JPH04281604A - Spiral antenna and array antenna using the spiral antenna - Google Patents

Abstract

PURPOSE:To attain excellent directivity, reflection attenuation characteristic and axial ratio characteristic. CONSTITUTION:A radiation element 7 made of a spiral conductor, and a strip conductor 3 connecting to its end are supported on a same plane and an upper ground conductor 1 and a lower ground conductor 2 are provided to the upper and lower part via an upper insulation layer 4 and a lower insulation layer 5, and an opening 6 is provided to a part corresponding to the radiation element 7 in the upper ground conductor 1. Thus, the array antenna using the spiral antenna as the component is most suited as a satellite broadcast reception antenna employing a circularly polarized wave.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a spiral antenna suitable for a component antenna of a planar array antenna used, for example, in a satellite broadcast receiving antenna using circularly polarized waves, and an array antenna using this antenna. It is.

0002

2. Description of the Related Art A conventional high-gain planar array antenna, such as a microstrip patch antenna, has a feeder line consisting of a plurality of radiating elements formed on a dielectric substrate and a microstrip transmission line on the same plane. The plurality of radiating elements are arranged in parallel and are configured to be fed in parallel by the feeder line.

0003

[Problems to be Solved by the Invention] Since the microstrip transmission line used as the feed line of the planar array antenna is an open line, the radiation loss from the line itself and the stability of the electrical characteristics are It depends on the physical properties of the insulator that makes up the line, and therefore, when selecting the material of this insulator, it is necessary to consider both loss and stability of electrical characteristics. It is not always possible to choose a material that is small.

[0004] When it is not possible to select an insulating material with sufficiently low loss to maintain the stability of electrical characteristics, the number of radiating elements is increased to increase the gain in order to compensate for the radiation loss in the transmission line. However, as the number of radiating elements increases, the feed line length increases, making it impossible to obtain an effective gain increase.

[0005] In order to solve these problems, triple-plate transmission has been proposed, which is more complex than a microstrip transmission line, but has a planar shape and can use insulators with low loss. Antennas have been proposed that are constructed using lines or suspended transmission lines to increase the effective gain.

[0006] Since both the triple-plate transmission line and the suspended transmission line have a structure in which a strip conductor is sandwiched between two ground conductors, it is difficult to couple these transmission lines to a radiating element using conventional is two arcs constituting a triple-plate transmission line or a suspended transmission line.
Among the ground conductors, a radiating element having a degenerate separation element arranged on one of the ground conductor surfaces is excited by electromagnetic coupling, or two A method is used in which a radiating element is excited through two monopole antennas.

[0007] A method of exciting a radiating element having a degenerate separation element disposed on one of the ground conductor planes by electromagnetic coupling is based on a method of exciting a radiating element having a degenerate separation element disposed on one of the ground conductor surfaces. If the positional relationship between the elements is not accurately maintained at the required positional relationship, the characteristics will deteriorate, so it is necessary to increase the accuracy of the mutual positional relationship between the strip conductor and the degenerate separation element.
As a result, an increase in manufacturing costs cannot be avoided, and the method of exciting a radiating element through two monopole antennas that are fed with phase difference requires a large number of parts and a complicated feeding system.

[0008]

[Means for Solving the Problems] The present invention provides an upper insulating layer and a lower insulating layer interposed between an upper outer conductor and a lower outer conductor, and a part of the upper outer conductor formed by removing an appropriate range. a radiating element made of a spiral conductor provided between an opening, the upper insulating layer and the lower insulating layer corresponding to the opening; and a radiating element interposed between the upper insulating layer and the lower insulating layer; The present invention attempts to eliminate the drawbacks of the prior art by realizing an antenna comprising a radiating element made of a spiral conductor and an internal conductor connected at high frequency.

[0009]

[Operation] The high-frequency current supplied from the internal conductor flows from one end of the radiating element made of a spiral conductor, and by appropriately adjusting the length of the radiating element, the current distribution on the radiating element is created as a traveling wave. It emits circularly polarized waves in a distributed manner.

