JP2002076751A - Loaded spiral monopole antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen the input impedance. SOLUTION: The first spiral arm 11 and the second spiral arm 12 are provided at the tip of a monopole element 15, in parallel with a ground plane 18. The first parasitic element 13 and the second parasitic element 14 are provided at the outside of the first spiral arm 11 and the second spiral arm 12. A wider input impedance is obtained by the effect of these parasitic elements 13 and 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line antenna, and more particularly to a low-profile and wide-band antenna suitable for a mobile communication system.

[0002]

2. Description of the Related Art A transmission line antenna is known as an antenna having a low attitude suitable for a mobile communication system. A transmission line type antenna is an antenna using a transmission line in which strip conductors are arranged in parallel on a ground plane, and an F type antenna or an inverted F type antenna is a typical antenna of the transmission line type antenna. The inverted-F antenna is an antenna in which a strip conductor is replaced with a rectangular conductor plate. At the time of replacement, since the voltage with respect to the ground plane is zero on the center line of the conductor plate, the end of the conductor plate is short-circuited to the ground plane by bending on the center line of the conductor plate. As a result, the length of the antenna operating at a half wavelength can be reduced to half of the length of a quarter wavelength.

Further, a strong electric field is generated between the open end of the bent conductor plate and the ground plane, and a capacitance is equivalently inserted into the conductor plate. Therefore, in order to correct this capacitance, the bent short-circuiting plate is cut out except for one side to form a thin conductor line. Then, a large current flows through the conductor wire to generate a strong magnetic field. This means that a large inductance was equivalently inserted into the conductor plate. As a result, the equivalently inserted capacitance and inductance cancel each other out, so that matching can be achieved even if the length of the conductor plate is reduced. As described above, since the inverted-F antenna is a small-sized and low-profile antenna, it is used as an antenna of a flying object or an antenna of a mobile phone.

[0004] The above-mentioned inverted F-type antenna is used for FM in the VHF band.
In order to realize an antenna for receiving terrestrial broadcasting (76 to 90 MHz) or VHF television broadcasting (92 to 222 MHz), the short side is 800 mm to 1000 mm.
There is a problem that the antenna becomes a rectangular antenna of about mm and it is difficult to mount the antenna on a moving body such as a vehicle. The solution to these problems is IEEE Transaction
s on Antennas and Propagation, Vol.AP-13, No.3, May
1965, pp.379-383, RCFenwick “A new class of electr
In this antenna, spiral elements are arranged in parallel on a ground plane, and the length of the spiral elements is set to 波長 wavelength.
The antenna is designed to be miniaturized by setting the winding start portion as a feeding point and grounding the other end.

[0005] However, although the above antenna can be miniaturized, the input impedance is very small at about 4Ω, and the characteristic impedance of the feed cable is generally 50Ω.
Alternatively, since it is set to 75Ω, the antenna becomes low in efficiency. In addition, VSW with sharp resonance
If the usable frequency band is the case where R is 2 or less, the frequency band is very narrow, about 0.2%, and can be applied to a communication system to which a wide frequency band is allocated such as mobile communication. Did not.

[0006]

Accordingly, the present inventors have proposed, as Japanese Patent No. 2997451, a small antenna capable of increasing the input impedance and obtaining a relative bandwidth of about 7%. However, although the above small antenna can increase the input impedance, in recent mobile communication, the fractional bandwidth is 1 unit.
Some communication systems exceed 0%, and there is a problem that it becomes difficult to apply the small antenna to a communication system having such a wide frequency band.

Accordingly, an object of the present invention is to provide a spirally-loaded monopole antenna capable of widening the input impedance.

[0008]

In order to achieve the above object, a spirally-loaded monopole antenna according to the present invention comprises a monopole element arranged substantially vertically on a ground plane, and a monopole element mounted on a tip of the monopole element. And a pair of spiral parasitic elements arranged substantially horizontally on the ground plane, and a pair of spiral parasitic elements arranged substantially symmetrically on the outer periphery of the spiral element, and a winding start end of the spiral parasitic element. Are bent in an L shape and short-circuited to the ground plane.

