JPH0131722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circularly polarized cone beam antenna that combines a linear antenna and an antenna using a radiation plate of approximately the same wavelength as used in wireless communication. It's about configuration.

FIG. 1A shows an explanatory diagram of the use of a conical beam. 101 is a ship, 102 is an antenna, 10
3 is the vertical axis, 104 is the isoelectric surface of the conical beam, 1
05 indicates a geostationary satellite, and 106 indicates a horizontal plane. When attempting to communicate between a satellite and a ship, the ship's antenna needs to have a beam pointing downward by θ ₀ from the vertical axis, as shown in the figure. Here, in order to eliminate the need for antenna control for vessel turning,
The beam must be rotationally symmetrical about the vertical axis. Such radiation characteristics are called a conical beam. Furthermore, since the plane of polarization relative to the satellite may rotate as the ship moves, it is preferable to use circularly polarized waves in the direction of the conical beam toward the satellite.

The present applicant previously proposed Japanese Patent Application Laid-open No. 107610/1983 as an antenna for radiating the circularly polarized conical beam as described above.

The structure of a conventional device of this type is shown in FIG. 1B. Here, 1 is the radiating element of the loop antenna, 2 is the small disk of the microstrip antenna, 3 is the large disk,
4 is a spacer, 5 is a feeder line to the loop antenna,
6 is the feed line to the microstrip antenna, 7
is the pillar of the loop antenna, 8 is the vertical axis, 9 is the horizontal axis, and 10 and 11 are the radiation directions from the loop and strip antennas, respectively. Here, the configuration of the loop antenna is similar to the loop antenna power feeding method described in "Ultra Short Wave Antenna" by Mushiaki Uchida, Corona Publishing, 1955, Chapter 12, P223. In addition, the distribution of the eight feed lines 5 is described in "Antenna Engineering Handbook" edited by the Institute of Electronics and Communication Engineers, Ohmsha, 1980.
This can be realized using the power divider described in Chapter 6, P244.

The operating principle of this antenna will be explained below. When the structural dimensions are given as shown in FIG. 1, the radiation characteristics from both antennas are expressed by the following equation.

Eθ ψ(θ)=Aθ ψJ ₁ (ka sinθ) (1) Here, E: radiated wave from the loop antenna with horizontal polarization, E〓: radiated wave from the strip antenna with vertical polarization, A 〓, A is the radiated wave intensity from the loop and strip antenna,
The independent variable of Eθ ψ is θ, J ₁ ( ) is a Bessel function of the first kind, k=2π/λ, λ: wavelength. By the way, when the distance between the plates (t) becomes large, the diameter of the radiation plate of the strip antenna is set to a', which is slightly smaller than a, so that the characteristic of equation (1) can be obtained. From equation (1), if A〓 and A are set to be equal, the radiation characteristics of the strip antenna and the loop antenna can be made completely equal. Therefore, circularly polarized wave characteristics can be obtained by providing a 90° phase difference between mutually perpendicular polarized waves from both antennas. Also, in order to obtain the radiation characteristics of a conical beam,
It is sufficient to design the circumferential length of the radiating elements of both antennas to be about 4 wavelengths. At this time, a radiation characteristic is obtained in which the radiation wave intensity (main beam) is maximum in the angular direction θ ₀ away from the zenith and is non-directional in the horizontal plane.

First, the basic operating principle of the antenna shown in FIG. 1B will be experimentally investigated. In the structure shown in FIG. 1, the radiation characteristics of the loop antenna are shown in FIGS. 2a to 2c. The solid line in the figure is the characteristic when power is fed only to the loop antenna. The dotted line is the characteristic of the strip antenna alone, which corresponds to the theoretical value of equation (1), and is obtained by removing the loop antenna from the structure shown in FIG. Figure 2 a is
2.5GHz, Figure 2b is 2.6GHz, Figure 2c is 2.7GHz
shows the characteristics of From the figure, it can be seen that over a wide band of 2.5 to 2.7 GHz, the radiation characteristics of the loop antenna in FIG. 1B are approximately similar to equation (1). Next, in FIG. 1B, actual measured values of the radiation characteristics of the strip antenna are shown in FIGS. 3a to 3c. Here, the solid line is the characteristic when power is supplied only to the strip antenna, and the dotted line is also equivalent to equation (1).
These are the characteristics of a single strip antenna. The measurement frequencies are 2.5 GHz and 2.5 GHz in Figure 3 a, b, and c, respectively.
2.6GHz, 2.7GHz. From the figure, it can be seen that in the configuration of FIG. 1B, the radiation characteristics of the strip antenna are significantly degraded from the characteristics of equation (1). Furthermore, in the configuration of FIG. 1B, the strip antenna
Figure 4 shows a comparison of the VSWR characteristics with those without a loop antenna. Here, the dotted line is the characteristic of the strip antenna alone, and the solid line is the characteristic when the loop antenna is attached. It can be seen that by installing the loop antenna above the strip antenna, the reflected waves are significantly increased. From this, it is considered that the cause of the deterioration of the radiation characteristics as shown in FIGS. 3a to 3c is due to the reflection of the radiation waves of the strip antenna by the loop antenna.

