JPS62203404A - Microstrip antenna - Google Patents

Abstract

PURPOSE:To attain light weight, thin profile, ease of manufacture and mass- production by optimizing the thickness of a base and arranging a ground member provided with a gap having a prescribed size to a lower part of a microstrip antenna element. CONSTITUTION:The microstrip antenna element 1 is formed on a thin dielectric base 5 together with a microstrip feeder 6 so as to reduce the feeding loss of the microstrip feeder 6, the base connecting member 2 at the lower side of the microstrip antenna element 1 is cut off by a size slightly larger than the outer ridge of the element and the microstrip antenna element 1 is opposed to an antenna element ground member 4 via a gap 3 made of a low dielectric material or an air layer. The feeder 6 is placed on a thin dielectric base and has a small loss, the effective base thickness is increased via the gap in the microstrip antenna element 1 and the effective dielectric constant is decreased, the Q is lowered, resulting that the frequency band is made broad.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an antenna used in a microwave band,
In particular, it relates to an antenna structure that achieves low loss and wideband microstrip antennas.

(Prior art) Although microstrip antennas have many advantages such as being IIJt, thin, and easy to manufacture, they suffer from a lot of loss due to microstrip feed lines.
The disadvantage is that the frequency band of the antenna is narrow.

Conventionally, methods such as power feeding using a waveguide have been used to reduce power feeding loss, but this method has the disadvantage that the advantages of microstrip antennas, such as their light weight and thinness, cannot be taken advantage of.

In addition, in order to widen the band, it is possible to install a parasitic element near the microstrip antenna element, or to combine microstrip antennas with different element dimensions.
There is a method that aims to widen the band by sharing two frequencies.

However, these methods have drawbacks such as complicated structures and high costs.

Furthermore, it is clear that if the conventional technology described above is used to satisfy both low loss and wide band, the problems mentioned above, such as the complexity of the structure and the increase in cost, will become even greater. .

On the other hand, when an array antenna is configured using a microstrip antenna, power feeding methods include a series type and a parallel type.

Series feed arrays have the drawback that the excitation phase of each element changes depending on the frequency and the gain drops, so it cannot be used in a wide band. On the other hand, with parallel feed arrays, although the antenna efficiency decreases due to feed loss, since the line length from the input terminal to each element is the same, it is possible to obtain broadband characteristics and keep feed loss as low as possible. If care is taken to suppress this, the antenna will be sufficiently practical.

There are three power supply losses that are problematic in parallel power supply arrays: copper loss, radiation loss, and dielectric loss. Of these, dielectric loss is determined by the dielectric substrate material, while copper loss and radiation loss are
The value varies depending on the thickness of the board and the characteristic impedance of the feed line.

Radiation loss also occurs from line discontinuities such as line bends and two-way distribution. Figure 6 is a calculation example showing the relationship between copper loss and radiation loss with respect to the thickness of the dielectric substrate when the line is curved and the two distribution points are uniformly distributed on the line. be. As you can see in this figure, there is a point where the power supply loss is the lowest, but this value varies depending on the material of the board. With the materials normally used, if you try to make the board thickness appropriate, the characteristic impedance will be quite low. It gets expensive. Furthermore, if an attempt is made to lower the characteristic impedance, the substrate thickness will become thinner, resulting in the problem that it cannot be put to practical use.

In addition, when constructing a microstrip line and a microstrip antenna element on the same board with the same board thickness, it is recommended to increase the board thickness to some extent in order to lower the Q value of the microstrip antenna and widen the band, as described later. If this is the case, the sum of copper loss and radiation loss cannot be reduced unless the characteristic impedance is extremely high.

Also, from the perspective of the feed line, due to the mutual relationship between dielectric constant, characteristic impedance, board thickness, and line width (see Electronic Communication Handbook, page 744), the ratio of line width to board thickness becomes extremely small, to the point where it is impossible to manufacture. , the track width becomes narrower.

Furthermore, if a certain amount of line width is secured, the substrate thickness becomes too thin and the frequency band of the antenna element becomes narrow.

Generally, the frequency band of a microstrip antenna is determined by the following equation.

