JPS63207206A - Micro-strip patch antenna - Google Patents

Abstract

PURPOSE:To make a using frequency band width into a wide band by providing a conductor at the prescribed forward position of an annular radiator and widening the flat area of a return loss characteristic. CONSTITUTION:An annular frame part 7a is the one in which the outer circumference shape is the same as the outer circumference shape of a radiator 1 and the size of the outer shape is the same or a little smaller. A shorting shaft part 7b shorts and connects the prescribed inner circumferential position section as the annular frame part 7 is divided into two and the shaft width comes to be the approximately equal width as the frame width of the frame part 7a. An annular conductor 7 composed of such the annular frame part 7a and the shorting shaft part 7b causes the forming direction of the shorting shaft part 7b to be consistent with the electric field direction of the radiation electromagnetic field and is provided at the prescribed forward position of the said radiator, for example, the position of an about 0.6 wave length. As the result, since the annular conductor 7 works as a compensating circuit to suppress the quick change of the reactance of an input impedance, the flat area of the return loss characteristic is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a microstrip patch antenna used in the UHF band or SHF band, and particularly relates to a technique for improving the frequency bandwidth used.

(Prior Art) As a microstrip patch antenna, the one shown in FIG. 3, for example, is conventionally known.

This microstrip patch antenna (hereinafter simply "
Antenna) consists of a radiator 1 made of a circular conductor plate, a ground plate 2 made of a circular conductor plate larger than the outer circumferential shape of the radiator 1 and arranged concentrically with the radiator 1, and a ground plate 2 arranged concentrically with the radiator 1, with the two separated at an appropriate distance. Dielectric material 4 arranged to be spaced apart
, and a shorting rod 5 embedded in the dielectric 4 in the thickness direction.

The thickness of the dielectric 4, that is, the separation distance between the radiator 1 and the ground plate 2, is set to a predetermined value that is sufficiently smaller than the radius of the radiator 1. As the dielectric material 4, a dielectric material having a relative dielectric constant ε of about 20 to 3.0 is usually used, but air (εr) may be used as the dielectric material. The radius of the radiator 1 is related to this dielectric constant ε, and is given by 0.293λo/67, where λ0 is the free space wavelength. The shorting rod 5 is for suppressing higher-order modes, and may be omitted depending on the application.

In addition, the power feeding methods are one using a microstrip line (Fig. 3 (a)) and one using a coaxial line (Fig. 3 (a)).
b)) In the former method, one end of the microstrip line 3a, which is a power feeding section provided on the same plane as the radiator 1, is connected to the outer circumferential end of the radiator 1, and the other end of the microstrip line 3a is connected to the other end of the microstrip line 3a. This is a method of supplying power. At this time,
For example, matching is performed using a quarter wavelength transformer. On the other hand, in the latter case, a coaxial connector 3b serving as a power feeding section is attached to the back surface of the ground plate 2, and the coaxial connector 3b
The tip of the center conductor is brought into contact with the back surface of the radiator 1 and electrically connected.

At this time, the connection position of the center conductor of the coaxial connector 3b is
This is a predetermined position in the radial direction of the radiator 1 where the VSWR (voltage standing wave ratio) is the lowest.

In any of the feeding systems, the direction parallel to the straight line connecting the center point of the radiator 1 and the feeding point is the electric field direction of the radiated electromagnetic field.

It is well known that in this type of antenna, the outer peripheral shape of the radiator 1 is not only circular but also various shapes such as rectangular and polygonal.

(Problems to be Solved by the Invention) By the way, the bandwidth of this type of antenna varies depending on the dielectric material used, but it is maximum when the dielectric material is air. For example, as shown in FIG. The characteristics shown in b) are obtained. The return loss characteristics shown in FIG. 2(a) were obtained under the following conditions. Center frequency f. = 1670M
Hz, free space wavelength λ, = 179.6 times, relative dielectric constant εr
Saki 1 (air), radius A of radiator 1 = 0.262λ0
, radius R of ground plate 2 = 0.530λ0, radiator 1
The distance between the ground plate 2 and the ground plate 2 is H = 0.050λ. , distance F = 0.150λ from the center point of radiator 1 to the feeding point
0° As is clear from Figure 2 (A), the bandwidth where the return loss is 110 dB or less (that is, VSWR is 2.0 or less) is approximately 140 MHz, and the center frequency f, 1
It is 0% or less. This is because the input impedance plus actance shows a rapid change in response to a change in frequency.

As described above, conventional antennas have a problem in that the usable frequency bandwidth is narrow.

The present invention was made in view of these conventional problems, and its purpose is to provide a microstrip patch antenna that can be used to widen the frequency bandwidth by adding a simple structure. There is a particular thing.

(Means for Solving the Problems) In order to achieve the above object, the microstrip patch antenna of the present invention has the following configuration. That is, the microstrip patch antenna of the present invention includes an annular frame portion whose outer circumferential shape is the same as the outer circumferential shape of the radiator of the microstrip patch antenna, and whose outer size is the same or slightly smaller, and this annular frame portion. An annular conductor consisting of a shorting shaft part that shorts between predetermined parts of the inner circumference of the annular frame part so as to be divided into two parts is arranged in front of the radiator with the formation direction of the shorting shaft part matching the electric field direction of the radiated electromagnetic field. It is characterized by being arranged at a predetermined position.

(Function) Next, the function of the microstrip patch antenna of the present invention configured as described above will be explained.