[0009] In the spiral loaded monopole antenna according to the present invention, the spiral element is constituted by arranging a pair of spiral arms in a rotationally symmetric manner, and at a predetermined point-symmetric position in the pair of spiral arms. Alternatively, a short-circuit pin that short-circuits to the ground plane may be connected. Further, in the spirally-loaded monopole antenna according to the present invention, a winding start end of the spiral parasitic element may be located near a line connecting a feeding point of the monopole element and the short-circuit pin.

According to the present invention, a pair of spiral parasitic elements are arranged substantially symmetrically on the outer periphery of the spiral element loaded at the tip of the monopole element, so that the impedance can be broadened. Is now available. In particular, by positioning the winding start end of the spiral parasitic element near the line connecting the feeding point of the monopole element and the arrangement position of the short-circuit pin provided on the spiral element, for example, the relative bandwidth of about 15% The width of the impedance can be widened by the width.

[0011]

1 to 3 show an example of the configuration of an embodiment of a spirally-loaded monopole antenna according to the present invention.
Shown in 1 is a plan view of a spirally-loaded monopole antenna of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a perspective view thereof. The spirally-loaded monopole antenna 1 according to the embodiment of the present invention shown in these figures has a ground plane 18 that can be regarded as having an infinite area with respect to the wavelength of the design frequency, and a substantially vertical plane on the ground plane 18. , A pair of first and second spiral arms 11, 12 connected to the tip of the monopole element 15 in a rotationally symmetric manner, a first spiral arm 11, and a second spiral A pair of parasitic elements 13 and 14 are respectively provided outside the arm 12.

That is, the tip of the monopole element 15 is connected to a center point B, and the start points of the first spiral arm 11 and the second spiral arm 12 are connected to the center point B. The first spiral arm 11 and the second spiral arm 12 are developed almost in parallel with the ground plane 18 and have a spiral curve shape based on a spiral function. Further, a first short-circuit pin 1 disposed substantially perpendicular to the ground plane 18 is provided at a junction P, which is a predetermined position of the first spiral arm 11.
One end of the 6 is connected, the other end of the first shorting pin 16 is connected to the position of the point P _G of the ground plane 18. Further, one end of a second short-circuit pin 17 arranged substantially perpendicular to the ground plane 18 is connected to a junction point Q, which is a predetermined position of the second spiral arm 12, and the second short-circuit pin 1
The other end of 7 is connected to the position of the point Q _{O on} the ground plane 18. In addition, the joining point P and the joining point Q are substantially point-symmetric with respect to the center point B. Monopole element 1
5 has a height h, and the other end of the monopole element 15 is inserted into an insertion hole formed substantially in the center of the ground plane 18 to form a coaxial cable fixed to the lower surface of the ground plane 18. Connected to the center conductor of the feeding line 19. The shield conductor of the power supply line 19 is electrically and mechanically connected to the lower surface of the ground plane 18 by soldering or the like. A point connected to the center conductor of the feed line 19 is a feed point S _fd to the monopole element 15.
It has been.

The winding start angle of the first spiral arm 11 and the second spiral arm 12 is represented by _φst, and the winding end angle is represented by _φend . Criteria winding start angle phi _st and the winding end angle phi _{end The} Although there is a x-axis, the reference of the winding start angle phi _st and the winding end angle phi _{end The} second spiral arms 12 are rotated by π radians . Further, the height, which is the distance between the first spiral arm 11, the second spiral arm 12, and the ground plane 18, is h. Note that the first spiral arm 11 and the second spiral arm 12
The center is started to be wound from the end of the linear conductor having a predetermined length connected to the center point B. That is, the angle between the straight conductor and the x-axis is the winding start angle φ _st . By the way, the first spiral arm 11 and the second spiral arm 12 are provided with a straight conductor with a winding start angle of φ _st , because the wire diameter of the first spiral arm 11 and the second spiral arm 12 depends on the strength and the like. This is because the thickness is set to a certain level to satisfy the user. That is, when the winding start angle is set to 0 °, the curvature of the winding start portion becomes large, and the wires having a large wire diameter come into contact with each other and cannot be spirally wound.

