JP3474056B2 - Helical antenna - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical linear array antenna used in a mobile station for mobile satellite communication and capable of transmitting and receiving without tracking regardless of the moving direction of the mobile station.

[0002]

2. Description of the Related Art Conventionally, a helical antenna has been used as a rod-shaped antenna of a mobile station for mobile satellite communication. This helical antenna has a cone beam,
As shown in FIG. 5, since the antenna is omnidirectional in the horizontal plane, a tracking mechanism is not required, and the antenna is capable of communication regardless of the orientation of the mobile station, and is characterized by being simple and having a small installation area.

However, since this helical antenna has a large frequency dependence, as shown in FIG. 6, when one helical antenna is used for both transmission and reception, coverage that satisfies a desired gain, that is, a required gain for both transmission and reception is obtained. The satisfying angular width Δθ is remarkably reduced as compared with the angular width which the transmitting beam or the receiving beam has alone. Therefore, it is necessary to reduce the frequency dependence when using this helical antenna for both transmission and reception. As shown in FIG.
It is known that a multi-element (two elements in the figure) array configuration is effective. In such an array configuration, it is required that an arbitrary array spacing D can be set in order to obtain a desired beam.

For example, as shown in FIG.
It is possible to narrow θ and increase the peak gain Gmax by increasing the feeding interval W (array interval D). On the contrary, in order to widen the coverage Δθ and lower the peak gain, it is possible to realize it by reducing the feeding interval W (array interval D). Generally, in a helical antenna, the peak gain can be increased by increasing the number of turns N1 and N2 of each element. Therefore, the coverage Δ
In order to widen θ and increase the peak gain, it is necessary to relatively narrow the feeding interval W and increase the number of turns N1 and N2 of each element, that is, increase the element lengths L1 and L2.

However, in FIG. 7, the element length L1
When = L2 is larger than the desired power feeding interval W, the elements 1 and 2 collide with each other, and it becomes difficult to obtain desired characteristics. One way to solve this is
As shown in FIG. 9, an array configuration in which the central axes Z1 and Z2 of each element are shifted can be considered. However, the pattern becomes asymmetric in the horizontal plane and the vertical plane, and the characteristics deteriorate.

Therefore, it is desirable to have a structure in which an arbitrary power feeding interval W can be set on the same axis. Further, in the array configuration as shown in FIG. 7, the element antennas 1 and 2 having the same specifications are used, and a desired beam can be obtained by adjusting the number of turns N, the pitch P, and the radius R. However, in the array configuration of the same element, the frequency dependence of the element is often not sufficiently reduced. That is, FIG.
As shown in FIG.
C) can be interpreted as the element pattern (FIG. 10A) multiplied by the array pattern (FIG. 10B), and the frequency dependence of the element pattern remains after all,
There is a problem that the peaks of the transmission beam SB and the reception beam RB are deviated from each other and the coverage Δθ is narrowed.

[0007]

A first object of the present invention is to widen the coverage Δθ of a helical array antenna,
And to increase the peak gain Gmax.
The purpose of is to reduce the frequency dependence of the helical array antenna so that the transmission beam SB and the reception beam RB substantially coincide with each other and to widen the coverage Δθ.

[0008]

(1) The invention according to claim 1 has a radius R1, a pitch P1, a number of turns N1, a pair of feeding points at the upper end, and a lower end connected by a short-circuit conductor. A linear helical linear antenna element (hereinafter referred to as a first antenna element) and a second two linear filament having a radius R2, a pitch P2 and a number of turns N2, a pair of feeding points at the upper end, and a lower end connected by a short-circuit ring. A helical linear antenna element (hereinafter referred to as a second antenna element) and a distributor / combiner that divides a transmission signal into two and supplies the divided signals to the first and second antenna elements, and combines reception signals of both antenna elements. Be equipped with
The first and second antenna elements have a common vertical axis and are arranged below the first antenna element so that the second antenna element does not come into contact with the first antenna element. One line from the lower end of the first antenna element is arranged. A helical antenna in which the strip extends downwards along the axis and is connected to the distributor / combiner through the center of the shorting ring of the second antenna element.