The annular frame has an outer circumferential shape that is the same as the outer circumferential shape of the radiator of the microstrip patch antenna, and an outer size that is the same or slightly smaller. Note that the frame width of the annular frame portion is sufficiently smaller than the distance from the center of the radiator to the outer peripheral end. Further, the short-circuiting shaft portion connects predetermined inner circumferential portions of the annular frame portion by short-circuiting so as to divide the annular frame portion into two equal parts, and the shaft portion has a width substantially equal to the width of the frame. The annular conductor including such an annular frame portion and a short-circuiting shaft portion aligns the formation direction of the short-circuiting shaft portion with the electric field direction of the radiated electromagnetic field, and is positioned at a predetermined position in front of the radiator, for example, at a predetermined position in front of the radiator. They are arranged at positions separated by about 6 wavelengths.

As a result, this annular conductor acts as a compensation circuit that suppresses sudden changes in input impedance and actance, so the flat region of return loss characteristics is expanded.
The frequency bandwidth used becomes wider.

As described above, according to the microstrip patch antenna of the present invention, since the annular conductor is arranged at a predetermined position in front of the radiator, the flat region of the return loss characteristic can be expanded, and the usable frequency bandwidth can be increased. This has the effect of widening the band.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an antenna in one embodiment of the invention.

Note that this embodiment shows a case in which the present invention is applied to the antenna shown in FIG. 3(b), and parts with the same names as those in FIG.

In FIG. 1, reference numeral 7 denotes an annular conductor according to the present invention, and this annular conductor 7 consists of an annular frame portion 7a and a short-circuit shaft portion 7b. The annular frame portion 7a has the same circular shape as the radiator 1,
Moreover, its size is slightly smaller than the radiator 1 in this embodiment. Note that the frame width of this annular frame portion 7a is sufficiently smaller than the radius of the radiator 1. Further, the short-circuiting shaft portion 7b short-circuits and connects the inner peripheral ends of the annular frame portion 7a on both sides in the diametrical direction, and its narrow width is approximately equal to the width of the frame. One end of a support 6 is fixed to the center of the short-circuit shaft portion 7b, and the other end of the support 6 is fixed to the center of the radiator 1. Note that the pillar 6 may be either a conductor or a non-conductor.

That is, the planar conductor 7 is disposed at a predetermined position determined by the length of the column 6 immediately in front of the radiator 1 by the column 6. At this time, the direction of the short-circuit shaft portion 7b is made to coincide with the electric field direction of the radiated electromagnetic field, that is, the direction of the straight line connecting the center point of the radiator 1 and the connection point of the power feeding section 3b. Note that the length of the support column 6 is adjusted to an appropriate length between 0.55 wavelength and 0.65 wavelength.

As a result, the flat region of the return loss characteristic of the antenna is greatly expanded compared to the conventional antenna, as shown in FIG. 2 (b), and the usable frequency bandwidth is greatly expanded.

The characteristic curve shown in FIG. 2(B) is obtained by adding the conditions for the annular conductor 7 to the same conditions as those used to obtain the characteristic curve shown in FIG. 2(A).

That is, center frequency fo = 1670 MHz, free space wavelength λo = 179.6 s + m, relative dielectric constant εr≠1 (air), radius A of radiator 1 = 0.262 λ0, ground plate 2
radius R = 0.530λ0, radiator 1 and ground plate 2
The conditions are that the distance between them is H=0.050^0, and the distance from the center point of the radiator 1 to the feeding point F=0.150λ0,
Frame width D of the annular frame portion 7a = 0.020λo, distance from the radiator 1 to the annular conductor 7 (that is, the length of the support column 6) L = 0
．． 557λ. It's Toshide.

As is clear from Figure 2 (b), the return loss is 11
The bandwidth at which the VSWR is 0 dB or less (that is, the VSWR is 20 or less) is approximately 300 MHz, which is approximately 18% of the center frequency f.
, and a significant difference is recognized compared to Figure 2 (a).

In this embodiment, the power feeding method shown in FIG. 3(b) has been described, but the present invention can obtain similar effects even with the power feeding method shown in FIG. 3(a). .

Further, it goes without saying that the outer peripheral shape of the radiator 1, that is, the outer peripheral shape of the annular frame portion 7a, is not limited to that shown in this embodiment.

(Effects of the Invention) As explained above, according to the microstrip batch antenna of the present invention, since the annular conductor is arranged at a predetermined position in front of the radiator, it is possible to widen the flat region of the return loss characteristic. This has the effect of widening the frequency bandwidth used.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a microstrip batch antenna according to an embodiment of the present invention, FIG. 2 is a return loss characteristic diagram,
FIG. 3 is a configuration diagram of a conventional microstrip batch antenna. 1...Radiator, 2...Ground plate,
3a. 3b...Power supply part, 4...Dielectric material,
5... Shorting rod, 6... Support column, 7.
......Annular conductor, 7a...Annular frame part,
7b...Short-circuit shaft part. Agent: Yoshihiro Yahata, Patent Attorney (a) Cross-sectional view (b) Tsutomuaki 0 Microphone υ Stoffs Antenna/) J71
;, (PI No./Ward J!l Number (MHz) (4)--One Handling/l Microphone U Sudonot 7'A~Na Antenna (B)-, Book, Micro Streets in Full Place 1- Figure 2

Claims (1)

[Claims] An annular frame portion whose outer circumferential shape is the same as the outer circumferential shape of the radiator of the microstrip patch antenna and whose outer size is the same or slightly smaller, and an inner portion of the annular frame portion that divides the annular frame portion into two equal parts. An annular conductor consisting of a short-circuiting shaft portion that shorts between predetermined circumferential portions is arranged at a predetermined position in front of the radiator, with the formation direction of the short-circuiting shaft portion matching the electric field direction of the radiated electromagnetic field. microstrip patch antenna.