Further, the position of the junction point P on the first spiral arm 11 is determined by the circuit consisting of S _fd -B-P-P _G and the S _fd -B- formed by the ground plane 18.
Closed circuit consisting of an image circuit of the P-P _G is a position that is substantially resonant at the frequency of interest. Similarly, the position of the joint point Q on the second spiral arm 12 is S _fd -B
A circuit consisting of -Q-Q _O, closed circuit comprising the S _fd -B-Q-Q _O image circuit created by the ground plane 18 is a position substantially resonant at the frequency of interest. Here, since the first spiral arm 11 and the second spiral arm 12 have the same configuration, the joint points P and Q are substantially point-symmetric with respect to the center point B.

In the thus configured spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the first spiral arm 11 and the second spiral arm 12 are arranged rotationally symmetrically with respect to the center point B. It is a spiral element, and the radiation field created by the image on the first spiral arm 11 and its ground plane 18 has almost the opposite phase when the height h of the first spiral arm 11 is low. Therefore, the first spiral arm 11
The radiation field created by the image and the radiation field created by the image cancel each other out, and no radiation pattern is formed. Further, since the second spiral arm 12 operates in the same manner, no radiation pattern is formed by the second spiral arm 12. After all, the large current flowing through the monopole element 15 and the current flowing through the first short-circuit pin 16 and the second short-circuit pin 17 form the radiation pattern of the spirally loaded monopole antenna 1. For this reason, linearly polarized waves perpendicular to the ground plane 18 are radiated from the spirally-loaded monopole antenna 1 of the present invention.
Further, the radiation pattern of the spirally-loaded monopole antenna 1 of the present invention in the horizontal plane (the xy plane shown in FIG. 1) is made almost non-directional, and is radiated in all directions.

The characteristic configuration of the spirally-loaded monopole antenna 1 according to the embodiment of the present invention is as follows.
Spiral arm 11 and second spiral arm 12
, A first parasitic element 13 and a second parasitic element 14 are provided respectively. The first parasitic element 13 and the second parasitic element 14 are configured to be bent in an L shape, and the ends bent so as to be perpendicular to the ground plane 18 are connected to the ground plane 18.
Is short-circuited. The portion substantially parallel to the ground plane 18 has a curved shape based on a spiral function. By providing the first parasitic element 13 and the second parasitic element 14 as described later, the frequency bandwidth of the impedance of the spirally-loaded monopole antenna 1 according to the embodiment of the present invention is about 15%. A wide bandwidth can be achieved. The winding start angle of the first parasitic element 13 and the second parasitic element 14 is represented by φ _Lst, and the winding end angle is represented by φ _Lend . Although the standard of the winding start angle φ _st and the winding end angle φ _end is the x-axis,
The reference of the winding start angle φ _Lst and the winding end angle φ _Lend of the second parasitic element 14 is rotated by π radians.
Further, the first parasitic element 13 and the second parasitic element 14
The height, which is the distance between the ground plane 18 and the ground plane 18, is h.

Next, an example of the dimensions of each part in the spirally loaded monopole antenna 1 according to the embodiment of the present invention having the structure shown in FIGS. 1 to 3 will be described. Radial function r in the second spiral arm 12 and radial function r in the first parasitic element 13 or the second parasitic element 14
Is represented by an Archimian spiral function as follows: _{r = a s · φ w ···} (1) However, (1) a _s is a spiral constant in the equation, φ _w is the winding angle of up to a winding start angle φ corner end of winding from _st φ _end or winding start, The winding angle from the angle φ _Lst to the winding end angle φ _Lend is shown.

An example of the dimensions of each part when the free space wavelength of the design frequency fo is λo is as follows. The height h, which is the distance between the first spiral arm 11, the second spiral arm 12, and the ground plane 18, is about 0.0613λ.
o and, the first spiral arm 11 second spiral arms 12, and a first parasitic element 13 is spiral constants a _s of the second parasitic element 14 about 0.0064λo [/ ra
d] is set. Further, the winding start angle φ _st of the first spiral arm 11 and the second spiral arm 12 is about 1.3413π [rad], and the winding end angle φ _end is variable, for example, about 7.153π [rad]. Is set. Furthermore, the first parasitic element 13 winding start angle phi _Lst of the second parasitic element 14 is approximately 7.5292π [rad],
The winding end angle φ _Lend is set to about 7.981π [rad]. Furthermore, the first spiral arm 11, the second spiral arm 12, and the first parasitic element 13
And the wire radius ρ of the second parasitic element 14 is about 0.00
3354λo, and the total length of the linear conductor located at the center of the spiral arm is set to about 0.05395λo.

