JPH0724361B2 - Dual polarization parabolic cylinder antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is used in a radar or a communication device using microwaves when switching or radiating radio waves of two polarizations orthogonal to each other. The present invention relates to a parabolic cylinder antenna for dual polarization.

(Prior Art) In fields such as radar and communication using microwaves, radio waves of mutually orthogonal polarized waves may be emitted simultaneously or by switching. For example, in the case of a parabolic cylinder antenna, when using a horn antenna formed of parallel conductor plates as a feed antenna,
A radio wave of a polarized wave orthogonal to the parallel conductor plate (hereinafter referred to as a orthogonal polarized wave) and a polarized wave parallel to the parallel conductor plate (hereinafter referred to as a parallel polarized wave) are radiated to the outside from the opening of the horn. When traveling, the traveling direction of radio waves may differ.

FIGS. 6a and 6b are diagrams for explaining the operation of the conventional horn antenna, and the side surfaces of each are composed of two parallel conductor plates. Fig. 6a shows the paths of radio waves inside and outside the horn antenna when the modified beam is generated so that the radiation pattern shows the cosec ² θ characteristic, and Fig. 6b shows the offset feed to the parabolic cylinder type reflector. 3 shows the paths of radio waves inside and outside the respective horn antennas when performing.

6a and 6b, 1 and 2 are horn antennas, and 1a and 2a.
Is the aperture surface of the horn antenna, 1b and 2b are equivalent power supply positions, L ₁ and L ₂ are emitted from positions 1b and 2b, and after being reflected by the reflective surface inside the horn, they are externally exposed from the open surfaces 1a and 2a. Of the radio waves radiated to, the traveling directions of orthogonally polarized radio waves whose traveling directions are not perpendicular to the opening faces 1a and 2a, respectively are shown. Since this orthogonally polarized radio wave propagates in the TEM mode in the parallel conductor plate of the horn antenna, the guide wavelength inside the horn antenna is almost equal to the free space wavelength and does not refract when exiting from the aperture 1a or 1b. Go straight. On the other hand, parallel polarized radio waves propagate in the TE mode (usually TE ₁₀ fundamental mode) in the parallel conductor plate of the horn antenna, so the guide wavelength inside the horn antenna becomes larger than the free space wavelength, and the The index becomes smaller than 1 with respect to the free space, and causes a refraction phenomenon when it goes out from the opening surface. In FIGS. 6a and 6b, L ₁ ′ and L ₂ ′ indicate the traveling directions of the parallel polarized radio waves.

In this way, when there is a radio wave whose traveling direction is not perpendicular to the opening surface of the horn antenna, the traveling direction of the radio wave is different between the case of orthogonal polarization and the case of parallel polarization when exiting from the opening surface. Like Therefore, when both polarized waves are switched and used, the radiation pattern is different.

(Problems to be Solved by the Invention) As described above, in the case of a parabolic cylinder antenna using a horn antenna as shown in FIG. 6a as a feed antenna, the shape of the modified beam is different for both polarizations. In the case of a parabolic cylinder antenna using a horn antenna as shown in FIG. 6b as a feed antenna, the main radiation directions become different for both polarized waves. In addition to not being able to obtain circularly polarized radio waves within a predetermined angle range, the problem that even when switching between both polarizations causes a difference in the reception levels of both polarizations There was a point.

According to the present invention, in a horn antenna used as a feed antenna of a parabolic cylinder antenna, even if there is a radio wave in which the traveling direction of the radio wave is not perpendicular to the opening surface, the radiation direction of the radio wave from each point on the opening surface is polarized at right angles. It is an object of the present invention to provide a dual-polarization dual-purpose parabolic cylinder antenna that solves the above-mentioned problems by making the same for waves and parallel polarized waves.

(Means for Solving the Problems) The present invention has an opening surface and a reflection surface, and two opposing surfaces are formed by parallel conductor plates, and can transmit radio waves of both parallel polarization and orthogonal polarization. A parabolic cylinder antenna using a horn antenna as a feed antenna, wherein when propagating and radiating the radio wave from an opening face, the traveling direction of all or part of the radio wave is not perpendicular to the opening face, the horn antenna Between the parallel conductor plates, a dielectric material having a uniform cross-section parallel to the parallel conductor plates in the vicinity of the opening surface and having a special relation to the output surface with respect to the radio wave input surface is provided. Even if the direction of propagation of radio waves from the reflecting surface to the input surface of the dielectric is not perpendicular to the opening surface by inserting it,
Both polarizations radiated from the parabolic cylinder antenna are made to pass through the dielectric so that the traveling directions of the radio wave when radiated to the outside from the aperture surface are the same for both polarizations. The beam shape of the radio wave and the main radiation direction are made equal to each other.