Bandwidth = (VSWR-1)/Q!
It is known that the VTW"FQ value is proportional to the dielectric constant of the substrate and inversely proportional to the substrate thickness. Therefore, it is known that the feed line and , a microstrip antenna reduces the feeding loss, but increases the Q value of the antenna element.
The antenna has a narrow frequency band.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a microwave band antenna that is lightweight, thin, easy to manufacture, and can be mass-produced. It is something.

Furthermore, it is an object of the present invention to realize a microwave band antenna with excellent characteristics that can reduce radiation loss from a feeder line to an antenna element and can be used in a wide frequency band.

[Means for solving problems]

Therefore, in the present invention, the thickness of the substrate is reduced so that the loss of the microstrip power line is minimized, and
By distributing a grounding member with a gap of a predetermined thickness at the bottom of the microstrip antenna element, we have created a means to realize a microwave band antenna with excellent characteristics without sacrificing the advantages of the microstrip antenna. I have something to offer. That is, a microstrip antenna element and a feed line connected to the microstrip antenna element are arranged on one main surface of the dielectric substrate, a grounding member is arranged on the other main surface of the dielectric substrate, The part of the grounding member facing the microstrip antenna element is removed in a shape that is slightly larger than the outer edge of the microstrip antenna element, and the microstrip antenna element is separated by a gap made of a low dielectric constant material of a predetermined thickness or an air layer. , characterized by having a structure facing the grounding member.

[For production]

Therefore, by implementing the present invention, the thickness of the dielectric substrate is selected so that the loss of the microstrip feed line is minimized, and there is no gap between the microstrip antenna element and the grounding member. Since the structure is provided with a Q value, the Q value can be appropriately set, and the frequency band can be widened. Furthermore, it is possible to take advantage of the advantages that the microstrip antenna is lightweight, thin, and easy to manufacture, and it is possible to realize an excellent antenna for the microwave band.

(Example) Embodiments of the present invention will be described using the drawings.

FIGS. 1A and 1B are diagrams showing an example of the structure of a microstrip antenna according to the present invention.

1 is a microstrip antenna element, 2 is a substrate grounding member, 3 is a gap, 4 is an antenna element grounding member, 5 is a dielectric substrate, and 6 is a feeder line.

In FIG. 1, a microstrip antenna element 1 is formed together with a microstrip feed line 6 on a thin dielectric substrate 5 such that the feed loss of the microstrip feed line 6 is reduced. The board grounding member 2 is for grounding the power supply line. The substrate grounding member 2 on the lower side of the microstrip antenna element 1 is removed in a size slightly larger than the outer edge of the element, and the microstrip antenna element 1 has a gap 3 made of a low dielectric constant material or an air layer. It faces the antenna element grounding member 4 via. Therefore, the feed line 6 is on a thin dielectric substrate with low loss, and the microstrip antenna element 1 itself has a gap, which increases the effective substrate thickness and increases the effective dielectric constant. became smaller,
The Q value decreases, and as a result, the frequency band widens.

FIGS. 2A and 2B are diagrams showing another embodiment of the structure of the microstrip antenna according to the present invention.

In FIG. 1(B), the explanation was made using a two-layer structure consisting of the grounding member facing the microstrip antenna element and the board grounding member, but as shown in FIG. 2(B), the grounding member 7 can also be combined. In this case, the member has a recessed hole larger than the outer edge of the microstrip antenna element.

Further, another embodiment of the present invention having a plurality of microstrip antenna elements is shown in FIGS. 3-5.

FIG. 3 is a sectional view showing the structure of a portion of a plurality of array antennas made of microstrip antenna elements shown in FIG. 1.

In the figure, 1-1 and 1-2 are microstrip antenna elements, 2 is a substrate grounding member, 3-1 and 3-2 are gaps, 4-1 and 4-2 are antenna element grounding members, and 5 is a dielectric substrate. and correspond to each portion 1 to 5 in FIG. 1, respectively.

FIG. 4 is a sectional view showing the structure of a portion of a plurality of array antennas made of microstrip antenna elements shown in FIG. 2.

In the figure, 1-1 and 1-2 are microstrip antenna elements, 3-1 and 3-2 are gaps, and 5 is a dielectric substrate, which correspond to each part 1 to 5 in FIG. 1, respectively. 7
is an antenna element grounding member integrally constructed with the substrate grounding member 2.