The input impedance of the spirally loaded monopole antenna 1 according to the embodiment of the present invention is about 50Ω at the design frequency fo when the dimensions are set as described above, so that a high input impedance can be obtained. Furthermore, the voltage standing wave ratio to the frequency (VSW
An example of the R) characteristic is as shown in FIG. This VSWR
Referring to the characteristics, by providing the first parasitic element 13 and the second parasitic element 14, the “present invention (φ
_end = 7.153π) ”.
It can be seen that the fractional bandwidth of 0 or less is a wide band of about 15%. For comparison, FIG. 4 also shows the VSWR characteristics with respect to the frequency of a conventional spirally-loaded monopole antenna having no parasitic element. In the conventional example, although the winding end angle φ _end of the spiral arm is changed by three types, the specific bandwidth is about 7%, and the parasitic element 1 is compared with these VSWR characteristics.
It can be seen that the fractional bandwidth of the spirally-loaded monopole antenna 1 of the present invention including 3 and 14 is approximately doubled.

In the spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the dimensions are set as described above, and the lower limit frequency f _L (f / fo =
The radiation pattern of the spirally-loaded monopole antenna 1 at 0.887) is shown in FIGS. FIG.
(A) is a radiation pattern in a φ = 0 ° plane (xz plane) with respect to the θ angle, which is a radiation pattern in a plane perpendicular to the ground plane 18. In the spirally-loaded monopole antenna 1 of the present invention, the currents flowing through the monopole element 15, the first short-circuit pin 16 and the second short-circuit pin 17 are in phase as described above, and the monopole element 15, the first short-circuit pin 16 and the second short-circuit pin 17, but the radiation from the first spiral arm 11 and the second spiral arm 12 is reduced.

[0021] That is, the radiation pattern monopole element 15 illustrated in solid lines, the first shorting pin 16, a E _theta component emitted from the second shorting pin 17, E _theta component horizontal ground plane 18 ( (θ = 90 °) is maximized, and is hardly emitted in the vertical direction (θ = 0 °). Further, the E _φ component radiated from the first spiral arm 11 and the second spiral arm 12 is radiated only at a slight level of about −20 dB or less in the θ = 45 ° direction as shown by the broken line. It is. Here, the _Eθ component is the ground plane 1
8, the ground plane 1
If 8 is positioned horizontally with respect to the ground, it will be vertically polarized. In addition, since the _Eφ component is a component horizontal to the ground plane 18, when the ground plane 18 is positioned horizontally with respect to the ground surface, horizontal polarization occurs. As described above, when the ground plane 18 is arranged horizontally with respect to the ground, the spirally-loaded monopole antenna 1 according to the embodiment of the present invention becomes an antenna for vertical polarization, and the ground plane 18 is positioned with respect to the ground. When it is positioned vertically, the spirally-loaded monopole antenna 1 of the present invention operates as an antenna for horizontal polarization.

FIG. 5B is a graph showing θ = θ with respect to the φ angle.
This is a radiation pattern in a 90 ° plane (xy plane), which is a radiation pattern in a horizontal plane with respect to the ground plane 18. In this case, the radiation pattern shown by the solid line is the _Eθ component radiated from the monopole element 15, the first short-circuit pin 16, and the second short-circuit pin 17, as described above, and the _Eθ component is the xy plane. Is emitted with almost equal intensity in all directions.
Deviations in the x-y plane of the E _theta component is approximately 4dB. However, the _Eφ component radiated from the first spiral arm 11 and the second spiral arm 12 is not illustrated because it is radiated only at a small level.

Next, in the spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the dimensions are set as described above, and the upper limit frequency f _H (f / f) is set.
6 (a) and 6 (b) show the radiation pattern of the spirally loaded monopole antenna 1 when o = 1.0261).
FIG. 6A shows a radiation pattern in a φ = 0 ° plane (xz plane) with respect to the θ angle, which is a radiation pattern perpendicular to the ground plane 18. In this case, the radiation pattern shown by the solid line is the monopole element 15, the first
The E _θ component radiated from the short-circuit pin 16 and the second short-circuit pin 17 is the E _θ component, and the radiation in the horizontal direction (θ = 90 °) of the ground plane 18 is _maximized , and the E _θ component is °) shows that it is hardly radiated. The _Eφ component radiated from the first spiral arm 11 and the second spiral arm 12 is not shown because it is radiated only at a small level.

