JPS62216407A - Spiral antenna - Google Patents

Abstract

PURPOSE:To simplify the structure production and design an antenna freely by providing a spiral element and a feeder on a common insulating substrate and allowing one feed point to suffice for the antenna. CONSTITUTION:Spiral slot elements 31 and 32 are formed by the printed wiring method so that they have the same winding direction. A coupling element 4 which couples respective outer end parts of spiral slot elements 31 and 32 consists of a slot formed by the printed wiring method. A linear metallic thin film 5 which is provided on the rear face of an insulating substrate 1 and has a proper width consists of a copper foil provided by the printed wiring method and forms a microstrip line feeder together with an earth surface forming metallic thin film 2 which faces said metallic thin film 5 with the insulating substrate 1 between them, and the end part of the feeder 5 faces an approximate center of the coupling slot 4 with the insulating substrate 1 between them to supply power to the approximate center of the coupling slot 4 by capacitive coupling.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a wideband spiral antenna suitable as a basic radiating element used, for example, in electromagnetic interference tests.

BACKGROUND ART Conventionally, linear Archimedean spiral antennas, plate-like conformal spiral antennas, planar log-periodic antennas, multi-wire spiral slot antennas, single-wire spiral slot antennas, etc. have been used as the above-mentioned antennas. .

Problems to be Solved by the Invention Conventional linear Archimedean spiral antennas and plate-shaped conformal spiral antennas are both unsuitable for radiating linearly polarized waves, and the feed system portion is a coaxial type that includes a balanced-unbalanced conversion element. It is difficult to manufacture because it consists of railroad tracks.

In a planar log-periodic antenna, a suitable broadband hybrid element or the like is required in order to radiate circularly polarized waves, which makes it difficult to manufacture the antenna in a straight line.

Multi-wire spiral slot antennas require two or more feeding points, making feeding complicated.
It is difficult to excite linearly polarized waves.

Is the single wire spiral slot antenna in the slot part? Since the a-flow distribution is not symmetrical, it is not possible to obtain directivity that is symmetrical about the central axis in the radial direction, and therefore,
Good circular polarization characteristics cannot be obtained in the front direction, and it is structurally difficult to excite linearly polarized waves.

Means for Solving Problems, Embodiments The present invention has been made to eliminate the various drawbacks of the above-mentioned conventional antennas, and will be described in detail below with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of the present invention, and FIG. 2 is a plan view showing an embodiment of the present invention.
The bottom view and FIG. 3 are side views, and in each figure, 1 is an insulating substrate, and 2 is a metal thin film provided on the surface of the insulating substrate 1 to form a ground plane, and is made of copper foil, for example. Reference numerals 31 and 32 denote spiral slot elements, which are each formed by, for example, a printed wiring method, and are formed so that the winding directions of the pixel elements are in the same direction. 4 is spiral slot element 3! and 3
A coupling element between each of the outer ends of the two, for example, a slot formed by a printed wiring method. Reference numeral 5 denotes a linear metal thin film having an appropriate width provided on the back surface of the insulating substrate 1, and is made of, for example, copper foil provided by a printed wiring method. A strip line type feeder line is formed so that the end of the feeder line 5 faces approximately the center of the coupling slot 4 via the insulating substrate l, so that power can be supplied to the approximate center of the coupling slot 4 by capacitive coupling. It is formed.

Instead of coupling the feeder line 5 and the coupling slot 4 by capacitive coupling, a portion of the metal thin film 2 near the edge at the midpoint of the coupling slot 4 and the end of the feeder line 5 are coupled via a through hole. You can force it.

FIG. 4 is a diagram for explaining the basic operating principle of the antenna of the present invention, in which P is a plane conductive plate provided with a slot S, which is assumed to have an infinite width and an infinite thinness. W is a linear element corresponding to a feed line, and assuming that this linear element W and the plane conductor plate P are made of perfect conductors, the width of the slot S and the radius of the linear element W are , 1(i
It is assumed that the wavelength is sufficiently smaller than the wavelength of n).

The current I on the linear element W and the magnetic current M on the slot S can be determined from the following equations.

(1) In equation (1), A is the magnetic field vector potential, F is the electric field vector potential, and is the unit tangent vector at the observation point.) (SC is the closed circuit magnetic field.

