JP5725415B2 - ANTENNA DEVICE AND WIRELESS COMMUNICATION DEVICE - Google Patents

Description

  The present invention relates to an antenna device used in a small wireless communication device such as a cellular phone, and more particularly to an antenna device configured with a plurality of antenna elements and a wireless communication device using the antenna device.

  Wireless communication devices such as mobile phones have become more and more multifunctional with downsizing, and there are wireless communication devices that can receive and view not only telephone calls but also broadcast waves such as FM broadcasts and digital television broadcasts. In such a wireless communication apparatus, the frequency band of a communication system (for example, GSM, CDMA, etc.) used for transmission / reception for a call is usually a frequency of 800 MHz or more, and a band of 500 MHz to 800 MHz is used in digital television broadcasting. In FM broadcasting, a bandwidth of about 70 MHz to 120 MHz is used.

  When transmitting and receiving multiple wireless communication signals, the frequency band to be used is wide, so it is difficult for one antenna to meet the required characteristics in each frequency band, and its performance is tailored to the frequency band for calls. Therefore, the antenna sensitivity is inferior in the frequency band of FM broadcasting where the frequency is greatly separated. Even with such an antenna, there are few problems in use in the vicinity of a transmitting antenna that easily obtains a high radiated electric field strength, but in a weak electric field environment, a large amount of noise is superimposed on the received signal, or no reception is possible. There was a problem that said. Therefore, it is common practice to separately provide an antenna corresponding to each frequency band in each wireless communication device.

  In the wireless communication, the FM broadcast band, which is the lowest frequency band, has a wavelength that is considerably longer than other frequency bands. If the receiving antenna is configured as a monopole antenna, it is 1/4 of the wavelength λ. A length of radiation conductor is required, which can be as much as 75 cm at 100 MHz. For this reason, the use of an earphone cable as an FM broadcast receiving antenna is mainly provided outside the wireless communication apparatus. When used in FM broadcasting, the antenna is dedicated to receiving high-frequency power and does not radiate high-frequency power. However, in this specification, the conductor used for the antenna is referred to as a radiating conductor for convenience. In particular, no distinction is made by function.

  Using an earphone cable as a receiving antenna is an effective means for obtaining good reception sensitivity, but according to the needs of the user, when enjoying broadcasts with a speaker built into the wireless communication device instead of from the earphone However, it is inconvenient to require an earphone cable for receiving FM broadcasts, and if it is desired to obtain an ideal characteristic as a receiving antenna with an earphone cable, it is preferable to use it while extending linearly. Since it is handled by winding it, the original performance may not be exhibited. For this reason, there is an increasing demand for an antenna device that has a reception antenna with excellent sensitivity built into the wireless communication device and can obtain a good reception state without using an earphone cable.

  When an antenna is configured in a small size, a helical antenna or a meander antenna is often used. This antenna is configured by forming a radiating conductor and winding it around a base made of a dielectric material or a magnetic material. The effective length of the radiating conductor is shortened by the wavelength shortening effect of the substrate, and the antenna can be downsized. However, on the other hand, there is a problem that the gain and the bandwidth are easily deteriorated. In environments where high radiation field strength can be obtained, gain and bandwidth degradation do not significantly affect reception conditions, but in weak field environments, there is a problem that noise is significantly superimposed on the received signal or that reception is not possible at all. there were.

Patent Document 1 discloses an antenna device that improves such a problem. The configuration of this antenna device is shown in FIG. The antenna device 80 includes a chip antenna 10 in which a part of a radiating conductor 12 and terminal electrodes 13 and 14 to which the conductor is connected are formed on a base 11 mainly made of ceramic, and a substrate 20 on which the antenna is mounted. Composed. A radiation conductor 40 is also formed on the mounting substrate, and the terminal electrode 14 of the chip antenna 10 and one end of the radiation conductor 40 are connected. The other end 41 of the radiation conductor 40 is an open end. The terminal electrode 13 is connected to a high-frequency circuit through a feed line 61 formed on the mounting substrate 20.
With only the radiating conductor 12 of the chip antenna 10, the effective length of the radiating conductor in the entire antenna device can be increased by supplementing the portion of the mounting substrate that is insufficient with the radiating conductor 40 of the mounting substrate. It is described that the current distribution increases and the radiation electric field becomes stronger, so that a high gain and a wide bandwidth can be obtained as an antenna device.

Japanese Patent Laid-Open No. 11-330830

  When the antenna device is operated in the 1 / 4λ mode, an image current generated on a ground plane existing in the vicinity of the antenna device is used. In general, when the image current generated on the ground plane has substantially the same vector as the current induced in the antenna device, an induced current of 1 / 2λ including the image current is generated, thereby improving the gain. On the other hand, if the image current is a vector different from the current flowing through the antenna device, for example, in the reverse direction, the current is canceled out, resulting in a decrease in gain.

