JPH02224506A - Composite antenna - Google Patents

Abstract

PURPOSE:To prevent the mutual effect between unit antennas by providing a helical antenna with a small projection area in coaxial with a circularly radiation element of a microstrip antenna and leading its feeder to the rear side of the antenna. CONSTITUTION:A microstrip 1st antenna 10 having a feeding point 13 f2 and a helical 2nd antenna 30 arranged to a circular radiation element 13 to the front side are provided to a position apart from the center of the circular radiation element 13 are provided. Conductor stripes 32a-32d as discharge elements are provided in spiral on the outer circumferential face of a support cylinder 31 whose projecting area with respect to the element 13 is small in the antenna 30 and the lower end is connected to a feeder 25 through a connection piece. Then the feeder 25 is led to the rear face of the antenna 10 through the center of the element 13 to operate the antennas 10, 30 in the different frequency band. Thus, the effect between unit antennas are prevented in the frequency bands close to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composite antenna suitable for multiple frequency bands.

[Summary of the invention]

The present invention arranges a back-fed antenna with a small projected area coaxially with the circular radiating element of a microstrip antenna that is offset-fed, and connects the feed line of this back-fed antenna through the center of the circular radiating element of the microstrip antenna. By leading out to the back side of the strip antenna, the structure is small and simple, and the influence of each unit antenna on each other's characteristics is reduced even in a plurality of relatively close frequency bands.

[Conventional technology]

Conventionally, wireless communication systems between a base station and a large number of mobile stations have been constructed or proposed via geostationary satellites.

Such a wireless communication system, for example, as shown in FIG.
Via the satellite STd, a large number of mobile stations M from the base station C3
A downlink to the base station C8 is configured, and an uplink from each mobile station to the base station C8 is configured via the satellite STu. The frequency used in the uplink is, for example, 1.6 GHz, and the frequency used in the downlink is, for example, 2.5 GHz or 4.2 GHz.
It is assumed to be GHz. For example, a user HQ, such as a transportation company, and base station C3 are connected via separate communication lines.

In the above-mentioned wireless communication system, the antenna on the mobile station side has a simple configuration, a small size and a low profile, and can adapt to the elevation angle of a geostationary satellite in transmitting and receiving frequency bands that are far apart from each other. A material that satisfies various conditions such as having a desired directivity is suitable.

[Problem to be solved by the invention]

In Japanese Patent Application No. 63-331494, the present applicant proposes a structure in which a plurality of conductors are arranged on a ground conductor in descending order of diameter through a dielectric layer, in order to satisfy the above-mentioned conditions of directivity, shape and structure. By stacking disc conductors and feeding power to the center of the disc conductor with the smallest diameter and offset power to the other disc conductors, the disc conductor with the smallest diameter becomes a radiating element for the highest frequency band. , the other disc conductor serves as a grounding conductor for the adjacent small-diameter disc conductor, and also serves as a radiating element for successively lower frequency bands, so that the main radiation beam in the vertical plane in the 1.6 GHz and 4.2 GHz frequency bands. We have already proposed a stacked microstrip antenna that covers the required elevation angle range and is non-directional in the horizontal plane.

First, a previously proposed stacked microstrip antenna will be described with reference to FIGS. 7 and 8.

In FIGS. 7 and 8, (IO3) is a previously proposed stacked microstrip antenna, in which a low-loss dielectric layer (12) such as a fluororesin is placed on a circular ground conductor (11). ) A medium-diameter disc conductor (13) is concentrically stacked, and a small-diameter disc conductor ( 15)
are arranged concentrically and stacked.

The radius of each conductor (11), (13), (15),
The dielectric constant and thickness of the dielectric layers (12) and (14) are:
For example, it is set as follows.

rII=90mm+r+3=55
mmr +5=26.5mm, e, =
2.6t12=t14go3.2m...The medium-diameter disc conductor (13) has r, equal distance from its center.
The feed points (13
f, ) and (13f2) are provided, and a small diameter disc conductor (
A power feeding point (15) is provided at the center of the power supply point (15). Feeding point (
The offset distance and angular interval of 13f, ) and (13fz) are set as follows, for example.

r t = 33 mm + θ = 135° Coaxial feed lines (21) and (22) are connected to the refeed points (13fυ and (13f2), respectively) of the medium diameter disc conductor (13). The outer conductors of the wires (21) and (22) are connected to the ground conductor (11).

Further, the inner conductor (26) of the coaxial feed line (25) is connected to the feed point (15f) of the small diameter disc conductor (15), and the outer conductor (27) of the feed line (25) is connected to the ground conductor (11). connected to.

