JPH01206705A - Non-directional micro-strip antenna - Google Patents

Abstract

PURPOSE:To cause an antenna to be compact and to be non-directional in a horizontal surface and to cause the change of an impedance to be small over a wide band by provided a cylinder-shaped secondary radiating element in the outer circumference of a primary radiating to be composed of a metal- covered film, which is attached on the surface of a conductor substrate. CONSTITUTION:A primary radiating element 2 to be composed of the metal- covered film is formed on the surface of a substrate 1 which is composed of a conductor. The lower edge part of the primary radiating element 2 is connected through a ribbon-shaped conductor 3 and an impedance matching element 4 to a feeding terminal 6. A secondary radiating element 7 to be composed of the cylinder-shaped conductor, whose both edges are opened, is provided so as to cover the surface of the primary radiating element 2. The shaft length of the secondary radiating element 7 is formed to be suitably shorter than the 1/2 of a wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an omnidirectional microstrip antenna suitable for use as the basic radiating element of a linear antenna for mobile radio base stations on land.

BACKGROUND ART FIG. 20 is a perspective view showing an example of a conventional microstrip antenna, in which 11 is a substrate made of a dielectric material that is sufficiently thin compared to the wavelength, and 12 is a rectangular conductor provided at the center of the surface of the substrate 11. 13 is a ribbon-shaped conductor,
Reference numeral 14 denotes a ground conductor provided on the back surface of the substrate 11, and 15 a coaxial power supply terminal, the outer conductor of which is connected to the ground conductor 14, and the inner conductor connected to the ribbon-shaped conductor 13.

When exciting in the fundamental mode via a microstrip line consisting of the feed terminal 15, the ribbon-shaped conductor 13, and the ground conductor 14, the required length a of the radiating element 120 is the same as that of the substrate 11.
If the relative dielectric constant ε' is input, the wavelength becomes input/2, and the upper end opposite to the lower edge of the radiating element 12 including the feeding point, that is, the connection point between the radiating element 12 and the ribbon-shaped conductor 13. When the edge is short-circuited to the ground conductor 14, the required length a of the radiating element 12 is approximately 1/48].

The basic characteristics of this microstrip antenna are that the feeding point of the radiating element I2 serves as a wave source, and the radiating element 12
The upper edge portion that is symmetrical to the feeding point with respect to the center point becomes a wave source, and the electromagnetic waves radiated from these two wave sources are combined, so the dielectric constant of the substrate 11 is uniform and the substrate 11 is a flat plate. Then, both the radiation electric surface and the magnetic surface have directivity only in the front direction.

The center of the radiating element 12 in FIG. 20 is aligned with the coordinate origin, and as shown by a solid line with an arrow, the radiating element 12
An example of the directivity of the 72 planes, that is, the directivity of the magnetic interface, is shown when the longitudinal direction is the X-axis direction, the width direction is the Y-axis direction, and the direction perpendicular to the plate surface of the substrate 11 is the X-axis direction. and as shown in Figure 21, and as is clear from the figure, the half width is approximately 80°
It is.

An example of the directivity of the XZ plane, that is, the directivity of the electric surface, is shown in FIG. 22, and the half width is approximately 76°.

Further, the impedance characteristics of this microstrip antenna are such that, since this antenna is composed of an unbalanced planar circuit resonator, Q is large and the fractional band is narrow.

FIG. 23 shows the substrate 1 in the antenna shown in FIG.
This is a diagram showing an example of the relationship between radiation frequency and return loss when the relative dielectric constant ε of 1 is selected as 3.6. The horizontal axis is frequency and the vertical axis is return loss (dB). As is clear from the return loss of 10 dB (voltage standing wave ratio VSW
At Cape R 1.9), the specific band is about 2.5%.

Fig. 24 is a diagram showing an example of a microstrip antenna that has been proposed and implemented in the past to make the directivity non-directional in the horizontal plane, and Fig. 25 is an exploded view of its main parts. 1G is a bullet-shaped support, 17 is a flexible base made of a dielectric material, and 18 is a radiating element made of a ribbon-shaped conductor, which is provided on the surface of the base 17. 19 is a power supply line.

Problems to be Solved by the Invention An antenna for a mobile radio base station on land is required to be vertically polarized and directional or omnidirectional in the horizontal plane, and especially when used for both transmission and reception. , the conventional microstrip antenna shown in FIG. 20 is not suitable as an antenna for a mobile radio base station on land.

The antenna shown in FIGS. 24 and 25 is omnidirectional in the YZ plane, but not only is the shape and structure large and complex, but the radiating element 17 is basically an unbalanced planar circuit resonator. Its frequency characteristics are narrow, making it unsuitable as an antenna for mobile radio base stations on land.

Means for Solving the Problems The microstrip antenna of the present invention is characterized in that a cylindrical secondary radiating element is provided around the outer periphery of a primary radiating element made of a metal film deposited on the surface of a dielectric substrate. It is something to do.

Effect: By configuring as described above, it is possible to have a small size and exhibit omnidirectionality in the horizontal plane, and to make changes in impedance characteristics extremely small over a wide band.

Embodiment FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a side view, FIG. 3 is a rear view, FIG. 4 is a plan view, and FIG. 5 is a front view of main parts. Figure 6 is a side view of the main parts, and in each figure, 1
is a substrate made of a dielectric material, 2 is a primary radiation element made of a rectangular conductor provided on the surface of the substrate 1, and 3 is a ribbon-shaped conductor provided on the surface of the substrate 1, the upper end of which is the lower end of the primary radiation element 2. It is connected to the part. 4 is an impedance matching element formed by widening the middle part of a ribbon-shaped conductor 3 over an appropriate length; 5 is a grounding conductor provided on the back surface of the substrate 1; 6 is a power supply terminal, such as a coaxial It consists of a terminal, the inner conductor of which is connected to a ribbon-shaped conductor 3, and the outer conductor of which is connected to a ground conductor 5.

The primary radiation element 2, the ribbon-shaped conductor 3, the impedance matching element 4, the ground conductor 5, etc. are formed of copper foil or the like that is deposited on the front or back surface of the substrate 1 by means such as printed wiring or vapor deposition. .

Reference numeral 7 denotes a secondary radiating element, which is the gist of the present invention, and is made of a cylindrical conductor with both ends open. Its central axis is approximately aligned with the central axis in the longitudinal direction of the substrate 1, and its axial length is determined by adjusting the wavelength. The side wall of the secondary radiating element 7 is formed to be appropriately short so that the side wall of the secondary radiating element 7 is the same as that of the primary radiating element 2.
In addition to covering the surface of the secondary radiating element 7, the inner diameter of the secondary radiating element 7 is appropriately adjusted so that the primary radiating element 2, the ribbon-shaped conductor 3, the grounding conductor 5, etc. do not come into contact with the secondary radiating element 7. be.

Reference numerals 81 to 84 denote supports made of dielectric material, each having a semicircular cross-sectional shape, and having a flat side wall on which the substrate 1 is attached.
A fitting recess is provided, supports 81 and 82 are installed inside one end of the secondary radiation element 7, supports 83 and 84 are installed inside the lower end of the secondary radiation element 7, and supports 81 to 84 are installed inside the lower end of the secondary radiation element 7.
The substrate 1 is sandwiched between each of the fitting recesses, and between the supports 81 to 84 and the secondary radiation element 7 and the supports 81 to 84.
and the substrate 1 are fixed with a suitable adhesive or the like.

The substrate 1 may be held between the flat side walls of the supports 81 to 84 without providing a fitting recess in each of the flat side walls.

The figure shows an example in which the outline shape of the primary radiating element 2 seen from the front is formed into a rectangular shape, but it may be formed into a circular or elliptical shape, or the cross-sectional shape of the secondary radiating element 7 The present invention can be practiced even if the shape is formed in any arbitrary shape such as a circle, an ellipse, a square, or a rectangle.

Of course, the shape of each cross section of the supports 81 to 84 is determined depending on the shape of the cross section of the secondary radiation element 7.

Furthermore, instead of forming the secondary radiation element 7 with a cylinder made of a conductive plate, it can be formed with a net-like or lattice-like conductor, or it can be formed with a printed wiring method or vapor deposition on the outer or inner surface of a cylindrical dielectric substrate. It may also be formed using a copper foil or the like deposited by a method such as the above.

When the secondary radiating element 2 in the microstrip antenna of the present invention is excited in the fundamental mode, the length a of the primary radiating element 2 is equal to ε/2, where the relative dielectric constant of the substrate 1 is ε'' and the wavelength is input. Form.

FIGS. 7 to 9 are diagrams for explaining the operating principle of the antenna of the present invention. The symbols in each figure are the same as those in FIGS. 1 to 6, and the solid lines with arrows indicate the electric field distribution, and the broken lines indicates the current distribution.

Point 0 in FIG. 7 is the connection point between the primary radiating element 2 and the feed line formed by the microstrip line consisting of the ribbon-shaped conductor 3 and the ground conductor 5, that is, the feed point. When excited, the current distribution based on the electric field generated near the open end of the primary radiating element 2 is maximum at the center point d2 of the primary radiating element 2, and the voltage at this point is minimum, so it corresponds to 62 points. Even if points 65 and 62 on the ground conductor 5 are short-circuited, no electrical problem will occur.

As shown in FIG. 8, an electric field is induced in the secondary radiating element 7 by the electric field generated in the primary radiating element 2, but this induced electric field acts to cancel the electric field generated in the primary radiating element 2, and A current flows through the inner and outer surfaces of the secondary radiation element 7 due to this induced electric field.

Focusing on the current flowing through the inner surface of the secondary radiating element 7, at 67 points on the inner surface of the secondary radiating element 7 corresponding to the center point d2 of the primary radiating element 2, the current is maximum and the voltage is minimum, so the primary radiation Even if all 62 points of the element 2, 67 points of the secondary radiation element 7, and 65 points of the ground conductor 5 are short-circuited, there is no problem electrically.

Focusing on the outer surface of the secondary radiation element 7, the secondary radiation element 7
Since the axial length of is approximately input/2, it is equivalent to feeding a voltage to both ends of a half-wave dipole antenna, and if the outer diameter of the secondary radiating element 7 is made smaller than the wavelength, the outer diameter of A current distribution similar to that shown in Fig. 8 is generated over the entire circumferential area of the surface, and the current distribution across the entire outer surface is similar to that shown in Fig. 9.
It will look like the figure.

Therefore, any point on the line of intersection between the plane perpendicular to the axis and the side wall of the secondary radiating element 7, including 67 points of the secondary radiating element 7,
Since both the center point d of the primary radiation element 2 and the 65 points of the ground conductor 5 have the maximum current and the minimum voltage, no electrical problem will occur even if any of the above points are short-circuited.

FIG. 10 is an equivalent circuit diagram of the antenna of the present invention, where L2 and C2 are the effective inductance and effective capacitance of the primary radiating element 2, L7 and C7 are the effective inductance and effective capacitance of the secondary radiating element 7, and C27 is the primary radiating element. 2 and the electric field coupling capacity of the secondary radiation element 7, Rr is a radiation resistance that contributes to radiation of electromagnetic waves, and Tf is a feeding point.

Either the width of the primary radiating element 2 is changed, the central axes of the substrate 1 and the secondary radiating element 7 are shifted, the substrate 1 is formed into a curved surface with an appropriate curvature, or the cross section of the secondary radiating element 7 is changed. By changing the shape to, for example, an ellipse or a rectangle, the size of the electric field coupling capacitance C27 can be changed, and by changing the size of the electric field coupling capacitance 027, the frequency characteristics of the return loss can be changed. .

The above description has been made of the case where the antenna of the present invention is excited in the fundamental mode, but as explained with reference to FIGS. will not cause any problems,
At the midpoint in the longitudinal direction of the primary radiating element 2 shown in FIGS. 1 to 6, the primary radiation The present invention can also be practiced by short-circuiting the radiating element 2 and the ground conductor 5 and removing the upper primary radiating element portion from the short-circuited point. In this embodiment, the excitation to the secondary radiating element 7 is equivalent to voltage feeding to one end of the secondary radiating element 7, and it operates isometrically as a half-wavelength dipole antenna.

FIG. 12 is a front view showing another embodiment of the present invention;
The figure is a side view, and in both figures, 1 is a common dielectric substrate,
21 and 22 are primary radiation elements, which are provided at appropriate intervals in the longitudinal direction of the substrate 1. 3 is a ribbon-shaped conductor, 41
and 42 are impedance matching elements, 5 is a ground conductor provided on the back surface of the substrate l, and 7I and 72 are secondary radiating elements, which are provided on the outer peripheries of the primary radiating elements 21 and 22, respectively.

In this embodiment, power is supplied to the primary radiating elements 21 and 22 in series through a power supply line formed by a microstrip line consisting of a ribbon-shaped conductor 3 and a ground conductor 5.

As shown in the front view in FIG. 14, a configuration in which a ribbon-shaped conductor 3 forming a main feed line and ribbon-shaped conductors 31 and 32 forming a branch feed line are provided to perform parallel power feeding may also be used. Able to carry out inventions.

In each of the above embodiments, the case where the feeder line is formed by a microstrip line consisting of ribbon-shaped conductors 3, 31 and 32 provided on the surface of the substrate 1 and a ground conductor 5 provided on the back surface of the substrate 1 is exemplified. However, the feed line may be formed using a balanced line instead of a microstrip line, and instead of forming a microstrip line or a balanced line using a metal film deposited on the front and back surfaces of the substrate 1, the feed line may be formed using a balanced line. The power supply line may be formed only on the back side without using it.

In addition, as shown in the front view in FIG. 15 and in the side view in FIG. It is also possible to form branch feed lines using ribbon-shaped conductors 31 and 32, or to form all feed lines using coaxial lines.

In addition, when using a coaxial line, it is desirable to connect the outer conductor of the coaxial line to the ground conductor 5 in order to reduce the influence on the radiation characteristics.

12 to 18 illustrate the case where two sets of primary radiating elements and secondary radiating elements are provided on a common dielectric substrate, but any two or more sets of primary radiating elements and secondary radiating elements The present invention can be carried out even if the following is provided.

Although not shown in FIGS. 11 to 16, a support may be interposed between the substrate and the secondary radiating element to hold the secondary radiating element in a desired position, and other symbols in each figure may be used. The configuration and the like are the same as the embodiment shown in FIGS. 1 to 6.

Effects of the Invention The microstrip antenna of the present invention is small and lightweight, has a simple structure, and can exhibit omnidirectional radiation characteristics over a wide band, and can be used as a co-linear antenna for mobile radio base stations on land. It is suitable for basic radiating elements, etc.

FIG. 17 shows that in the antenna of the present invention shown in FIGS. 1 to 6, the length a of the primary radiating element 2 is 0.2B1,
The width W of the ground conductor 5 is 0.075 mm, and the thickness of the substrate 1 is 0.07 mm.
005 people, the relative dielectric constant εr is 3.6, the axial length of the secondary radiating element 7 is 0.377 people, and the outer diameter of the secondary radiating element 7 is 0.0.
This shows the actual measured value of the change in the frequency characteristic of the return loss when the width of the primary radiation element 2 is changed for the prototypes formed by 87 people, and the horizontal axis is the frequency;
The vertical axis is the return loss (dB), and the curve b1 is 0.058 when @b of the primary radiating element 2 is selected.
．． 048 people, curve b3 is 0.035 people, curve b4 is 0
．． This is the case where 023 people each selected the following.

As is clear from the figure, increasing the width of the primary radiating element 2 tends to increase the return loss and widen the bandwidth.
At 0 dB, the fractional bandwidth is 12%, and when b = 0.035 people, the return loss is 2EidB and the fractional bandwidth is 4%, which can be adjusted depending on the purpose of use.

Figure 18 shows the width of the primary radiating element 2 in the prototype above selected to be 0.048 mm, and all other mechanical dimensions and relative permittivity, etc., being the same, and the primary radiating element in Figures 1 to 6 2 is the coordinate origin, and as shown by solid lines with arrows, the X axis is in the length direction of the primary radiation element 2, the Y axis is in the width direction, and the Z axis is in the direction orthogonal to the plate surface of the substrate 1. This shows the actual measured values of the directivity in the YZ plane for each case, and as is clear from the figure, extremely good omnidirectionality is exhibited.

Figure 19 shows the measured values of the directivity in the XZ plane for the "-allocation work," and it is clear from the figure that it has a figure-eight directivity similar to that of a half-wavelength dipole antenna.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an embodiment of the present invention, Fig. 2 is a side view, Fig. 3 is a rear view, Fig. 4 is a plan view, Fig. 5 is a front view of main parts, Fig. 6 is a side view of the main part, FIGS. 7 to 9 are diagrams for explaining the operating principle of the antenna of the present invention, and FIG.
12, 14 and 15 are front views showing other embodiments of the present invention, and FIGS. FIG. 16 is a side view, FIGS. 17 to 19 are diagrams showing an example of the characteristics of the antenna of the present invention, FIG. 20 is a perspective view showing an example of a conventional antenna, and FIGS. 21 to 23 are diagrams showing an example of the characteristics of the antenna of the present invention. , FIG. 24 is a diagram showing an example of the characteristics of a conventional antenna, FIG. 24 is a diagram showing another example of the conventional antenna, and FIG. 25 is a developed view of the main parts. 1:
Dielectric substrate, 2, 2I and 22 primary radiating element, 3, 3
1 and 32: Ribbon-shaped conductor, 4° 41 and 42: Impedance matching element, 5: Ground conductor, 6: Power supply terminal, 7
, 71 and 72: secondary radiating element, 81 to 84: support body, 81 to 83: shorting pin, single coaxial line, 11: dielectric substrate, 12: radiating element, 13: ribbon-shaped conductor, 14
: Ground conductor, 15: Power supply terminal, 16: Bullet-shaped support, 1
7: Flexible base made of dielectric, 18: Radiation element, 19
:It is a power supply line.

Claims (19)

[Claims] (1) A primary radiating element made of a metal coating coated on the surface of a dielectric substrate thinner than the wavelength, a ground conductor made of a metal coating coated on the back side of the dielectric substrate, and the primary radiating element 1. An omnidirectional microstrip antenna comprising: a feed line connected to the primary radiating element; and a cylindrical secondary radiating element having an axial length with a shorter wavelength and provided around the outer periphery of the primary radiating element. (2) a plurality of primary radiating elements made of metal films deposited at appropriate intervals on the surface of a common dielectric substrate that is thinner than the wavelength; and a plurality of primary radiating elements made of metal films deposited on the back surface of the common dielectric substrate. A common ground conductor made of a metal film, a feeder line connected to the plurality of primary radiating elements, and a common ground conductor provided on the outer periphery of each of the plurality of primary radiating elements, each having an axial length shorter than 1/2 of the wavelength. 1. An omnidirectional microstrip antenna comprising a plurality of cylindrical secondary radiating elements. (3) Claim 1 in which the primary radiating element and the secondary radiating element are arranged so that their central axes in the longitudinal direction substantially coincide with each other.
The omnidirectional microstrip antenna according to item 1 or 2. (4) The omnidirectional micro as claimed in claim 1 or 2, wherein the ground conductor provided on the back surface of the dielectric substrate and the approximately central portion in the longitudinal direction of the secondary radiation element are connected at high frequency. strip antenna. (5) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the cross-sectional shape of the secondary radiating element is circular or elliptical. (6) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the secondary radiating element has a rectangular cross-sectional shape. (7) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the secondary radiating element is formed of a cylinder made of a conductive plate. (8) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the secondary radiating element is made of a mesh or lattice conductor. (9) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the secondary radiating element comprises a metal coating deposited on the surface of a cylindrical dielectric substrate. (10) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the front profile of the primary radiating element is rectangular. (11) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the front profile of the primary radiating element is circular or elliptical. (12) The non-direction according to claim 1 or 2, wherein a support made of dielectric is interposed between the dielectric substrate and the secondary radiation element at an appropriate interval in the longitudinal direction. Microstrip antenna. (13) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the primary radiating element is connected to a ground conductor provided on the back surface of the dielectric substrate at the minimum voltage portion. (14) The device according to claim 1 or 2, wherein either the feed point side end of the primary radiating element or the opposite end thereof is connected to a ground conductor provided on the back surface of the dielectric substrate. Directional microstrip antenna. (15) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the feed line is a microstrip line provided on a dielectric substrate. (16) The omnidirectional microstrip antenna according to claim 1 or 2, wherein the feed line is a balanced line provided on a dielectric substrate. (17) Claim 1 in which the feeder line is a coaxial line
The omnidirectional microstrip antenna according to item 2. (18) The omnidirectional microstrip antenna according to claim 2, wherein the feed line is a series feed line. (19) The omnidirectional microstrip antenna according to claim 2, wherein the feed line is a parallel feed line.