  The antenna device of the cited document 1 is also configured based on such technical common sense. The substrate 20 has a ground surface 21 for generating an image current, and the chip antenna 10 and the radiation conductor 40 are arranged on the non-ground forming portion 22 and are configured on the same plane. It is also described that the chip antenna 10 and the radiation conductor 40 are arranged on the same plane on a mounting board separate from the board 20 having the ground surface 21. In any case, the chip antenna 10 and the radiation conductor 40 are arranged on the same plane with respect to the ground plane 21, so that an appropriate image current is generated on the ground plane 21 of the substrate 20.

  However, in the housing of the wireless communication device, other constituent devices such as a speaker and a display device are arranged in the vicinity of the antenna device. Since a large number of conductors are used in the component device, the antenna performance is not sufficiently exhibited due to an inappropriate image current being induced therein, and there is a problem in that performance degradation such as a decrease in antenna gain occurs. . Further, in a limited space, it is substantially difficult to dispose the constituent devices so as not to affect the antenna device because the wireless communication device is increased in size.

  Therefore, the present invention solves the above-described conventional problems, and an object of the present invention is to provide an antenna device that can be configured as a wireless communication device and has excellent antenna characteristics, and a wireless communication device using the antenna device.

A first invention is an antenna device including a first antenna element, a second antenna element, and a substrate on which the first antenna element is mounted, wherein the first antenna element has flanges on both ends, and the flange A body part provided between the parts, a mounting terminal provided on each of the flange parts, a base made of a resin material provided with a recess reaching both ends, a magnetic body housed in the recess of the base, A helical antenna in which a body wire enclosing the magnetic body is wound as a first radiation conductor, and an end of the first radiation conductor is connected to a mounting terminal of the body; A second radiating conductor provided on a different plane from the first antenna element, having one end connected to one end of the first radiating conductor via a connecting means and the other end being an open end; antenna device der and a second antenna elements .

  In the present invention, a ground electrode may be formed on the substrate. In that case, the first antenna element and the second antenna element are formed in a portion that does not overlap the ground electrode. The base can be made of ceramic or resin made of dielectric material or magnetic material. The first radiating conductor formed on the base is formed by a conductive wire or a conductive plate, an electrode pattern formed by a technique such as printing or etching, or a flexible printed wiring board. The second radiating conductor can be similarly configured.

  Contact springs, contact pins, screws, conductive rubber, or the like can be used as connection means for connecting the first radiation conductor and the second radiation conductor.

A second invention is a communication device in which the antenna device of the first invention is mounted and another component device speaker such as a speaker or a display device is disposed in the vicinity of the first antenna element .

  ADVANTAGE OF THE INVENTION According to this invention, it can comprise in a radio | wireless communication apparatus and can provide the antenna apparatus excellent in the antenna characteristic, and a communication apparatus using the same.

It is principal part sectional drawing of the radio | wireless communication apparatus provided with the antenna device which concerns on one Embodiment of this invention. It is a top view inside the housing | casing of the radio | wireless communication apparatus of FIG. It is a top view which shows the 2nd radiation | emission conductor formed in the housing | casing of the radio | wireless communication apparatus of FIG. It is a perspective view of the 1st antenna element used for the antenna device concerning one embodiment of the present invention. It is a figure which shows the evaluation result of the gain of the antenna device which concerns on one Embodiment of this invention, and the conventional antenna device. It is a figure for demonstrating the evaluation method of the antenna device which concerns on one Embodiment of this invention. This is a conventional antenna device.

  An antenna device according to the present invention will be described. FIG. 1 is a cross-sectional view of a main part of a wireless communication device provided with an antenna device according to an embodiment of the present invention. FIG. 2 is a plan view of the substrate mounted with the first antenna element inside the housing of the wireless communication apparatus. FIG. 3 is a plan view showing a second radiation conductor formed in the casing of the wireless communication device.

  The antenna device is used for receiving FM broadcasting, and a first radiating conductor is formed on a substrate 20 on which a ground electrode surface 21, a power feeding unit 4, and a contact unit 6 are formed. A second radiating conductor 2 serving as a second antenna element provided on the housing 30 (30a) of the wireless communication device 100a, the first radiating conductor and the second radiating conductor 2 are mounted. It consists of connecting means 3 to connect. Although not shown, a speaker is disposed in the vicinity of the first antenna element.

In this embodiment, a helical antenna is used as the chip antenna 1. FIG. 4 is an external perspective view showing the configuration. The chip antenna 1 is configured by winding a conducting wire serving as a first radiation conductor around a base 16 made of a liquid crystal polymer. The conducting wire is wound around the body portion of the base body 16, and both ends thereof are connected to mounting terminals 13 and 14 of the flange portions 11 and 12 provided on both end sides of the base body 16. The base 16 is provided with recesses 15 extending to both ends, and a magnetic body 18 is accommodated in the recesses 15 to increase the inductance value of the chip antenna 1. In the FM broadcast receiving antenna, the self-inductance is adjusted to 0.6 to 4 μH.
The chip antenna of this embodiment has an external dimension of 10 mm × 2 mm × 1.5 mm, and a copper wire of φ80 μm is wound around the trunk for 45 turns. What is the length of the first radiating conductor in the chip antenna? About 220 mm.

