JP3384524B2 - Microstrip antenna device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print-type microstrip antenna device having multiple resonances and high performance.

[0002]

2. Description of the Related Art FIG. 10 shows an example of a conventional two-resonant plate-shaped inverted F-shaped antenna proposed in Japanese Patent Application No. 59-162690.
21 is a radiation plate a, 22 is a radiation plate b, 23 is a ground plate,
24 and 25 are stubs, 26 is a feeding point, and 27 is a feeding line. Here, the size of the radiating plate a (L1 × L2) and the size of the radiating plate b (L3 × L4) are different.
And radiating plate b resonate at their respective resonance frequencies, resulting in two resonances. That is, the plate-shaped inverted F-shaped antenna A composed of the radiation plate a and the plate-shaped inverted F-shaped antenna B placed on the antenna A resonate independently, and they are fed by one feed line. It is a thing. Therefore, the thickness h2 needs to be approximately twice the thickness h1 of a single plate inverted F-shaped antenna.

Another example is A to C in FIG. 11 ("H
andbook of MICROSTRIP ANTENNAS ", JR James & PSH
all). This is a microstrip antenna (MS
(A)), 31 is a radiation plate a, 32 is a radiation plate b, 33 is a ground plate, and 34 and 35 are feeder lines. Also in these, the radiation plate a and the radiation plate b are different in size and structure, and each of them resonates independently to give two resonances. Therefore, although there is an advantage that each frequency can be taken relatively arbitrarily, there is a drawback that the antenna volume is large and the structure is complicated because the structure basically has two antennas stacked.

A structure proposed in order to solve these drawbacks is a structure in which a narrow gap is formed in an MSA to cause two resonances as shown in FIG. 12 (Japanese Patent Application No. 7-314988).
In this structure, by shorting one side of both elements, both frequencies operate as λ / 4MSA. Here, assuming that the resonance wavelengths are λe1 and λe2, the length L of the rectangular radiation conductor plate 1 is (1/4) λe2, (1/4) λe.
Less than 1. Currents I1 and I2 flowing through each element
Image current flows to the ground conductor plate 2. If the short-circuit plate 4 is installed in the metal casing 11 of the size shown in FIG. 13A in place of the ground conductor plate 2 with the short-circuit plate 4 facing upward, the image current will flow in the metal casing 11 as in the case of the ground conductor plate 2. And the housing itself also operates as an antenna.
Therefore, the length of the housing affects the radiation pattern. The degree of the effect changes depending on the frequency.

For example, L = 30 mm, W = 30 mm, t = 4.
FIG. 13B is a return loss diagram when an antenna having a dielectric of 8 mm and a relative permittivity of 2.6, a capacitor C1 of about 3 pF and a capacitor C2 of about 0.5 pF is installed in the metal housing 11 of FIG. 13A. Show. F = 820MHz, C on the C1 side element
It can be seen that the element on the second side resonates at f = 1.49 GHz and two resonances occur. The radiation pattern at each resonance frequency at this time is shown in FIG. It can be seen that the Eθ component is high in both cases.

[0006] removed and the capacitor C2 in FIG. 12, C2
Eliminate the length of the conductor plate that was attached to L2 (C
1 side remains L), L = 30mm, L2 = 25.5mm, W =
FIG. 15 shows a return loss diagram when an antenna having a dielectric constant of 25 mm, t = 4.8 mm and a relative dielectric constant of 2.6 and a capacitor C1 of about 3 pF is installed in the metal housing 11 of FIG. 13A. F = 820 MHz for the C1 side element, f for the C2 side element
It resonates at = 2.14 GHz, and it can be seen that there are two resonances. FIG. 16 shows the radiation pattern at each resonance frequency at this time. At f = 820 MHz, the Eθ component is high as in FIG. However, f = 2.14 GHz
, The Eθ component is low, and especially the level in the + X axis direction drops to about -4 dB.

It is considered that as the frequency becomes higher, the wavelength becomes shorter, the apparent size of the housing becomes larger, the influence of the image current on the housing becomes higher, and the level of the radiation pattern is lowered.

[0008]

The conventional antenna device has a drawback that the level of the radiation pattern is lowered when the resonance frequency is increased as described above. The present invention has been made in order to reduce the size of the antenna and solve such a problem.

[0009]

[Means for Solving the Problems]

(1) The invention of claim 1 relates to a microstrip antenna device comprising a ground conductor plate, a rectangular radiation conductor plate, a short-circuit plate, a coaxial feeder line and a plurality of capacitors. The ground conductor plate and the rectangular radiating conductor plate are arranged parallel to each other, and a slit is formed at a right angle from approximately the center of one side of the rectangular radiating conductor plate. The conductors are respectively connected to the ground conductor plate.

Capacitors are respectively connected between each divided side divided by a slit on one side of the rectangular radiating conductor plate and the ground conductor plate immediately below, and the divided side of the other side facing the one side of the rectangular radiating conductor plate. A short-circuit plate is connected between the part facing one side and the ground conductor plate directly below it, and a capacitor is placed between the part of the other side of the rectangular radiating conductor plate facing the other of the divided sides and the ground conductor plate directly below it. Connected.

A first type of antenna corresponding to one half which is divided by a slit of a rectangular radiating conductor plate and has a short-circuit plate connected to the other side thereof to operate as a λ / 4 (λ is a wavelength) radiating plate. The wavelength inside the tube at the resonance frequency (f1) is λe1, and it is divided by the slit of the rectangular radiating conductor plate, the capacitor is connected to the other side, and the other half of the antenna that acts as a λ / 2 radiating plate corresponds to Two types of resonance frequencies (f2; f1 <f2)
When the guide wavelength at λe2 is λe2, the length of the side of the rectangular radiation conductor plate perpendicular to the side where the slit is formed is (1/4)
It is set smaller than λe1 and (1/2) λe2.

(2) In the invention of claim 2, in the above item (1), a plurality of short-circuit plates are provided. (3) In the invention of claim 3, in the above-mentioned (1), it is substantially perpendicular to one of the divided sides of the rectangular radiating conductor plate divided by the slit (opposing the connected portion of the short-circuit plate on the other side). One or a plurality of second slits are formed in each of the divided slits, and one of the divided sides is divided into n pieces (n ≧ 2) by the second slits. Capacitors are connected between the ground conductor plates directly below.

Inside the tube at the first resonance frequency (f1-1 ... f1-n) of the antenna corresponding to the subdivided into n pieces by the second slit in one half of the rectangular radiating conductor plate. When the wavelength is λe1-1 ... λe1-n, the length of the side of the rectangular radiating conductor plate perpendicular to the side where the slit is formed is (1/4) λe1-i (i = 2 ... n) It is set small.

(4) According to the invention of claim 4, in the above (3), each of the n divided by the second slits in one half of the rectangular radiation conductor plate is connected by a capacitor. (5) In the invention of claim 5, in (1), a capacitor is connected instead of the short-circuit plate. Resonant frequencies (f1, f2) of the first and second types of antennas corresponding to the two halves, which are divided into two by the slit of the rectangular radiating conductor plate and respectively operate as λ / 2 (λ is the wavelength) radiating plate. ), Where the in-tube wavelengths are λe1 and λe2, the length of the side of the rectangular radiation conductor plate perpendicular to the side where the slit is formed is (1 /
2) It is set smaller than λe1 and (1/2) λe2.

(6) In the invention of claim 6, in the antenna device of (1) or (5), a dielectric is inserted between the rectangular radiation conductor plate and the ground conductor plate.

[0016]

DETAILED DESCRIPTION OF THE INVENTION

(Embodiment 1) FIG. 1 shows an embodiment of the invention of claim 1, parts corresponding to those in FIG. The width of the short-circuit plate 4 is shortened to the half where the capacitor C1 is attached, and the capacitor C3 is attached to the other half. With such a structure, dual resonance can be achieved. The element with the capacitor C1 attached is (1/4)
It operates as λMSA and is set to a low resonance frequency.
The element to which the capacitors C2 and C3 are attached is (1 /
2) It operates as λMSA and is set to a high resonance frequency. (1/2) compared to the case of (1/4) λMSA
In the case of λMSA, it becomes difficult for current to flow onto the ground conductor plate. The reason is that the side connecting the short-circuit plate 4 in one half of the radiation plate is the antinode of the current distribution of the λ / 4 radiation plate (the amplitude is maximum).
And the side with the capacitor C1 is a node (minimum amplitude)
And the other half of the radiation plate has capacitors C2 and C3.
This is because the sides marked with become the nodes of the current distribution of the λ / 2 radiation plate.

(Embodiment 2) FIG. 2 shows an embodiment of the invention of claim 2. This is a structure in which the short-circuit plate 4 of FIG. 1 is replaced by two thin short-circuit plates as shown in FIG. Not only the waves in the direction parallel to the slit 7 from the short-circuit plate but also the waves of different wavelengths up to the diagonal direction are carried, so that the bandwidth is widened. Other operations are the same as those in FIG.

The antenna of FIG. 2 is replaced by the metal housing 11 of FIG. 13A.
Then, the return loss characteristics and the radiation pattern were measured. The dimensions of the antenna element are antenna length L = 30 mm, antenna width W = 30 mm, and antenna height t = 4.8 mm in FIG. Further, a dielectric having a dielectric constant ε _r = 2.6 is used, the capacitor C1 is about 3 pF, and the capacitors C2 and C are
3 is about 0.5 pF. Here, the element on the C1 side resonates at f = 820 MHz, and the element on the C2 side f
= Resonating at 2.14 GHz. Figure 3 shows the return loss characteristics.

FIG. 4 shows a radiation pattern at each resonance frequency. The pattern surface is the XY plane in FIG. 13A. The radiation pattern at f = 820 MHz is shown in FIG.
The radiation patterns at f = 2.14 GHz are shown in FIG. 4B, respectively. Looking at the Eθ components in FIGS. 4A and 4B, the radiation level is high. The efficiencies are 0 dB at f = 820 MHz and -1.2 dB at 2.14 GHz, which are high efficiencies at each frequency. Also, unlike the radiation pattern of FIG. 16B described in the related art, the Eθ component is strong at f = 2.14 GHz and is almost 0 dBd on the + X axis.

The guide wavelength of the antenna of FIG. 2 is λe = c / f√
Calculate ε _r . Here, c is the speed of light = 3 × 10 ¹¹ mm, f is the frequency, and ε _r is the relative permittivity. λe1 is the guide wavelength of the low frequency f1 corresponding to the element with C1
2 is a high frequency f2 corresponding to the element with C2
The in-tube wavelength of. f1 = 820MHz, f2 = 2.14G
Since Hz and ε _r = 2.6, λe1 = 227 mm, λe2
= 87 mm. Therefore, 1 / 4λe1 = 57mm, 1 /
Since 2λe2 = 44 mm, L <1 / 4λe1 and L <
It satisfies 1 / 2λe2.

Thus, it is understood that a highly efficient two-resonance antenna can be realized by dividing the antenna into two by providing the radiation plate with a slit. Also, by setting one antenna element to 1/2 λMSA, it is possible to increase the level of the Eθ component on the XY plane at 2.14 GHz. (Embodiment 3) FIG. 5 shows an embodiment of the invention of claim 3, in which a second slit 14 is formed on the divided side to which the capacitor C1 of FIG. 2 is connected, and operates as λ / 4. The element is divided into two (n = 2) and each has a capacitor C1.
It has a structure in which -1, C1-2 are connected. By inserting a narrower gap, the antenna can resonate (n + 1).

(Embodiment 4) FIG. 6 shows an embodiment of the invention of claim 4. Capacitor C on the antenna of FIG.
4 has been added. Without the capacitor C4, the adjacent radiating elements influence each other and the two resonance frequencies cannot be arbitrarily approximated. However, when the capacitor C4 is installed, the resonance points of the capacitors C1-1 and C1-2 can be adjusted separately.

The antenna of FIG. 6 is replaced by the metal housing 11 of FIG. 13A.
And the return loss and radiation pattern were measured. Antenna size is L = W = 30mm, length of thin wire = 2
8mm, width and length of fine wire 14 are 6mm and 5mm, t = 4.8
A dielectric material having a relative permittivity of 2.6 in mm is used. C2, C3
C1-1 is about 0.5 pF, C1-2 is about 1.5 pF, and C4 is about 3.0 pF. The return loss diagram is shown in Fig. 7. f = 8
It resonates at 36 MHz, f = 860 MHz and f = 2.14 GHz. Furthermore, it is understood that the resonance occurs at frequencies close to f = 836 MHz and f = 860 MHz, and that the capacitors C1-1 and C1-2 can be separately resonated by the capacitor C4.

FIG. 8 shows the radiation pattern at each resonance frequency. As compared with the radiation pattern of FIG. 4, it can be seen that the shape has not changed and the level has hardly deteriorated. Efficiency is -0.4dB at f = 836MHz,
-1.1 dB at f = 860 MHz, -1.0 dB at f = 2.14 MHz
Therefore, even with the three-resonance structure, there is no efficiency deterioration. Although the present embodiment is an antenna in which two slits are inserted to cause three resonances, it is possible to realize multiple resonances by further increasing the slits.
This also applies to the third embodiment shown in FIG.

(Embodiment 5) FIG. 9A shows an embodiment of the invention of claim 5. A capacitor C5 is connected instead of the short-circuit plate 4 in FIG. 1, and the two elements have an antenna structure of ½λMSA. When the frequencies of both resonances exceed 1.5 GHz, this structure can suppress the influence of the housing, and the X-ray frequency can be reduced as in the second embodiment of FIG.
The level of the Eθ component on the −Y plane can be increased.

FIG. 9B shows a return loss diagram when it is attached to the metal casing 11 of FIG. 13A. Antenna size is L
= 30mm, W = 25mm, t = 4.8mm, dielectric is the relative permittivity
I'm using 2.6. C1, C2 and C3 are about 0.5
pF and C5 are about 1.0 pF. 2 at 1.5 GHz and 2.26 GHz
You can see that they are resonating. λe1 / 2 = 62mm, λe
Since 2/2 = 41.1 mm, both are larger than L = 30 mm.

[0027]

As described above, the antenna is provided with one or more slits, and the capacitor is attached between the end of the divided rectangular radiating conductor plate and the ground conductor plate. Alternatively, it is possible to obtain an antenna having multiple resonances and increase the level of the Eθ component. The higher the frequency, the greater the influence of the casing and the radiation pattern. However, the influence of the casing can be reduced by setting at least half of the antenna to 1 / 2λMSA. Furthermore, the resonance can be arbitrarily adjusted by installing the capacitor so as to bridge the divided rectangular radiation conductor plate.

[Brief description of drawings]

FIG. 1 is a diagram showing an antenna device according to claim 1.

FIG. 2 is a diagram showing the antenna device according to claim 2;

FIG. 3 is a return loss characteristic diagram of the antenna of FIG.

FIG. 4 is a radiation pattern diagram of the antenna of FIG.

FIG. 5 is a diagram showing the antenna device according to claim 3;

FIG. 6 is a diagram showing the antenna device according to claim 4;

7 is a return loss characteristic diagram of the antenna of FIG.

FIG. 8 is a radiation pattern diagram of the antenna of FIG.

9A is a diagram showing the antenna device according to claim 5, and B is A
Of antenna return loss characteristics.

FIG. 10 is a diagram showing a conventional antenna device.

FIG. 11 is a diagram showing another conventional antenna device.

FIG. 12 is a diagram showing still another conventional antenna device.

13A is a diagram showing the outer shape of a metal housing to which the antenna device to be measured is mounted, and B is a return loss characteristic diagram of the antenna of FIG.

14 is a radiation pattern characteristic diagram of the antenna of FIG.

15 is a return loss characteristic diagram when the length of a radiation plate on the C2 side of the antenna of FIG. 12 is shortened.