The first term on the left side of equation (1) is related to the magnetic field from the linear element W, and is the dogleg-shaped fold formed by the n-1 section and the n section in the linear element W in Fig. 4. Focusing on the curved part, the magnetic field due to this bent part is expressed in local cylindrical coordinates (ψn, ρn,
Zn), (ψn-1, ρ.-1, 2n-+), and a partial sine wave function is used as the expansion function of the current on the bent part, and the first term on the left side of equation (1) is If the magnetic field component due to the folded line portion shown is )In:wire, then φn-1= ((jcosθn-1-sinβan-1
-cosβen-1)・e-jβRn-1-jβ""-
' )*n−++e ・ ・ ・ ・ (3) φn = (−Cjcosθ−, −5inβen+ c
osβel)-e-""'-jβR0):n+e ・ ・ ・ ・ ・ (4) The distance and angle are shown, and an = zn + I zn en-1 + = zn-Zn-1.

The second term on the left side of equation (1) is a term related to the magnetic field radiated from the slot S.
Focusing on the dogleg-shaped bent slot section consisting of 1 section and n section, and again adopting a partial sine wave expansion function for the magnetic current M on the slot, the magnetic field component of the second term is finally calculated as follows: It is derived as follows.

... (5) Here, Po-1= (cosβel-1,0O3on-1'
e-jβRn-1-8゜8. . −,,8−jβ2°− −jsinβb ・ ・ ・ ・ (6) −−jβRrl Pn= (cosβen−CoSon−e・ ・ ・
・ (7) ・ ・ ・ ・ (9) Next, the following equation can be obtained using the fact that on the surface of a perfect conductor, the tangential component of the combined electric field of the incident wave and scattered wave is zero.

+・A(z))・Z=o...(lo) The electric field components in the first and second terms on the left side of the above equation are formed by the slot s and the linear element W, respectively, and are partially Since the sine wave function is used as the expansion function of magnetic current and current, n-1
The electric field components for the doglegged slot part and doglegged linear element part, which are made up of sections and n sections, are expressed by the first term and the second term.
The following equation is obtained from the terms:

o − + )・Z ... (11) ρ mouth Sln
βen... (12) After applying the test function, magnetic field component due to the folded line portion hn:wire, magnetic field component due to the folded slot portion hn:5lot, electric field component due to the folded line portion en:w
Electric field component el'l due to ire and bent slot portion:
5 lots, respectively hs+n:vlrp, hen
: 5 lots.

Assuming emn+wire and eln:5lot, (
Equation 1) and Equation (lO) are respectively expressed by the following equations.

(m=1.2...) ... (13) From the above, the complex expansion coefficients In and M regarding electric current and magnetic current
n is found by ordinary matrix solving.

In the embodiments illustrated in FIGS. 1 to 3, the feeder line 5
When the spiral slot elements 31 and 32 are excited through the magnetic current flowing into each slot, the rotation direction of each electric field vector in the circularly polarized waves radiated from each spiral slot element 3I and 2 becomes the same direction, and they harmonize with each other. are combined and one circularly polarized electromagnetic wave is radiated.

In the above embodiment, the spiral slot elements 31 and 32 are wound in the same direction, but as shown in FIG. 5, the spiral slot elements 3I and 32 are wound in the same direction. The present invention can be carried out even if the spiral slot elements are formed in opposite directions, and in this case, the rotation directions of the electric field vectors in each circularly polarized wave generated by the magnetic current flowing into each spiral slot element are opposite to each other. The electric field vector components in the direction perpendicular to the feed line are differentially combined with each other, and the electric field vectors in the direction parallel to the feed line are summarily combined with each other, so the electric field vector in the direction of the arrow shown in Figure 5 A linearly polarized wave having .

The above example illustrates the case where the spiral slot elements 31 and 32 are formed using linear Archimedean spiral slot elements, but as shown in FIG. 6, the spiral slot elements may be formed using equiangular spiral slot elements. As shown in FIG. 7, the present invention can also be implemented by forming a rectangular spiral slot element.

In each of the above examples, the spiral element is formed using a slotted spiral element and configured to excite a magnetic current inflow, but the spiral element may also be configured to be formed using a conductor and configured to excite a current inflow. The invention can be practiced.

FIG. 8 is a plan view showing an example of this, and FIG. 9 is a bottom view. In both figures, l is an insulating substrate, and 2' is a metal thin film forming a ground plane. It is provided on the back side of 1.

