JPH02172306A - Microstrip antenna for two-frequency use - Google Patents

Abstract

PURPOSE:To improve the impedance matching with a feeder circuit and to reduce power loss by short-circuiting a 2nd radiation element conductor at its center with an outer conductor of a coaxial line and short-circuiting an end ridge of a 1st radiation element conductor with the 2nd radiation element conductor or a conductor plate. CONSTITUTION:A 1st circular radiation element conductor 1, a 1st dielectric plate 2, a 2nd circular radiation element conductor 3 larger than the 1st radiation element conductor 1, a 2nd dielectric plate 4 and a ground conductor 5 are laminated from the upper part sequentially. Then a feeding coaxial line of the 1st radiation element conductor 1 is penetrated nearly the center of the 2nd radiation element conductor 13 and the ground conductor 5, and the outer conductor 8 of the coaxial line is connected to the 2nd radiation element conductor 3 and the ground conductor 5 and part of the end ridge of the 1st radiation element conductor 1 and the 2nd radiation element conductor 3 are short-circuited by a short-circuit 9. Thus, impedance matching is take easily and the power loss by the dielectric substance is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a microstrip antenna that can be used in two frequencies.

(Prior Art) Microstrip antennas are constructed by forming a thin film conductor on the surface of a dielectric plate, so they are suitable for reduction in thickness and weight, and are used in a wide variety of applications including antennas for mobile objects.

Figure 3 is an example of a general microstrip antenna using a circular radiating element conductor, (a) is a two-sided view, (
b) shows a cross-sectional view, and assumes that power is fed from the back of the antenna. In FIG. 3, 31 is a circular radiating element conductor, 32 is a dielectric plate, 33 is a ground conductor, 34 is a linear short-circuit conductor, 35 is a feed line, and 36 is a coaxial connector for the feed 4j. As shown in this figure, by providing the shorting conductor 34 at the center of the radiating element conductor 3 and appropriately selecting the radius of the radiating element conductor 31, the resonant frequency of the antenna determined by the fundamental mode can be set. Furthermore, by appropriately selecting the position of the feeding point, impedance matching between the antenna and the feeding circuit can be achieved.

Such microstrip antennas generally have a narrow band width, so if they are to be used for two different relatively distant frequencies, it is necessary to provide separate antennas.

However, if multiple antennas are arranged side by side, the size of the entire antenna becomes large, which is inconvenient when forming an array. In addition, when configuring an anti-two that operates at different frequencies for transmission and reception, it is important to supply power independently for transmission and reception to achieve a sufficient two-to-one region level. As an example of solving these problems, a dual-frequency antenna using a microstrip antenna with a multilayer structure is known.

FIG. 4 shows an example of such a dual-frequency microstrip antenna, in which (a) is a two-sided view and (1) is a cross-sectional view. In FIG. 4, 40 is a circular radiating element conductor;
2 is a ring-shaped radiating element conductor, 4143 is a dielectric plate, 47
．． 50 is a power supply line, 46 is a linear short-circuit conductor, 48.49 is a power supply connector, and 45 is a cavity. Here, the outer diameter of the ring-shaped radiating element conductor 42 is set to be larger than the diameter of the circular radiating element conductor 40. Ring-shaped radiating element conductor 4
2 acts as an antenna with a resonant frequency determined by its own size. On the other hand, the ring-shaped radiating element conductor 42 also serves as a ground conductor for the circular radiating element conductor 40, and also serves as an antenna with a resonant frequency determined by the size of the circular radiating element conductor 40.

This antenna is conveniently designed because the two resonant frequencies are independently and directly fed.

However, in this dual-frequency micro-lip antenna, 1. The disadvantage is that forming the cavity 45 in the dielectric plate 43 is not easy in manufacturing. Furthermore, in order to improve the impedance matching of the upper antenna consisting of the circular radiating element conductor 40 and the dielectric plate 42, if the feeding point F is to be located outside, the inner diameter of the cavity 45 must be increased. In that case, in order to secure a predetermined resonant frequency, the outer diameter of the ring-shaped radiating element conductor 42 must be increased in accordance with the increase in the inner diameter of the cavity 45, which increases coupling between elements when arrayed. There are also drawbacks.