16 is a radiation pattern diagram corresponding to FIG. 15. FIG.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01Q 13/08

Claims (6)

(57) [Claims] 1. A microstrip antenna device comprising a ground conductor plate, a rectangular radiation conductor plate, a short-circuit plate, a coaxial feed line, and a plurality of capacitors, wherein the ground conductor plate and the rectangular radiation conductor plate are arranged in parallel. A slit is formed at a right angle from a substantially central portion of one side of the rectangular radiating conductor plate without reaching the other side facing the one side. conductors are connected to the ground conductor plate, a capacitor is connected the said one side said slit in two divided each divided side of the rectangular radiating conductor plate and the ground conductor plates immediately below, the rectangular radiation of the other side opposite to the side of the conductor plate,
Wherein said short-circuiting plate between one portion facing the split sides and said ground conductor plate immediately below is connected to the other side of the rectangular radiating conductor plate and the other facing the portion of the divided side and its capacitor is connected to the ground conductor plates immediately below, the is partitioned by the narrow gap of the rectangular radiating conductor plate, said short-circuiting plate is connected to the other side, (the lambda wavelength) lambda / 4 operates as a radiation plate the guide wavelength and λe1 in the one of the resonant frequency of the corresponding antenna and one half portion (f1), the is divided by the fine gap of the rectangular radiating conductor plate, the capacitor is connected to the other side, lambda When the guide wavelength at the second-type resonance frequency (f2; f1 <f2) of the antenna corresponding to the other half that operates as a 1/2 radiation plate is λe2, the slit of the rectangular radiation conductor plate is formed. Right angle Length of, (1/4) λe1 and (1/2) λe2 microstrip antenna and wherein the smaller. 2. The microstrip antenna device according to claim 1, wherein the short-circuit plate is plural. 3. The method of claim 1, wherein in one of said slit in two divided divided side of the rectangular radiating conductor plate, and before
Serial second slit substantially perpendicular to one or more on the divided side short-circuiting plate is opposed to the connection portion is formed, the one n number of the divided edges by their second slit (N ≧ 2), capacitors are respectively connected between the respective divided portions and the ground conductor plate immediately below, and the second slit of the one half of the rectangular radiation conductor plate is connected. When the guide wavelength at the first-type resonance frequency (f1-1 ... f1-n) of the antenna corresponding to each of the parts subdivided into n by the above is set to λe1-1 ... λe1-n, the rectangular radiation conductor plate The length of a side perpendicular to the side in which the slit is formed is smaller than (1/4) λe1-i (i = 2 ... n). 4. The microstrip antenna device according to claim 3, wherein each of the one half of the rectangular radiating conductor plate divided into n pieces by the second slits is connected by a capacitor. 5. A microstrip antenna device comprising a ground conductor plate, a rectangular radiation conductor plate, a coaxial feed line and a plurality of capacitors, wherein the ground conductor plate and the rectangular radiation conductor plate are arranged in parallel, A slit is formed at a right angle from a substantially central portion of one side of the conductor plate, the inner conductor of the coaxial feed line is connected to the rectangular radiating conductor plate, and the outer conductor is connected to the ground conductor plate. Capacitors are respectively connected between the respective divided sides divided by the slit on one side of the plate and the ground conductor plate immediately below, and the divided side of the other side opposite to the one side of the rectangular radiating conductor plate. Capacitors are respectively connected between the portions facing each other and the ground conductor plate immediately below, and are divided into two by the slits of the rectangular radiating conductor plate, each of which has a wavelength of λ / 2 ( The two halves and the one of the corresponding antenna, Ramudai1 the guide wavelength in the two resonant frequencies (f1, f2), when the Ramudai2, the rectangular radiating conductor plate that operates as a wave) radiation plate The length of the side perpendicular to the side where the slit is formed is smaller than (1/2) λe1 and (1/2) λe2. 6. The microstrip antenna device according to claim 1, wherein a dielectric is inserted between the rectangular radiation conductor plate and the ground conductor plate.