(Operation) As described above, the present invention is one in which a dielectric is inserted inside a parallel conductor plate inside an opening surface of a horn antenna used as a feed antenna of a parabolic cylinder antenna.

When a radio wave propagates inside a dielectric inserted inside a parallel conductor plate, the wavelength inside the dielectric differs between parallel polarization and orthogonal polarization. The refractive indices when the light enters the parallel conductor plate are different from those when the light is radiated from the dielectric body into the parallel conductor plate, and the parallel polarized light is refracted more. When a radio wave propagates in a parallel conductor plate, the guide wavelength is almost the same as the free space wavelength in the case of orthogonal polarization, but becomes larger than the free space wavelength in the case of parallel polarization, and the refractive index is Becomes less than 1 and refracts when it is radiated to the outside from the aperture surface. Utilizing such characteristics, in the present invention, an inclination that satisfies a certain relationship is provided between the input surface and the output surface of the electric wave of the dielectric, and the electric wave of parallel polarization is transmitted from the dielectric to the parallel conductor plate. By adjusting the angle of radiation of parallel polarized waves, the angle when parallel polarized waves are radiated from the aperture to free space can be made to approximately match the angle of radiation of orthogonal polarized waves, eliminating the above-mentioned problems. can do.

(Embodiment) FIG. 1 is a diagram for explaining the operation of a horn antenna used as a feed antenna of a parabolic cylinder antenna of the present invention, and FIG. 1a is a side view of the horn antenna of one embodiment of the present invention. FIG. 1b is a sectional view taken along the line AA of FIG. 1a. In FIGS. 1a and 1b, 10 is a horn antenna whose side plate is composed of a parallel conductor plate, 10a is an opening face of the horn antenna, and 10b is an equivalent power supply which is linear in a direction perpendicular to the parallel conductor plate. Position, 10c is a radio wave input surface (in this embodiment, it is used as a transmitting antenna), 10d is a reflecting surface, 11 is a dielectric, and β is a surface of the dielectric 11 whose input surface is parallel to the opening surface 10a. Angle L, L ₁₀ is the traveling direction of a part of the radio waves emitted from the power supply position 10b, and a is a horn antenna
It is the distance between 10 parallel conductor plates. FIG. 2 is a view for explaining the action of the dielectric, and shows a cross section in a plane parallel to the parallel conductor plate of the dielectric 11. The cross section is uniform in the direction perpendicular to the parallel conductor plate. In FIG. 2, T ₁ and T ₂ are the radio wave input and output surfaces of the dielectric 11, P is the incident point of the radio wave in the traveling direction L ₁₀ on the input surface T ₁ , and Q is the radio wave incident on the incident point P. Where R is parallel polarization, the output point from the output plane T ₂ is R, the output point from the aperture plane 10a of the radio wave of parallel polarization is Q ′ and R ′.
Is an output point from each output surface T ₂ and the aperture surface 10a when the radio wave incident on the incident point P is orthogonally polarized, and i ₀ is a right angle to the traveling direction of the radio wave incident on the incident point P and the aperture surface 10a. , I ₁ and r ₁ are the angle of incidence and the refraction angle at the incident point P of the parallel-polarized power source (hereinafter, the angle between the incident surface and the perpendicular to the output surface at the output point). say), i ₂ and r ₂ are each, refraction and incident angles at the output point Q of the radio wave of the polarization parallel incident from the incident point P, i ₃ and r ₃ is the radio wave passing through the respective output point Q The incident angle and the radiation angle at the output point R, α is the inclination angle of the output surface T ₂ with respect to the input surface T ₁ , and L ₁₀ ′ is the incident point P.
Direction of orthogonal polarization incident on
The origin of the coordinates provided at an arbitrary position on the line of intersection of T ₁ , u is the coordinate axis taken in the direction of the line of intersection, and v is the coordinate axis taken in the direction perpendicular to the coordinate axis u on the cross section.

