JP3326160B2 - Horn antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a horn antenna connected to a circular waveguide.

[0002]

2. Description of the Related Art In general, horn antennas are characterized by higher antenna efficiency and wider bandwidth than microstrip antennas, and are widely used as primary radiators of reflector antennas and element antennas of array antennas. It's being used.

FIG. 1 shows a method of feeding a horn antenna.
Generally, power is supplied by mode conversion from a coaxial line to a waveguide as shown in FIG. Here, reference numeral 91 denotes a horn flare portion, and 92 denotes a circular waveguide, which has an axially symmetric structure with respect to the central axis. Reference numeral 94 denotes a connector, and 93 denotes a probe. As a similar method, there is a power supply method having a configuration as shown in FIG. Here, a circular-rectangular waveguide converter 95 is connected behind the circular waveguide 92, and a probe 97 is provided in the rectangular waveguide 96. Feeding using this coaxial-waveguide conversion is considered to be a simple and good method when a horn antenna is used alone, but here a coaxial-waveguide converter with good matching is constructed. For this purpose, it is necessary to complicate the shape of the probe, cover the probe with a dielectric, or the like, which complicates the configuration of the coaxial-waveguide converter.

Next, the case where circular polarization is attempted will be considered. In this case, circular polarization is achieved by inserting a dielectric plate inside the circular waveguide or connecting a circular polarizer formed by changing the inner diameter of the circular waveguide on an orthogonal plane. This is a common method. However, in this case, there is a disadvantage that the horn antenna becomes long. As a method of circular polarization, there is a method of extracting orthogonal polarization components with an orthogonal probe and synthesizing circular polarization with a feed system separate from the antenna, but in this case, the disadvantage that the entire antenna becomes complicated is obtained. is there.

Next, a problem in the case of arraying will be considered. When a horn antenna is used as an array antenna element or cluster-type primary radiator, a feed circuit composed of a waveguide system should be used to reduce the power loss of the feed system and achieve the desired excitation conditions. is necessary. However, the components of the waveguide system such as the power distributor and the phase shifter become large, so that the configuration of the feed system becomes complicated and the weight becomes large. In addition, in order to increase the gain without generating grating lobes in an array, it is necessary to set the element spacing to a value of one wavelength or less. In this case, the power supply system is arranged very densely. The construction of the system becomes mechanically difficult.

[0006]

As described above, in the conventional horn antenna, in the case of feeding using a coaxial-waveguide converter, the structure of the probe is complicated in order to improve the matching. was there. Further, in the case of arraying, circular polarization, and the like, there is a problem that the power supply system becomes large and often becomes mechanically complicated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a horn antenna in which matching can be easily achieved in antenna excitation, and a feed system can be easily and compactly formed even in the case of arraying and clustering.

[0008]

According to a first aspect of the present invention, there is provided a horn antenna comprising a circular waveguide and an end portion of an outer conductor having a smaller diameter than the circular waveguide. Department
A coaxial waveguide coaxially connected to an end of the circular waveguide through a flat feeder circuit provided orthogonally to the coaxial waveguide and configured by a triplate line or a suspended line And formed in the planar power supply circuit.
Is electrically exposed between the inner and outer conductors of the coaxial waveguide.
A horn antenna comprising an excitation unit .