Further, FIG. 6B shows that θ = θ with respect to the φ angle.
This is a radiation pattern in a 90 ° plane (xy plane), which is a radiation pattern in a horizontal plane with respect to the ground plane 18. In this case, the radiation pattern shown by the solid line is the _Eθ component radiated from the monopole element 15, the first short-circuit pin 16, and the second short-circuit pin 17, as described above, and the _Eθ component is the xy plane. Is emitted with almost equal intensity in all directions.
The deviation of the E _θ component in the xy plane is a small deviation of about 1.6 dB. However, the first spiral arm 1
The _Eφ components radiated from the first and second spiral arms 12 are not shown because they are radiated only at a small level. Note that VSWR = 2 or less and a horizontal plane (xy)
The fractional bandwidth in which the deviation in the radiation pattern in the plane is 3 dB or less is about 12.6%.

Next, in the spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the VSWR characteristic when the winding start angle φ _Lst of the first parasitic element 13 and the second parasitic element 14 is changed will be described. As shown in FIG. The winding start angle φ _Lst of the first parasitic element 13 and the second parasitic element 14 is _set to about 5.
A schematic configuration of a spiral loaded monopole antenna 1 at the time of the 529π [rad] is shown in FIG. 7 (a), a spiral loaded mono upon the winding start angle phi _Lst about 6.529π [rad] The schematic configuration of the pole antenna 1 is shown in FIG.
(B), the winding start angle φ _Lst is about 7.
FIG. 7 (c) shows a schematic configuration of the spirally-loaded monopole antenna 1 at 529π [rad]. As described above, the first parasitic element 1 according to the winding start angle φ _Lst
The winding start ends of the third and second parasitic elements 14 rotate counterclockwise with respect to the x-axis, and gradually move away from the center point B. Referring to the VSWR characteristics shown in FIG. 7D, the first parasitic element 13 and the second parasitic element 1
The fourth winding start angle phi _Lst about 5.529π (rad), about 6.
It can be seen that the VSWR becomes a good value every time the rotation is π, ie, 529π [rad] and about 7.529π [rad].
It can be seen that such a winding start angle φ _Lst exists near an extension of a line connecting the joining points P and Q and the center point B. That is, by setting the winding start angle φ _Lst of the first parasitic element 13 and the second parasitic element 14 near the extension of the line connecting the junction points P and Q and the center point B,
Good VSWR spiral loaded monopole antenna 1
It can be.

Next, in the spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the winding start angle φ _Lst of the first parasitic element 13 and the second parasitic element 14 is _set so that the VSWR characteristics are _improved . FIG. 8 shows the VSWR characteristics with respect to the frequency when set. FIG. 8A shows a case where the winding start angle φ Lst of the first parasitic element 13 and the second parasitic element 14 is _set to 5.529π [rad], and VSWR = 2
The following fractional bandwidths are not significantly expanded. FIG.
(B) is divided into a first parasitic element 13 the winding start angle phi _Lst of the second parasitic element 14 is a case of the 6.529π (rad), VSWR = 2 or less fractional bandwidth is two It has been slightly expanded. FIG. 8C shows the winding start angle φ _{Lst of} the first parasitic element 13 and the second parasitic element 14.
Is set to 7.529π [rad], and VSWR =
It can be seen that the fractional bandwidth of 2 or less is divided into two and slightly expanded. Thus, the first parasitic element 13
It can be seen that as the winding start angle φ _Lst of the second parasitic element 14 increases, the fractional bandwidth of VSWR = 2 or less tends to increase.

Next, in the spirally loaded monopole antenna 1 according to the embodiment of the present invention, the winding end angle φ _end of the first spiral arm 11 and the second spiral arm 12 is set to about 5.453π [rad]. , The winding start angle φ of the first parasitic element 13 and the second parasitic element 14
About the _{Lst 7.529π} (rad), the winding end angle φ _{Le nd}
FIG. 9 shows the VSWR characteristics with respect to the frequency when is set to about 7.981π [rad]. For comparison, FIG. 9 also shows the VSWR characteristics with respect to the frequency of a conventional spirally-loaded monopole antenna having no parasitic element. In the conventional example, the winding end angle φ _end of the spiral arm is set to 5.453π [rad].
It can be seen that the fractional bandwidth of the spirally loaded monopole antenna 1 of the present invention including the parasitic elements 13 and 14 is expanded as compared with the SWR characteristic.

