JPS5922403A - Electromagnetic lens for horn antenna - Google Patents

Abstract

PURPOSE:To reduce possibly a reflecting loss, by forming concentrically many recessed grooves having a depth being 1/4 of the operating wavelength to the center axial line of a curved surface. CONSTITUTION:Many recessed grooves 111-11n are formed concentrically to the center axial line (l) of the curved surface of an electromagnetic lens 10 so that side face is provided along the axial line (l) and the other side face is placed with an angle of 45 deg. to said axial line (l), and the depth (d) in the direction of said axial line (l) is set to lambda/4 (where; lambda is the operating wavelength). When a ratio wave is made incident to the lens 10, the radio wave reflected at the bottom of the recessed grooves 111-11n is cancelled by a radio wave incident to the top.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radio wave lens for a horn antenna.
Since the radio waves radiated from the point travel inside the horn 1 as spherical waves, the phase of the radio waves at the horn aperture is shifted.

Conventionally, as shown in the figure, a radio wave lens 2 made of a dielectric material such as Teflon is placed in the opening of the horn 1, thereby correcting the phase shift. In other words, this radio wave lens 2 is connected to the path OAA' and the path O, for example.
Since the radio waves passing through BB' reach the aperture surface 4 (lens flat surface) at the same time, the phases of the radio waves at the aperture surface 4 can be matched.

By the way, in a horn antenna equipped with such a radio wave lens 2, in order to increase the effective aperture surface that contributes to radio wave radiation without changing the horn length, it is sufficient to increase the thickness of the lens 2. This reduces the efficiency of the antenna.

That is, on the surface of the lens 20, power is reflected, and when the electric field vector is parallel and perpendicular to the plane of incidence of the radio wave, the power reflection coefficients I'1' and F2' are equal to the normal line at the time of incidence of the radio wave. If the angle (incident angle) between the radio wave in the air and the direction of travel is φ, it is expressed as follows. 17''II, +7'!+, as the thickness of the lens 2 increases, the curvature of the curved surface of the lens becomes thicker, and the incident angle φ also increases accordingly.

It is clear from the graph shown in Figure 2 that the incident angle φ
When the power reflection coefficient becomes large, the power reflection coefficient becomes large, and as a result, the so-called power reflection loss increases.

An object of the present invention is to provide a radio wave lens that can reduce the reflection loss as much as possible.

Therefore, in the present invention, a large number of grooves having a depth of 1/4 of the wavelength used are formed in the curved surface concentrically with respect to the central axis of the curved surface.

will be explained in detail.

3, 4, and 5 are a plan view, a side view, and a sectional view taken along the line A--A in FIG. 4, showing an embodiment of a radio wave lens for a horn antenna according to the present invention.

As shown in the figures, this radio wave lens 10 has a large number of concave grooves IIl, 11*, .

The concave grooves 1b to lln are formed such that one side surface thereof is along the axis l, the other side is at an angle of 45°I with respect to the axis l, and the depth d in the direction of the axis l is λ/ 4(λ
is the used wavelength) K is set.

The lens 10 is formed so that the profile connecting the bottoms of the grooves 11+ to lln matches the curved shape of a commonly used radio wave lens.

The radio wave lens according to the present invention having the above configuration is arranged and fixed in the opening of the horn l shown in FIG. 1 in the same manner as the lens 2 shown in FIG.

Now, when radio waves are incident on this lens 10 from the virtual wave source 0 shown in FIG. 1, the radio waves reflected at the bottoms of the grooves 11+ to lln are canceled by the radio waves incident on the tops. That is, since the depth of the groove is set to 1/4λ, the reflected radio wave has a phase difference of λ/2 at the top portion from the radio wave incident on the top. be canceled out.

In this way, each of the above grooves 11! Since ~lln acts on the so-called matching layer, it corresponds to lens blooming with a refractive index of 9 and a thickness of 1/4λ, thereby reducing the reflection loss of the electric power transmitted to the surface of the lens 10.

In the above embodiment, the groove is formed to have a triangular cross section, but it may be formed to have a square cross section, or it may be formed to have a triangular shape different from that in the embodiment.

Further, as the number of grooves 111 to lln increases, the effect of reducing reflection becomes higher.

Note that the groove having the shape shown in the above embodiment can be formed using a single cutting tool with the cutting edge 45', so that machining is extremely easy.

As described above, according to the radio wave lens according to the present invention, the power reflection loss on the curved surface can be reduced.
It is ideal as a radio wave lens for horn antennas, which require a small size and a large effective aperture.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view conceptually showing a conventional horn antenna equipped with a radio wave lens, Fig. 2 is a graph illustrating the reflection characteristics of the radio wave lens, and Figs. A plan view and a side view showing one embodiment of the lens, and FIG. 5 is a sectional view taken along line A--A in FIG. 4. 10...Radio wave lens, -111~lln...Concave groove. Figure 1 Figure 2 IF7 Irishima Sunjida Figure 4 A Figure 5

Claims (1)

[Scope of Claims] α) A radio wave lens for a horn antenna, characterized in that a large number of concave grooves having a depth of 1/4 of the wavelength used are formed on a curved surface concentrically with respect to the central axis of the curved surface. (2) A radio wave lens for a horn antenna according to claim 12, wherein the groove is formed to have a triangular cross section.