FIG. 5 shows another example of a conventional dual-frequency microstrip array antenna. ．． 53 is a circular radiating element conductor, 52.54 is a dielectric plate, 575 is a feeder line, 56 is a short-circuit conductor, 60. ．． 61 is a power supply connector, and 58 is a coaxial line for feeding power to the circular radiating element conductor 5. Fourth
Similar to the configuration shown in the figure, it has two resonance frequencies determined by the sizes of the circular radiating element conductors 51 and 53, and power can be directly fed to each of them independently. In addition, this configuration has the advantage that since the circular radiating element conductor 51 is arranged offset from the center on the dielectric plate 52, impedance matching of the upper antenna consisting of the circular radiating element conductor 51 and the dielectric plate 52 can be performed. have

On the other hand, in the configuration of FIG. 5, when two frequencies are close to each other, the radiating element conductor 51. ．． There is little difference in the size of 53, and the circular radiating element conductor 51 of the upper antenna
Otherwise, the circular radiating element conductor 53 of the lower antenna is blocked, and radiation from the lower antenna is no longer possible. In order to avoid this, it is possible to make the dielectric constant of the dielectric plate 52 larger than that of the dielectric plate 54 to make the circular radiating element conductor 51 smaller, but this increases the power loss due to the dielectric.

(Problems to be Solved by the Invention) As mentioned above, among the conventional dual-frequency microslip antennas, a circular number U=j element conductor is used for the two-part antenna, and a ring-shaped radiating element conductor is used for the upper antenna. However, it is not easy to manufacture the antenna, and when trying to improve impedance matching, the antenna becomes large, which is disadvantageous for array formation.

In addition, in the case where circular radiating element conductors are used for both the two-part antenna and the bottom antenna, if the two frequencies are close to each other, -1 the dielectric constant of the dielectric plate of the part antenna is equal to the dielectric constant of the bottom antenna. Since it is necessary to make the radiating element conductor of the upper antenna larger than the dielectric constant of the body plate and smaller than the radiating element conductor of the lower antenna, there is a problem that power loss due to the dielectric of the upper antenna increases.

The present invention has a simple 4'lX'l configuration, good impedance matching with the power supply circuit, and power J
The purpose of the present invention is to provide a dual-frequency microstrip antenna with a small loss.

[Structure of the Invention] (Means for Solving Problem 4) In order to solve the above problem, the present invention includes a first radiating element conductor, a first dielectric plate, and a first radiating water conductor larger than the first radiating water conductor. In a dual-frequency microstrip antenna in which a second radiating element conductor, a second dielectric plate, and a ground conductor are laminated, a coaxial line for feeding the first radiating element conductor is connected to the second radiating element conductor.
Pass through approximately the center of the radiating element conductor and the ground conductor, and
The outer conductor of the coaxial line is connected to a second radiating conductor and a ground conductor, and further, a part of the edge of the first radiating element conductor and the second radiating element conductor are short-circuited by a shorting conductor. do.

Further, a first radiating element conductor, a conductor plate larger than this first radiating element conductor, a second radiating element conductor larger than this conductor plate, and a ground conductor are laminated with dielectric plates interposed between each other. A coaxial line for power feeding the first radiating element conductor is passed through approximately the center of the second radiating element conductor and the ground conductor, and an outer conductor of the coaxial line is connected to the second radiating conductor and the ground conductor. Furthermore, a part of the edge of the first radiating element conductor and the conductor plate may be short-circuited by a short-circuit conductor.

(Function) Since the center of the second radiating element conductor is short-circuited by the outer conductor of the coaxial line, it is excited only at the resonance frequency of the fundamental mode. Further, the second radiating element conductor or conductor plate is
Since it is larger than the second radiating element conductor, it also acts as a ground conductor for the second radiating element conductor.

Then, the first radiating element conductor is connected to its edge or to the second radiating element conductor.
= 1 to the second radiating element conductor, which is short-circuited with the J element conductor or conductor plate, from the center to the 31ti-circuited second radiating element conductor.
The resonant frequency of the fundamental mode is achieved with a relatively small shape.

Therefore, even when using three frequencies close to each other, -11
Since the first radiating element conductor, which is the radiating element of the lower antenna, is smaller than the second radiating element conductor, which is the radiating element of the lower antenna, the first radiating element conductor absorbs the radiation from the second radiating water r conductor. There will be no hindrance. In this case, the dielectric constant of the first dielectric plate does not need to be greater than that of the second dielectric plate, so an increase in power loss due to the dielectric can be avoided.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a dual-frequency micro-Slip antenna according to an embodiment of the present invention, in which (a) is a top view 1λ, and (1) is a cross-sectional view.