Next, the operation of the horn antenna of the above embodiment will be described with reference to FIGS. 1 and 2. The radio wave input from the input surface 10c of FIG. 1 is reflected from the equivalent power supply position 10b to the reflection surface 10d.
After being emitted toward and reflected by the reflecting surface 10d,
It passes through the dielectric 11 and is radiated to the outside through the opening 10a. The distance a between the parallel conductor plates is selected as λ / 2 <a <λ for the free space wavelength λ of the radiated radio wave, and the aperture plane 10a
If the length of is larger than the wavelength λ, the input surface 10c
When the radio wave input from is parallel polarized, the propagation mode in the horn antenna 10 is TE ₁₀ mode in the parallel conductor plate, and when it is orthogonal polarized, it is almost TEM mode.

Therefore, the guide wavelength in the horn antenna 10 is different for both polarizations, and the traveling directions of the radio waves of both polarizations after entering the dielectric 11 are different.

Below, in order to consider the behavior of radio waves in terms of geometrical optics, first the refractive indices of both polarizations are obtained.

The guide wavelength in the parallel conductor plate for parallel polarized waves is λg, the guide wavelength in the dielectric 11 is λg _D , the refractive index of the dielectric 11 with respect to the outside of the dielectric is n _D , and the outside of the parallel conductor plate opening surface 10a Is n _P , the guide wavelength in the dielectric 11 for the orthogonally polarized radio wave is λ _D , the refractive index of the dielectric 11 outside the dielectric is n _D ′, and the relative permittivity of the dielectric is ε. Then, the following equations (1) to (6) are established.

However, from the above description, it is assumed that the guide wavelength of the orthogonally polarized radio wave in the parallel conductor plate is equal to the free space wavelength λ. Therefore, the orthogonally polarized radio wave is not refracted when radiated from the opening surface 10a.

Since the relative permittivity ε> 1, the above equation (4),
From (5) and (6), the relationship of n _D > n _D ′>I> n _P (7) holds. Therefore, in FIG. 2, the orthogonally polarized radio wave is refracted upward at the incident point P to a lesser degree than the parallel polarized radio wave, so that the output point Q ′ is below the output point Q. Similarly, the orthogonally polarized radio wave is less refracted downward at the output point Q ′ than the parallel polarized radio wave. Further, the orthogonally polarized radio wave is not refracted when radiated from the aperture 10a, whereas the parallel polarized radio wave is refracted upward at the aperture 10a. Therefore, it can be seen that there is a possibility that the radiation angles of the orthogonally polarized waves and the parallel polarized waves from the aperture surface 10a can be made equal by appropriately selecting the value of the inclination angle α. Hereinafter, this point will be described in more detail using an equation.

The refraction angle at the incident point P for the orthogonally polarized radio wave is
r ₁ ′, the incident angle and the refraction angle at the output point Q ′ respectively
i ₂ ′, r ₂ ′, the incident angle and the radiation angle at the output point R ′ (the angle between the direction perpendicular to the opening surface 10a and the traveling direction of the radio wave) i
₃ ′, r ₃ ′, and the input surface T ₁ of the output surface T _{2 at} the output point Q ′
When the inclination angle with respect to is α ′, the following equations (8) to (12) are obtained from the geometrical conditions for the parallel polarization and the orthogonal polarization.

i ₁ = i ₀ −β (8) i ₂ = r ₁ + α (9) i ₃ = r ₂ −α + β (10) i ₂ ′ = r ₁ ′ + α ′ (11) i ₃ ′ = r ₂ ′ −α ′ + Β (12) Further, when Snell's law regarding refraction is applied at the incident point P, the output points Q and Q ′, and the output points R and R ′, the following equations (13) to (18) are obtained.