3'1 and 3'2 are linear Archimedean spiral elements, which are composed of conductors provided on the surface of the insulating substrate 1 by, for example, a printed wiring method. 4' is a coupling element, 5' is a feeder line,
These also consist of conductors provided on the surface of an insulating substrate l, for example by printed wiring techniques, and the feeder lines 5' are gold H thin 11! i
Together with 2', a microstrip line is formed.

This example differs from the previous example shown in FIGS. 1 to 3 in that the spiral element 31.3; and the coupling element 4' are formed of conductors, but its radiation characteristics are completely different from those of the previous example. The same is true.

Although not shown in the figure, it is of course necessary to interpose an impedance matching element between the feed line 5' and the feeding point depending on the characteristic impedance of the feed line 5'.

In the embodiments shown in FIGS. 8 and 9, the spiral element made of a conductor is formed using a linear Archimedean spiral element, but the present invention can also be practiced by forming it using an equiangular spiral element or a rectangular spiral element. I can do it.

In each of the above embodiments, two pairs of spiral elements are provided on the insulating substrate, but as shown in FIGS. 10 and 11, two pairs of spiral elements are provided on the surface of the insulating substrate. 31 and 32, and a pair of spiral elements 33 and 34 are provided at appropriate intervals from this pair of spiral elements, and a common power supply line 5 (10th The radiated power can be increased by configuring each spiral element to be excited through the coils shown in FIG. Note that FIG. 10 shows the case of series power supply, and FIG. 11 shows the case of parallel power supply.

In both FIG. 10 and FIG. 11, the case where two pairs of four spiral elements are provided is shown as an example, but by providing three or more pairs of six spiral elements with appropriate spacing in each row, it is possible to radiate radiation. Power can be further increased.

Although FIGS. 10 and 11 illustrate the case in which a linear Archimedean spiral slot element is provided, the spiral element may also be formed with an equiangular spiral slot element or a rectangular spiral slot element, and the spiral element may be formed of a conductor. Of course, it may also be formed using.

In the embodiments shown in FIGS. 6 to 11, the winding direction of each pair of spiral elements is set in the same direction so that circularly polarized wave radiation can be performed. Of course, the winding directions of the spiral elements may be opposite to each other so that linearly polarized radiation can be performed.

In any of the above embodiments, as shown in FIG.
By providing a suitable reflector 6 in front or behind the insulating substrate 1 and adjusting the distance between the insulating substrate 1 and the reflector 6 as appropriate according to the radiation wavelength, the radiation directivity can be adjusted to the beam behind or in front of the insulating substrate 1. It can be made into a shape.

Further, in each of the embodiments, the case where the insulating substrate 1 is formed into a planar shape is exemplified, but the present invention can be applied even if it is formed into a curved surface, such as a part of a cylindrical surface, a part of a spherical surface, or a conical surface. It can be implemented.

When the insulating substrate is formed with a curved surface that forms part of a cylindrical surface, for example, as shown in a schematic plan view in FIG. By arranging the reflector 7 in a shape and providing a cylindrical reflector 7 at the center axis position, the combined directivity can be made non-directional.

Effects of the Invention In the present invention, since the spiral element and the feed line are provided on a common insulating substrate and only one feed point is required, the structure is simple and easy to manufacture, and an antenna including the antenna of the present invention as a component can be designed freely. It becomes possible to do so.

Furthermore, by winding the spiral elements in a pair in the same direction or in opposite directions, it is possible to radiate either circularly polarized waves or linearly polarized waves, and in either case, the magnetic current or Since the structure is capable of making the current distribution symmetrical, the directivity is symmetrical over a wide band and the polarization characteristics are good.

FIG. 14 is a diagram showing an example of the magnetic wave distribution in the spiral slot elements 31 and 32 of the embodiment shown in FIGS. 1 to 3, in which the horizontal axis represents the length SL of the slot, that is, the coupling in FIG. The length of the slot of each spiral slot element from the feeding point located approximately at the center of the slot 4 for
In FIG. 14, the feeding point is indicated by F. The vertical axis is M(Z)
/ input E, where M(Z) is the magnitude of the magnetic current along the slot whose origin is the feeding point in Fig. 1, input is the radiation wavelength, and E is the electric field strength of the radiation wave. Figure 14 shows the case where the input is 3.2 GH2.

