JP2536155B2 - Cone horn antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used as a primary horn of a reflector antenna or as a horn antenna alone, and is applicable to TE ₁₁ mode, which is a fundamental mode of a circular waveguide, and higher mode. The present invention relates to a conical horn antenna excited in a plurality of modes including a TM ₁₁ mode and a TE ₁₂ mode.

[Conventional technology]

FIG. 4 is a structural explanatory view of a conventional multi-mode horn antenna as shown in, for example, Japanese Patent Laid-Open No. 63-107206.
In the figure, (1) is a conical horn, (2h) and (3h) are circular waveguides and flares for low frequency bands, (2i) and (3i) are circular waveguides and flares for high frequency bands, (4f) is a feed waveguide for both frequency bands. The inner diameter of the circular waveguide (2h) is dimensioned so that TE ₁₁ mode and TM ₁₁ mode propagate in the low frequency band and TE ₁₁ mode, TM ₁₁ mode and TE ₁₂ mode propagate in the high frequency band. . Also,
The inner diameter of the circular waveguide (2i) is set so that the TE ₁₁ mode propagates in the low frequency band and the TE ₁₁ mode and the TM ₁₁ mode propagate in the high frequency band.

In the horn antenna constructed in this way, TM _{11 is used} at the discontinuity at both ends of the circular waveguide (2h) in the low frequency band.
By generating a mode and synthesizing the TM ₁₁ mode with a predetermined ratio to the TE ₁₁ mode, good radiation characteristics can be obtained as a multiple mode. In the high frequency band, TM ₁₁ mode and TM ₁₂ mode are generated at the discontinuity at both ends of the circular waveguide (2h). Considering this generation amount, both ends of the circular waveguide (2i) are generated. The desired TM ₁₁ mode can be generated at the discontinuity of, and a good radiation characteristic as a triple mode can be obtained by combining the TE ₁₁ mode with a predetermined ratio of TM ₁₁ mode and TE ₁₂ mode. .

FIG. 5 is a structural explanatory view of another conventional multi-mode horn antenna as shown in, for example, JP-A-58-204604, in which (1) is a conical horn, (2j), (3j )
Is circular waveguide and flare for low frequency band, (2k), (3
k) is a circular waveguide and flare for high frequency band, (4g),
(4h) Feeding waveguides for low and high frequency bands, respectively. The inner diameter of the circular waveguide (2j) is the same as above, and the inner diameter of the circular waveguide (2k) is
TM ₁₁ mode does not propagate, it is sized to TE ₁₁ mode and the TM ₁₁ mode is to transfer general in the high frequency band.

In the horn antenna configured as described above, not only the same operation as described above with reference to FIG. Since the high frequency band and the high frequency band are separately provided, there is an advantage that the two frequency bands can be separated from the case of the configuration shown in FIG.

[Problems to be Solved by the Invention]

In the horn antenna as shown in FIGS. 4 and 5,
When the frequencies of the low frequency band and the high frequency band are greatly separated, the low frequency band of the circular waveguides (2h) and (2j)
Circular waveguide (2h), (2j) to propagate TM ₁₁ mode
It is necessary to increase the inner diameter of the antenna, and higher-order modes higher than the TE ₁₂ mode in the high frequency band also propagate, and there is the problem that the radiation characteristics deteriorate due to these higher-order modes.

Next, each mode and their combination will be explained, and conventional problems will be shown.