r ₃ ′ = i ₃ ′ (18) Here, assuming that i ₀ = β = O, and considering α from FIG. _It can be seen that ₃ = r ₃ ′ = 0 and they are equal. From this, it can be inferred that when the angles i ₀ and β are considerably smaller than 1, all other angles are also significantly smaller than 1. Therefore, if an approximate expression such as sin i ₁ i is used, and if the change of the angle i ₀ with respect to the position on the input surface T ₁ is gradual, an approximation αα ′ can be made, and therefore the following expressions (19) and (20) And can be derived. That is, equations (8), (9),
From (13) and (14), r ₂ i ₀ −β + n _D α is obtained, and from this equation and equations (10) and (15), r ₃ n _P i _O ＋ n _P (n _D −1) α (19 ) Get Similarly, equations (8), (11), (12), (1
6) to give (17) and (from _{18) r 3 'i O +} (n D' -1) α (20). From the formulas (19) and (20), the condition for the radiation angles from the aperture plane 10a of both polarized waves of parallel and right angles to be equal is r ₃
By setting = r ₃ ′, the following equation can be obtained.

α = Ki _O (21) That is, in order to equalize the radiation angle for both polarizations, the equation (21) is an inclination angle α with respect to the input face T ₁ of the output face T ₂ of the dielectric 11, the traveling direction of the radio wave incident on the input face T ₁ It can be seen that it suffices to be proportional to the angle i ₀ which is the direction perpendicular to the opening surface 10a. The proportional constant K at this time is given by the equation (22).

Since equations (21) and (22) are independent of the angle β, the input surface T ₁
Does not have to be a flat surface, but may be a curved surface that changes gently within a range in which the value of β does not become too large.

The angle i ₀ in the equation (21) is the value at the input point P,
When the change of the angle i ₀ with respect to the position on the input surface T ₁ is gradual as described above, the value i ₀ (u) of the angle i _{0 at} the same u coordinate as the output point Q is approximately used. You can

If the coordinates of the output point Q is (u, v), then dv / du = −α, so using equation (21) and the above approximation, To get Integrating the above equation gives To get Where u ₁ is the value of u at the lower end of the dielectric 11, and v ₁ is u =
It is the value of v in u ₁ . Equation (23) is the output surface of the dielectric 11.
It is a display formula of the section curve of T ₂ , and the value of the angle i ₀ in the u coordinate
It is shown that when i ₀ (u) is given, the relationship between u and v that determines the shape of the cross-sectional curve can be obtained.

Until now, the angles i ₀ and β were considerably smaller than 1, but when the angles i ₀ and β were much larger, the above equation (8) was used.
By satisfying (18) as it is, the relation between α and i ₀ such that r ₃ = r ₃ ′ is obtained. However, the calculation in this case becomes complicated.

In the embodiment described above, the distance a between the parallel conductor plates of the horn antenna has a constant value, but in order to make the directivity spread in a plane perpendicular to the parallel conductor plate appropriate, the width of the opening surface 10a (parallel conductor In some cases, it is desired to set the width in the direction perpendicular to the plate) to a value different from the distance a.

FIG. 3 is a view showing a method of converting into an opening when the horizontal width and the distance between the parallel conductor plates are different, and is a sectional view perpendicular to the parallel conductor plate and the opening surface 10a of the horn antenna. FIG. 3a is an example of step conversion, and B is a step part. Also, FIG. 3b
Is an example of taper conversion, and C is a tapered portion. b indicates the width of each opening surface 10a. In the case of step conversion as shown in FIG. 3a, when a radio wave passes through it, it does not refract in the case of orthogonal polarization but refracts in the case of parallel polarization.

In the case of parallel polarization, the refractive index to the outside from the opening surface 10a of the parallel conductor plate portion whose width is b The incident angle to the step portion B is ia, the refraction angle is ra, and the opening surface 10a
Let ib be the incident angle at and rb be the radiation angle, then the relational expression of sin ia / sin ra ＝ n _Q / n _P , sin ib / sin rb ＝ 1 / n _Q , ib ＝ ra holds. From the above relational expression, sin rb ＝ n _P sin
ia is obtained.

On the other hand, if there is no step, the parallel polarized radio wave will enter the aperture surface 10a at the incident angle ia, and if the radiation angle at this time is rc, sin ia / sin rc = 1 / n _P The equation holds, and sin rc = n _P sin ia is obtained from this equation. Therefore, the relation rc = rb can be obtained from the relational expression sin rb = sin ia. That is, the aperture plane 10
It can be seen that the emission angle from a is the same with or without steps.