0010

[Embodiment] FIG. 1(a) is a plan view showing an embodiment of the present invention, and FIG. 1(b) is a cross-sectional view taken along line AA in FIG. 1(a). is the upper outer conductor (hereinafter referred to as the upper ground conductor), 2 is the lower outer conductor (hereinafter referred to as the lower earth conductor), 3 is the inner conductor (hereinafter referred to as the strip conductor), and 4 is the upper The upper insulating layer 5 interposed between the ground conductor 1 and the strip conductor 3 is a lower insulating layer interposed between the lower ground conductor 2 and the strip conductor 3, and these constitute a triple plate transmission line. .

Reference numeral 6 denotes an opening formed by removing a suitable part of the upper ground conductor 1. Although the figure shows an example in which the outline is circular, it can be formed into any arbitrary outline. The present invention can be practiced by forming it into a shape.

Reference numeral 7 denotes a radiating element, which is made of a spiral conductor attached to the surface of the lower insulating layer 5 corresponding to the opening 6.
Its outer end is connected to the end of the strip conductor 3 directly or via a capacitor in a high frequency manner. Therefore, the radiating element 7 and the strip conductor 3 are provided on the same plane.

Although the figure shows an example in which the radiating element 7 is formed of an Archimedean spiral conductor, it may also be formed of an equiangular spiral conductor. In addition to connecting the outer end to the strip conductor 3, it is also possible to connect the inner end. Hereinafter, a case will be described in which the radial element 7 is formed of an Archimedean spiral conductor.

The figure shows an example in which the upper insulating layer 4 and the lower insulating layer 5 are formed of solid insulators, but
It may be replaced with air, in which case a spacer made of a suitable insulator is formed to hold the strip conductor 3 and the radiating element 7 in the required position.

Reference numeral 8 denotes a shielding conductor, and if the end of the strip conductor 3 is left protruding into the corresponding part of the opening 6, it will adversely affect the circularly polarized radiation from the radiating element 7. Therefore, it is provided integrally with the upper ground conductor 1 so as to cover directly above the protruding portion of the strip conductor 3. The shielding conductor 8 is formed of a relatively wide conductor, and both edges of the shielding conductor 8 are bent downward so as to cover not only the upper part of the strip conductor 3 protruding into the opening 6 but also both sides thereof. may be formed. Note that when the radiating element 7 is formed of a conductor in the form of an equiangular spiral, when connecting its outer end to the end of the strip conductor 3, the strip conductor 3
Since it is also possible to connect the end portions of the conductors without extending and projecting them to the corresponding locations within the opening 6, it is of course unnecessary to provide the shield conductor 8 in such a case.

When manufacturing the antenna of the present invention in which the upper insulating layer 4 and the lower insulating layer 5 are formed of a solid material, the strip conductor 3 and the radiation are printed on the same surface of a film-like insulator, for example. The conductor forming the element 7 is attached, and a thin film made of foamed plastic with low dielectric loss, such as polyethylene foam or urethane foam, is overlaid on the front and back surfaces to form an upper insulating layer 4.
and a lower insulating layer 5 are formed, and a film-like insulator having a metal thin film adhered to the surface is layered on each surface of the upper insulating layer 4 and the lower insulating layer 5 to form an upper ground conductor 1 and a lower ground conductor 1.
A conductor 2 is formed. An upper ground conductor 1, a lower ground conductor 2, a strip conductor 3, and a radiating element 7 are formed by pressing or electrical discharge machining on a metal thin plate, and an upper insulating layer 4 is formed.
It may also be overlapped with the film-like insulator forming the lower insulating layer 5. When formed in this way, mechanical stability can be improved.

In the figure, the spiral direction of the radiating element 7 is indicated by the Z axis (an axis perpendicular to the surface of the radiating element 7 at the center of the radiating element 7; the Y axis, which will be described later, is the longitudinal direction of the triple plate transmission line). around the axis, the X-axis is perpendicular to the Y-axis),
Although a case is illustrated in which the radiating element is formed to rotate clockwise from the inner end, the present invention can also be practiced by providing a spiral radiating element that rotates in the opposite direction.

A ring-shaped conductor is provided on the extended circumferential surface of the peripheral wall of the opening 6, and its upper edge is connected to the upper ground conductor 1 and its lower edge is connected to the lower ground conductor 2. A hole is bored in the part of the conductor in the shape of a ring where the strip conductor 3 is led out to the corresponding part in the opening 6, and the ring-shaped conductor and the strip conductor 3 are formed so as not to come into contact with each other. It may be configured to prevent the electromagnetic waves radiated from the radiating element 7 from leaking and propagating into the upper insulating layer 4 and the lower insulating layer 5 without interfering with power feeding from the conductor 3.