FIG. 6 shows a schematic diagram of the electric field and its X component and Y component in the cross section of the circular waveguide for each of TE ₁₁ , TM ₁₁ and TE ₁₂ modes of the circular waveguide. Y component is a cross-polarization component in the figure, TM the Y component of the TE ₁₁ mode ₁₁ mode and the TE
The Y components in the ₁₂ modes are all inverted, and the Y components in the TE ₁₁ mode can be canceled in almost the same manner in the TM ₁₁ mode and the TE ₁₂ mode. Regarding the X component, which is the main polarization component, the TM ₁₁ mode mainly contributes to the correction of the E plane, which is the polarization excitation direction, compared to the X component of the TE ₁₁ mode, and the TE ₁₂ mode mainly It contributes to the correction of the H plane perpendicular to the excitation direction. In addition, Fig. 7 shows the radiation patterns when the conical horn is excited in each of TE ₁₁ , TM ₁₁ and TE ₁₂ modes alone on the E-plane, H-plane and 45 ° plane. Further, the radiation pattern when the modes are combined and excited can be obtained by combining the radiation patterns of the modes shown in FIG. Therefore,
From Fig. 7, when the TM ₁₁ mode or TE ₁₂ mode is combined with the TE ₁₁ mode, TM ₁₁
It can be seen that the mode has a large effect on the radiation pattern on the E plane, and the TE ₁₂ mode has a large effect on the radiation pattern on the H plane.
From the above description, it can be seen that the conventional horn antenna has the following problems. That is, in the conventional horn antenna, the circular waveguide (2h) or (2j) is considered to have a circular waveguide (2h) or (2j) in consideration of the generation amount of TM ₁₁ mode and TE ₁₂ mode in the high frequency band generated at the discontinuity. Tube (2i) or (2k)
When the side is designed, the only higher mode that can be added is the TM ₁₁ mode. Therefore, the cross polarization component can be made small, but the contributions of the TM ₁₁ mode and the TE ₁₂ mode are different for the main polarization component, so that both ends of the circular waveguide (2h) or (2j) are It is difficult to correct the TE ₁₂ mode generated at the discontinuity only with the TM ₁₁ mode generated on the circular waveguide (2i) or (2k) side, and the desired radiation pattern cannot be obtained. There is.

The present invention has been made in order to solve the above problems, and in a large number of frequency bands and frequency bands widely separated from each other, the cross polarization component is small and the main polarization component has a desired shape. The purpose is to obtain radiation characteristics.

[Means for solving the problem]

This multi-frequency-band conical horn antenna has a structure in which a conical horn and high-order mode generators corresponding to each frequency band from low frequency band f ₁ to high frequency band f _n are sequentially connected from the opening side to the feeding side. , A high-order mode generator for at least one frequency band f _{i of} the above-mentioned high-order mode generators,
In the frequency band f _i the frequency band f _i-1 is lower than the condition A higher-order mode does not propagate in the frequency band f _i
Condition B for propagating higher order modes of TM ₁₁ mode and TE ₁₂ mode
And a second circular waveguide having an inner diameter satisfying the condition C for propagating the higher-order mode of only TM ₁₁ mode in the condition A and its frequency band f _i . The tubes are combined, the first circular waveguide is arranged on the opening side, and the above two circular waveguides are connected.

[Action]

In the present invention, the higher-order mode generator for a certain frequency band f _i is constructed by combining the first and second circular waveguides having the predetermined inner diameters as described above. Higher-order modes of TM ₁₁ mode and TE ₁₂ mode propagate in the tube, and higher-order modes of TM ₁₁ mode propagate in the second circular waveguide. Therefore, first, in order to obtain the desired TE ₁₂ mode generation amount in the first circular waveguide part, then in the second circular waveguide part, the TM ₁₁ mode is generated in the first circular waveguide part. In order to obtain the desired TM ₁₁ mode generation amount in consideration of the generation amount, the axial length of each circular waveguide and the flare opening angle on both sides can be designed to appropriate values in two steps. The amount of TM ₁₁ mode and TE ₁₂ mode generated can be obtained. Also, since higher-order modes do not propagate in the frequency band lower than the above frequency band f ₁ ,
Due to the difference in the shape of the discontinuity at both ends of these circular waveguides, the radiation characteristics in the low frequency band do not change. From the above, in a certain frequency band f _i , the desired TM ₁₁ mode can be obtained without degrading the radiation characteristics in the frequency band lower than the frequency band f _i.
The TE ₁₂ mode can be generated, and the desired radiation characteristics can be obtained not only for the cross polarization component but also for the main polarization component.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration explanatory view showing an embodiment of the present invention.
(1) is a conical horn, (2a), (3a) is circular waveguide and flared for the frequency band f _1, (2b), (2c) is first of different inner diameter for the frequency band f _2, a second Circular waveguides, (3b) and (3c) are first and second flares for the frequency band f ₂ , and (4a) and (4b) are feed waveguides for the frequency bands f ₁ and f _2, respectively. Is. Note that this horn antenna is used in frequency bands f ₁ and f ₂ , and the frequency of frequency band f ₁ is lower than the frequency of frequency band f ₂ . In addition, the case where the frequencies of the frequency band f ₁ and the frequency band f ₂ are far apart from the conventional one will be described. Here, the inner diameter of the circular waveguide (2a) is set to the dimension in which the TM ₁₁ mode propagates in the frequency band f ₁ . Furthermore, the inner diameter of the first circular waveguide (2b) is the frequency band f ₁
, The dimensions satisfy the following condition A _{1 in} which higher-order modes do not propagate and the condition B _{1 in} which TM ₁₁ mode and TE ₁₂ mode propagate in the frequency band f ₂ and the second circular waveguide (2
The inside diameter in c) is a dimension that satisfies the above condition A ₁ and the following condition C _{1 in} which the TM ₁₁ mode propagates in the frequency band f ₂ .

