JP2007081903A - Dipole antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dipole antenna device, of which the impedance can be readjusted easily at the mounting the antenna into a casing. <P>SOLUTION: A dipole antenna device 21 is configured with two antenna elements 22, formed with cylindrical conductor and a removable dielectric block 28 for adjusting the impedances. The cylindrical conductor is divided into two at the center, and is provided with an antenna output terminal 23 for extracting received electric wave output from the center side of the conductor. As for fixing the dielectric block 28, a convex part 30 is arranged at the antenna element 22, and a concave part 29 that corresponds to the convex part 30 is arranged at the dielectric block side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dipole antenna device that facilitates impedance adjustment.

  2. Description of the Related Art Conventionally, devices using wireless technology, such as devices compatible with a wireless LAN and Bluetooth conforming to the IEEE 802.11a / b / g standard, are becoming widespread. Devices that apply these wireless technologies are required to further reduce costs, and one of the means for realizing them is to use a built-in antenna in common.

  On the other hand, a dipole antenna is used as the simplest and practical antenna. In general, a dipole antenna is composed of two antenna elements. In designing a device incorporating a dipole antenna, the impedance of the antenna output terminal 23 connected to the dipole antenna 21 composed of the two antenna elements 22 and the transmission source 26 using a matching circuit 24 as shown in FIG. It is required to match the impedance of the feeder line 25 connected to. This is because, if there is a difference between both impedances, the power reflected from the transmission source 26 to the dipole antenna 21 increases in the direction of the transmission source, and the radio wave radiation intensity from the dipole antenna 21 decreases. It is for preventing. However, when a dipole antenna is actually installed in a device, the antenna impedance changes slightly due to factors that are not assumed during design, such as the housing material and shape, and the matching circuit must be readjusted for each device. There was a problem.

  As a conventional technique for solving this problem, there is a dipole antenna provided with a loading coil and a matching circuit at the center (see, for example, Patent Document 1). FIG. 4 shows a dipole antenna described in Patent Document 1. In FIG. In FIG. 4, 2 is an antenna element, 3 is an antenna output terminal, 4 is a matching circuit, 5 is a loading coil, and the loading coil 5 is connected to the center of the dipole antenna 1 made of the antenna element 2, and an inductor and a matching capacitor And a matching circuit 4 composed of a variable capacitance diode.

According to this configuration, by controlling the voltage applied to the variable capacitance diode, it is possible to match the impedance of the feeder line without redesigning the matching circuit.
JP-A-9-130132

  However, the conventional configuration has a complicated circuit configuration due to the large number of parts, and has problems in terms of simplification and cost reduction.

  The present invention solves the above-described conventional problems, and an object thereof is to facilitate impedance readjustment when an antenna is incorporated in a housing.

  In order to solve the above-described conventional problems, in the dipole antenna of the present invention, a dielectric is formed in a space in which a pair of antenna elements are opposed to each other, and the dipole antenna is incorporated into a device casing.

  With this configuration, the impedance of the dipole antenna changes according to the dielectric constant of the inserted dielectric. If several types of dielectrics having different dielectric constants are prepared, impedance matching can be achieved by inserting appropriate dielectrics.

  According to the dipole antenna of the present invention, since the dielectric insertion port for impedance adjustment is provided, adjustment by a matching circuit is not required even when a built-in device is changed, and impedance readjustment can be facilitated.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of a dipole antenna device according to the present embodiment.

  In FIG. 1, a dipole antenna device 21 is formed of a cylindrical conductor, and is formed of two antenna elements 22 arranged in a straight line and a dielectric block 28 for impedance adjustment. The dielectric block 28 is detachable from the dipole antenna device 21 and is attached to a dielectric block insertion port 27 formed between two antenna elements. The dipole antenna device 21 in the present embodiment was formed as follows.

  First, the cylindrical conductor is divided into two at the center, and an antenna output terminal 23 is provided to extract the received radio wave output from the center of the conductor. The total length L of the antenna element is selected to be approximately ½ wavelength of the frequency used. For example, when the center frequency FL = 2400 MHz, the antenna element length L can be calculated by the speed of light / frequency / 2, and L = 6.25 cm. The antenna element 22 is provided with a dielectric block fixing convex portion 30 for fixing the dielectric block 28 and a corresponding dielectric block fixing concave portion 29 on the dielectric block side.

  When the antenna element 22 is incorporated in the housing, a shift occurs in impedance matching with the antenna output terminal 23 because the resonant frequency of the antenna is shifted. Depending on the material of the housing, the resonance center frequency FL often shifts higher.

  Even when the dielectric block is inserted, the center frequency FL shifts. If this phenomenon is used to correct the deviation of the center frequency after mounting the housing, impedance matching between the feeder and the antenna can be improved.

  First, a dielectric block 28 having an appropriate dielectric constant is mounted on the dipole antenna device 21, and an antenna having a necessary center frequency is designed by adjusting the matching circuit and the antenna length. When incorporated in the case, the center frequency FL shifts to the higher side as described above, so the desired characteristics (dielectric constant close to the center frequency) among several types of dielectric blocks prepared in advance. The necessary characteristics can be obtained by selecting and replacing them.

  In this embodiment, the example of the cylindrical dipole antenna has been described. However, the shape is not particularly limited, and the present invention can also be implemented in a prismatic or flat dipole antenna. Further, the concave and convex portions for fixing the dielectric are not indispensable for the present embodiment, and if the dielectric can be mechanically fixed to the dipole antenna, the present invention can be implemented even if the concave convex portion is missing. It is included in the form.

(Embodiment 2)
FIG. 2 is a perspective view showing a configuration of a dipole antenna device according to Embodiment 2 of the present invention.

  FIG. 2 shows a substrate dipole antenna in which a radiation conductor is formed on a dielectric printed circuit board 31. The difference between the first embodiment and the second embodiment is that the antenna element 22 in the first embodiment is replaced with two thin film conductors 32 having a width W and a length L in the second embodiment. The two antenna elements 32 are connected to the antenna output terminal 33 at the center, and a dielectric block insertion port 34 for allowing the dielectric block 35 to be inserted is provided in a region between the conductors.

  Also in the present embodiment, first, a dielectric block 35 having an appropriate dielectric constant is mounted on a dipole antenna device, and an antenna having a necessary center frequency is designed by adjusting a matching circuit and an antenna length. Next, when the dielectric block 35 is incorporated into a dipole antenna device, the center frequency FL shifts to a higher side, so that among several types of dielectric blocks prepared in advance, a dielectric constant that is close to the desired center frequency. Necessary characteristics can be obtained by selecting and replacing them.

  Since the impedance of the dipole antenna according to the present invention can be adjusted only by changing the dielectric, the cost of the device incorporating the dipole antenna can be reduced, and the performance can be easily improved.

The perspective view which shows the structure of the dipole antenna apparatus in Embodiment 1 of this invention. The perspective view which shows the structure of the dipole antenna apparatus in Embodiment 2 of this invention. Circuit diagram showing the configuration of a general dipole antenna Circuit diagram showing the configuration of a dipole antenna in the prior art

Explanation of symbols

21 Dipole antenna 22, 32 Antenna element 23, 33 Antenna feed terminal 27, 34 Dielectric block insertion slot 28, 35 Dielectric block 29 Concave portion for fixing dielectric block 30 Convex portion for fixing dielectric block 31 Dielectric printed circuit board

Claims (4)

Between antenna elements arranged in a straight line by a predetermined interval,
A dipole antenna device characterized in that an insertion port for inserting a dielectric for impedance adjustment is provided. The dipole antenna device according to claim 1, wherein the dielectric is detachable from the insertion opening. The dipole antenna device according to claim 1, wherein a plurality of the dielectrics are selected and a dielectric having a desired characteristic is selected and attached to the insertion slot. The dipole antenna device, wherein the antenna element is formed of a thin film conductor on a dielectric substrate.

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