Instead of providing a ring-shaped conductor on the extended peripheral surface of the peripheral wall of the opening 6, an envelope line is formed on the portion of the upper ground conductor 1 forming the outer peripheral portion of the opening 6. An appropriate number of through holes are bored at appropriate intervals in the circumferential direction so as to form approximately concentric circles, and these through holes are
Drill a similar through hole in the part of the lower ground conductor 2 corresponding to the location where the hole was drilled, and connect the upper and lower corresponding through holes.
The shielding body may be formed by connecting the wires with each other with a rod-shaped or wire-shaped conductor.

Regarding the size of the circumference of the opening 6, as will be described later, when an array antenna is constructed using the antenna of the present invention as a component antenna, the size of the element antenna can be reduced without increasing the size of the entire array antenna. In order to maintain a wide mutual spacing and to ensure flexibility in arranging the feeder lines of each element antenna, it is desirable to make the circumference of the opening 6 as small as possible. In order to allow the electromagnetic waves radiated from the aperture 6 to pass through the aperture 6 without being attenuated over a wide band, the circumference of the aperture 6 should be appropriately larger than the outermost circumference of the radiating element 7. It is desirable to define it as follows.

The length and width of the spiral radiating element 7 are appropriately adjusted so that the high frequency current fed by the triple plate transmission line becomes a traveling wave distribution in the radiating element 7 and radiates circularly polarized waves. This adjustment is necessary, but this adjustment depends on the distance between the upper ground conductor 1 and the lower ground conductor 2 in the triple plate transmission line, the electrical properties of the dielectric material forming the upper insulating layer 4 and the lower insulating layer 5, and Although it depends on the size of the aperture 6, etc., the circumference ratio π is calculated as the sum of the distance from the approximate center of the radiating element 7 to the inner end and the distance from the approximate center to the outer end of the radiating element. The circumference equal to the multiplied length (hereinafter referred to as virtual circumference) is approximately 1 of the frequency used.
Adjustment is possible within the range of a virtual circumference that is an integral multiple of the wavelength (free space wavelength, λ).

In the antenna of the present invention, for example, assuming that the dielectric constant of the dielectric material forming the upper insulating layer 4 and the lower insulating layer 5 is 1.0, the radial function of the spiral radiating element 7 is γ=
In aφ-Δ (a is the spiral constant, φ is the angle from the starting point of the spiral, and Δ is the starting point constant), the spiral constant a is 0.19 mm/rad, and the starting point constant Δ is,
The range of 0.86mm φ is 6.72π (rad) ≦φ≦10π
(rad) When the radius R of the opening 6 is formed to be 8.19 mm, the operating frequency is 11.85 mm.
The directional characteristics of the antenna of the present invention at GHz are as shown in FIGS. 2 and 3.

FIG. 2 shows the directional characteristic in the Z-X plane, where the half-width (beam width) of the directional characteristic is 76°. FIG. 3 shows the directional characteristic in the Z-Y plane, where the half-width (beam width) of the directional characteristic is 76°. - width) 7
It is 8°. The half widths in two perpendicular planes, that is, the Z-X plane and the Z-Y plane, are 76° and 78°, respectively.
Since they almost match, when configuring an array antenna using the antenna of the present invention as an element antenna, the element antenna spacing in the X direction and Y direction can be made the same, and the design and manufacture of the array antenna can be simplified. It's easy.

FIG. 4 is a curve diagram showing an example of return loss in the antenna of the present invention, and the horizontal axis represents the operating frequency f (GHz
), the vertical axis is the return loss RL (dB). Figure 5 shows
1 is a curve diagram showing an example of the axial ratio of the antenna of the present invention, where the horizontal axis is the operating frequency f (GHz), and the vertical axis is the axial ratio AR (dB). The return loss and axial ratio of an antenna are parameters that determine how efficiently circularly polarized radio waves can be received.As is clear from FIGS. 4 and 5, the antenna of the present invention has a Both in terms of quantity and axial ratio, it has extremely good characteristics in the frequency band of 11.7 GHz to 12.0 GHz used for satellite broadcasting in Japan.

The above description has been made for the case where the virtual circumference of the radiating element 7 is approximately one wavelength, but even if the length of the radiating element is selected so that the virtual circumference is approximately two wavelengths, the radiating element The current distribution can be made into a traveling wave distribution, and by appropriately making the circumference of the aperture 6 larger than the virtual circumference selected to be approximately twice one wavelength, the current distribution can be made into a traveling wave distribution. It can have bidirectional directional characteristics.

By selecting the virtual circumference of the radiating element 7 to be an arbitrary integer multiple of approximately one wavelength and appropriately increasing the size of the aperture according to the size of the virtual circumference, the directivity characteristics in circularly polarized waves can be improved. can be varied in various ways. These directional characteristics can be easily determined by replacing the antenna with a loop antenna through which a traveling wave current of an arbitrary wavelength flows for one round, and the relationship between the size of the virtual circumference and the directional characteristics. The purpose can be achieved by determining how many times the size of one wavelength is to be made and by making the size of the aperture appropriately larger than the size of the virtual circumference.

FIG. 6(a) shows the maximum value of the traveling wave current at a certain time when the virtual circumference is approximately one wavelength, and FIG. 6(b) shows the maximum value of the traveling wave current at a certain time by a solid line with an arrow. Figure 7(a) shows the maximum value of the traveling wave current at a certain time when the virtual circumference is approximately two wavelengths, as a solid line with an arrow. b) shows its bidirectional directional characteristics.

FIG. 8 is a schematic plan view showing an example of an array antenna in which the antenna of the present invention is constructed as an element antenna. Numerals 9 to 12 are element antennas made of the antenna of the present invention, and the figure shows four element antennas. Although the example is shown in which the centers of the antennas are arranged in a row on the same line, the array antenna can be constructed by increasing or decreasing the number of antennas as appropriate. The broken line is an internal conductor constituting a triplate transmission line, which excites each element antenna in parallel. When multiple element antennas are installed, they are affected by coupling between the element antennas, so
It is necessary to appropriately adjust the virtual circumference length of the radiating element made of the spiral conductor in each element antenna to find an optimum value.

FIGS. 9 to 12 show the array shown in FIG.
This is a diagram showing various characteristics of the antenna, and the data for each diagram is shown in Figure 8.
The center spacing of the element antennas at the working frequency 11.
The coordinate axes in FIGS. 9 and 10 are the Z-axis in the direction perpendicular to the radiation surface from the center point of the center spacing between the element antennas 10 and 11 in FIG. The direction of the line connecting the centers of is the X-axis, the Z-axis, and the direction perpendicular to the X-axis is the Y-axis.

FIG. 9 shows the Z angle of the array antenna shown in FIG.
- Directional characteristics in the X plane, FIG. 10 shows the directivity characteristics in the Z-Y plane, and in the Z-X plane, the array shown in FIG. -The antenna is extremely sharp at 14 degrees and has a high gain. Furthermore, the axial ratio characteristics for wide angles are not impaired compared to the case of using only the antenna of the present invention.

FIG. 11 is a curve diagram showing the return loss in the array antenna shown in FIG. 8, and the horizontal axis represents the operating frequency f.
(GHz), and the vertical axis is the return loss RL (dB). In the array antenna shown in Fig. 8, the frequency is approximately 1
The voltage standing wave ratio (VSWR) is 1.5 or less from 1.55 GHz to 12.3 GHz, which is good.

FIG. 12 is a curve diagram showing the axial ratio characteristics in the Z-axis direction of the array antenna shown in FIG.
It exhibits good circular polarization characteristics of less than b.

In FIG. 8, four openings are provided in a common upper ground conductor, an upper insulating layer, a lower insulating layer, and a lower ground conductor are also formed in common, and a hole is formed corresponding to each opening. An example is shown in which an array antenna is constructed by arranging radiating elements and arranging strip conductors for parallel excitation of each radiating element between a common upper insulating layer and a lower insulating layer. The formed antenna of the present invention may be arranged as element antennas on the same or substantially the same plane, and a feeder line may be externally attached to each element antenna to form an array antenna.

Although the above description has been made of the case where the feeder line is formed by a triple-plate transmission line, the present invention can be carried out in exactly the same way even when the feeder line is formed by a suspended transmission line.

[0035]

[Effects of the Invention] The antenna of the present invention uses a transmission line that inherently has low loss, such as a triple-plate transmission line or a suspended transmission line, as a feed line, and attaches a radiating element by performing simple processing on a part of the transmission line. Not only is this possible, but the coupling structure between the radiating element and the feeder line is much simpler and easier to manufacture than in the past, so the manufacturing cost is low. It has excellent directivity characteristics and axial ratio characteristics, and an array antenna having this antenna as a component is extremely suitable, for example, as an array antenna for receiving satellite broadcasting using circularly polarized waves.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing an embodiment of the present invention. (b) is a sectional view showing one embodiment of the present invention.

FIG. 2 is a diagram showing an example of the directivity characteristics of the antenna of the present invention.

FIG. 3 is a diagram showing an example of the directivity characteristics of the antenna of the present invention.

FIG. 4 is a diagram showing an example of return loss characteristics of the antenna of the present invention.

FIG. 5 is a diagram showing an example of the axial ratio characteristic of the antenna of the present invention.

FIG. 6(a) is a diagram for explaining the operation of the antenna of the present invention. (b) is a diagram showing an example of the directional characteristics of the antenna of the present invention.

FIG. 7(a) is a diagram for explaining the operation of the antenna of the present invention. (b) is a diagram showing an example of the directional characteristics of the antenna of the present invention.

FIG. 8 is a diagram showing an example of an array antenna using the antenna of the present invention as an element.

FIG. 9 is a diagram showing an example of the directivity characteristics of an array antenna using the antenna of the present invention as an element.

FIG. 10 is a diagram showing an example of the directivity characteristics of an array antenna using the antenna of the present invention as an element.

FIG. 11 is a diagram showing an example of return loss characteristics of an array antenna using the antenna of the present invention as an element.

FIG. 12 is a diagram showing an example of the axial ratio characteristic of an array antenna using the antenna of the present invention as an element.

[Explanation of symbols]

1 Upper outer conductor 2 Lower external conductor 3. Internal conductor 4 Upper insulating layer 5 Lower insulating layer 6 Opening 7 Radiating element 8 Shielded conductor 9. Antenna of the present invention 10 Antenna of the present invention 11 Antenna of the present invention 12 Antenna of the present invention

Claims (7)

[Claims] 1. An upper insulating layer and a lower insulating layer interposed between an upper external conductor and a lower external conductor, an opening formed by removing a portion of the upper external conductor, and an opening formed in the opening. A radiating element made of a spiral conductor provided between the corresponding upper insulating layer and lower insulating layer; and a radiating element interposed between the upper insulating layer and the lower insulating layer and made of the spiral conductor. A spiral antenna characterized by comprising an internal conductor connected in a high frequency manner. Claim 2: The sum of the distance from approximately the center of a radiating element made of a spiral conductor to the start of winding of the spiral conductor, and the distance from approximately the center of the radiating element comprised of a spiral conductor to the end of winding of the spiral conductor. 2. The spiral antenna according to claim 1, wherein a value obtained by multiplying by a circumference is approximately an integral multiple of one wavelength of the electromagnetic wave used. 3. The spiral antenna according to claim 1, wherein the high-frequency connection point with the internal conductor is an outer end of the radiating element made of the spiral conductor. 4. The spiral antenna according to claim 1, wherein an electromagnetic shield is provided between the lower outer conductor portion and the upper outer conductor portion corresponding to the periphery of the opening except for the location where the inner conductor is disposed. 5. The spiral antenna according to claim 1, wherein the upper insulating layer and the lower insulating layer are made of solid material. 6. The device according to claim 1, wherein the upper insulating layer and the lower insulating layer are made of air, and the radiating element and the inner conductor made of a spiral conductor are held in a predetermined position by a spacer made of an insulator. spiral antenna. 7. An upper insulating layer and a lower insulating layer interposed between an upper external conductor and a lower external conductor, an opening formed by removing a portion of the upper external conductor, and an opening formed in the opening. A radiating element made of a spiral conductor provided between the corresponding upper insulating layer and lower insulating layer; and a radiating element interposed between the upper insulating layer and the lower insulating layer and made of the spiral conductor. 1. An array antenna comprising an appropriate number of spiral antennas each having a high-frequency connected internal conductor arranged on the same plane.