The substrate 16 may use a resin material such as an epoxy resin. Further, an insulator such as alumina or a ceramic material mainly composed of alumina, or a dielectric ceramic material such as magnesium titanate, calcium titanate, zirconia / tin / titanium, or barium titanate may be used. Further, a magnetic ceramic material such as Ni-based or Li-based ferrite may be used. In this case, the magnetic body provided in the concave portion of the base is not necessary. Further, as the magnetic body 18, a magnetic ceramic material such as Ni-based or Li-based ferrite, or a metallic magnetic material such as amorphous or nanocrystalline alloy may be used. Further, a rectangular sheet layer made of dielectric ceramics or magnetic ceramics that can be fired at a low temperature can be laminated and integrally fired with the electrode pattern constituting the first radiation conductor.

  The second radiation conductor 2 is composed of a strip-shaped copper foil formed on the housing 30b. Its external dimensions are 40 mm × 0.5 mm × 0.15 mm. The total length of the first and second radiation conductors excluding the connection means is about 260 mm, which is about 1/3 of 1 / 4λ at 100 MHz, and the proportion of the second radiation conductor 2 in the antenna device is about 15%. Degree. The copper foil which comprises the 2nd radiation | emission conductor 2 may be comprised in a seal | sticker shape, may be affixed on a housing | casing, may be fixed as a printed wiring board, and a fixing means is not limited. The second radiation conductor may be embedded in a resin casing by insert molding or may be fixed to the inner surface of the casing. If insert molding is performed inside the housing, damage is less likely to occur due to impact such as when the wireless communication device is dropped.

  The second radiating conductor 2 has an open end and is not connected to other circuits or the ground. Since the voltage becomes maximum at the open end, it is preferable to dispose it at a position as far as possible from other conductors and the ground plane. In the present embodiment, the second radiation conductor 2 is formed in a straight line along the short side of the substantially rectangular casing 30b.

  The first and second antenna elements are electrically connected to the connecting means via the contact portion. As the connecting means, it is possible to adopt a structure such as a plate spring member that can be elastically deformed, a connector pin that is slidable in the thickness direction of the mounting substrate, or a connector pin that is extendable in the thickness direction of the mounting substrate. A screw, conductive rubber, or the like may be used.

  The average gain was evaluated for the antenna device of the present invention. The average gain is measured by connecting a signal generator to the power supply terminal of the transmission reference antenna in the anechoic chamber and receiving the power radiated from the transmission reference antenna by the antenna under test. Yes. In the test, as a conventional example, an antenna device in which the second radiating conductor was configured on the surface of the substrate 20 together with the first antenna element was also evaluated. The result is shown as a characteristic diagram showing the relationship between gain and frequency in FIG. In most of the measured frequencies of 88 MHz to 108 MHz, the antenna device of the present invention shown as an example in the figure obtained a gain larger than that of the conventional example.

  The reception sensitivity of the antenna device was evaluated by the following procedure. FIG. 6 is a diagram for explaining the evaluation method. An FM transmitter is installed and FM radio waves are transmitted at 89.7 MHz, 96.5 MHz, 102.3 MHz, and 106.5 MHz, and FM radio waves are received by a wireless communication device incorporating an antenna device at a position 3 m away. The observer evaluated how the received voice was heard with a score of 0-4. Zero point is a state where the received signal is at a noise level and voice reception is not possible. One point is a state where the noise level is large and it is difficult to confirm the voice. Two points are in a state where the noise level is small and the voice can be confirmed and there is no problem in use. Three points indicate a state in which the noise level is slight and hardly noticed, and four points indicate that there is no noise that can be confirmed and the voice is clear. The results are shown in Table 1.

  In the antenna device of the present invention, voice reception was possible at each frequency even in a weak electric field environment.

DESCRIPTION OF SYMBOLS 1 1st antenna element 2 2nd antenna element 3 Connection means 4 Feeding part 20 Board | substrate 21 Ground surface 22 Non-ground surface 30a, 30b Case

Claims (2)

An antenna device including a first antenna element, a second antenna element, and a substrate on which the first antenna element is mounted,
The first antenna element is made of a resin material having a flange on both ends, a body provided between the flanges, a mounting terminal provided on each of the flanges, and a recess reaching both ends. A substrate
A magnetic body housed in the recess of the base;
A conductive wire wound around the body of the base body and enclosing the magnetic body as a first radiation conductor;
A helical antenna in which an end of the first radiation conductor is connected to a mounting terminal of the base;
A second radiation conductor formed of a strip-shaped copper foil provided on a different plane from the first antenna element, one end of which is connected to one end of the first radiation conductor via a connecting means, and the other end is an open end ; An antenna device comprising: a second antenna element provided. A wireless communication apparatus , wherein the antenna apparatus according to claim 1 is mounted and another component apparatus is disposed in the vicinity of the first antenna element .

Images