Judging from the above measured values, when using a loop antenna with the structure shown in Figure 1B, the loop feed line and radiating element reflect the radiation wave 11 from the strip antenna, and the radiation characteristics and VSWR characteristics The disadvantage was that it deteriorated the

The present invention aims to eliminate these drawbacks, and the feed line for the loop antenna is placed in the great circle of the strip antenna directly below each radiating element so that the feed line for the loop antenna is no longer in the same plane as the radiating element. It is configured to be lowered onto a board, and its characteristics are:
A circular microstrip antenna has a large circular plate and a small circular plate facing parallel to each other with a dielectric in between, and a radiating element arranged annularly in a plane, and the plane is a circular microstrip antenna. In a circularly polarized conical beam antenna that is placed on the side of the small circular plate of the strip antenna, parallel to the circular microstrip antenna, and so that the circular microstrip antenna and the center line of the ring coincide, The circumference of the ring is about 4 wavelengths, the circumference of the small disk of the circular microstrip antenna is slightly smaller than 4 wavelengths, and the large disk is sufficiently larger than the small disk, so that each radiation There is a circularly polarized cone beam antenna in which a plurality of coaxial cable feed lines to the elements are provided perpendicular to the plane and vertically through the large disk without touching the small disk.

Examples will be described below with reference to the drawings.

FIG. 5 shows an embodiment of the present invention. Compared to the configuration shown in FIG. 1B, the configuration has been changed so that the feed line to the loop antenna is directly lowered from the radiating element of the loop onto the large circular plate of the strip antenna below.
Each feeder line is configured to pass through the large circular plate and then be converged at one location to form a single feeder line.

In this configuration, since the radiation wave 11 from the strip antenna is vertically polarized, the rate of shielding by the loop feeding line and radiating element in the main beam direction θ ₀ can be significantly reduced.

The circumference of the loop antenna is approximately 4 wavelengths as in the case of Figure 1B, the circumference of the small disk is slightly smaller than 4 wavelengths, and the large disk is sufficiently larger than the small disk. .

Figures 6a to 6c show radiation characteristics in the .theta. direction when feeding power to the strip antenna, achieved by this configuration.
Compared to the radiation characteristics of a single strip antenna,
It can be seen that even when a loop antenna is added, the deterioration of radiation characteristics can be significantly improved. In Figure 6 a to c, the measurement frequencies are 2.5 GHz, 2.6 GHz, and 2.6 GHz, respectively.
The frequency is 2.7GHz, and the solid line shows the characteristics when power is supplied only to the strip antenna, and the dotted line shows the characteristics of the strip antenna alone, which corresponds to equation (1).

FIG. 7 shows radiation characteristics in the horizontal plane in the main beam direction. An almost uniform radiation level is achieved even in the horizontal plane, resulting in good cone beam properties. In addition, the radiation characteristics of the single loop are unchanged from the configuration shown in Figure 1B, and if the feeding phase is adjusted so that a 90° phase difference is given to the radiation waves from both antennas,
Good circularly polarized conical beam characteristics can be obtained.

From FIG. 7, it can be seen that with the structure shown in FIG. 5, the variation width of the characteristic electric field strength during power feeding to the strip antenna is 0.6 dB or less within a 360° angle change.

FIG. 8 shows the VSWR characteristic when feeding power to the strip antenna in the configuration according to the present invention. Here, the dotted line is the characteristic of the strip antenna alone,
The solid line shows the characteristics when the loop antenna is installed. Even with the addition of a loop antenna, performance can be obtained with almost no deterioration in VSWR characteristics.

In addition, by configuring the feed line to the loop antenna as in the present invention, there is an advantage that the feed line can also be used as a support pillar for the radiating element of the loop antenna, resulting in a small and strong circularly polarized conical beam. It has the feature that it is possible to realize an antenna with specific characteristics.

As explained above, by configuring the feeder line to the loop antenna's radiating element to fall vertically from the radiating element to the strip antenna surface below, the feeder line can be used as a support pillar for the loop antenna's radiating element. This feature allows the strip antenna to function effectively without deteriorating the radiation characteristics and VSWR characteristics of the strip antenna, making it possible to construct a compact and strong antenna and achieve excellent circularly polarized cone beam characteristics.

[Brief explanation of drawings]

FIG. 1A is an explanatory diagram of a conventional conical beam antenna, FIG. 1B is a configuration diagram of a conventional circularly polarized conical beam antenna, and FIGS. 2 a to c are antenna radiation characteristics when feeding with a loop antenna in the conventional structure. Figure 3a
~c shows antenna radiation characteristics when feeding power to a microstrip antenna in a conventional structure; FIG. 4 shows VSWR characteristics in a conventional structure; FIG. 5 shows a configuration diagram of a circularly polarized cone beam antenna according to the present invention; Figures a to c show the antenna radiation characteristics in this configuration.
Figure 7 is a diagram showing the antenna radiation characteristics in the horizontal plane in this configuration, and Figure 8 is a diagram showing the antenna radiation characteristics in the horizontal plane in this configuration.
FIG. 3 is a diagram showing VSWR characteristics. 1...Radiating element of loop antenna, 2...Small disk of microstrip antenna, 3...Large disk, 4...Spacer, 5...Feeding line to loop antenna, 6...Microstrip Feed line to strip antenna, 7... Support of loop antenna, 8... Vertical axis, 9... Horizontal axis, 10, 11... Direction of radiation from the loop and strip antenna.

Claims (1)

[Scope of Claims] 1 A circular microstrip antenna having a large circular plate and small circular plates facing in parallel with a dielectric sandwiched therebetween, and a radiating element arranged in a circular shape within a plane. and the plane is on the side of the small disk of the circular microstrip antenna and is parallel to the circular microstrip antenna, and the center line of the circular microstrip antenna and the ring coincide with each other. In the circularly polarized conical beam antenna arranged as shown in FIG. is sufficiently larger than the small disk, and a plurality of coaxial cable feed lines to each of the radiating elements are perpendicular to the plane and are provided so as to perpendicularly pass through the large disk without touching the small disk. A circularly polarized cone beam antenna characterized by: