JPS593042B2 - microstrip antenna - Google Patents

Description

Detailed Description of the Invention The present invention provides a microstrip antenna that actively utilizes the radiation loss of an unbalanced planar circuit resonator.
This invention relates to a structure that achieves a wide band by loading a conductor plate.

Microstrip antennas using unbalanced planar circuit resonators generally have the advantages of being small, lightweight, and low-profile.

Among them, FIG. 1 shows an example of the structure of a circular microstrip antenna in which the radiating element 1 is circular (radius a).

2 is a dielectric substrate that is sufficiently thin compared to the wavelength (relative permittivity εr,
3 is a ground plane conductor, and radio waves are radiated from the open peripheral end 4.

The resonant angular frequency of the fundamental mode of this resonator is α=1.841/ρ7. υ.

= can be approximated to the speed of light in a vacuum (3 x 8 m/Sec).

The feed point 5 can be provided at any suitable position inside the resonator or at the peripheral edge.

The equivalent Q value when power is supplied from the peripheral edge can be approximated as follows.

Here, Gr is the equivalent conductance representing radiation loss, and c
o is the equivalent capacitance of the circular resonator (λ0; wavelength in vacuum), tan δ is the loss angle of the dielectric substrate 2, and δ8 is the skin depth of the conductive foils 1 and 30.

Gr is a decreasing function with respect to ε1, εr−1 (air)
It is maximum when Gr<, 0.006 [mho]
It is.

Therefore, Gr10). Since δ7h<tanδz10-2~10-3, Q'=625Gr(h/λ0)+tanδ (
5).

hkuλ. Since it must be, h//2゜zlo-
If it is assumed that Qz is 2, the Q value is about 102 to 103, which is too large for an antenna.

Therefore, this type of antenna essentially has a narrow band, and the higher the dielectric substrate used, the higher the Q value (Qr=ω), which represents radiation loss.

Co/Gr) increases, the band becomes narrower. Therefore, when applying this type of antenna to a multi-channel system such as mobile communication, it is necessary to tune each channel by adjusting the LC circuit connected to the outside of the antenna, as shown in Figure 2. However, there were practical drawbacks.

The present invention aims to solve this problem by loading a conductive plate on the radiation surface side of the antenna and feeding power through this conductor by spatial coupling.

Thereby, the resonant frequency characteristic due to the conductor plate loading is superimposed on the resonant frequency of the microstrip antenna without the conductor plate loading, and it is possible to equivalently increase the width of equation (5) and widen the band.

The drawings will be described in detail below.

FIG. 3 shows an example of the structure of a microstrip antenna according to the present invention, in which 8 is a radiating element, 9 is a dielectric substrate, 10 is a ground plane conductor, 11 is a feed point, 12 is a feed line, 13 is an input terminal, and 14 is a The conductor plate support rod 15 is a conductor disk.

The center of the radiating element 8 is short-circuited to the ground plane conductor 10.

This is to fix the mode to be used, which in this case is a mode in which the electric field component at the center of the radiating element 8 is zero.

At this time, the input impedance seen from the input terminal 13 can be selected in the range from zero to almost infinity by moving the feeding point 11 in the radial direction of the radiating element 8.

Therefore, the feed point 11 can be set to achieve matching.

In the present invention, as shown in the embodiment of FIG.
5 is loaded by a conductor plate support rod 14, and the conductor disk 15 is spatially powered and operates as a new radiating element.

By appropriately selecting the radius and position of the conductor disk 150, the staggered bimicrostrip antenna can have a wide band.

FIG. 4 shows frequency characteristics of a microstrip antenna configured according to the present invention and an example of frequency characteristics of a conventional microstrip antenna.

16 shows the characteristics of a microstrip antenna not loaded with a conductor plate, and 17 shows the characteristics of a microstrip antenna loaded with a conductor plate.

Comparing these, it is clear that the bandwidth of the microstriped knob antenna of the present invention is expanded compared to the conventional one.

Although a circular microstrip antenna has been described as an example, it is not limited to a circular radiating element, and similarly, the conductor plate support rod 1 in FIG.
It should be noted that the same effect can be obtained by supporting the conductor plate using a suitable dielectric plate instead of 4.

As explained above, the microstrip antenna of the present invention can expand the band with a simple configuration of loading a conductor plate without sacrificing the advantages of being small, lightweight, and low profile. When this type of antenna is applied to a multi-channel system such as mobile communication, it is possible to provide necessary resonance band characteristics.

In the embodiment, the case where the number of conductor plates 15 is one is illustrated, but it is presumed that the effects of the present invention can be further improved by arranging a plurality of conductor plates in parallel at appropriate intervals.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional microstrip antenna.
Figure 2 is a resonance frequency tuning diagram when a conventional microstrip antenna is used in a multi-channel system, Figure 3 is a structural example of the microstrip antenna of the present invention, and Figure 4 is a diagram of resonance frequency tuning when a conventional microstrip antenna is used in a multi-channel system.
The figure shows a comparison of experimental data of the resonant frequency characteristics of the microstrip antenna with the configuration of the present invention and the resonant frequency characteristics of the microstrip antenna with the conventional configuration. 1.8...Radiating element, 2,9...Dielectric substrate, 3.10...Ground conductor, 4...
・Open peripheral edge, 5°11...Power supply point, 6.12
...Feeding line, I, 13...Input terminal,
14...Conductor plate support rod, 15...Conductor disk, 16...Frequency characteristics of conventional microstrip antenna, 17...Micro according to the present invention Frequency characteristics of strip antenna.

Claims (1)

[Claims] 1. In a microstrip antenna using an unbalanced planar circuit resonator consisting of a dielectric thinner than the wavelength and a radiation conductor element and a grounded conductor plate facing each other, a conductor plate parallel to the radiation conductor element is placed on the radiation surface side. , a microstrip antenna characterized by being arranged with an air layer or a dielectric layer sandwiched therebetween.