Here, the above conditions A ₁ , B ₁ , and C ₁ are the inner diameter of the circular waveguide is D, the lowest frequency of the frequency band f ₁ is f _1l , and the highest frequency is f ₁ .
_1h , the lowest frequency of the frequency band f ₂ is f _2l , and the highest frequency is f _2h .

Condition A ₁ Condition B ₁ Condition C ₁ However, in the formulas (1) to (3), C is the speed of light. Indicates.

The axial length of each circular waveguide and the opening angle of each flare shall be determined as described later.

In the conical horn antenna with such a structure, the radio wave in the frequency band f ₁ is fed from the feed waveguide (4a) to TE ₁₁ which is the fundamental mode of the circular waveguide, and then the circular waveguide (2a ) The TE ₁₁ mode is the higher mode TM at the discontinuity at both ends
Converted to ₁₁ . Since there are two degrees of freedom here, the axial length of the circular waveguide (2a) and the opening angle of the flare (3a), it is possible to control the amplitude and phase of the TM ₁₁ mode generation amount, and the TE ₁₁
Since the desired ratio TM ₁₁ mode can be combined with the mode, the cross polarization component is small and the E plane and H of the main polarization component are
It is possible to obtain good radiation characteristics in which the shapes of the surfaces are almost equal.

Next, for radio waves in the frequency band f ₂ , the feed waveguide (4b)
Power is supplied from TE ₁₁ mode. Each In discontinuity across TM ₁₁ and TE ₁₂ mode of the first circular waveguide from the structure (2b) and the second circular waveguide (2c), to generate the TM ₁₁ mode. In addition, when the frequencies of the frequency band f ₁ and the frequency band f ₂ are separated to some extent, some of the TE ₁₁ modes are TM ₁₁ , TE ₁₂ , TM _{12 at} the discontinuity at both ends of the circular waveguide (2a). , TE ₁₃ ,
Converted to each higher-order mode such as TM ₁₃ . However, the axial length of the circular waveguide (2a) and the opening angle of the flare (3a) depend on the frequency band f ₁
And constant pine from the conditions in, there is no degree of freedom with respect to the number fraction band f _2. Therefore, the radiation pattern of each mode generated in the above discontinuity is obtained, and for the H plane of the main polarization component of the above radiation pattern, the TE ₁₂ mode generated at both discontinuities of the circular waveguide (2b). And the E-plane occurs at the discontinuity at both ends of the circular waveguide (2b).
After considering TM ₁₁ mode it can be corrected by the TM ₁₁ mode generated by the discontinuous portions at both ends of the circular waveguide (2c).

Thus, the TM ₁₁ mode and the TE ₁₂ mode in the frequency band f ₂ can be maintained without changing the amount of higher-order modes generated in the frequency band f ₁ .
Since the amount of generated modes can be controlled individually, good radiation characteristics can be realized in both of the above frequency bands.