Next, increase the number of steps and set the width value of each step to a
Since the radiation angle from the opening surface 10a does not change even if the order is changed from 1 to b, the radiation angle from the opening surface 10a is tapered even in the limit of taper conversion as shown in FIG. 3b. Will be the same as if there were no.

It can be seen that even if the step conversion or the taper conversion is performed in this way, the characteristic of the present invention that the radiation angles of the radio waves of both parallel and orthogonal polarizations from the aperture surface 10a are equal is maintained.

As described above, in the horn antenna, it is possible to make the radiation angles of both polarized waves parallel and perpendicular to the same,
The beam shape of the horn antenna and the main radiation direction are almost the same for both polarized waves. (To be precise, a slight difference in the beam shape due to the difference in the power distribution of both polarizations at the aperture surface of the horn antenna remains, but it is practically negligible.) FIG. 4 is a configuration diagram in the case where a dual polarization dual parabolic cylinder antenna is configured by combining the horn antenna of the example with a parabolic cylinder type reflecting mirror. FIG. 4a shows a modified beam, and FIG. 4b shows an offset feed. is there.

In FIGS. 4a and 4b, 12 and 13 are parabolic cylinder type reflecting mirrors, and F ₁ and F ₂ are the focal axes of the reflecting mirrors 12 and 13, respectively. Intersection line between a plane perpendicular to the focal axis F ₁ and F ₂ of each of the reflecting mirror 12 and 13 has a parabola the intersection of the focal axis F ₁ and F ₂ and the plane and focal point. The line of intersection between the plane including the reflecting mirror 12 and the focal axis F ₁ of each of the 13 and F ₂ has a straight line parallel to each focal axis F ₁ and F _2.

In FIGS. 4A and 4B, the horn antenna 10 is a mirror 12 of the husband and the husband.
The aperture planes are placed near the focal axes F ₁ and F _{2 of} and 13. In the case of FIG. 4a, the horn antenna 10 radiates a modified beam of radio waves, which is reflected by the reflecting mirror 12,
The final beam is formed, but the beam shape in the plane including the focal axis F ₁ is almost the same as the modified beam of the horn antenna 10.

In the case of FIG. 4b, the horn antenna 10 radiates a radio wave that is inclined upwards from the direction perpendicular to the opening surface, and this radio wave is reflected by the reflecting mirror 13 to form the final beam. Is in a direction different from the direction perpendicular to the focal axis F ₂ .

5a and 5b are horn antennas used as feed antennas of the parabolic cylinder antenna of the present invention shown in FIG.
FIG. 5 is a diagram showing an example of a traveling direction of a radio wave within 10, wherein FIG. 5A shows a modified beam and FIG. 5B shows an offset feed. FIG. 5a shows an inverse cosecant 2 as a deformed beam.
In the case of obtaining the beam characteristics, some radio waves in the lower part are radiated in the main direction, while some radio waves in the upper part are gradually radiated in the direction away from the main direction. In such a case, the dielectric 11 has a shape such that the lower portion has a constant thickness and the upper portion has a gradually decreasing thickness. Since the inclination angle β is not set to zero, the radio wave does not enter the dielectric 11 at a right angle below, and therefore the radio wave reflected by the input / output surface of the dielectric takes a path different from the radio wave path until it enters. Therefore, the input standing wave ratio of the horn antenna 10 is improved. In this way, the inclination angle β is useful for improving the input standing wave ratio characteristic of the horn antenna. In the case of FIG. 5b, since the inclination angle β is selected to be zero, the electric wave is incident on the dielectric 11 at an obliquely constant angle, and the shape of the dielectric 11 becomes linear as it goes upward. Will be bigger. Further, in this case, even if the inclination angle β is zero, the radio wave does not hit the input / output surface at a right angle, so that the input standing wave ratio of the horn antenna 10 becomes good. In the offset feed shown in FIG. 5b, the directivity in the plane parallel to the parallel conductor plate of the horn antenna 10 is not deformed, but the offset beam as shown in FIG. It is possible to In this case, the shape of the dielectric 11 is such that the output surface of the dielectric 11 in FIG. 5b is overlaid with the input surface of the dielectric 11 in FIG. 5a.