As shown in FIG. 1, a circular first radiating element conductor 1, a first dielectric plate 2, a circular second radiating element conductor 3, a second dielectric plate 4, and a ground conductor 5 <4 They are laminated in order from -.

The end edge of the first radiating element conductor is short-circuited to the second radiating element 3 by a short-circuiting conductor 6. The short-circuiting conductor 6 is a linear conductor, which passes through a through hole drilled in the dielectric plate 2 in advance, and has both ends electrically connected to the first and second radiating element conductors 1 and 3 by soldering, etc. Ru.

Further, the center portion of the first radiating element conductor 1 is provided to pass through approximately the center of the first dielectric plate 2, the second radiating element conductor 3, the second dielectric plate 4, and the ground conductor 5. , is connected to one end of the center conductor 7 of the first coaxial line. The outer conductor 8 of this first coaxial line is provided to pass through the first radiating element conductor 3, the second dielectric plate 4, and the ground conductor 5, and one end thereof is connected to the second
is connected to the radiating element conductor 3, and the other end is connected to the ground conductor 5. Similarly, the second radiating element conductor 3 is connected at an off-center position to one end of the center conductor 9 of a second coaxial line provided through the second dielectric plate 4 and the ground conductor 5. ing.

The other end of the first coaxial line consisting of the center conductor 7 and the outer conductor 8] and the other end of the second coaxial line having the center conductor 9 are connected to the outside (not shown) via a coaxial connector 10.11 for power supply. connected to the power supply circuit (transmission circuit or reception circuit). The outer conductor of the coaxial connector 1.0.11 is also connected to the ground conductor 5.

The first and second radiating element conductors], 3 and the ground conductor 5 are made by etching a copper film or other thin film conductor formed by vapor deposition on one or both sides of the first and second dielectric plates 2 and 4, for example. It is formed by removing unnecessary parts.

This microstrip antenna consists of two antennas each having different resonance frequencies, an upper antenna having a first radiating Ω/J element conductor 1 as a radiating element, and a lower antenna having a second radiating element conductor 3 as a radiating element. This is a structure in which antennas coexist.

Next, the operation of the dual-frequency microstrip antenna of this embodiment will be explained. In the lower antenna, the second radiating element conductor 3 is fed with power via the center conductor 9 of the second coaxial line, thereby exciting an electric field between it and the ground conductor 15, and operates as an antenna.

At this time, the first radiating element conductor 3 is connected to the first radiating element conductor 3. Since the center of the coaxial line is short-circuited by the outer conductor 8, excitation of modes other than the fundamental mode is suppressed.

Therefore, the resonant frequency of the second radiating element conductor 3 is the resonant frequency of the fundamental mode determined by its diameter and the dielectric constants of the first and second dielectric plates 2 and 4. Since the position of the feeding point A of the second radiating element conductor 3 can be freely set between the center and the edge of the radiating element conductor 3, impedance matching with the feeding circuit can be easily obtained.

Next, consider the upper antenna. By setting the diameter of the second radiating element conductor 3 of the lower antenna to be larger than the first radiating element conductor 1 of the upper antenna, the second radiating element conductor 3 can be used as a ground conductor for the first radiating element conductor 1. can be considered.

In the upper antenna, the first radiating element conductor 1 is fed with power via the first coaxial line consisting of the center conductor 7 and the outer conductor 8, thereby exciting an electric field between it and the second radiating element conductor 3. and operates as an antenna.

At this time, by short-circuiting one end B of the edge of the first radiating element conductor 1 with the second radiating element conductor 3 via the shorting conductor 6, a radiating element larger than the first radiating element conductor] It is possible to obtain the same resonant frequency as that achieved when excited by the mode. In other words, a certain desired resonant frequency is achieved with a radiating element conductor having a smaller size than using a radiating element conductor short-circuited at the center. The principle of this effect will be explained with reference to FIGS. 6 and 7.

