JPH09260934A - Microstrip antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the microstrip antenna covering two frequency bands while keeping miniaturization. SOLUTION: Two radiation conductors 1, 2 are arranged in parallel. The radiation conductors 1, 2 are opposed to a ground conductor 4 via a dielectric layer 3 and the radiation conductors 1, 2 are electrically short-circuited to the ground conductor, one radiation conductor 1 is formed as a feeding element having a feeding section 5 and the other radiation conductor 2 is formed as a parasitic element without a feeding part. Plural slits 6 to each of the radiation conductors 1, 2. Two resonance states consisting of the resonance of the feeding element by the radiation conductor 1 and the resonance by the radiation conductor 2 of the parasitic element operated by electromagnetic coupling with the radiation conductor 1 of the feeding element are formed. Furthermore, the circumferential length of the radiation conductors 1, 2 is extended by the circumferential length of the slits 6 to reduce the area of the radiation conductors 1, 2 to make the microstrip antenna small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact microstrip antenna suitable for being incorporated in a mobile communication device such as a mobile phone.

[0002]

2. Description of the Related Art Recently, with the spread of mobile communication devices such as mobile phones, the number of wireless stations has increased remarkably with respect to the frequency band used, and communication congestion has become a problem. In particular, for mobile phones in the 800 MHz band, channels are congested due to the narrow frequency band used, which hinders communication. Therefore, mobile phones use the difference in frequency band between digital and analog systems, and when one frequency band channel is congested, switch to the other frequency band channel to reduce the degree of congestion. It is supposed to be.

On the other hand, as an antenna incorporated in a mobile communication device such as a mobile phone, an inverted F-type microstrip antenna is often used because it is easy to form a small antenna volume.

[0004]

However, the inverse F-type microstrip antenna has a narrow resonance frequency band as compared with a dipole antenna or the like, and it is very difficult to cover both digital and analog frequency bands. is there.
There is a method of increasing the height of the antenna as a method of widening the band, but in this case, the volume of the antenna becomes large and it is difficult to incorporate the antenna in the mobile communication device, which is not a realistic method.

The present invention has been made in view of the above points, and an object thereof is to provide a microstrip antenna capable of covering two frequency bands while being downsized.

[0006]

In the microstrip antenna according to the present invention, two radiation conductors 1 and 2 are arranged in parallel, and each radiation conductor 1 and 2 is grounded through a dielectric layer 3 to a ground conductor 4.
And the respective radiation conductors 1 and 2 are electrically short-circuited with the grounding conductor to form one radiation conductor 1 as a feeding element having a feeding portion 5 and the other radiation conductor 2 without feeding a feeding portion. Formed as an element, each radiation conductor 1, 2
Is provided with a plurality of slits 6.

Further, the invention of claim 2 is characterized in that the two radiation conductors 1 and 2 are arranged at a distance of 0.011λ (λ = wavelength at a use frequency) or more.

[0008]

Embodiments of the present invention will be described below. FIG. 1 shows an embodiment of the present invention.
The dielectric layer 3 is laminated on the surface of the end portion of the ground conductor 4 formed of a metal plate by bonding or the like, and a patch-shaped metal foil such as a copper foil is laminated on the surface of the dielectric layer 3 to form two layers. Radiation conductor 1,
2 are provided. The two radiating conductors 1 and 2 are arranged in parallel so that they are on the upper side and the lower side when the microstrip antenna is incorporated in a portable communication device. A short-circuit portion 7 is provided at one end of each radiation conductor 1, 2. The short-circuit portion 7 is formed, for example, by providing metal plating on the inner circumference of a through hole that penetrates the dielectric layer 3. The short-circuit portion 7 electrically connects the radiation conductors 1 and 2 to the ground conductor 3. I am trying to connect.

Further, one of the two radiating conductors 1 and 2 (the radiating conductor 1 which is on the upper side when the microstrip antenna is incorporated in a portable communication device) is provided with a feeding portion 5 near the short-circuit portion 7. The power feeding part 5 is formed by providing metal plating on the inner circumference of a through hole penetrating the dielectric layer 3, and power is fed from the ground conductor 4 side. As described above, one of the two radiation conductors 1 and 2 is formed as a feeding element having the feeding portion 5, and the other radiation conductor 2 is formed as a parasitic element having no feeding portion. is there.