According to the first aspect of the invention, in particular, the feeding points of the first and second antenna elements have the same facing direction, and the short-circuit conductor of the first antenna element is a linear short circuit parallel to the facing direction of the feeding point. The distributor / combiner composed of wires has a function of obtaining distributed outputs in phase, and R1 = R2, P1 = P2, N between the radius, pitch, and number of turns of the first and second antenna elements.
The relationship of 1 = N2 is satisfied, and the first and second antenna elements are arranged so as to overlap each other so that the upper end of the second antenna element is located above the lower end of the first antenna element.

(2) In the invention of claim 2, the opposing direction of the feeding point of the second antenna element in the helical antenna of (1) is changed so as to be perpendicular to the opposing direction of the feeding point of the first antenna element. The distribution / combiner is modified to have a function of obtaining distribution outputs having phases different from each other by 90 °.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] An embodiment of claim 1 is shown in FIGS. The helical antenna HA has an array configuration of upper and lower two-line helical linear antenna elements. The helical antenna HA has a structure in which the short-circuited portion of the upper element 1 is a short-circuit wire 1d of a straight conductor, and the windings 2a and 2b of the lower element 2 are not in contact with each other, and the elements 1 and 2 overlap each other. An enlarged view of the overlapping part is shown in FIG. This part has the same structure as the four-wire winding. The position of the feeding point 2c of the lower element 2 is limited to discrete points as shown by the arrow in FIG. In this case, feed point 1
The polarities of c and 2c are in phase. The distributor / combiner 5 used is one that distributes in phase. The feed line length between the divider / combiner and each of the elements 1 and 2 is adjusted so that a predetermined beam direction can be obtained.

When the present helical antenna is used, even when the element length L1 is larger than the desired feeding interval W, it is possible to form an array on the same axis although the feeding interval is discrete, and the desired radiation characteristics can be obtained. Can be obtained. Set the radii of the first and second antenna elements 1 and 2 to R1 and R
2, pitch (pitch interval) P1, P2, number of turns N1,
If N2, in the example of FIG. 1, R1 = R2, P1 = P
2, N1 = N2 is set. Therefore, L1 = L2
Has become. Further, the facing directions of the end faces of the pair of filaments (windings) at the feeding points 1c and 2c are made equal to each other. The direction of the short-circuit wire 1d is parallel to the facing direction of the feeding point 1c.

[Embodiment 2] An embodiment of claim 2 is shown in FIGS. The antenna is similar to the antenna of the first embodiment (FIGS. 1 and 2), but the feeding point 2c of the second antenna element 2 faces at right angles to the feeding point 1c of the first antenna element 1. This is different from the point that the distributor / combiner 5 has a function (for example, like a 90 ° hybrid circuit) of obtaining distributor outputs having different phases by 90 °.

[Others] In addition, the case where the antenna element has a two-tier structure is described.
Obviously, it is possible to extend to more than two stages.

Although each antenna element is composed of two wires (two windings), it is conceivable that the antenna element is expanded to two or more wires, for example, four wires and six wires. The cases where the polarities of the power feeds are in phase (for example, FIG. 1) and 90 ° (for example, FIG. 3) have been described.
It is also possible to make the polarity of power feeding arbitrary (for example, 45 °) by providing a phase difference of (°).

[0016]

(1) According to the inventions of claims 1 and 2,
By forming the short-circuit conductor at the lower end of the upper antenna element 1 with a linear short-circuit wire, the upper end of the lower antenna element 2 is arranged above the lower end of the upper antenna element without contact between the antenna elements 1 and 2. , It became possible to have a structure in which both elements partially overlap. According to this structure, since the element lengths L1 and L2 can be made larger than the power feeding interval W, the windings N1 and N2 can be made large to obtain high gain, and the power feeding interval W can be made small to provide the coverage Δθ. Can be widely used.

[Brief description of drawings]

FIG. 1A is a front view of the helical antenna according to claim 1, and FIG.
FIG. 3 is a diagram showing a radiation characteristic of A.

2A and 2B are plan views of the antenna elements 1 and 2 of FIG. 1 seen from above, and C is the antenna element 1 of FIG. 1A.
The perspective view which expanded and showed the vicinity where 2 and 2 overlap.

