JPS60217702A - Circularly polarized wave conical beam antenna - Google Patents

Abstract

PURPOSE:To obtain a circularly polarized wave conical beam with simple constitution by feeding power to a microstrip antenna from two points with a phase difference of 90 deg. at the higher harmonic mode of TM210. CONSTITUTION:The antenna of microstrip constitution is formed with a radiation element 9, a feeding circuit 10 with 90 deg. phase difference, a feeding point 16 and termination circuits 14, 15. In exciting the radiation element 9 in the TM210 mode, the radiation electromagnetic field in the direction of the vertical axis is zero and the radiation directivity forms a conical beam. In feeding power to the radiation element 9 from the two points with the electric phase difference of 90 deg., a circularly polarized wave is obtained and the directivity keeps the said conical beam. Moreover, in adopting the higher order mode of the THmno for the exciting mode with the spatial angle of the feeding point selected to (90/m) degrees, the circularly polarized conical beam is obtained even when the power is fed with the electric phase difference of 90 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a circularly polarized antenna having a simple configuration and a thin shape *a, and radiating a conical beam.

(Prior art and problems) Fig. 1 is a diagram showing an example of the use of a conical beam antenna, in which 1 is a ship, 2 is an antenna, and 3 is a line connecting points of equal electric field strength of the conical beam of the antenna. , 4 is a geostationary satellite,
5 represents a vertical axis, and 6 is a line indicating the main beam direction.

For example, when communicating between a ship and a satellite, in order to enable communication without being tracked regardless of the movement or direction of the ship, the antenna beam pattern should be such that its main beam is as shown in Figure 1. It is sufficient that the beam has a shape close to a cone, with the generating line being the line in the direction from the antenna toward the satellite with respect to the vertical axis 5, and this is called a conical beam.

Conventionally, as a circularly polarized antenna having such a conical beam, there has been a Los Gui ball array antenna as shown in FIG. In FIG. 2, 3 is a line connecting points of equal electric field strength of the conical beam of the antenna, 5 is a vertical axis, 6 is a line indicating the main beam direction, 7 is a die ball, and 8 is a feed line.

However, this antenna has a three-dimensional structure, increases the height of the antenna, and has the drawback that the coaxial line length for power feeding is different, making power feeding complicated.

FIG. 3 is a diagram showing another configuration example of a conventional circularly polarized antenna having a conical beam, in which 8 is a feed line, 9 is a radiation conductor plate, 11 is a dielectric, 12 is a conductor substrate, and 16 is a feeding point,
17 indicates a microstrip feed line.

This antenna has a planar structure compared to the antenna shown in Figure 2, but in order to obtain a conical beam, it is necessary to excite opposing elements in opposite phases, and multiple elements and feed distribution lines are connected. Although the shape is thin, the structure is large in plan.

(Objective of the Invention) In order to eliminate these drawbacks, the present invention uses a one-element TMmno mode excitation microstrip antenna in which m is 2 or more, and has a phase difference of 90 degrees in the radiation direction. By arranging a feeding circuit that excites the radiating conductor plate from two points on two straight lines passing through the center of the radiating conductor plate and forming an angle of 90/m degrees (m in TMmno mode) from each other in a phase relationship, the radiating element 1 A conical beam is obtained with a simple structure consisting of an element and a feeder circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and the like of the present invention will be described in detail below based on drawings of embodiments.

(Embodiments of the Invention) The resonant frequency f0 of the TMmno mode excitation microstrip antenna is given by the following equation, as is well known.

Here, KIIIn is a Bessel function of the first kind J'
The n-th solution of m (X)=0 is shown, where C is the speed of light in vacuum and εr is the relative permittivity of the dielectric of the substrate. In addition, 1. ae in equation (1) indicates the effective equivalent radius of the radiation conductor plate, and the edge effect (fringing effect)
et ), the radius a of the radiation conductor plate is
is related to by the following equation.

where d is the dielectric thickness.

TMmn, mode excitation microstrip antenna 1
Radiation directivity g (θ, φ) when feeding from two feeding points
is given by the following equation.

g (θ, φ) = 60 E; ・・・・・・・・・・・・
・(3) Here, Eθ= −CJ m−+ (u)−J 114−l (
u) ) cosmφ ・Old... (4) Eφ= (J m
-+ (u)+ J m++ (u) )c086'
sir+IIlφ...(5).

where J is a Bessel function of the first kind, Ko is a propagation constant in free space, and ae is an effective equivalent radius given by equation (2).

In addition, the radiation directivity gc (θ, φ) when exciting circularly polarized waves by two-point feeding is given by g (θ, φ) given by equation (3).
φ) is given by the following equation.

FIG. 4 is a diagram showing an embodiment of the present invention, in which T M !
The case of a one-element microstrip antenna excited in 10 modes is shown. In FIG. 4, 9 is a radiation conductor plate, 10 is a 3 dB hybrid as a 90 degree phase difference feeding circuit, 11 is a dielectric, 12 is a conductor substrate, and 14 is a 1
74 wavelength line, 15 is a chip resistor, and 16 is a feeding point.

When exciting in T M 21° mode, K in equation (1)
mn hani 2. =3,054.

Figure 5 shows T M z +. Figures showing the surface current distribution of a mode-excited microstrip antenna.
This shows the case where power is supplied from two points on a straight line.