By thus providing the radiation conductor 1 formed as a feeding element and the radiation conductor 2 formed as a parasitic element side by side, resonance due to the radiation conductor 1 of the feeding element and electromagnetic coupling from the radiation conductor 1 of the feeding element. It is possible to create two resonances, that is, the resonance by the radiation conductor 2 of the parasitic element operated by. Therefore, two resonances are used in the frequency band of the digital type of the mobile phone (the center frequency is 818 MHz and the range of ± 8 MHz is the frequency band) and the frequency band of the analog type of the mobile phone (the center frequency is The frequency is 873MHz, ± 1
It is possible to cover two frequency bands by adjusting the range of about 3 MHz to the frequency band.

However, if the radiation conductor 1 of the feeding element and the radiation conductor 2 of the parasitic element are arranged vertically, the area of the dielectric layer 3 is doubled, and the volume of the microstrip antenna is approximately doubled. For this reason, in the present invention, the radiation conductor 1 of the feeding element is used.
And a plurality of slits 6 on the radiation conductor 2 of the parasitic element, respectively.
Is provided, the area of each radiation conductor 1 and 2 is reduced, and the microstrip antenna is downsized. That is, by providing the slits 6 on the radiation conductors 1 and 2, the radiation conductors 1 and 2 are divided by the circumferential length of the slit 6.
And the wavelength λ of the resonance frequency becomes longer (that is, the resonance frequency becomes lower). Therefore, even if the areas of the radiation conductors 1 and 2 are formed small, by providing the slits 6, the circumferential lengths of the radiation conductors 1 and 2 can be formed to have the same size, and if they are resonated at the same frequency,
By providing the slit 6, the area of the radiation conductors 1 and 2 can be reduced, and the microstrip antenna can be miniaturized.

Further, when the slits 6 are provided in the radiation conductors 1 and 2 as described above, the electromagnetic coupling between the radiation conductor 1 of the feeding element and the radiation conductor 2 of the parasitic element is strengthened, and is generated by the radiation conductor 1 of the feeding element. It becomes difficult to independently adjust each resonance frequency of the resonance and the resonance generated by the radiation conductor 2 of the parasitic element. For this reason, in the invention of claim 2, the radiation conductor 1 of the feeding element and the radiation of the parasitic element are adjusted so that the respective resonance frequencies of the radiation conductor 1 of the feeding element and the radiation conductor 2 of the parasitic element can be adjusted independently. Conductor 2 to 0.0
They are formed at intervals of 11 λ (λ = wavelength at the used frequency) or more. The larger the distance between the radiating conductor 1 of the feeding element and the radiating conductor 2 of the parasitic element, the more preferable it is. However, if the distance is increased, it becomes difficult to downsize the microstrip antenna. Therefore, the upper limit of this distance is about 0.2λ. preferable. In the present invention, the radiation conductor 1 of the power feeding element
2 and the radiation conductor 2 of the parasitic element cause two resonances, and the peak of the reception frequency is 2 as shown in FIG.
However, in the present invention, the above-mentioned used frequency means the center frequency of these two peaks.

[0013]

EXAMPLES Next, the present invention will be specifically described with reference to examples. Example 1 A printed wiring board having a relative dielectric constant εr = 3.5 is used as the dielectric layer 3, and copper foil is used as the radiation conductors 1 and 2.
A brass plate was used as the grounding conductor 4 to fabricate a microstrip antenna in which two radiation conductors 1 and 2 are arranged in parallel as shown in FIG. The two radiation conductors 1 and 2 are electrically connected to the ground conductor 4 by a short-circuit portion 7 formed by plating a through hole with copper. Further, one of the two radiation conductors 1 and 2 is provided with a feeding portion 5 formed by plating a through hole with copper to form a feeding element, and the grounding conductor 4 of the feeding portion 5 is formed. A power supply cable is connected to the end on the side of. The other radiation conductor 2 is formed as a parasitic element having no such feeding portion. The dimensions of each part of this microstrip antenna are as shown in FIG. 1 (unit: mm).
Two slits 6 each having a width of 0.8 mm and a length of 6.2 mm were provided in each of the 2 pieces. The distance between the radiation conductors 1 and 4 is 4
It was set to mm (0.011λ).

Comparative Example 1 The dielectric layer 3 has a relative permittivity ε.
Using a printed wiring board of r = 3.5, using a copper foil as the radiation conductor 10 and a brass plate as the grounding conductor 4,
A standard inverted F-type microstrip antenna as shown in FIG. 4 was manufactured. The radiation conductor 10 is electrically connected to the ground conductor 4 by a short-circuit portion 7 formed by plating the through hole with copper, and the side of the ground conductor 4 of the power feeding portion 5 formed by plating the through hole with copper. A power supply cable is connected to the end of the. The dimensions of each part of this microstrip antenna are as shown in FIG. 4 (unit is mm).

