JPH1174720A - Small helical antenna device for mobile terminals - Google Patents

Abstract

(57) [Problem] To provide a small-sized helical antenna device for a portable terminal, in which an antenna unit and a power supply unit are integrated and can reliably track radio waves from a satellite or the like. A quad filer helical antenna element is formed by winding an antenna element N times around a cylindrical member 1 and having a radius sufficiently smaller than a reception wavelength N times. The antenna element 2 has a structure in which the end is opened and power is supplied from the tip. The columnar member 1 has, for example, a helical overall length H.
Is set to 100 mm and the diameter D is set to 10 mm.
Then, a feeder 3 is connected to the lower part of the columnar member 1, and the feeder 3 forms a circuit having a current value of the antenna element 2, that is, a 90 ° phase difference with the same amplitude, thereby obtaining a circularly polarized wave. Generate directivity. As a result, the device can be integrated, and the antenna beam can be directed in a fixed direction even when the satellite moves, so that it can be used in a wide area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small helical antenna device for a portable terminal used for mobile communication, particularly for communication between a satellite and the ground.

[0002]

2. Description of the Related Art Conventionally, cellular phones for automobiles, cellular phones, P
An antenna used in an HS or the like is used for mobile communication for communicating with a ground station. In general, the directivity of the antenna used for the mobile communication need not necessarily be directed toward the zenith.

[0003]

However, an antenna of a type in which the directivity does not need to be directed to the zenith direction as described above causes a decrease in the gain in the satellite direction in satellite-to-ground communication, so However, there is a problem that a high communication performance cannot be obtained.

On the other hand, as an antenna capable of directing a beam in a desired direction, there is a phased array antenna. However, this antenna is not suitable for versatility because of its expensive system and complicated circuit configuration. The present invention has been made to solve the above problems, and has as its object to provide a helical antenna device for a small portable terminal by integrating an antenna unit and a power supply unit.

[0005]

A small helical antenna device for a portable terminal according to the present invention comprises a helical antenna and a feeder provided at one end of the helical antenna and having a phase difference of 90 degrees. The antenna and the feeder are integrated, and the directivity of the circularly polarized wave is configured to have a constant value from the zenith direction to a low elevation angle.

[0006] As described above, the current supplied to each antenna element is supplied by the power supply unit provided at the end of the helical antenna so that the amplitude of the current is the same and the phase is 90 degrees. It can be set in a wide range and can be used by moving satellites.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a structural diagram of a small helical antenna for a portable terminal according to one embodiment of the present invention. 2A and 2B are diagrams showing an integrated structure of the antenna unit and the feeding unit. FIG. 2A is a diagram of the antenna element 2 viewed from the front side, and FIG. 2B is a diagram of the antenna element 2 viewed from the back side. It is.

In FIG. 1 and FIG. 2, reference numeral 1 denotes a cylindrical member (film substrate: base film thickness 7) made of an insulating material.
5 μm, copper thickness 35 μm, εr = 2.82, tan δ =
0.011), an antenna element (radiating part: filament (copper foil) wire) 2 having a radius sufficiently smaller than the receiving wavelength is wound N times around the cylindrical member 1 and is wound N times.
It constitutes a helical antenna element. The antenna element 2 has a structure in which a terminal end (upper end) is opened and power is supplied from a front end (lower end).

The columnar member 1 has a helical overall length (height) H of 100 (mm) and a diameter D of 10 (mm). Then, a feeder 3 is connected to the lower part of the columnar member 1, and the feeder 3 forms a circuit configuration in which the current value of the antenna element 2 has the same amplitude and a phase difference of 90 degrees. Is obtained. The power supply section 3 is formed by winding a thin copper foil around a dielectric cylinder and printing a helical filament on the dielectric cylinder. Specifically, the configuration of the power supply unit 3 is shown in FIG.
As shown in (b), it is composed of a Wilkinson type two distribution circuit 34.

FIG. 3A shows a phase difference portion (electrical length 90 °).
31 shows an example in which 31 is linearly configured. That is, the phase difference unit 31 includes the antenna filament output port 11, the other antenna filament (basic length: electrical length 0 °) 32, and the output port 12, and the output port 1
2 is longer than the output port 11. The resistor 33 inserted between the output port 11 and the output port 12 is a matching load for the output ports 11 and 12. By inserting the matching resistor 33, the isolation results are sufficiently satisfactory. Then, power is supplied from the power supply end 4.

