JPH0685530A - Microstrip antenna and portable radio equipment - Google Patents

Abstract

PURPOSE:To miniaturize the microstrip antenna by providing a short-circuiting member installed at the apex of a square radiating conductor so as to short- circuit a ground conductor and the rectangular radiating conductor and plural slits on the square radiating conductor vertically to the diagonal of the square radiating conductor including the apex. CONSTITUTION:A square radiating conductor 13 is arranged on a dielectric layer, namely, on a substrate 11. A short-circuit conductor part 14 is the short- circuiting member provided at an apex P so as to short-circuit a ground conductor 12 and the square radiating conductor 13. Plural slits S are alternately mounted from the different sides of the square radiating conductor 13 and form a conductor peel part as a slit part so that the square radiating conductor 13 can be strip line shaped, for example. Therefore, the square radiating conductor 13 is constituted so as not to be disconnected by these slits S up to the position of the apex P and the position of the diagonal. Further, the resonance frequency of the micro-strip antenna is changed corresponding to the number of slits S, the length of slits and the width of slits or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip antenna and a portable radio device, and more particularly to a microstrip antenna suitable for use in a portable radio device which is required to be downsized.

[0002]

2. Description of the Related Art Conventionally, miniaturization of a microstrip antenna has been desired and various researches have been made. As one of the miniaturization techniques, a one-side short-circuit type microstrip antenna having a short-circuit surface for short-circuiting the zero potential surface at the center of the radiation conductor and the ground conductor, a plate-shaped inverted F antenna in which the width of the short-circuit surface is narrow, and the like are known. Has been.

Actually, the structure of a microstrip antenna for beam tilting is, for example, a relative permittivity ε shown in FIG.
_The radiation conductor 1 is arranged on the dielectric substrate 2 having a thickness h of a substrate made of _r, and the ground conductor 3 is arranged on the surface facing the radiation conductor 1. The power supply connector 5 is provided on the side of the ground conductor 3. The feeding point 4 is provided on the radiation conductor 1 at a point where the input impedance on the radiation conductor 1 becomes equal to the characteristic impedance of the feeding system. The power supply causes the microstrip antenna to operate as an antenna.
FIG. 5A is a plan view of an ordinary microstrip antenna, and FIG. 5B is a cross-sectional view taken along the broken line II ′.

A configuration of a one-side short-circuit type microstrip antenna different from the configuration of the rectangular microstrip line for beam tilting is shown in FIG. 5 (c). 5C is a plan view of the one-side short-circuited microstrip antenna, and FIG. 5D is a cross-sectional view taken along the broken line JJ ′ of FIG. 5C. As shown in these figures, the one-side short-circuit type microstrip antenna is excited in a dominant mode operating at the same resonance frequency by loading a short-circuit conductor 6 that short-circuits the zero potential surface of a normal microstrip antenna with the ground conductor 3. Compared with the area a × b of a normal square microstrip antenna,
The ratio of / 2 × b is as small as 1/2.

Further, as an antenna for reducing the size of the microstrip antenna, there is a plate-shaped inverted F antenna microstrip antenna shown in FIG. This microstrip antenna is an antenna having a width W _S smaller than the width b of the short-circuit conductor 6 of the one-side short-circuit microstrip antenna shown in FIG. FIG. 6A shows a plan view of the type A antenna, and FIG. 6B shows a plan view of the type B antenna. FIG. 6C shows a broken line K- in both FIG. 6A and FIG. 6B.
The cross-sectional view at the time of cutting along K'and LL 'is shown.

In the type A microstrip antenna described above, the offset amount W _X indicating the distance between the center of the short-circuit conductor 6 and the center line KK 'of the radiation conductor is set to zero, and the short-circuit conductor is centered at the end of the radiation conductor. It is provided in. Further, the microstrip antenna of the type B has set the offset amount indicated broken line L-L 'and _{W X = (b-W S} ) / 2.