Furthermore, FIG. 5 is a cross-sectional view of the structure of a portion where two antenna elements are arranged.

In the figure, 1-1 and 1-2 are microstrip antenna elements, 2 is a substrate grounding member, 3 is a gap, 4 is an antenna element grounding member, and 5 is a dielectric substrate.

Also in this example, microstrip antenna element 1-
The lower substrate grounding members 2 of each of microstrip antenna elements 1 and 1-2 are slightly larger in size than the outer edge of the antenna element, and are removed.
and 1-2 face a common antenna element grounding member 4 via a gap 3 made of a low dielectric constant material or an air layer.

〔Effect of the invention〕

As mentioned earlier, microstrip antennas are
Because it is small in size, thin, and easy to manufacture,
This is an antenna that can be mass-produced.

The frequency band of a microstrip antenna becomes wider as the dielectric substrate thickness increases, but at the same time, the loss of a microstrip feed line created on the same substrate also increases due to discontinuities such as bends and distribution points. The radiation loss from the substrate increases as the substrate thickness increases. In particular, when an array configuration is used, this power supply loss becomes a problem.

Therefore, in the conventional method, without losing the above advantages,
It has been difficult to realize microstrip antennas and array antennas that have low loss and satisfy wide frequency bands.

The present invention optimizes the substrate thickness so that the loss of the microstrip feed line is minimized, and provides a gap with a predetermined thickness at the bottom of the microstrip antenna element.
By making the grounding member have a two-layer structure, both of the advantages of the microstrip antenna can be satisfied without sacrificing the advantages of the microstrip antenna. Therefore, by implementing the present invention, a microstrip antenna with low loss and a wide frequency band can be easily realized.

In addition, as explained above with reference to FIG. 2(B), the grounding member may not have a two-layer structure but may be integrated.
This can be easily achieved.

Furthermore, the shape of the microstrip antenna element is not limited to the square patch shown in FIG.
The present invention can be applied in various ways.

Furthermore, the present invention is not limited to antenna polarization, and can be applied to both circularly polarized elements and linearly polarized elements. By constructing the gap at the bottom of the antenna element with a low dielectric constant material or an air layer, it can be inexpensively and easily made to have any thickness and any shape, and the effective dielectric constant can be reduced. This makes it possible to lower the frequency and contribute to widening the frequency characteristics. Furthermore, there is no decrease in antenna gain or deterioration of the radiation pattern due to this configuration method, and good characteristics can be obtained.

Due to the various advantages described above, the present invention can be applied to a parallel feeding type microstrip array antenna. It is clear that the microstrip array antenna according to this configuration method has a small feeding loss, and the frequency characteristic becomes wider by arraying. Furthermore, since the feed line and the antenna element can be formed on the same substrate surface, the array antenna is easy to manufacture and suitable for low cost.

[Brief explanation of drawings]

FIGS. 1(A) and (B) are views showing one embodiment of the structure of the microstrip antenna according to the present invention, and FIGS. 2(A) and (B) are views showing another example of the structure of the microstrip antenna according to the present invention. Figures 3 to 5 are cross-sectional views showing the structure of three embodiments of the microstrip array antenna according to the present invention. Figure 6 shows copper loss and radiation with respect to dielectric substrate thickness of a parallel-fed planar antenna. This is an example of calculating loss. 1.1-1.1-2... Microstrip antenna element, 2... Board grounding member, 3.3-1.3-2... Gap, 4.4-1.4-2...・Antenna element grounding member, 5・
...Dielectric substrate, 6...Feeding line, 7...Antenna element grounding member. Agent Patent Attorney Yoshi Tani - Figure 2 □ Dormitory Yokostophe Goku 4 Figure 6

Claims (1)

[Claims] A microstrip antenna element and a feed line connected to the microstrip antenna element are arranged on one main surface of the dielectric substrate, and a grounding member is arranged on the other main surface of the dielectric substrate, A portion of the grounding member facing the microstrip antenna element is removed in a shape that is slightly larger than the outer edge of the microstrip antenna element,
The microstrip antenna is characterized in that the microstrip antenna element has a structure in which it faces a grounding member with a gap made of a low dielectric constant material or an air layer having a predetermined thickness therebetween.