Next, in the spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the winding end angle φ _end of the first spiral arm 11 and the second spiral arm 12 is set to about 7.153π [rad]. , The winding start angle φ of the first parasitic element 13 and the second parasitic element 14
V with respect to the frequency when Lst is _set to about 7.529π [rad] and winding end angle φ _Lend is set to about 7.981π [rad]
The SWR characteristic is shown as the present invention A, the winding end angle φ _end of the first spiral arm 11 and the second spiral arm 12 is set to about 5.453π [rad], and the first parasitic element 13 and the second parasitic element Element 14 winding start angle φ
V with respect to the frequency when Lst is _set to about 7.529π [rad] and winding end angle φ _Lend is set to about 7.981π [rad]
The SWR characteristic is shown in FIG. 10 as the present invention B. For comparison, FIG. 10 also shows the VSWR characteristics with respect to the frequency of a conventional spirally-loaded monopole antenna having no parasitic element. In the conventional example, the winding end angle φ _end of the spiral arm is set to 5.453π [rad]. From the VSWR characteristics shown in FIG. 10, when the winding end angle φ _end of the spiral arms 11 and 12 is increased, V
It can be seen that the fractional bandwidth of SWR = 2 or less tends to increase. Then, the first spiral arm 11 and the second spiral arm 11
The winding end angle φ _end of the spiral arm 12 is about 7.1
Assuming 53π [rad], a maximum fractional bandwidth of about 15% is obtained as a fractional bandwidth of VSWR = 2 or less.

Next, in the spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the winding end angle φ _Lend of the first parasitic element 13 and the second parasitic element 14 is set to about 6.529π [rad]. When fixed, the winding end angle φ _end of the first spiral arm 11 and the second spiral arm 12 is set to about 5.703π [rad] and about 5.933π [ra].
d] and about 6.203π [rad] are shown in FIG. 11, FIG. 12, and FIG. Referring to the VSWR characteristics shown in FIGS. 11, 12, and 13, as the winding end angle φ _end of the first spiral arm 11 and the second spiral arm 12 increases, V
It can be seen that the fractional bandwidth of the SWR does not increase but increases at a certain value.

According to the above analysis results, in the spirally-loaded monopole antenna 1 according to the embodiment of the present invention, the radiation pattern is the monopole element 15 and the first
The first spiral arm 11 and the second spiral arm 11 are formed by a current flowing through the short-circuit pin 16 and the second short-circuit pin 17.
It can be seen that the current flowing through the spiral arm 12 hardly contributes to the formation of the radiation pattern. Further, the radiation pattern in the horizontal plane (xy plane) of the spirally-loaded monopole antenna 1 according to the embodiment of the present invention is substantially uniform in all directions, and the 50Ω-based VSWR is 2.
Fractional bandwidths below 0 will reach up to 15%.

The spiral-loaded monopole of the present invention
The spiral arm in the antenna is limited to two
Not two or more spiral arms
Can be. Also in this case, it becomes symmetric with respect to the center point B.
If you try to arrange multiple spiral arms
Good. That is, the number of spiral arms is n (n = 2,
3, 4 ...), each spiral arm is 2π
The angle should be shifted by / n and placed almost concentrically
No. Further, the spiral loading according to the embodiment of the present invention.
Length of each part shown above in monopole antenna 1
Dimensions are an example, and the spirally loaded
The antenna is not limited to this value. Sand
Chi, S_fd-B-P-P _GCircuit and ground plane 18
A closed circuit consisting of an image circuit created by the
S_fd-BQQQ_GCircuit and ground plane 18
A closed circuit consisting of an image circuit made by
What is necessary is just to set it as the length which resonates substantially at a frequency. In addition,
The graph of the first spiral arm and the second spiral arm
The higher the height h with respect to the ground plane, the better the antenna characteristics
Although it is improved, about 0.06λo
Preferably, it is height. Also, the first spiral lure
And the second spiral arm and the ground plane
Be sure to form them on each side of a dielectric
Then, it becomes possible to lower the posture.

