, and the circular waveguide Since the inner diameter of A is set to a value within the range of 1.7 to 2.23 times the wavelength of the highest frequency used, it is possible to obtain the desired amount of TM and mode generation at frequency f1, and at frequency ft. is T M
+ r mode and TEI! A desired amount of generation can be obtained in both modes, and good radiation characteristics can be obtained in both frequencies.

Therefore, it is possible to cancel each of the cross-polarized components in multiple frequency bands, and to obtain the desired amount of higher-order mode generation that can correct the E-plane and H-plane of the main polarization component. It is possible to obtain a good radiation pattern in which the cross-polarized component is small and the main polarized component is rotationally symmetrical.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a corrugated horn antenna according to an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of a conventional corrugated horn antenna. In the figure, ■ is a corrugated conical horn, 2a. 2b is a feeding waveguide, 3 is a higher-order mode generator, 4a to 4C
is a circular waveguide, 5a to 5C are tapered waveguides, and 6 is a feeding waveguide. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a corrugated horn antenna that is used in multiple frequency bands and in which a corrugated conical horn, a higher-order mode generator, and a feeding waveguide are sequentially connected from the opening side, the higher-order mode generator is connected to three circular shapes with different inner diameters. Consisting of a waveguide (designated A, B, and C from the feeding waveguide side) and three tapered waveguides connecting each of the circular waveguides and the feeding waveguide, the circular waveguide The inner diameter D_a of the tube A is within the range of 1.22 to 1.7 times the wavelength of the highest frequency used, and the inner diameter D_b of the circular waveguide B is 1.22 to 1.7 times the wavelength of the highest frequency used.
．． A corrugated horn antenna characterized by having a value within the range of 7 times to 2.23 times.