According to a second aspect of the present invention, there is provided a horn antenna comprising a circular waveguide, a tapered portion, and a small-diameter side of the tapered portion.
And a cylindrical portion of the same diameter following the large diameter side of the tapered portion.
Is an outer conductor connected to the circular waveguide, and the outer conductor
A cylindrical portion located within the cylindrical portion and the outer conductor from the cylindrical portion;
Tapered portion extending into the tapered portion
A coaxial waveguide with a conductor, and orthogonal to the coaxial waveguide.
And a triplate line or suspender
A planar power supply circuit composed of
Formed in the type feeding circuit, between the inner and outer conductors of the coaxial waveguide.
And an electrically exposed excitation unit . The horn antenna according to the third aspect of the present invention has a circular shape.
A waveguide and one end of the circular waveguide through a first step.
A cylindrical first end having a smaller diameter than the circular waveguide to which the end is connected;
An outer conductor and the other end of the first outer conductor via a second step
The second outer conductor having a smaller diameter than the first outer conductor to which one end is connected.
A conductor and a first coaxially disposed first coaxial conductor within the first outer conductor.
And the first conductor disposed in the second outer conductor.
A larger diameter than the first inner conductor coaxially connected to the inner conductor;
A coaxial waveguide having a second inner conductor, and the coaxial waveguide
Installed at right angles to the triplate line or suspension
A planar power supply circuit composed of pendant lines,
The planar power supply circuit is formed inside and outside the coaxial waveguide.
And an exciting portion electrically exposed between the conductors . A horn antenna according to a fourth aspect of the present invention is a horn antenna according to any one of the first to third aspects.
A tener, wherein the excitation unit is provided in the planar power supply circuit.
Two excitation parts are provided, and the two excitation parts are orthogonal to each other.
And the excitation phase difference is 9
Power is supplied so as to be 0 degrees . The horn antenna according to the fifth aspect of the present invention provides the horn antenna according to the first to fourth aspects.
The horn antenna according to any one of the preceding claims, wherein
Set the outer conductor inner diameter and inner conductor outer diameter of the axial waveguide
Outside, a value such that only TE11 mode radio waves propagate
It is characterized by having been set .

In the horn antenna according to the present invention, a part of the planar feeder circuit constituted by the triplate line or the suspended line is electrically exposed in the coaxial waveguide, so that the exposed part becomes an excitation source and becomes coaxial. Emit radio waves into the waveguide. This radio wave is transmitted from the coaxial waveguide to the circular waveguide after being converted from the propagation mode of the coaxial waveguide to the propagation mode of the circular waveguide, and is radiated from the horn antenna opening surface.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a horn antenna according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the configuration of a horn antenna according to the present invention. The horn antenna is connected from the top in the order of a horn flare 31, a circular waveguide 32, a coaxial waveguide 33, a planar feed circuit 34, a coaxial waveguide 35, and a conductor plate 36. Here, horn flare 31, circular waveguide 3
2. The coaxial waveguide 33, the coaxial waveguide 35, and the conductor plate 36 are all axially symmetric with respect to the central axis AA.

The planar power supply circuit 34 includes a coaxial waveguide 33
And the coaxial waveguide portion 35 and the dielectric substrate 3
8, 39. A conductive film pattern 40 is formed on the dielectric substrate 38 by etching. FIG. 2 shows the state of the conductor film pattern 40 as viewed from above the dielectric substrate 39.

In the excitation section 41, a triplate line is formed by the conductor film pattern 40, and this is connected to the connector 37 at a point B. The triplate line is partially formed in the coaxial waveguide 3 in the portion A.
3 and 35, which are electrically exposed. This portion serves as an excitation unit 41, and radiates radio waves into the coaxial waveguides 33 and 35.

Here, in order to improve the transmission of radio waves from the triplate line to the coaxial waveguides 33 and 35, it is necessary to match the input impedance observed at the point C with the line impedance. This is facilitated by using the / 4 wavelength transformer 42 and the stub 43. That is, for the resistance component of the input impedance, the line width of the quarter-wave transformer 42 is adjusted, and for the reactance component, the line length of the stub 43 is adjusted, so that the matching can be easily improved.

In order to propagate the radio waves generated in the coaxial waveguides 33 and 35 in one direction of the coaxial waveguide, a conductor plate 36 is provided at the end of the coaxial waveguide 35 to reflect the radio waves. By selecting the depth of the coaxial waveguide 35 to be about 1/4 of the guide wavelength, the reflected wave from the bottom surface propagates in phase with the radio wave propagating to the upper portion. Radio waves propagating through the coaxial waveguides 33 and 35 are converted and propagated in the propagation mode of the circular waveguide, and are radiated from the horn aperture.

The outer conductor inner diameter and the inner conductor outer diameter of the coaxial waveguide 33 and the coaxial waveguide 35 are the same, and the outer conductor inner diameter of the coaxial waveguide is a and the inner conductor outer diameter is b. Here, a and b are set so that the coaxial waveguide propagates to the fundamental mode TE11 and cuts off to the next higher-order mode TE21 mode. That is,

(Equation 1) A and b are set so that the following equation is satisfied.

Here, c = a / b, λ 0 is the free space wavelength of the radio wave, and π is the pi. xm1 (m = 1, 2) is the first root of the following differential equation of the Bessel-Neumann function. )

(Equation 2) J'm is the derivative of the m-order Bessel function, and N'm is the derivative of the m-order Neumann function.