In the embodiment shown in Fig. 4, power is supplied from two points on two straight lines passing through the center and forming an angle of 45 degrees, so the surface current distribution is
As shown in Figure (b), the internal electromagnetic fields for power feeding from each point are orthogonal to each other. That is, the radiated electromagnetic fields of the T M 21° mode excitation microstrip antenna are also orthogonal, and circularly polarized waves are radiated by feeding the two feeding fish so that the feeding phase difference between them is 90 degrees.

At this time, TM2. . Since it is excited by the mode, the radiation electromagnetic field in the vertical axis direction is zero, and the radiation directivity remains a conical beam. Therefore, in the case of a T M 210 mode excitation microstrip antenna like this example, it is possible to
By feeding with a phase difference of 0 degrees, a circularly polarized conical beam can be obtained with one element.

FIG. 6 shows an example of radiation directivity calculated using equation (7). The parameter in the figure is the dielectric constant of the dielectric material of the substrate.

In addition, as a circuit for generating a 90 degree phase difference, #
Figure 4 shows the case where a 3 dB hybrid is used. In this way, by providing the power supply circuit on the same surface as the radiating element, power can be supplied from the back of the board using one connector.

In this case, a simpler antenna configuration can be achieved by terminating one end of the hybrid gummy using a 1/4 wavelength line and a chip resistor.

Above, we have shown the TM21G mode here, but
The same applies to other higher-order modes, for example, T M
In the case of 310 mode, Kmn=4.201,
A similar result can be obtained by feeding power with a phase difference of 90 degrees from a point on a straight line forming 30 degrees.

Further, the radiating element need not be limited to a circular shape, and similar results can be obtained with a rectangular element.

FIG. 7 is a diagram showing another embodiment of the present invention, 131
It shows a parasitic conductor plate. As in this example, by loading the parasitic conductor plate in parallel above the radiation conductor plate,
The resonant frequency characteristics due to the loading of the parasitic conductor plate are superimposed on the resonant frequency characteristics of the microstrip antenna when the parasitic conductor plate is not loaded, and the resonant frequency characteristics change. Therefore, 2
A wide band can be achieved by appropriately selecting the spacing and size ratio of the conductor plates.

Figure 8 shows the VSWR when the parasitic conductor plate is loaded and when it is not loaded.
An example of the characteristics is shown below. It can be seen that the band is widened by loading the parasitic conductor plate.

Furthermore, if a parasitic conductor plate as shown in Fig. 7 is constructed by printing on a printed circuit board, and a dielectric material such as foamed plastic is sandwiched and bonded between the parasitic conductor plate and the radiation conductor plate, Since the radiation conductor plate, feeder circuit, etc. are hidden and weather resistance is increased, a stable antenna that is less affected by aging can be obtained.

(Effects of the Invention) As explained above, the circularly polarized conical beam antenna of the present invention uses a single-element high-order mode excitation microstrip antenna and a 90-degree phase difference circuit placed on the same plane as the antenna. By feeding power from two points, there is an advantage that a conical beam can be obtained with a simple configuration, and it can be applied, for example, as an antenna mounted on a mobile body in communication using a satellite.

[Brief explanation of the drawing]

Figure 1 shows an example of the application of a conical beam antenna, Figure 2
The figure shows a conventional cross guiball array antenna.
FIG. 3 is a diagram showing another configuration example of a conventional circularly polarized antenna having a conical beam, FIG. 4 is a diagram showing an embodiment of the present invention, and FIG. 5 is a TM. FIG. 6 is a diagram showing a calculation example of radiation directivity, FIG. 7 is a diagram showing another embodiment of the present invention, and FIG. 8 is a diagram showing the distribution of surface current of a mode-excited microstrip antenna. It is a figure showing an example of actual measurement. 1... Ship, 2... Antenna, 3...
... Line connecting the points of equal electric field strength of the conical beam of the antenna, 4 ... Geostationary satellite, 5 ... Vertical axis, 6 ... Main beam direction. The line shown is 7...
...Cross dipole, 8...Feed line, 9.
... Radiation conductor plate, 10 ... 90 degree phase difference feeder circuit, 11 ... Dielectric, 12 ...
・Conductor board, 13...Passive conductor plate, 14...
...1/4 wavelength line, 15...Chip resistor, 16...Feed point, 17...Microstrip feed line agent Patent attorney Izumi Honma 2 times Figure 3 Figure 5 (a) (b) Figure 6 1 Darkness θ (dt4

Claims (1)

[Claims] The invention has a structure in which a conductor substrate is spread on one side of a dielectric plate, and a radiation conductor plate or a radiation conductor plate and a parasitic conductor plate are arranged on the other side of the dielectric plate. A TM with a coefficient of 2 or more where the radiated electromagnetic field on the vertical axis passing through the center of the radiating conductor plate is minimal.
In the mn0 mode excitation microstrip antenna, the antennas pass through the center of the radiation conductor plate and form 90/m degrees from each other (m is TM haze n. mode) with a phase relationship such that there is a 90 degree phase difference in the radiation direction. 2i on two straight lines. A circularly polarized conical beam antenna characterized by having a feeding circuit that excites a radiation conductor plate from a radiating conductor plate.