Further, the solid line is a curve corresponding to the real part in the complex number representation of a vector, the broken line is a curve corresponding to the imaginary part, and the dotted line is a curve corresponding to the absolute value.

It is clear from the figure that the magnetic current distribution in the present invention is approximately symmetrical with respect to the feeding point, and therefore good directivity characteristics can be obtained in both cases of circularly polarized waves and linearly polarized waves.

FIG. 15 is a curve diagram showing an example of the radiation directivity characteristics in the embodiment shown in FIGS. 1 to 3, with the feed point in FIG. 1 as the origin, and the X and Y coordinate axes in the X and Y directions. This is a curve diagram expressed in spatial polar coordinates when the X coordinate axis is taken vertically upward from the origin, and the curve shown by the solid line represents the electric field component E in the plane where the deviation angle φ from the xZ plane is 00 and 900. , radiation frequency 3.0 GH2
, 3,2GH2, and 3.40H2, the dotted curve shows the electric field component Ee in the direction of polarization angle θ from the X coordinate axis, and all exhibit good circularly polarized wave directivity characteristics. ing.

FIG. 16 is a diagram showing the axial ratio characteristic in the case of circularly polarized radiation in the embodiment shown in FIGS. 1 to 3, that is, the relationship between the circular polarization coefficient and frequency, and the horizontal axis is the radiation frequency f (G)II),
The vertical axis is the axial ratio AR (dB), that is, the ratio of the long axis to the short axis of the arc drawn by the electric field vector in circularly polarized waves, which is generally 201
og+o, which is OdB for perfectly circularly polarized waves.

As is clear from the figure, the spiral antenna of the present invention exhibits good axial ratio characteristics over a range of approximately 3.0 GHz to 3.7 cH2.

[Brief explanation of drawings]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a bottom view thereof, Fig. 3 is a side view thereof, Fig. 4 is a diagram for explaining its operation, and Figs. 5 to 7 are Diagrams showing main parts of other embodiments,
FIG. 8 is a plan view showing another embodiment, FIG. 9 is a bottom view thereof, FIGS. 1θ to 13 are also views showing other embodiments, and FIG.
FIG. 4 is a diagram showing an example of magnetic current distribution in the spiral element of the present invention. FIG. 15 is a diagram showing an example of radiation directivity characteristics, and FIG. 16 is a diagram showing an example of axial ratio characteristics. 1: Insulating substrate, 2 and 2':
Metal thin film forming the ground plane, 31.32.31.3'
2.33 and 34: Spiral element, 4 and 4゛: Coupling element, 5.5' and 5'': Feeding line, 6: Reflector. 7 Two cylindrical reflectors, P: Planar conductor plate, S Ni slot, W
: It is a linear element.

Claims (13)

[Claims] (1) A pair of spiral elements is provided on an insulating substrate, and a coupling element is provided between each outer end of the pair of spiral elements, and a common coupling element is coupled to approximately the midpoint of the coupling element. A spiral antenna characterized in that a feed line is provided on the insulating substrate. (2) The spiral antenna according to claim 1, wherein the pair of spiral elements are wound in the same direction. (3) The spiral antenna according to claim 1, wherein the winding directions of the pair of spiral elements are opposite to each other. (4) The spiral antenna according to claim 1, wherein the spiral element is a linear Archimedean spiral slot element, and the coupling element is a slot. (5) The spiral antenna according to claim 1, wherein the spiral element comprises a conformal spiral slot element and the coupling element comprises a slot. (6) The spiral antenna according to claim 1, wherein the spiral element is a rectangular spiral slot element, and the coupling element is a slot. (7) The spiral antenna according to claim 1, wherein the spiral element comprises a linear Archimedean spiral element formed of a conductor, and the coupling element comprises a conductor. (8) The spiral antenna according to claim 1, wherein the spiral element comprises a conformal spiral element formed of a conductor, and the coupling element comprises a conductor. (9) The spiral antenna according to claim 1, wherein the spiral element is a rectangular spiral element formed of a conductor, and the coupling element is a conductor. (10) The spiral antenna according to claim 1, wherein the common feed line to each pair of spiral elements is a series feed line. (11) The spiral antenna according to claim 1, wherein the common feed line to each pair of spiral elements is a parallel feed line. (12) The spiral antenna according to claim 1, wherein the insulating substrate is planar. (13) The spiral antenna according to claim 1, wherein the insulating substrate has a curved surface.