In FIG. 3A, the phase difference section 31 of the output port 12 is linearly configured.
As shown in FIG. 3B, the length of the output port 12 is U-shaped, and the heights of the power supply portions of the two output ports 11 and 12 are made to match each other, so that a phase difference of 90 degrees is formed on the substrate. It may be realized by.

As shown in FIG. 3A, the output port 1
In the case where the two phase shift portions 31 are linearly configured, the helical overall length H of the columnar member 1, that is, the height H of the antenna is 100 (mm), the diameter D is 10 (mm), and the frequency f is 1985 MHz. , 2090MHz, 2200M
Hz, the number of turns N of the antenna element 2 and the height H of the antenna are variously changed, and various characteristics such as directivity, gain, axial ratio, and impedance are shown in FIGS. In addition, as shown in FIG.
Even in the case of a character shape, substantially the same characteristics as in the case of FIG. 3A can be obtained.

First, FIGS. 4A, 4B, 5A,
The directivity shown in (b) is such that the height H of the antenna is 100 to
40 (mm), and the antenna height H
It can be understood that when the distance is shortened, the directivity in the rear direction increases. Also, by shortening the height H of the antenna, FIG.
As shown in FIGS. 7A and 7B and FIGS. 7A and 7B, the axial ratio also increases. From the above, it is understood that the height H of the antenna cannot be made too small.

Next, FIGS. 8 (a), (b) to FIG. 15 show the case where the height H (100 mm) of the antenna is fixed and the number of turns N of the antenna element 2 is in the range of 0.5 to 3.5 turns. 3 shows the directivity and the axial ratio when variously changed. When the number of turns N is 0.5 turns, the directivity is directed in the rear direction, and the best result is obtained when the number of turns is 1.5 to 2 turns.

[Study 1: Optimization for Height H of Antenna] When the number of turns N of the antenna element 2 is fixed to 1.5 turns and the height H of the antenna is reduced (H = 40, 6).
As a result of the study of (0, 80 mm), when the height H of the antenna is reduced as shown in FIGS. 16 (a), (b) to 17 (a), (b), the front-to-back ratio (F / B ratio) is deteriorated. I found out. If the F / B ratio is targeted at 20 dB or less, H = 80 mm is satisfied. The change of the axial ratio when H = 80 mm was good at θ = 70 °, 80 °, and 90 °.

[Study 2: Optimization for Number of Windings] FIG. 18
(A), (b) and FIGS. 19 (a), (b) show the directivity when the height H of the antenna is fixed to 80 mm and the number of turns N of the antenna element 2 is changed. It is. As a result, a study was made to lower the level in the zenith direction. As a result, when the number of turns N was smaller than 1.5 turns, the level in the zenith direction was lowered, but the F / B ratio could deteriorate. Do you get it.

[Study 3: Influence by Housing]
In the case where the antenna height H = 80 mm and the number of turns N = 1.5 turns, which are the optimum values from 2, the change in the characteristics when the housing (30 × 50 × 150 mm) 5 shown in FIG. investigated. The characteristics when φ = 0 ° and φ = 90 ° at this time are shown in FIGS. 21 (a) and 21 (b). When the housing 5 is attached, the F / B ratio and the symmetry are somewhat lost as is apparent from the figure, but the influence on the directivity is relatively small.

[Study 4: Experimental Results] In view of the above calculation results, experiments were performed to confirm the theory. In the experiment, f =
2.2 GHz, H = 80 mm, N = 1.5 turns,
The circuit shown in FIG. 3B was used as a power supply unit. FIG.
2 (a) and (b) and FIG. 23 show the characteristics of only the power supply circuit section. 22A shows the input impedance characteristics of the power supply circuit section, FIG. 22B shows the current amplitude ratio, and FIG. 23 shows the current phase characteristics.
FIG. 24 shows an input impedance characteristic in which the antenna and the feeding unit are connected. FIG. 25 shows the directivity at that time.
It can be seen that circular polarization characteristics are obtained from the zenith direction to a low elevation angle.

Designed based on the theoretical results as described above,
It was confirmed by experiments and good results were obtained. The small helical antenna device for a portable terminal according to the present invention can perform transmission and reception with a circular polarization to a low elevation angle, and can transmit and receive even if the moving range of the moving object changes more widely.

In the above embodiment, the antenna element 2
Has a configuration in which the tip (upper end) is opened and power is supplied from the end (lower end). However, the opposite configuration is adopted, that is, a configuration in which the lower end of the antenna element 2 is opened and power is supplied from the upper end. Also in this case, it is possible to obtain substantially the same characteristics as in the above embodiment.