In the embodiment shown in FIG. 1, the case where the feed waveguide (4a) for the frequency band f ₁ is connected in the middle of the horn antenna has been described, but the feed waveguide (4b) for the frequency band f ₂ is described. The same effect can be obtained by installing a feeding waveguide of a size that can be shared by frequency band f ₁ and frequency band f ₂ at position () and feeding radio waves in both frequency bands. Further, in FIG. 1, the case where the circular waveguide and the flare are used as the structure for generating the higher-order mode has been described, but as shown in FIG.
The same effect can be obtained when the iris (5) is provided inside one or both of the second and second circular waveguides or when a step is used instead of the flare.

Further, FIG. 3 is a structural explanatory view showing another embodiment of the present invention. This horn antenna has three frequency bands f ₁ , f ₂ ,
Used in f ₃ . Here, it is assumed that the frequency in the frequency band f ₁ is the lowest and the frequency in the frequency band f ₃ is the highest.

In the figure, (1) is a conical horn, (2d) and (3d) are high-order mode generators for the frequency band f ₁ , circular waveguides and flares, (2e) and (3e) are for the frequency band f ₂ . Circular waveguide and flare in the higher-order mode generator of (2f), (2g), (3f), (3
g) is a high-order mode generator for frequency band f ₃
And the second circular waveguide and the first and second flares, (4c),
(4d) and (4e) are feed waveguides for the frequency bands f ₁ , f ₂ , and f ₃ , respectively.

Here, the case where the inner diameter of each circular waveguide is determined as follows will be described as an example, depending on the relationship of each frequency band. That is, in the frequency band f ₁ , only the TM ₁₁ mode propagates as a higher-order mode inside the circular waveguide (2d), and in the frequency band f ₂ higher-order inside the circular waveguides (2d) and (2e). TM ₁₁ as mode
Only mode propagates and circular waveguide (2d) in the fractional band f ₃
And, a number of higher-order modes such as TM ₁₁ , TE ₁₂ and TM ₁₂ propagate inside (2e), and the inner diameter of the first circular waveguide (2f) is higher in the frequency bands f ₁ and f ₂ . The following conditions for the mode to propagate
TM ₁₁ mode as a higher-order mode in A ₂ and frequency band f ₃
The following condition B _{2 in which the} TE ₁₂ mode propagates is satisfied, and the inner diameter of the second circular waveguide (2g) is as follows: In the condition A ₂ and the frequency band f ₃ , only the TM ₁₁ mode propagates as a higher-order mode. conditions
Satisfy C ₂ .

Here, the above conditions A ₂ , B ₂ , and C ₂ are the inner diameter of the circular waveguide is D, the minimum frequency of the frequency band f ₂ is f _2l , and the maximum frequency is f ₂ .
_2h , the lowest frequency of frequency band f ₃ is f _3l , and the highest frequency is f _3h .

Condition A ₂ Condition B ₂ Condition C ₂ However, in equations (4) to (6), Is the same as the expressions (1) to (3).

In the horn antenna having such a structure, radio waves in the frequency bands f ₁ , f ₂ , and f ₃ are fed from the feeding waveguides (4c), (4d), and (4e) in the same manner as described above, and the TE ₁₁ mode is obtained. After that, a part of it is converted into higher-order modes as described below at the discontinuities at both ends of each circular waveguide (2d) to (2g). In the frequency band f ₁ , the desired amount of TM ₁₁ mode can be obtained by designing the circular waveguide (d) and flare (3d). In the frequency band f ₂ , both ends of the circular waveguide (2d) can be obtained. After considering the TM ₁₁ mode generated from the discontinuity part, the desired generation amount of TM ₁₁ mode can be obtained by designing the circular waveguide (2e) and flare (3e). In the frequency band f ₃ , after considering various higher-order modes generated from both ends of the circular waveguide (2d) and both ends of the circular waveguide (2e), the first circular waveguide (2f) and the first circular waveguide (2f) are considered. flare (3f) can be obtained a desired generation amount of TE ₁₂ mode by designing further TM ₁₁ be generated from the discontinuity of the two ends of the circular waveguide (2f)
By designing the second circular waveguide (2g) and the second flare (3g) taking the mode into consideration, it is possible to obtain a desired TM ₁₁ mode generation amount. As described above, desired generation amounts of higher-order modes can be obtained in each of the three frequency bands f ₁ , f ₂ , and f ₃ , so that good radiation characteristics can be obtained in each frequency band.