By selecting a and b in this way, the fundamental mode is propagated through the coaxial waveguides 33 and 35, and the TE 21
Unnecessary higher-order modes or more can be prevented from propagating. For example, when c = 1.1, 0.17λ0 <a <
If it is 0.33λ0, the TE11 mode propagates and the higher-order mode does not propagate. If the same conditions are applied to the case of a circular waveguide, 0.29λ0 <radius <0.49λ0, so that in the case of the coaxial waveguides 33 and 35, the fundamental mode has a smaller diameter than the circular waveguide. Can be transmitted.

As can be seen from the above description, the horn antenna of this embodiment can be integrated with the feed system, and the use of the coaxial waveguide and the planar feed circuit makes the whole antenna very simple. Become compact. Further, the matching at the excitation point can be easily performed by using the planar circuit. Further, the use of a feeder circuit having a triplate structure allows components including MMICs to be installed therein, which is very effective as an active antenna.

In the embodiment described above, if the size of the waveguide is set so that the characteristic impedance of the propagation mode of the coaxial waveguide and that of the circular waveguide are the same, radio waves can propagate with good matching. Go. However, since the characteristic impedance of the propagation mode of the coaxial waveguide and that of the circular waveguide are not necessarily the same, in this case, the reflection characteristic is deteriorated at the connection point between the coaxial waveguide and the circular waveguide. Hereinafter, a method of improving this point will be described.

FIG. 3 shows an embodiment of the present invention in which the above problem is solved.

This embodiment is characterized in that a coaxial waveguide taper 50 is connected between the circular waveguide 32 and the coaxial waveguide 33 of the horn antenna shown in FIG. The coaxial waveguide taper portion 50 is provided to gradually convert the characteristic impedance of the coaxial waveguide 33 into the characteristic impedance of the circular waveguide, and to improve the matching of radio wave propagation. In this case, a configuration in which a coaxial waveguide transformer section 51 is provided as shown in FIG. The length of the coaxial waveguide transformer section 51 is selected to be 1/4 of the guide mode wavelength in the propagation mode, and its characteristic impedance Z
The inner diameter of the outer conductor and the outer diameter of the inner conductor are set so that r is as follows.

[0024]

(Equation 3) Here, ZCR is the characteristic impedance of the circular waveguide 32, Z
cx is the characteristic impedance of the coaxial waveguide 33. By doing so, the consistency of radio wave propagation is improved as in the case of the configuration of FIG.

With the configuration shown in FIGS. 3 and 4, matching can be achieved without matching the characteristic impedances of the circular waveguide and the coaxial waveguide, so that the diameter of the coaxial waveguide can be set freely.
Its size can be made as compact as possible.

Up to this point, the case of exciting linearly polarized waves has been described, but circularly polarized waves can be easily excited by changing the structure of the exciting section 41. An embodiment in that case will be described below.

When circular polarization is performed, circular polarization can be easily performed only by changing a part of the planar feed circuit 34 in the horn antenna shown in the embodiment of FIG. FIG. 5 shows the configuration of the planar power supply circuit 34 when circularly polarized wave excitation is performed. Here, a conductive film pattern 60 is formed on the dielectric substrate 39 by etching, and serves as a feeder circuit for a triplate line. Here, the excitation unit 61,
Reference numerals 62 are perpendicular to each other, are connected to a 90-degree hybrid, are excited by a 90-degree phase difference, and can emit circularly polarized waves. Here, mutually opposite circularly polarized waves are generated at the feeding points D and F, so that right-handed and left-handed circularly polarized waves can be simultaneously transmitted or received. With the above configuration, an antenna capable of simultaneously transmitting or receiving left and right circularly polarized waves can be easily realized by slightly changing the configuration of the planar power supply circuit, and can be formed compact.

Next, consider a TEM mode that may occur in the coaxial waveguide regardless of the diameter.

The above description does not particularly discuss the TEM mode. Because the coaxial waveguides 33, 3
This is because even if a TEM mode is generated in 5, the TEM mode does not propagate in the circular waveguide, so that the radiation characteristic from the antenna does not matter much. But,
In some cases, a resonance phenomenon occurs in the coaxial waveguides 33 and 35, which may adversely affect the characteristics of the entire antenna.

