JPH0352243B2 - - Google Patents

Description

Detailed Description of the Invention The present invention aims to obtain a desired pattern in each of the vertical and horizontal planes of a shaped beam antenna that shapes a radiation pattern by modifying the shape of a single reflecting mirror. One example is an antenna that performs fan-shaped beam shaping in the horizontal plane and cosecant square beam shaping in the vertical plane.

Traditionally, it has been found that it is impossible to perfectly shape the radiation pattern with this type of antenna. For example, when we say perfectly formed beams, we mean a fan-shaped beam in the horizontal plane and a cosecant squared beam in the vertical plane. This means that the beams are fan-shaped beams of equal level, and will be used in this sense below.

Therefore, as an approximate mirror surface shape, we have a shape that provides the desired radiation pattern only for the vertical center cross-section curve and the horizontal center cross-section line of the reflecting mirror, and for cross sections other than the center cross-section, A shape in which the cross-sectional curve was translated in parallel was used.

However, in an antenna having such a reflector shape, the elevation angle of the geometrical optical reflection direction of the reflected wave at a point other than the central cross-sectional curve is different from the elevation angle of the geometrical optical reflection direction of the reflected wave on the central cross-sectional curve. There is a phenomenon called getting tired. For this reason, there is a drawback that the pattern is different from the target perfectly formed pattern, and the degree of this is more noticeable in antennas with narrow beam widths in the vertical plane, which are often used in practical applications. .

In order to solve the above-mentioned drawbacks, the present invention brings the radiation pattern closer to a perfectly formed pattern by aligning the elevation angles of the reflected wave directions, and will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 1 is a primary radiator, 2 is a quadratic curved reflector, 3 is a vertical central cross-sectional curve, 4 is a horizontal central cross-sectional curve, and 5 and 5' are primary radiators. This figure shows the geometrical optical reflection direction of the radio waves that hit the non-quadratic curved reflector 2 from the device 1.

P and Q are specular points obtained by viewing the non-quadratic curved reflector 2 from the primary radiator 1 at a constant elevation angle α, of which P is on the vertical central cross-sectional curve 3.

Specifically speaking, the features of this antenna are as follows: The elevation angles θe and θ′e of the reflected waves at P and Q.
This makes it possible to align the directions in which radio waves should be concentrated and make the radiation pattern closer to a perfectly formed pattern.

Next, we will explain the mirror surface shape used in this antenna.The incident direction vector from the primary radiator 1 to the point Q on the reflector is Rin (R ^x in, R ^y in, R ^z in), and the normal to the reflector is When the vector is n (N _x , n _y , n _z ), the reflection direction vector Rout (R ^x out, R ^y out, R ^z out) is expressed by equation (1).

Rout＝Rin−2(Rin・n)n (1) Here, Rin is expressed by equation (2), and n is expressed by equation (3).

Rin＝sinαx^＋cosαsinβy^＋cosαcosβz(2) Here, ρ is the distance from the primary radiator 1 to the reflective surface of the non-quadratic curved reflector 2.

On the other hand, the elevation angle θ′ _e of the reflection direction vector can be found using equation (4).

Therefore, in order for the elevation angles of the reflection direction vectors to be equal at point Q and point P, the x component of the reflection direction vectors must be equal at each point. formula
(2) and equation (3) are substituted into equation (1) to find this condition, equation (5) is obtained. However, ρv is the distance from the primary radiator 1 to the vertical central cross-sectional curve 3 expressed as a function of α.

∂ρ／∂αsinαcos ² α＋2ρ∂ρ／∂αcos ³ α
＋∂ρ／∂βsinα−ρ ² sinαcos ² α／∂ρ／∂αcos ²
α＋∂ρ／∂β＋ρ ² cos ² α ＝dρv／dαsinαcos ² α＋2ρvdρv／dαcos
³ α−ρ ² _v sinαcos ² α／dρv／dαcos ² α＋ρ ² _v cos ² α(
5) By solving equation (5) under the condition that α = 0 and the solution matches the shape of horizontal center cross section curve 4,
The shape of the reflecting mirror can be determined.

Although this shape cannot be determined analytically,
It is easy to solve numerically using a computer.

Although no mention has been made here of how to obtain the vertical and horizontal central cross-sectional curve shapes, this can be easily obtained by a known method such as a method using power flux conditions and the law of reflection.

Above, we have described how to obtain the reflector shape using as an example the case where the horizontal central cross-section curve 4 intersects with the Z axis, but when the two do not intersect, that is, connecting the primary radiator 1 and the horizontal central cross-section curve 4. Even when the straight line and the Z _- axis form an angle θ _p , in the above calculation, the formula is
It is obtained by solving (5).

As explained above, in this antenna, the shape of the reflector determined as described above is used, that is, the elevation angle θ _e in the direction of the reflected wave at each point on the reflector viewed from the primary radiator at a constant elevation angle α. Since the shape is such that the beam width is equal, the radio waves are well aligned and concentrated in the direction in which they should be concentrated within the vertical plane with a narrow beam width, making it possible to bring the radiation pattern close to a perfectly formed state. Therefore, it is possible to effectively utilize the power radiated from the antenna, and it is possible to contribute to making the communication system more economical.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention. 1...Primary radiator, 2...Non-secondary curved reflector,
3...Vertical center cross-sectional curve, 4...Horizontal center cross-sectional curve, 5, 5'...Geometric optical reflection direction of reflected wave.

Claims (1)

[Claims] 1. In a shaped beam antenna having a primary radiator or a primary radiation system consisting of a primary radiator and a reflecting mirror, and one reflecting mirror consisting of a non-quadratic curved surface, the vertical and horizontal The central cross-section curve has a reflector cross-sectional shape that provides a desired radiation pattern within each central cross-section, and the reflector shape other than both central cross-sections has the final reflection of the primary radiator or primary radiation system. The non-quadratic curved reflecting mirror is characterized by having a reflecting mirror shape in which the directions of reflection of geometrical optical reflected waves at each point on the reflecting mirror all have the same elevation angle when looking at the non-quadratic curved reflecting mirror from the focal point of the mirror at a constant elevation angle. Shaped beam antenna.