FIG. 3A is a front view of the helical antenna according to claim 2, and FIG.
FIG. 4B is a diagram showing a radiation beam of A

4A and 4B are plan views of the antenna elements 1 and 2 of FIG. 3 as seen from above, and C is the antenna element 1 of FIG. 3A.
The perspective view which expanded and showed the vicinity where 2 and 2 overlap.

FIG. 5 is a perspective view for explaining a helical antenna and its radiation beam.

6A is a front view of a conventional single-element two-wire helical linear antenna, and FIG. 6B is a diagram showing a radiation characteristic of A;

7A is a front view of a conventional two-element two-line helical linear array antenna, and FIG. 7B is a diagram showing a radiation characteristic of A;

8A is a front view of a conventional two-element two-wire helical linear array antenna in which the feeding interval W is widened, the coverage Δθ is narrowed, and the peak gain Gmax is increased; FIG. 8B is a diagram showing the radiation characteristic of A. FIG. .

FIG. 9A is a conventional two-element two-wire strip in which the central axes of the respective elements are shifted in order to make the element lengths L1 and L2 larger than the feeding interval W to widen the coverage Δθ and increase the peak gain Gmax. The front view of a helical array antenna, B is a perspective view which shows the radiation characteristic of A. FIG.

10A and 10B are diagrams showing an element pattern and an array pattern, respectively, which constitute the radiation characteristic of the helical antenna of FIG. 7, and C is a diagram showing a combined characteristic of A and B (the same as FIG. 7B).

Continuation of front page (56) Reference JP-A-7-263946 (JP, A) JP-A-3-274904 (JP, A) JP-A-63-30006 (JP, A) JP-A-7-193422 (JP , A) Japanese Unexamined Patent Publication No. 6-164232 (JP, A) Japanese Unexamined Patent Publication No. 9-27710 (JP, A) Actually Unexamined Japanese Patent Publication No. 7-33013 (JP, U) US Patent 5587719 (US, A) US Patent 4608574 (US, A) Registered utility model 3009985 (JP, U) Noriyoshi Terada, Conical beam 2-wire helical antenna for mobile satellite communication, IEICE technical report, Japan, Institute of Electronics, Information and Communication Engineers, June 1991 20th, VOL. 91, NO. 92, PAGE19-24 Ryo Yamaguchi et al. Utilization of satellite mobile phones and car phones Design of in-vehicle helical antenna, IEICE technical report, Japan, Institute of Electronics, Information and Communication Engineers, July 3, 1997, Vol. 97, NO. 146, PAGE. 35-40 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01Q 11/08 H01Q 1/36 H01Q 21/08

Claims (2)

(57) [Claims] 1. A first two-wire helical linear antenna element (hereinafter referred to as a first antenna element) having a radius R1, a pitch P1, a number of turns N1, a pair of feeding points at its upper end, and a lower end connected by a short-circuit conductor. ) And a second two-line helical linear antenna element (hereinafter referred to as a second antenna element) having a radius R2, a pitch P2, a number of turns N2, a pair of feeding points at the upper end, and a lower end connected by a short-circuit ring. , And a divider / combiner that divides the transmission signal into two and supplies the divided signals to the first and second antenna elements and combines the reception signals of both antenna elements, and the first and second antenna elements have a common vertical direction. A second antenna element is arranged below the first antenna element so as not to contact the first antenna element, and one of the filaments extends downward from the lower end of the first antenna element along the axis. , No. 2 In the helical antenna connected to the distribution combiner through the center of the short-circuit ring of the antenna element, the feed points of the first and second antenna elements are in the same facing direction, and the short-circuit conductor of the first antenna element is , A straight short-circuit wire parallel to the opposing direction of the feeding point, the distribution combiner has a function of obtaining a distributed output of the same phase, the radius of the first and second antenna elements, the pitch, the number of turns Between,
R1 = R2, P1 = P2, N1 = N2, and the first and second antenna elements overlap each other so that the upper end of the second antenna element is located above the lower end of the first antenna element. A helical antenna characterized by being arranged so that 2. The helical antenna according to claim 1, wherein the opposing direction of the feeding point of the second antenna element is changed to be orthogonal to the opposing direction of the feeding point of the first antenna element, and the distribution combiner is phased by 90 °. Of the helical antenna, which is modified to have the function of obtaining different distributed outputs.