[0032]

As described above, according to the present invention, a pair of spiral parasitic elements are arranged substantially symmetrically on the outer periphery of the spiral element loaded at the tip of the monopole element, so that the impedance can be broadened. You can now plan. In particular, by positioning the winding start end of the spiral parasitic element near the line connecting the feeding point of the monopole element and the arrangement position of the short-circuit pin provided on the spiral element, for example, the relative bandwidth of about 15% The width of the impedance can be widened by the width.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration example of a spirally loaded monopole antenna according to an embodiment of the present invention.

FIG. 2 is a front view showing a configuration example of a spirally loaded monopole antenna according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration example of a spirally loaded monopole antenna according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a VSWR characteristic with respect to a frequency of a spirally-loaded monopole antenna according to an embodiment of the present invention in comparison with a conventional example.

FIG. 5 is a vertical plane (xz) at the lower limit frequency of the spirally loaded monopole antenna according to the embodiment of the present invention;
FIG. 4 is a diagram showing a radiation pattern in a horizontal plane (xy plane).

FIG. 6 shows a vertical plane (xz) at the upper limit frequency of the spirally-loaded monopole antenna according to the embodiment of the present invention.
FIG. 4 is a diagram showing a radiation pattern in a horizontal plane (xy plane).

FIG. 7 is a diagram illustrating a spiral starting monopole antenna according to an embodiment of the present invention.
FIG. 9 is a diagram illustrating VSWR characteristics when _Lst is changed.

FIG. 8 is a diagram showing the VSWR characteristic with respect to the frequency when the winding start angle φ _Lst of the parasitic element is set so that the VSWR characteristic is good in the spirally-loaded monopole antenna according to the embodiment of the present invention. .

FIG. 9 shows a VSWR with respect to the frequency of one configuration example of the spirally loaded monopole antenna in the embodiment of the present invention.
FIG. 9 is a diagram showing characteristics in comparison with a conventional example.

FIG. 10 shows V with respect to the frequency of two configuration examples of the spirally loaded monopole antenna according to the embodiment of the present invention.
FIG. 9 is a diagram showing SWR characteristics in comparison with a conventional example.

FIG. 11 is a diagram showing VSWR characteristics with respect to frequency when the winding end angle φ _end of the spiral arm of the spirally loaded monopole antenna according to the embodiment of the present invention is set to about 5.703π [rad].

FIG. 12 is a diagram illustrating VSWR characteristics with respect to frequency when the winding end angle φ _end of the spiral arm of the spirally loaded monopole antenna according to the embodiment of the present invention is set to about 5.933π [rad].

FIG. 13 is a diagram illustrating VSWR characteristics with respect to frequency when the winding end angle φ _end of the spiral arm of the spirally loaded monopole antenna according to the embodiment of the present invention is set to about 6.203π [rad].

[Explanation of symbols]

Reference Signs List 1 spiral loaded monopole antenna, 11 first spiral arm, 12 second spiral arm, 13 first parasitic element, 14 second parasitic element, 15 monopole element, 16 first short circuit pin, 17 second short circuit pin, 18
Ground plane, 19 feeder, B center point, P
Junction point, Q junction point, S _fd feed point

Claims (3)

[Claims] 1. A monopole element disposed substantially vertically on a ground plane, a spiral element loaded on a tip of the monopole element and deployed substantially horizontally on the ground plane, and the spiral element And a pair of spiral parasitic elements arranged substantially symmetrically on the outer periphery of the spiral parasitic element, and the winding start end of the spiral parasitic element is bent into an L shape and short-circuited to the ground plane. Spiral loaded monopole antenna. 2. The spiral element comprises a pair of spiral arms arranged rotationally symmetrically, and a short-circuit pin for short-circuiting to a ground plane is connected to a predetermined point-symmetric position of the pair of spiral arms. The spirally-loaded monopole antenna according to claim 1, wherein: 3. The spiral loading according to claim 1, wherein a winding start end of the spiral parasitic element is located near a line connecting a feeding point of the monopole element and the short-circuit pin. Monopole antenna.