In the above, the case where the number of frequency bands is two or three has been described, but the same effect can be obtained even when the number of frequency bands is generally n. That is, the lowest frequency band is f ₁ , the highest frequency band is f _n, and the higher-order mode generators corresponding to each frequency band from frequency f ₁ to frequency band f _n are sequentially connected from the opening side to the feeding side. In addition, at least one high-order mode generator for each frequency band f _i among the above-mentioned higher-order mode generators has a higher-order mode in a frequency band f _i-1 lower than the above-mentioned certain frequency band f _i. A first circular waveguide having an inner diameter satisfying the following condition B in which the higher-order modes of TM ₁₁ mode and TE ₁₂ mode propagate in the following condition A in which it does not propagate and its frequency band f _i , and the above condition A And in the frequency band f _i , the following condition C in which the higher mode of TM ₁₁ mode only propagates
With a combination of a second circular waveguide having an inner diameter satisfying
The circular waveguide is placed on the opening side, and the two circular waveguides are connected by flare, so that good radiation characteristics can be obtained in the frequency band f _i . By performing such a design sequentially from the lower frequency band, good radiation characteristics can be realized in each frequency band.

Here, the above conditions A, B, and C are the inner diameter of the circular waveguide is D, the lowest frequency of the frequency band f _i-1 is f _i-1l , and the highest frequency is
f _i-1h , the lowest frequency of the frequency band f _i is f _il , the highest frequency is f _ih
Then, it can be expressed as the following equation.

Condition A Condition B Condition C However, in equations (7) to (9), Is the same as the expressions (1) to (3).

Further, also in the case of the embodiment shown in FIG. 3 and the case where the number of the frequency bands is a plurality of n, it is the same as described above for the embodiment shown in FIG. 1, and the following (1) to ( It is obvious that the same effect can be obtained in the embodiment of 3). That is, (1) a plurality of feed waveguides for each frequency band are also used as one feed waveguide on the feed side of the horn antenna,
(2) An iris is provided inside one or both of the first and second circular waveguides as a structure for generating a higher-order mode, and (3) a step is used instead of flare as a structure for generating a higher-order mode. ,.

〔The invention's effect〕

Since the present invention is configured as described above,
Since it is possible to obtain the desired amount of higher-order modes that can cancel the cross polarization components and correct the E and H planes of the main polarization components in a plurality of frequency bands, the cross polarization components can be obtained in each frequency band. It is possible to obtain a good radiation pattern in which the main polarization component is rotationally symmetric.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention, and FIGS. 2 and 3 are structural explanatory views showing another embodiment of the present invention.
4 and 5 are explanatory views of the structure of a conventional multi-mode horn antenna, and FIG. 6 is a schematic view showing electrolysis of each mode and its X and Y components in a cross section of a circular waveguide, and FIG. FIG. 4 is a characteristic diagram showing a radiation pattern when a conical horn is excited in each mode. In the figure, (1) is a conical horn, (2a) to (2k) are circular waveguides, (3a) to (3k) are flares, (4a) to (4h) are feeding waveguides, (5a) to (5b) is an iris. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A conical horn antenna which is used in a plurality of frequency bands and which is excited in a plurality of modes in which a higher mode is added to a fundamental mode (TE ₁₁ ) of a circular waveguide, wherein the conical horn antenna is a conical horn. And a structure in which the higher-order mode generators corresponding to each frequency band from the lower frequency band f ₁ to the higher frequency band f _n are sequentially connected from the opening side to the feeding side. At least one frequency band
Condition A in which the higher-order mode generator for f _i does not propagate higher-order modes in the frequency band f _i-1 lower than the above-mentioned frequency band f _i
And the frequency band f _i , the first circular waveguide having an inner diameter satisfying the condition B for propagating the higher modes of the TM ₁₁ mode and the TE ₁₂ mode, and the condition A and the frequency band f _i The second circular waveguide having an inner diameter satisfying the condition C for propagating the higher-order mode of TM ₁₁ is combined, the first circular waveguide is arranged on the opening side, and the two circular waveguides are connected. A conical horn antenna having the above configuration.