Here, when the resonance frequency f ₀ is standardized when the short-circuit conductor width b of the one-side short-circuit conductor type microstrip antenna is equal to the width W _S , the short-circuit conductor width W _S is reduced as shown in FIG. with the resonance frequency f _r and have shown a tendency to decrease. This type difference indicates that the resonance frequency is lower in the setting of type B than in type A. This indicates that the type B microstrip antenna is more advantageous than the type A microstrip antenna in terms of downsizing of the antenna.

As described above, in the case of the plate-shaped inverted F antenna, the frequency can be controlled by the short-circuit surface width of the antenna, and excitation is performed in the dominant mode operating at the same resonance frequency with respect to the lowest controllable frequency. The area ratio can be reduced to about 1/16 as compared with the area of a normal square microstrip antenna.

As described above, due to the miniaturization of the antenna, the portable radio device can incorporate an inverted F antenna in its housing. Although the built-in antenna prevents the mobile wireless device from accidental damage to the antenna during operation, the gain of the antenna is not sufficiently higher than that of the dipole antenna.

As a method for solving this problem, in Japanese Laid-Open Patent Publication No. 2-131001, a telephone is attached to the upper part of the front of the housing in which a radio unit is housed in a vertically long, substantially rectangular parallelepiped housing and a telephone is attached to the lower part. Loss of damage accident prevention effect by including a one-sided short-circuited rectangular microstrip antenna installed with the short-circuit side up at the upper back or side of the housing of a portable radio with a transmitter attached to However, the antenna gain is higher than before.

[0011]

By the way, recently, the microstrip antenna has been further miniaturized by the user side. On the other hand, in the miniaturization of the conventional microstrip antenna, even the microstrip antenna by the plate-shaped inverted F antenna, which has been most miniaturized as described above, is The area ratio can be only about 1/16.

[0012] In particular, the above-mentioned user's request is a demanded element for downsizing, for example, a portable wireless device equipped with this microstrip antenna.

Therefore, the present invention has been made in view of such circumstances, and a microstrip antenna which is smaller than the size of a conventional microstrip antenna is used, and the microstrip antenna is used. An object of the present invention is to provide a microstrip antenna and a portable wireless device that can reduce the size of the portable wireless device.

[0014]

A microstrip antenna according to the present invention is a microstrip antenna provided with a rectangular radiation conductor facing a ground conductor with a dielectric layer interposed between the ground conductor and the rectangular radiation conductor. By providing a short-circuit member provided at the apex of the rectangular radiation conductor to be short-circuited and a plurality of slits provided on the rectangular radiation conductor in a direction perpendicular to the diagonal line of the rectangular radiation conductor including the apex, Solve the problem of.

The slits are alternately loaded from different sides of the rectangular radiation conductor. The dielectric layer is air.

The portable radio device solves the above-mentioned problems by using the microstrip antenna having the above-mentioned configuration and having slits and dielectric layers.

[0017]

The microstrip antenna of the present invention is a microstrip antenna provided with a rectangular radiation conductor facing a ground conductor through a dielectric layer, wherein the ground radiation conductor and the rectangular radiation conductor are short-circuited. Ordinary micros that operate at the same resonance frequency by a structure in which a short-circuit member provided at the apex and a plurality of slits on the rectangular radiation conductor in a direction perpendicular to the diagonal line of the rectangular radiation conductor including the apex are provided. By comparing the area with the strip antenna, the size of the antenna is reduced to 1/100 or less.

Further, by using the above microstrip antenna also in the portable wireless device, further miniaturization is promoted.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a microstrip antenna according to the present invention will be described below with reference to the drawings.

First, regarding the structure of the microstrip antenna of the present invention, a plan view shown in FIG. 1 (a) and a fracture surface taken along a broken line AA 'in this plan view are shown in FIG. 1 (b).

The microstrip antenna 1 shown in FIG.
In the microstrip antenna having a rectangular radiation conductor 13 facing the ground conductor 12 with the dielectric layer 11 interposed therebetween, 0 is the vertex P of the rectangular radiation conductor 13 that short-circuits the ground conductor 12 and the rectangular radiation conductor 13. A short-circuit conductor portion 14 which is a short-circuit member provided in the
Diagonal line D of the rectangular radiation conductor 13 including the apex P above
And a plurality of slits S are provided in the V direction perpendicular to.