FIG. 6 shows a configuration example of the planar power supply circuit 34 for preventing the occurrence of the TEM mode. Here, a conductive film pattern 65 etched on the dielectric substrate 9 is shown. Exciters 63 and 64 are located at 180-degree symmetry about the central axis of the horn antenna, and are connected to a 180-degree hybrid. Here, the points G and H are connected to the connector, terminated at the point G, and the point H is an input / output port. With such a configuration, the excitation units 63 and 64 are excited in mutually opposite phases, and only the TE11 mode is excited in the coaxial waveguide. For the TEM mode, the excitation from the two excitation units cancels each other out, and therefore does not occur in the coaxial waveguide. With such a configuration, the occurrence of the TEM mode in the coaxial waveguide does not adversely affect the antenna characteristics.

The same effect can be obtained by changing the configuration of the antenna of the present invention as follows.

Although FIG. 1 shows the case of a cone horn antenna, a corrugated horn or a dual mode horn antenna can be constructed by using a corrugated horn or a step horn in the horn flare portion. In this case, an efficient primary radiator can be configured as a reflector antenna.

In the planar power supply circuit, an example of a two-layer structure using a dielectric substrate has been described. However, a honeycomb sandwich structure may be used instead of the dielectric substrate, and a power supply system using a suspended line may be used. The same effect can be obtained even if it is configured. Further, it is easy to make a complicated power supply circuit having a multi-layered planar circuit by increasing the number of layers very small, and a multifunctional antenna can be formed by incorporating an MMIC device.

Next, an embodiment in which the horn antenna of the present invention is formed into an array will be described.

FIG. 7 shows an array of the horn antenna of the present invention, in which four elements (horn antennas P, Q, R,
The figure which took out only S) and was seen from the upper surface is shown. A- of FIG.
FIG. 8 is a cross-sectional view when the antenna is cut vertically along the line A. Here, the horn antennas P, Q, R, and S, which are element antennas, are respectively horn flare 71, circular waveguide 72, coaxial waveguide taper 73, and coaxial waveguide 7 from the top.
4. Planar feeding circuit 77, coaxial waveguide 78, conductor plate 79
Are connected in this order. The planar power supply circuit 77 is configured by superposing dielectric substrates 75 and 76, and uses a screw 80 to fix them. The diameter of the coaxial waveguides 74 and 78 is set so that the TE11 mode propagates and no higher-order mode propagates. By doing so, the coaxial waveguides 74 and 7 are compared with the circular waveguide 72 as described above.
8 can be made smaller, and even if the element spacing of the array antenna is made smaller, a feeder system configuration using the planar feeder circuit 77 is possible.

FIG. 9 shows a configuration example of a planar power supply circuit. This figure is a view of the conductor pattern 81 etched on the dielectric substrate 76 as viewed from above, and constitutes a feed circuit by a triplate line. Triplate line is A
The portion is electrically exposed to the inside of the coaxial waveguides 74 and 78, and serves as an excitation unit and radiates radio waves to the coaxial waveguides 74 and 78. The coaxial waveguide taper portion 73 is provided in order to perform radio wave propagation from the coaxial waveguide 74 to the circular waveguide 72 with good matching.

By configuring the above array antenna, the feed system can be easily realized by a planar feed circuit, and an arbitrary excitation distribution can be easily realized.
It is also very easy to incorporate a circuit for matching a quarter-wave transformer or a stub, or a circuit such as a hybrid coupler for circular polarization or a T-branch. Also in this case, since the feeding system can be configured to be thin, the size of the entire antenna is very small and light. Therefore, it is effective as an antenna for mounting on a satellite or a mobile object. In addition, the diameter of the coaxial waveguide can be reduced as compared with the case of using a circular waveguide, so that an array antenna can be configured by a dense arrangement in which the element spacing is set to one wavelength or less, and the generation of grating lobes is suppressed. Can also be used to maximize Furthermore, MMIC devices can be incorporated relatively easily, and are also important as active array antennas, which will increase in demand in the future.