[0021]

As described above in detail, according to the present invention, a feed section having a phase difference of 90 degrees is provided at one end of the helical antenna, and the helical antenna and the feed section are integrated. Therefore, a very small and high-performance antenna can be obtained. Therefore, the helical antenna according to the present invention can be used as a mobile terminal antenna that is an antenna for a mobile body that can tilt the elevation angle of a beam within a use range.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a small helical antenna device for a portable terminal according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing details of an antenna unit in the embodiment.

FIG. 3A is a configuration diagram illustrating details of a power supply unit according to the embodiment, and FIG. 3B is a diagram illustrating another configuration example of the power supply unit.

FIG. 4 is a view showing the height of the antenna according to the embodiment;
FIG. 8 is a diagram showing directivity in the case of the distance of 80 mm and 80 mm.

FIG. 5 is a view showing directivity when the antenna height is 60 mm and 40 mm in the embodiment.

FIG. 6 is a diagram illustrating the height of the antenna according to the embodiment;
FIG. 7 is a characteristic diagram showing an axial ratio in the case of and 80 mm.

FIG. 7 is a characteristic diagram showing axial ratios when the antenna height is 60 mm and 40 mm in the same embodiment.

FIG. 8 shows a case where the number of turns of the antenna element in the embodiment is set to 0.
The figure which shows the directivity at the time of 5 turns and 1 turn.

FIG. 9 shows the number of turns of the antenna element in the embodiment as 1.
The figure which shows the directivity at the time of 5 turns and 2 turns.

FIG. 10 is a diagram showing directivity when the number of turns of the antenna element in the embodiment is 2.5 turns and 3 turns.

FIG. 11 is a view showing directivity when the number of turns of the antenna element in the embodiment is 3.5 turns.

FIG. 12 is a characteristic diagram showing an axial ratio when the number of turns of the antenna element in the embodiment is 0.5 turn and 1 turn.

FIG. 13 is a characteristic diagram showing an axial ratio when the number of turns of the antenna element is 1.5 turns and 2 turns in the same embodiment.

FIG. 14 is a characteristic diagram showing an axial ratio when the number of turns of the antenna element is 2.5 turns and 3 turns in the same embodiment.

FIG. 15 is a characteristic diagram showing an axial ratio when the number of turns of the antenna element in the embodiment is 3.5 turns.

FIG. 16 shows the number of turns N of the antenna element in the embodiment.
Is fixed at 1.5 turns and the height H of the antenna is 40 mm
FIG. 7 is a diagram showing directivity when the distance is set to 60 mm.

FIG. 17 shows the number of turns N of the antenna element in the embodiment.
FIG. 9 is a diagram showing directivity and axial ratio when the height of the antenna is set to 80 mm while the height is fixed to 1.5 turns.

FIG. 18 is a diagram showing directivity when the height of the antenna is fixed to 80 mm and the number of turns is 1 and 1.125.

FIG. 19 is a diagram showing directivity when the height of the antenna is fixed to 80 mm and the number of turns is 1.25 and 1.375.

FIG. 20 is an exemplary view showing a configuration example of a housing to which the antenna according to the embodiment is mounted.

FIG. 21 is a diagram showing directivity when φ = 0 ° and φ = 90 ° when the height of the antenna is set to an optimum value and a housing is attached in the same embodiment.

FIG. 22A is a diagram illustrating input impedance characteristics of only a power supply circuit unit according to the embodiment, and FIG. 22B is a diagram illustrating an amplitude ratio of a current.

FIG. 23 is a view showing the phase characteristics of the current of only the power supply circuit unit in the embodiment.

FIG. 24 is a diagram showing input impedance characteristics when the antenna and the power supply unit in the embodiment are connected.

FIG. 25 is a diagram showing directivity when an antenna and a power supply unit according to the embodiment are connected;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical member (helical antenna) 11, 12 Output port 2 Antenna element (filament (copper foil) wire) 21 Film substrate 3 Feeding part 31 Phase difference part (electric length 90 °) 32 Antenna filament (electric length 0 °) 33 Matching resistor 34 Wilkinson 2 distribution circuit 4 Power supply

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Haruo Kawakami 4-72 Miyagaya Tower, Omiya City, Saitama Prefecture Inside Antena Giken Co., Ltd. (72) Inventor Shinichi Nomoto 2-1-1 Ohara, Kamifukuoka City, Saitama 15 International Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A helical antenna, and a feeder provided at one end of the helical antenna and having a phase difference of 90 degrees. The antenna and the feeder are integrated to improve the directivity of circularly polarized waves. A small helical antenna device for a portable terminal, wherein the helical antenna device has a constant value from a zenith direction to a low elevation angle.