Note that the medium-diameter disc conductor (13) is electrically connected to the ground conductor (11) by through-hole processing at its center, so that the outer conductor (13) of the coaxial feeder (25)
27) will be connected to the center of the medium diameter disc conductor (13).

The operation of the previously proposed example is as follows.

The small diameter disc conductor (15) is centrally fed, and its radius is r
ts=26.5mm, TM mode, 4.
2GI (resonates with z and becomes a vertically polarized radiating element. At this time, the medium diameter disc conductor (13) is the small diameter disc conductor (15)
This provides a nearly conical vertical directivity with the main beam having the desired elevation angle range.

On the other hand, the medium-diameter disc conductor (13) has an impedance of 50Ω each, and the first feeding point (13f,) has a reference phase (
0°), the second feed point (13fz) is -90° phase 1
．． It is excited in the TM mode by a 6Gflz signal, becomes a circularly polarized wave radiating element, and obtains the desired vertical directivity in the shape of a cone.

In addition, since the impedance at the center of the radiating element is basically OΩ in modes other than TM mode, the central part of the medium-diameter disc conductor (13) is connected to the ground conductor (11) as described above. Stability of operation is achieved.

In the proposed example mentioned above, the desired directivity is a conical beam that does not require gain in the front direction, so focusing on the fact that the environment in the front direction has little effect on the characteristics of the antenna itself, By stacking a higher frequency band antenna in the front center of the band antenna, the desired directivity is achieved with a small and simple configuration.

However, when the 2.5 GHz band is used for the downlink, the radius rls of the small-diameter disc conductor (■5) increases in inverse proportion to the frequency, so as shown by the broken line in FIGS. 7 and 8, A problem arises in that the offset feeding points (13f, ) and (13f2) of the medium-diameter disk conductor (13) for the 1.6 GHz band are covered, and desired characteristics such as directivity are impaired.

In view of this, an object of the present invention is to provide a composite antenna that is small and has a simple configuration and can reduce the influence of each unit antenna on each other's characteristics even in a plurality of relatively close frequency bands. It's there to do.

[Means for Solving the Problems] The present invention includes a microstrip-shaped first antenna (10) having feeding points (13r+) and (i3rz) at positions distant from the center of a circular radiating element (13); This first
A second antenna (30) of a back-feed type that is disposed coaxially with the circular radiating element on the front side of the antenna and has a small projected area with respect to the circular radiating element, and a feeding line (25) of the second antenna. the first through the center of the circular radiating element.
This is a composite antenna in which the first and second antennas are operated in different frequency bands.

[Effect]

According to this configuration, even in a plurality of relatively close frequency bands, mutual influence between the unit antennas can be prevented.

[Example] Hereinafter, an example of the composite antenna according to the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows the overall structure of an embodiment of the present invention, and FIG. 2 shows the structure of its main parts. In both figures, parts corresponding to those in FIGS. 7 and 8 are given the same reference numerals, and redundant explanation will be omitted.

In FIG. 1, (10) is a microstrip antenna, which is a small-diameter dielectric layer (
14) and the disc conductor (15) are separated and removed.

As before, the disc conductor (13) is excited in the T M z + mode in the 1.6G) (z band) and emits circularly polarized waves.

(30) is a known backfire type helical antenna, in which four conductor strips (32a) as radiating elements are attached to the outer peripheral surface of a support cylinder (31) made of a low-loss insulator such as steatite ) to (32d) are each wound twice in a helical manner with an angular spacing of 90° and the same pitch angle.

As shown in Figure 2, the outer conductor (
The end portion of 27) is divided by an X-wavelength slit (27s), and the end (26e) of the internal conductor is connected to one of the slits (27s) to form a split coaxial balun (28).

The upper ends of two adjacent conductor strips (32a) and (32b) are commonly connected to one end of the balun (28) by connection pieces (33a) and (33b), and the other two conductor strips are connected to one end of the balun (28). (32c) and (32d) each upper end (connection piece (
33c) and (33d) are commonly connected to the other end of the balun (28).

The lower ends of the conductor strips (32a) to (32d) are commonly connected to the outer conductor (27) of the power supply line (25) by connection pieces (34a) to (34d), respectively.