[0038]

According to the horn antenna of the present invention, a horn antenna integrated with a feed system can be realized thin and compact. Moreover, circular polarization can be performed by a feed circuit having a simple configuration, and switching between right-handed and left-handed polarization can be easily performed. Further, it is possible to easily match the input impedance at the excitation point of the feeder circuit and to match the circular waveguide from the coaxial waveguide, thereby realizing an efficient antenna. In addition, even in the case of an array, a power supply system that sets an arbitrary excitation distribution can be configured compactly.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a horn antenna according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a planar power supply circuit of the horn antenna of FIG. 1;

FIG. 3 is a sectional view of a horn antenna according to another embodiment of the present invention.

FIG. 4 is a sectional view of a horn antenna according to another embodiment of the present invention.

FIG. 5 is a diagram showing another example of the configuration of the planar power supply circuit of the horn antenna of the present invention.

FIG. 6 is a diagram showing still another example of the configuration of the planar power supply circuit of the horn antenna of the present invention.

FIG. 7 is a plan view showing an embodiment in which the horn antenna of the present invention is formed into an array.

FIG. 8 is a sectional view of the horn antenna shown in FIG.

FIG. 9 is a diagram showing a configuration of a planar power supply circuit when a horn antenna of the present invention is formed into an array.

FIG. 10 is a sectional view showing a configuration of an example of a conventional horn antenna.

FIG. 11 is a sectional view showing another configuration of a conventional horn antenna.

[Explanation of symbols]

 31, 71 Horn flare 32, 72 Circular waveguide 33, 35, 74, 78 Coaxial waveguide 34, 77 Planar power supply circuit 38, 39, 75, 76 Dielectric substrate 36, 79 Conductor plate 41, 61, 62 Excitation section 42 1/4 wavelength transformer 43 Stub 50, 73 Coaxial waveguide taper section 51 Coaxial waveguide transformer section

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-262702 (JP, A) JP-A-63-39206 (JP, A) JP-A-57-168506 (JP, A) US Patent 4,996,535 (US , A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01Q 13/02 H01P 1/16 H01P 5/107

Claims (5)

(57) [Claims] 1. A coaxial waveguide in which a circular waveguide and an end of an outer conductor smaller in diameter than the circular waveguide are coaxially connected to an end of the circular waveguide via a step. A tube, a planar power supply circuit provided orthogonal to the coaxial waveguide, and configured by a triplate line or a suspended line; and a planar power supply circuit formed between the inner and outer conductors of the coaxial waveguide. A horn antenna comprising an electrically exposed excitation unit. (2) A circular waveguide; A tapered portion and a cylindrical portion of the same diameter following the smaller diameter side of the tapered portion
And the large-diameter side of the tapered portion corresponds to the circular waveguide.
A connected outer conductor, located within the cylindrical portion of the outer conductor
A cylindrical portion extending from the cylindrical portion into the tapered portion of the outer conductor;
Coaxial with an inner conductor consisting of a tapered portion
A waveguide, A tri-plate line is provided orthogonal to the coaxial waveguide.
Plane consisting of two or suspended lines
Type power supply circuit, The planar power supply circuit is formed inside and outside the coaxial waveguide.
Having an exciting part electrically exposed between the conductors.
Horn antenna featured. (3) A circular waveguide; One end is connected to one end of the circular waveguide via a first step portion
Cylindrical first outer conductor smaller in diameter than the circular waveguide
And one end of the first outer conductor via a second step portion to the other end of the first outer conductor.
A second outer conductor smaller in diameter than the first outer conductor to which the first outer conductor is connected
And a first inner shaft coaxially arranged in the first outer conductor.
A conductor and the first inner conductor disposed within the second outer conductor;
A second inner conductor having a larger diameter than the first inner conductor coaxially connected to the body;
A coaxial waveguide having an inner conductor of A tri-plate line is provided orthogonal to the coaxial waveguide.
Plane consisting of two or suspended lines
Type power supply circuit, The planar power supply circuit is formed inside and outside the coaxial waveguide.
Having an exciting part electrically exposed between the conductors.
Horn antenna featured. Wherein provided at two of the excitation portion in the planar feeding circuit, the polarization components the two excitation portion are perpendicular to each other and excited in the coaxial waveguide, the difference between the excitation phase is 9
Claim 1, characterized in that it is powered so that the 0 °
A horn antenna according to any one of claims 1 to 3 . 5. A claims the outer conductor internal diameter and the inner conductor outer diameter of the coaxial waveguide, other than TEM mode is characterized by being set to a value such that only radio waves TE11 mode propagates
The horn antenna according to any one of items 1 to 4 .