As shown in FIG. 1B, the microstrip antenna shown in FIG. 1 has a dielectric layer (that is, a substrate) 11 having a relative permittivity ε _{r where} the thickness of the substrate is h.
The rectangular radiation conductor 13 is arranged on the top of the. Above rectangular radiation conductor 1
The size of 1 is set here to b = a, and the size a × b
It is represented by. Such a radiation conductor may be formed in, for example, an elliptical shape including a circular shape in addition to the rectangular shape.
In the case of FIG. 1, a square is adopted.

[0023]

The plurality of slits S are alternately loaded from different sides of the rectangular radiation conductor, and for example, the conductor peeling portion 17 is formed as a cut portion so that the rectangular radiation conductor 13 has a strip line shape. Therefore, FIG.
The rectangular radiating conductor 13 shown in (1) is configured such that the slit S does not break the position of the apex P and the position of the diagonal line.

The resonance frequency of the microstrip antenna changes depending on the number of the slits S, the length of the slits, the width of the slits, and the like.

Further, the position where the slit S is formed shows an effective tendency with respect to the change of the resonance frequency in the region near the short-circuit conductor portion 14. A feeding point 15 to which power is fed from a feeding connector 16 provided on the ground conductor 12 side is provided. The position of the feeding point 15 is set to a point where the input impedance on the radiation conductor 11 becomes equal to the characteristic impedance of the feeding system. The dielectric layer is air.

Next, the operation of this microstrip antenna will be described with reference to FIGS. 2 and 3 as a more specific embodiment.

Here, a Teflon fiber substrate is used as the substrate. The factors of this substrate are the relative permittivity ε _r
= 2.6, and the thickness h of the substrate is 1.6 mm. As a factor of the structure and electrical characteristics of the microstrip antenna, the dimension of the radiation conductor is set to a = b = 10.0 mm.

The radiation pattern generated by these settings can radiate the same radiation pattern as that of the normal microstrip antenna at the resonance frequency f _r = 818 MHz. At this time, the radiation conductor dimension of the above-mentioned normal microstrip antenna is It is 112.2 mm × 112.2 mm.

Therefore, the area ratio of the radiation conductor of the microstrip antenna of the present invention to the ordinary microstrip antenna shows that the miniaturization of about 1/125 is realized. Further, by loading a slit on the microstrip antenna of the plate-shaped inverted F antenna, the microstrip antenna of the present invention with respect to the area of the radiation conductor size of 28.6 mm × 28.6 mm of the conventional microstrip antenna of the plate-shaped inverted F antenna. The area ratio is about 1/8.

The Smith chart shown in FIG.
100 to 100MHz from 8MHz to 868MHz
The locus when sweeping between MHz is shown. In FIG. 2, the marker 1 is 817.490009 MHz, and the marker 2 is
Indicates 819.5 MHz. From the point of intersecting the real axis between these frequencies, the bandwidth where the voltage standing wave ratio (VSWR) is 2 or less is 814.87 MHz to 823.8.
It was shown to be 2 MHz. This bandwidth is
This corresponds to 1.1% with respect to the frequency of the marker 2 of 819.5 MHz. This shows a value equivalent to that of the conventional plate-shaped inverted F antenna microstrip antenna. Also, the microstrip antenna shown in FIG.
The relative level indicates that the level of the marker 1 is -13.633 dB and the level of the marker 2 is -15.519 dB. The impedance Z of this microstrip antenna is calculated to be Z = 65.758-
It turns out that it becomes j11.422Ω.

As described above, in the microstrip antenna of the present invention, the area is reduced to about 1/100 of the area of the ordinary microstrip antenna where the resonance frequency is generated without impairing the bandwidth even when the slit is loaded. The size can be reduced to about 1/8 as compared with the conventional inverted F antenna.

A portable wireless device equipped with the microstrip antenna of the present invention will be described with reference to FIG. Here, common parts are given the same reference numerals, and description thereof is omitted.