(Comparative Example 2) As the dielectric layer 3, the relative permittivity ε
Using a printed wiring board of r = 3.5, using a copper foil as the radiation conductor 10 and a brass plate as the grounding conductor 4,
An inverted F type microstrip antenna as shown in FIG. 6 was produced. The radiation conductor 10 is electrically connected to the ground conductor 4 by a short-circuit portion 7 formed by plating the through hole with copper, and the side of the ground conductor 4 of the power feeding portion 5 formed by plating the through hole with copper. A power supply cable is connected to the end of the. The dimensions of each part of this microstrip antenna are as shown in FIG. 6 (unit: mm).
1 slit 0 with width 1.0mm and length 14.5mm
Book provided.

FIG. 2 shows the impedance characteristic of the microstrip antenna of Example 1, FIG. 5 shows the impedance characteristic of the microstrip antenna of Comparative Example 1, and FIG. 7 shows the impedance characteristic of the microstrip antenna of Comparative Example 2. In each figure, (a) is a Smith chart, (b) is a diagram showing VSWR (voltage standing wave ratio) with respect to frequency, where the horizontal axis represents frequency and the vertical axis represents VSWR.
Is shown.

First, considering FIG. 5 showing the impedance characteristics of Comparative Example 1, the Smith chart of FIG. 5A shows a locus when the frequency is swept from 750 MHz to 950 MHz, and FIG. In b), the marker 1 indicates 810 MHz, the marker 2 indicates 826 MHz, the marker 3 indicates 860 MHz, and the marker 4 indicates 885 MHz.
Then, as shown in FIG. 5B, VSWR is 4.8 at the lower end of 810 MHz of the digital frequency band of the mobile phone, and VSWR is 2.5 at the upper end of 826 MHz.
860M at the lower end of the mobile phone analog frequency band
VSWR is 2.3 at Hz, V at 885MHz at the upper end
SWR is 4.5. As described above, since the standard inverted F-type microstrip antenna has only one resonance peak, the frequency at the lower end of the digital frequency band of the mobile phone and the upper end of the analog frequency band of the mobile phone are It becomes difficult to cover two frequency bands because VSWR becomes large at the frequency of.

Next, Comparative Example 2 is an inverted F type microstrip antenna in which the slit 8 is provided in the radiation conductor 10,
By providing the slit 8 in the radiation conductor 10, the size of the dielectric layer 3 becomes 30 × 20 × 5 mm, and 32 × 28.
It was possible to reduce the size and size of the microstrip antenna of Comparative Example 1 having a size of × 5 mm. Further, considering FIG. 7 showing the impedance characteristics of Comparative Example 2, the Smith chart of FIG. 7A shows a frequency of 750 MHz.
7 shows a locus when swept from 950 MHz to 950 MHz, and the marker 1 is 810 MH in FIGS.
z, marker 2 is 826 MHz, marker 3 is 860 MH
z and marker 4 indicate 885 MHz. And FIG. 7 (b)
As can be seen in Fig. 7, the VSWR at the lower end of the mobile phone digital frequency band is 6.4 MHz, the VSWR is 6.4 at the upper end of 826 MHz, and the VSWR is 2.9 at the lower end of the mobile phone analog frequency band. The VSWR is 2.4 at the end of 860 MHz, and the VSWR is 5.6 at the upper end of 885 MHz. As described above, the microstrip antenna of the comparative example 2 can be made smaller than that of the standard inverse F-type microstrip antenna of the comparative example 1, but the resonance peak is similar to that of the comparative example 1. To be one
It is difficult to cover two frequency bands because the VSWR becomes large at the frequency at the lower end of the digital frequency band of the mobile phone and at the frequency at the upper end of the analog frequency band of the mobile phone.