Figures 6(a) and 6(b) show the cross-sectional view and electric field distribution of a microstrip antenna in which the center of the radiating element conductor is shorted to the ground conductor, and Figure 7(a) and (b) show the edge of the radiating element conductor. A cross-sectional view and electric field distribution of a microstrip antenna short-circuited to a ground conductor are shown. In the case of FIG. 6, a fundamental mode is excited on the radiating element conductor, and an electric field as shown in the figure is generated between it and the ground conductor.

The electric field (voltage) distribution at this time is zero at the center of the radiating element conductor and maximum at the edges. On the other hand, in the case of FIG. 7, a distribution is excited in which the electric field is zero at the short-circuited edge and the electric field is maximum at the opposite edge as shown in the figure.

Comparing these two cases, it can be seen that the distribution in FIG. 7(b) corresponds to half of the distribution in FIG. 6(b). From this, it can be said that if the diameter of the radiating element conductor in the case of FIG. 7 is set to about half the diameter of the radiating element conductor in the case of FIG. 6, the same resonance frequency will be excited.

The power is supplied to the first radiating element conductor 1 through the second radiating element conductor 3.
By slightly shifting the position of the first radiating element, impedance matching with the feeder circuit can be easily achieved. Further, since it is not necessary to make the dielectric constant of the dielectric plate 2 higher than that of the dielectric plate 4 in order to make the first radiating element conductor 1 smaller, an increase in power loss due to the dielectric is also prevented.

In addition, in conventional dual-frequency microstrip antennas in which fundamental mode operation antennas are stacked one above the other, the radiating element conductor of the lower antenna is made larger than the radiating element conductor of the two-part antenna to lower the resonant frequency. However, according to the present invention, it is also possible to reverse the setting of the resonant frequency, which has the advantage of increasing the number of frequencies by 11 compared to the previous design.

Furthermore, when the two frequencies are close to each other, in the conventional method, the two circular radiating element conductors are of approximately the same size, making it difficult for the lower antenna's radiating element conductor to act as a ground conductor for the upper antenna's radiating element conductor. In addition, in the present invention, even if the two frequencies are close to each other, the first radiating element conductor 1 of the partial antenna is smaller than the second radiating element conductor 3 of the lower antenna, so the second radiating element conductor 3 is 1st
Since the antenna acts as a ground conductor for the radiating element conductor, there is no problem with the operation as an antenna.

Furthermore, since the present invention does not require a cavity, it can be implemented relatively easily, and since the power feeding corresponding to the two frequencies is performed independently, high isolation can be achieved between the two antennas when they are shared for transmitting and receiving. It is effective when required.

In addition, in the embodiment described in IU, the second radio element [5] child conductor 3 has two functions as a radiating element and a ground conductor for the first radiating element conductor 1, but both of these functions are provided. It is also possible to realize this using separate radiating element conductors, and an example thereof is shown in FIG.

The dual-frequency microstrip antenna shown in FIG. 2 is of a type in which the radiating element conductors of the part and lower antenna corresponding to two resonant frequencies are excited by slots. In Figure 2, (a) is a - side view, (b) is a cross-sectional view,
(e) is a two-sided view showing the slotted conductor plate 12 and the triplate line in the upper antenna, and (d) is the slotted conductor plate 16 and the center conductor 18 of the triplate line in the lower antenna. FIG.

As shown in FIG. 2, in this embodiment, between the first dielectric plate 2 and the second radiating element conductor 3 in the embodiment of FIG. A circular conductor plate] 2 smaller than the second radiating element conductor 3, a third dielectric plate 13, and a fourth dielectric plate 15 are laminated in this order. The edge of the first radiating element conductor 1 is short-circuited to the conductor plate 2 by a short-circuit conductor 6. Conductor plate 12
As shown in FIG. 2(e), a slot 20 for exciting the first radiating element conductor 1 is formed in the fourth dielectric plate]5, and a trigger for feeding power to the slot 20 is formed in the fourth dielectric plate. One end of the plate center conductor 14 is connected to the center conductor 7 of the first coaxial line.
connected to one end of the

In addition, in this embodiment, a conductor plate 16, a fifth dielectric plate 16, and a sixth dielectric plate ]9 are also arranged between the second dielectric plate 4 and the ground conductor 5 in this order. Laminated. The conductor plate 16 is formed with a slot 21 for exciting the second radiating element conductor 3, as shown in FIG. A center conductor] 8 of a triplate line is formed, and one end of this center conductor 18 is connected to one end of a center conductor 9 of the first coaxial line.