The portable wireless device is a housing 2 for housing the wireless device portion.
The shape of 0 is a substantially rectangular parallelepiped. The handset 21 is attached to the upper side of the surface of this housing. A transmitter 22 is attached to the lower side. Here, the surface of the housing to which the receiver 21 and the transmitter 22 are attached is referred to as a front surface 23. A recess 24A is formed by providing a gap on a back surface 24 facing the front surface 23 of the housing 20. The microstrip antenna 10 is arranged in parallel with the surface 24B corresponding to the bottom surface of the recess 24A.

The microstrip antenna 10 has a connecting conductor plate 25 on the side of the apex P on the rectangular radiation conductor 13. The connecting conductor plate 25 and the short-circuit conductor portion 1 on the apex P side
4, the microstrip antenna 10 is connected to the housing 20 and short-circuited. Further, the microstrip antenna 10 is fed by the feeding point 15. Here, the antenna protection cover is not shown.

As described above, the portable radio has the microstrip antenna 10 mounted thereon. With this implementation,
The portable wireless device can be made smaller and lighter than the conventional portable wireless device. It can be used without impairing the bandwidth due to the reduction in size and weight.

[0037]

As is apparent from the above description, according to the microstrip antenna of the present invention, in the microstrip antenna provided with the rectangular radiation conductor opposed to the ground conductor via the dielectric layer, the ground conductor is provided. And a short-circuit member provided at the apex of the rectangular radiation conductor to short-circuit the rectangular radiation conductor, and a plurality of slits in a direction perpendicular to the diagonal line of the rectangular radiation conductor including the apex on the rectangular radiation conductor. By providing the above, it is possible to meet the user's request by comparing the area with a normal microstrip antenna that operates at the same resonance frequency and downsizing the size of the antenna to 1/100 or less. The bandwidth of this antenna is not impaired at all.

By mounting a microstrip antenna on the portable wireless device, the portable wireless device can be made smaller and lighter.

[Brief description of drawings]

FIG. 1 is a schematic view of a microstrip antenna according to the present invention, in which (a) is a plan view and (b) is a broken line A.
A cross-sectional view along -A 'is shown.

FIG. 2 is a Smith chart showing antenna characteristics when the microstrip antenna shown in FIG. 1 is used.

FIG. 3 is a diagram showing relative levels of signals with respect to frequencies when the microstrip antenna shown in FIG. 1 is used.

FIG. 4 is an external perspective view when a microstrip antenna of a plate-shaped inverted F antenna is mounted on a portable wireless device.

5A is a plan view of a normal microstrip antenna, FIG. 5B is a cross-sectional view taken along a broken line, FIG. 5C is a plan view of a one-side short-circuit type microstrip antenna, and FIG. FIG.

FIG. 6 shows a microstrip antenna in a conventional plate-shaped inverted F antenna, (a) shows a plan view of a type A microstrip antenna, and (b) shows a plan view of a type B microstrip antenna.
(C) is the break line KK 'of FIG.
A cross-sectional view along -L 'is shown.

FIG. 7 is a graph showing the relationship between the resonance frequency and the width of the type A and type B short-circuit conductors shown in FIG. 6;

[Explanation of symbols]

 10 ... Microstrip antenna 11 ... Dielectric (layer) 12 ... Ground conductor 13 ... Rectangular radiating conductor 14・ ・ ・ ・ ・ ・ ・ ・ Short-circuit conductor 15 ・ ・ ・ ・ ・ ・ Feed point 16 ・ ・ ・ ・ ・ ・ Feed connector

Claims (4)

[Claims] 1. A microstrip antenna provided with a rectangular radiation conductor facing a ground conductor via a dielectric layer, wherein a short circuit provided at the apex of the rectangular radiation conductor short-circuits the ground conductor and the rectangular radiation conductor. A microstrip antenna comprising a member and a plurality of slits provided on the rectangular radiation conductor in a direction perpendicular to a diagonal line of the rectangular radiation conductor including the apex. 2. The microstrip antenna according to claim 1, wherein the slits are alternately loaded from different sides of the rectangular radiation conductor. 3. The microstrip antenna according to claim 1, wherein the dielectric layer is air. 4. The portable wireless device according to claim 1, comprising the microstrip antenna.