JP5008602B2 - antenna - Google Patents

Description

  The present invention relates to a multi-frequency small antenna, and more particularly to a planar monopole pair antenna using a bent structure.

  Various types of mobile terminal antennas have been proposed. Conventionally, a planar inverted F antenna (for example, see Non-Patent Documents 1 and 2), a loop antenna (for example, see Non-Patent Document 3), a patch antenna (for example, see Non-Patent Document 4), a monopole antenna and a patch An antenna that is a combination of antennas (see, for example, Non-Patent Document 5) and a short-circuited monopole antenna are employed.

The frequency band used by the mobile terminal system is generally a plurality of frequency bands. For example, in the PDC (Personal Digital Cellular) system in Japan, an 800 MHz band of 810 MHz to 956 MHz and a 1.4 GHz band of 1429 MHz to 1501 MHz are used. In the digital cellular system in the United States, at least 900 MHz band of 824 MHz to 894 MHz is used as AMPS (Advanced Mobile Phone Service), and 1.8 GHz band of 1850 MHz to 1990 MHz is used as PCS (Personal Communication Services) system. In addition, a 2.0 GHz band from 1920 MHz to 2170 MHz is used as a UMTS (Universal Mobile Telecommunications System) system, and a 2.4 GHz band from 2400 MHz to 2500 MHz is used as a Bluetooth system. As described above, due to the shortage of the use frequency accompanying the increase in subscribers, it is necessary to use a plurality of frequency bands.
K. -L. Wong, J. et al. -H. Chou, S.M. -W. Su, and C.I. -M. Su, '' Isolation between GSM / DCS and WLAN antennas in a PDA phone, '' Microwave and Optical Technology Letters, vol. 45, no. 4, pp. 347-352, May 2005 K. -L. Wong, J. et al. -H. Chou, C.I. -L. Tang, and S.M. -H. Yeh, '' Integrated internal GSM / DCS and WLAN antennas with optimized isolation for a PDA phone, '' Microwave and Optical Technology Letters, vol. 46, no. 4, pp. 323-326, Aug. 2005 C. -H. Hao, K .; -L. Wong, and F.W. -S. Chang, '' Internal GSM / DCS dual-band open-loop antenna for laptop application, '' Microwave and Optical Technology Letters, vol. 49, no. 3, pp. 680-684, Mar. 2007 K. -L. Wong, Y .; -L. Lin, and B.B. Chen, '' Internal patch antenna with a thin air-layer subformat for GSM / DCS operation in a PDA phone, '' IEEE Transactions on Antenna Propagation. 55, no. 4, pp. 1165-1172, Apr. 2007 G. -Y. Chen, J. et al. -S. Sun, K .; -L. Wu, C.I. -H. Lin, K .; -K. Tiong, Y .; -D. Chen, “Cellular antenna design for PDA phone application,” in Proc. IEEE Antenas Propag. Int. Symp. , Hawaii, USA, 2007, pp. 2634-2737

  In portable terminals such as a PDA equipped with a short-range wireless data communication system that receives or transmits a plurality of frequency bands, there is an increasing demand for miniaturization as the frequency of antennas increases. However, the conventional antenna takes away the volume inside the mobile terminal housing and is not suitable for miniaturization of the mobile terminal. For this reason, there has been a problem that the above-mentioned plurality of frequency bands cannot be fully accommodated.

  A quarter-wave antenna is a promising antenna that satisfies such requirements. However, when an inverted-F planar antenna is used, the weight and size of the substrate for supporting the antenna, the position with respect to the ground, and the increase in price become problems for widespread use.

  In addition, when using any one of a loop antenna, a patch antenna, a monopole antenna, and a combination of a monopole antenna and a patch antenna, the size of the antenna is large and it is difficult to incorporate it in a portable terminal.

  Therefore, an object of the present invention is to provide an antenna that can be multi-frequency and miniaturized.

  In order to achieve the above object, the present invention aims to achieve multi-frequency and miniaturization by using a radiating conductor of a monopole pair antenna with two arms and utilizing two resonances generated therefrom.

Specifically, an antenna according to the present invention includes a ground plate, a power supply arm connected to an outer edge of the ground plate, to which high-frequency power is supplied, a short-circuit portion connecting the ground plate and the power supply arm, A first radiating element having a plurality of arms bent on the same plane as the ground plate, one end of which is connected to the feeding arm, and the first radiating element with respect to the feeding arm. A second radiating element that is arranged on the side facing the one end of the element and that includes a plurality of arms in which one radiating conductor is bent on the same plane as the ground plate, and one end connected to the feeding arm And the first radiating element is connected to the power supply arm at a position closer to the ground plate side than the second radiating element, and the short-circuit portion is more than the first radiating element than the first radiating element. On the ground plate side Is connected to the feeding arm have position, one of the arms constituting the arm and the second radiating element constituting the end of the first radiating element is provided in the opposite direction with respect to the feeding arm , wherein the portion of the first arm constituting a second end of the radiating element is substantially parallel to the one of the arms constituting the second radiating element, the other end of said second radiating element, wherein It is bent at a point close to the ground plate, and the bent tip is disposed substantially parallel to the outer edge of the ground plate.