Further, Example 1 is a microstrip antenna in which the slits 8 are provided in the radiation conductors 1 and 2, and the size of the dielectric layer 3 is 30 × 20 × 5 mm, which is the same as that of Comparative Example 2, and the size of Comparative Example 1 is It was possible to reduce the size and size of the microstrip antenna. Example 1
Considering FIG. 2 showing the impedance characteristic of
The Smith chart of FIG. 2A shows a locus when a frequency is swept from 750 MHz to 950 MHz.
2A and 2B, the marker 1 indicates 810 MHz, the marker 2 indicates 826 MHz, the marker 3 indicates 860 MHz, and the marker 4 indicates 885 MHz. Then, as shown in FIG. 2B, VSWR is 3.9 at the lower end of 810 MHz of the digital frequency band of the mobile phone and 826 at the upper end.
VSWR is 4.2 at MHz, VSWR is 2.5 at 860 MHz at the lower end of the analog frequency band of the mobile phone,
The VSWR is 3.1 at 885 MHz at the upper end. As described above, since the microstrip antenna of the first embodiment has two resonance peaks, the VSWR of the lower and upper end frequencies of the mobile phone digital frequency band and the analog frequency band of the mobile phone The VSWR of the frequencies at the lower end and the upper end becomes smaller, respectively, and it is possible to cover two frequency bands.

Further, in the microstrip antenna of the first embodiment, the gap between the radiating conductor 1 which is the feeding element and the radiating conductor 2 which is the non-feeding element is changed, and the difference between the two resonance frequency peaks is measured. Indicated. As shown in FIG. 3, when the distance between the radiation conductor 1 which is a feeding element and the radiation conductor 2 which is a parasitic element is small, the peaks of the resonance frequencies are close to each other, and it is difficult to adjust each resonance frequency independently. It is confirmed that Then, the difference between the digital frequency band of the mobile phone and the analog frequency band (55 MH
In order to be larger than z), it is necessary that the distance between the radiation conductor 1 which is a feeding element and the radiation conductor 2 which is a parasitic element is 0.011λ or more as seen in FIG.

[0021]

As described above, according to the present invention, two radiation conductors are arranged in parallel, each radiation conductor is opposed to the ground conductor via the dielectric layer, and each radiation conductor is electrically short-circuited with the ground conductor. , Because one radiation conductor is formed as a feeding element having a feeding portion and the other radiation conductor is formed as a parasitic element having no feeding portion, resonance by the radiation conductor of the feeding element and radiation of the feeding element It is possible to create two resonances, that is, a resonance due to a radiation conductor of a parasitic element that operates by electromagnetic coupling from a conductor, and it is easy to cover two frequency bands. Since multiple slits are provided, the circumference of the radiating conductor is lengthened by the circumference of the slit, and the area of the radiating conductor can be reduced, thus making the microstrip antenna compact. It is possible to be.

According to the second aspect of the invention, the two radiation conductors are arranged so as to be separated by 0.011λ (λ = wavelength at the working frequency) or more. Therefore, the radiation conductor of the feeding element and the radiation conductor of the parasitic element are arranged. It is possible to prevent the electromagnetic coupling from becoming too strong, and to independently adjust the resonance frequencies of the resonance generated by the radiation conductor of the feed element and the resonance generated by the radiation conductor of the parasitic element. It will be easier.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment (Example 1) of the present invention.

2A and 2B show impedance characteristics of the microstrip antenna of Example 1, where FIG. 2A is a Smith chart and FIG. 2B is a graph showing a relationship between frequency and VSWR.

FIG. 3 is a graph showing the relationship between the distance between the radiation conductors of Example 1 and the difference between two peaks of the resonance frequency.

FIG. 4 is a perspective view showing an example of a conventional form (Comparative Example 1).

5A and 5B show impedance characteristics of the microstrip antenna of Comparative Example 1, where FIG. 5A is a Smith chart and FIG. 5B is a graph showing a relationship between frequency and VSWR.

FIG. 6 is a perspective view showing an example of a conventional form (Comparative Example 2).

7A and 7B show impedance characteristics of the microstrip antenna of Comparative Example 2, where FIG. 7A is a Smith chart and FIG. 7B is a graph showing the relationship between frequency and VSWR.

[Explanation of symbols]

 1 radiating conductor 2 radiating conductor 3 grounding conductor 4 feeding part 5 slit

Claims (2)

[Claims] 1. Two radiation conductors are arranged in parallel, each radiation conductor is opposed to a ground conductor via a dielectric layer, and each radiation conductor is electrically short-circuited with the ground conductor, and one radiation conductor is fed. And the other radiation conductor is formed as a parasitic element having no feeding part,
A microstrip antenna comprising a plurality of slits provided on each radiation conductor. 2. The microstrip antenna according to claim 1, wherein the two radiation conductors are arranged at a distance of 0.011λ (λ = wavelength at a used frequency) or more.