Japanese Patent Application Laid-open No. 63-30006 (Patent Application No. 61/1983) by the present applicant
-173270), one pair of symmetrical connecting pieces (34a) and (34c) is
Since it is formed to be longer than the other pair of connecting pieces (34b) and (34d) alternately by a predetermined amount, the longer connecting piece (34b) and (34d) are arranged alternately.
One of the loops formed including a) and (34c) is inductive, and the shorter connecting pieces (34b) and (34
The other loop formed by including d) is capacitive, so that a phase difference of 90° can be provided between the currents flowing through each antenna element (32a) to (32d),
For example, right-handed circularly polarized waves are efficiently radiated from this helical antenna (30).

The vertical directivity of this helical antenna is, for example, a cardioid type as shown in FIG. 3, and it is non-directional in the horizontal direction.

2.5G) (When used in z, the outer diameter and length of the support cylinder (31) are set as follows, for example.

D31=15111111. I, ++=88mm
In addition, a disk conductor (1
The vertical directivity of 3) has a conical shape, as shown in FIG.

In the embodiment shown in Fig. 1, a 2.5 GHz band helical antenna (30) with a small projected area is placed in front of a 1.6 GHz band microstrip antenna (10) that does not require a gain.
Since we installed 1 antenna, like the previously proposed stacked antenna,
．． 6GI (has no adverse effect on the z-band characteristics.

In addition, the feed line (25) of the helical antenna (30) is
The circular conductor (13) passes through the center of the circular conductor (13) and is led out to the back of the microstrip antenna (10), so the impedance is basically zero as described above.
13) is grounded to stabilize operation in the 1.6 GHz band.

Furthermore, in the embodiment of FIG. 1, a helical antenna (30)
Since this is adopted, it is possible to radiate circularly polarized waves without disturbing the current distribution of the disc conductor (13) by feeding at one point.

Next, another embodiment of the composite antenna according to the present invention will be described with reference to FIG.

The configuration of another embodiment of the present invention is shown in FIG. In FIG. 5, parts corresponding to those in FIG. 1, FIG. 7, and FIG. 8 described above are given the same reference numerals, and redundant explanation will be omitted.

In Fig. 5, perpendicular to the center of the disc conductor (13),
Conductive wires (41) of two wavelengths are arranged to constitute a monopole antenna. This conductive wire (41) is a coaxial feeder line (2
It is connected to the internal conductor (26) of 5) and is supplied with power.

In addition, in this case, the disc conductor (13) is a conductive wire (41)
acts as a grounding conductor.

Moreover, the internal conductor (26) of the power supply line (25) may be exposed by a predetermined length as the conductive line (41).

From the monopole antenna (41) of the embodiment shown in FIG.
As with the small diameter disc conductor (15) of the previously proposed example, vertically polarized waves are emitted. Although not shown, the vertical directivity has a desired conical shape.

The remaining functions and effects are the same as those of the embodiment shown in FIG. 1 above.

〔Effect of the invention〕

As described in detail above, according to the present invention, a back-fed antenna with a small projected area is disposed coaxially with the circular radiating element of a microstrip antenna that is offset-fed, and the feed line of this back-fed antenna is connected in a circular manner. By penetrating the center of the radiating element and leading out to the back of the microstrip antenna, the structure is small and simple, and even in multiple frequency bands that are relatively close to each other, the influence of each unit antenna on the characteristics of each other can be minimized. A composite antenna can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view showing the structure of an embodiment of a composite antenna according to the present invention, FIG. 2 is a perspective view showing the structure of main parts of an embodiment of the present invention, and FIGS. 1 is a line diagram showing the vertical directivity of the embodiment, FIG. 5 is a sectional view showing the configuration of another embodiment of the present invention, FIG. 6 is a conceptual diagram for explaining the present invention, FIGS. FIG. 8 is a plan view and a sectional view showing an example of the structure of a stacked antenna according to an existing proposal. (10) and (IOS) are microstrip antennas, (11) are ground conductors, (12) and (14) are dielectric layers, and (13). (15) is a disk conductor, (13fl), (13fri), (1
5f) is the feeding point, (21), (22), (25
) is a coaxial feed line, (28) is a balun, (30) is a helical antenna, and (32a) to (32d) are antenna elements. Tweet fhfEI of “Tsusen 9PJ Figure 1 Jikei” -1,! fGHx) 3rd
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Claims (1)

[Claims] A microstrip-type first antenna having a feeding point at a position away from the center of the circular radiating element; a second antenna of a back-feed type having a small projected area with respect to the circular radiating element, a feeding line of the second antenna passing through the center of the circular radiating element and leading out to the back of the first antenna; A composite antenna characterized in that the first and second antennas are operated in different frequency bands.