(Effect of the Invention) As described in detail above, according to the present invention, two opposing surfaces in the vicinity of the opening are made of parallel conductor plates and propagate a two-polarization radio wave of parallel polarization and orthogonal polarization. In the two-polarization parabolic cylinder antenna using a horn antenna as a feed antenna such that all or some of the radio waves radiated from the opening face are not perpendicular to the opening face, A dielectric is provided between the parallel conductor plates in close proximity to each other, and the dielectric has a uniform cross section in a plane parallel to the parallel conductor plates, and the inclination of the output surface with respect to the input surface is in the traveling direction of the incident electric wave and the opening surface. By forming so as to be proportional to the angle formed by the perpendicular direction with a specific relationship, even if the traveling direction of the electric wave incident on the input surface of the dielectric is not perpendicular to the opening surface, Opening The angles of radiation from the surfaces can be equal.

Even when the width of the aperture and the distance between the parallel conductor plates are different, the radiation angles of the two polarized waves can be equalized by providing the stepwise or tapered propagation portion. Therefore, in a dual-polarization common parabolic cylinder antenna using the horn antenna configured as described above as a feed antenna of the parabolic cylinder antenna, even if the modified beam, the offset feed, and the offset feed of the modified beam are performed, The beam shape and the main radiation direction with respect to can be made substantially equal. In this way, in the parabolic cylinder antenna, the conventional problems when forming circularly polarized waves can be solved, and when the two polarized waves are switched and used, the phase of the beam shape and the direction of the main beam with respect to the two polarized waves can be solved. The conventional inconvenience due to the difference can be eliminated.

Therefore, the present invention can be applied to various fields such as a transmitter device and a communication device using microwaves, and great effects can be expected.

[Brief description of drawings]

1a is a side view of an embodiment of a horn antenna used in the present invention, FIG. 1b is a sectional view taken along the line AA of FIG. 1a, and FIG. 2 is a view for explaining the action of a dielectric. FIG. 3 is a sectional view showing a method of converting the horn antenna into an aperture plane, FIG. 4 is a configuration diagram of an embodiment of the present invention, and FIG. 5 is an example of a traveling direction of a radio wave in the horn antenna used in the present invention. FIG. 6 and FIG. 6 are diagrams for explaining the operation of the conventional horn antenna. 1,2 …… Horn antenna, 1a, 2a …… Aperture, L ₁ , L ₂ ……
Direction of orthogonally polarized radio waves, L ₁ ′, L ₂ ′ ... Direction of parallel polarized radio waves, 10 …… Horn antenna, 10 a …… Aperture surface, 10 c …… Radio wave input surface, 10 d …… reflecting surfaces, 11 ...... dielectric, T ₁ ...... radio wave input surface of the dielectric 11, T ₂ radio wave output surface of the ...... dielectric 11, L ₁₀ ...... traveling direction of the part of the radio wave, a ......
Distance between parallel conductor plates, b ... lateral width of the opening surface when converted to the opening surface, B ... step portion, C ... taper portion,
F ₁ , F ₂ ...... Focal axis, 12, 13 ...... Reflector.

Claims (2)

[Claims] 1. An electric wave which has an opening surface and two opposing surfaces are formed by parallel conductor plates, propagates an electric wave polarized in parallel or at a right angle to the parallel conductor plate, and radiates from the opening surface. In the dual-polarization parabolic cylinder antenna configured as a feed antenna, the horn antenna having a radiation characteristic such that the traveling direction of all or some of the radio waves is not perpendicular to the aperture surface, inside the aperture surface of the horn antenna. A dielectric is inserted inside the parallel conductor plate, and the shape of the dielectric is constant in a direction in which a cross section parallel to the parallel conductor plate is perpendicular to the parallel conductor plate. The angle (α) formed between the input surface and the output surface is the angle (i ₀ ) formed between the traveling direction of the radio wave incident on the input surface and the direction perpendicular to the opening surface, and the dielectric constant for the radio waves of the two polarized waves. To the outside of the body's dielectric The horn antenna formed so as to be proportional to the product of the refractive index and a constant (K) determined by the refractive index of the parallel polarized radio wave from the aperture plane to the outside is configured as a feed antenna. Parabolic cylinder antenna for dual polarization. 2. A propagating portion having a stepwise or tapered shape in a cross section of a plane orthogonal to the parallel conductor plate symmetrically between the opening surface of the horn antenna and the dielectric is provided. Parabolic cylinder antenna for dual polarization described.