The operation of the dual frequency antenna of the embodiment shown in FIG. 2 is basically the same as that of the embodiment shown in FIG. The feature of the antenna of this embodiment is that the ground conductor for the first radiating element conductor of the upper antenna is the conductor plate 12, and the shorting conductor 6 short-circuits the first radiating element conductor 1 and the conductor plate 2. The excitation of the radiating element conductors 1 and 3 is carried out by the slots I-20 and 21, and the radiating element conductors 1 and 3 are
] A triplate line is used to supply power to the

Here, the conductor plate 12 acts as a ground conductor for the first radiating element conductor 3, and the size of the second radiating element conductor 3 is adjusted so as not to interfere with its radiation. element conductor] and smaller than the radiating element conductor 3. In addition, since there is a feed line with a triplate structure, it is possible to configure a feed circuit here, making it easy to match the impedance at the feed point.Furthermore, two orthogonal slots are provided to radiate circularly polarized waves. It is very convenient in some cases. When this embodiment is applied to a circularly polarized antenna, it is necessary to provide a point E or a point F in addition to the dot as a short-circuit position at the edge of the first radiating element conductor. This configuration can be easily realized using a multilayer structure, but in that case, as in this example, the radiating element conductor]
By providing a ground conductor (conductor plate 12) for the two frequencies, even higher isolation can be obtained between the two frequencies.

In the following embodiments, the shape of the radiating element conductor is circular, but the same effect can be obtained by using a rectangular or other shape.

[Effects of the Invention] The dual-frequency micro-stub antenna according to the present invention has a simple structure and is easy to manufacture, is easy to match impedance, and has little power loss due to dielectric material. Furthermore, even when two resonant frequencies are close to each other, this can be easily handled and the design freedom JU is high. Furthermore, since the feeds 71i corresponding to the two resonance frequencies are performed independently, this is convenient in terms of design, and the isolation between the two frequencies can be increased.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are two-sided views and ] of a dual-frequency microstrip antenna according to an embodiment of the present invention.
9. Cross-sectional view, FIG. 2 shows the configuration of a dual-frequency microstrip antenna according to another embodiment of the present invention, in which (a) is a top view, (b) is a cross-sectional view, and (c) and (d) are slot views. 3(a) and 3(b) are plan views and cross-sectional views showing the basic structure of the microslip antenna, and FIGS. 4(a) and 4(b) show the conventional two-way conductor plate. 5(a) and 5(b) show another example of a conventional dual frequency microstrip antenna; FIG. 6 and FIG. 7 are diagrams for explaining the present invention in detail. 1..first radiation element conductor, 2..first dielectric plate, 3.
- Second radiating element conductor, 4... Second dielectric plate, 5...
Ground conductor, 6... Short-circuit conductor, 7 Center conductor of the first coaxial line, 8... Outer conductor of the first coaxial line, 9 Center conductor of the second coaxial line. 0. ]1... Coaxial connector for power supply, ], 2.16... Conductor plate, 13.1517.19...
Dielectric plate, 14.18... Center conductor of triplet line, 20.21... Slot. Applicant's agent Patent attorney Takehiko Suzue (a) (b) Figure 2 (C) (d) Figure (a) (b) Figure (a) Figure

Claims (2)

[Claims] (1) A first radiating element conductor, a first dielectric plate, and a first radiating element conductor.
a second radiating element conductor larger than the radiating element conductor;
A coaxial line for feeding the first radiating element conductor is passed through approximately the center of the second radiating element conductor and the ground conductor, and the outer conductor of the coaxial line is connected to the second radiating element conductor.
A dual-frequency microstrip antenna is connected to a radiating conductor and a ground conductor, and further short-circuits a part of the edge of the first radiating element conductor and the second radiating element conductor with a shorting conductor. (2) A first radiating element conductor, a conductor plate larger than this first radiating element conductor, a second radiating element conductor larger than this conductor plate, and a ground conductor are laminated with dielectric plates interposed between each other. A coaxial line for power feeding the first radiating element conductor is passed through approximately the center of the second radiating element conductor and the ground conductor, and an outer conductor of the coaxial line is connected to the second radiating conductor and the ground conductor. A dual-frequency microstrip antenna further comprising a short-circuit conductor between a part of the edge of the first radiating element conductor and the conductor plate.