  Since the first radiating element and the second radiating element are provided, two resonances can be generated. As a result, the interval between the higher-order mode on the low frequency side and the fundamental mode on the high frequency side can be adjusted and the bandwidth on the high frequency side can be widened to cope with multi-frequency. In addition, since the first radiating element and the second radiating element form a planar antenna, it can be easily incorporated into a portable terminal. Furthermore, since the short circuit portion is provided, the height of the antenna can be reduced.

Further, since the second radiating element and the ground plate are close to each other, the current flowing through the second radiating element can be increased, and matching can be adjusted together with the frequency on the high frequency side.

In the antenna according to the present invention, it is preferable that a basic resonance frequency of the second radiating element is substantially the same as a triple resonance frequency of the first radiating element.
According to the present invention, the triple resonance frequency of the first radiating element can be moved to the low frequency side.

In the antenna according to the present invention, both ends of the feeding arm, respectively, it is preferably connected to the ground plate and the second radiating element.
Since the second radiating element is connected to the tip of the power supply arm, the antenna can be made small.

  ADVANTAGE OF THE INVENTION According to this invention, the antenna which enables multi-frequency reduction and size reduction can be provided.

Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.
FIG. 1 is a schematic configuration diagram of an antenna according to the present embodiment. The antenna according to this embodiment includes a first radiating element 1, a second radiating element 2, a short-circuit portion 3, a flat ground plate 4, and a feeding arm 5.

  The ground plate 4, the first radiating element 1 and the second radiating element 2 are arranged on the same plane, and the entire antenna has a planar structure. The material constituting the antenna is preferably a flexible printed circuit board 7 (FPC) at a low cost. In this case, an antenna is formed on the flexible printed circuit board 7. By configuring the antenna with the flexible printed circuit board 7, the antenna can be easily bent and can be easily mounted on a portable terminal.

  The feeding arm 5 is connected to the outer edge of the ground plate 4, and high-frequency power is fed from the feeding point 6. The feeding point 6 excites the first radiating element 1 and the second radiating element 2 through the feeding arm 5. The feeding arm 5 is connected to the first radiating element 1 and the second radiating element 2 and supplies power to the first radiating element 1 and the second radiating element 2. The short-circuit portion 3 is in contact with the ground plate 4 and the power feeding arm 5 and connects the ground plate 4 and the power feeding arm 5.

  Here, the distance from the ground plate 4 where the feeding arm 5 is connected to the short-circuit portion 3 is the distance from the ground plate 4 where the feeding arm 5 is connected to the first radiating element 1 and the second radiating element 2. Preferably it is different from the distance. In the case of a general bent antenna, it is difficult to achieve matching because of attenuation of radiation resistance and increase of reactance component of antenna impedance. Therefore, in order to cancel the increase in the radiation resistance and the reactance component, the short-circuit portion 3 is connected near the feeding point 6. For example, the arm 3b is connected to a position on the feeding arm 5 and closer to the feeding point 6 than the arms 1a and 2a. If the length of the antenna is about ¼ of the wavelength, the short-circuit unit 3 gives an induction component to the feeding point 6, and the induction component cancels the capacitance component at the feeding point 6. For this reason, the height of the antenna can be reduced.

  Moreover, it is preferable that both ends of the feeding arm 5 are connected to the feeding point 6 and the second radiating element 2, respectively. For example, the second radiating element 2 is connected to the end of the feeding arm 5, and the first radiating element 1 is connected between the feeding point 6 of the feeding arm 5 and the connection point with the second radiating element 2. The Further, the first radiating element 1 is connected to the feeding arm 5, and the second radiating element 2 is connected to the first radiating element 1. With such an arrangement, the arm 2b of the second radiating element 2 in FIG. 3 to be described later can be shortened.

  The basic resonance frequency of the second radiating element 2 is substantially the same as the triple resonance frequency of the first radiating element 1. By combining the second radiating element 2 and the first radiating element 1, the triple resonance frequency of the first radiating element 1 can be moved to the low frequency side. In addition, the frequency band on the high frequency side can be expanded. The first radiating element 1 has an arm shape and receives power supply from the power supply arm 5 from one end. The second radiating element 2 has an arm shape, and receives power supply from the power supply arm 5 from one end of the arm.

  The first radiating element 1 is bent and includes three arms 1a, 1b, and 1c. The arms 1a, 1b, and 1c are arranged in order of the arms 1a, 1b, and 1c from one end of the first radiating element 1. The second radiating element 2 is bent and includes four arms 2a, 2b, 2c, and 2d. Since the first radiating element 1 and the second radiating element 2 are bent, the distance from the frequency band on the high frequency side can be adjusted. The four arms 2a, 2b, 2c, and 2d are arranged in order of the arms 2a, 2b, 2c, and 2d from one end of the second radiating element 2.

  The arm 1 a and the arm 2 b are provided in the opposite directions with respect to the power feeding arm 5. The arm 1a and the arm 1c are bent so as to face each other. A part of the arm 1c extends in parallel with the arm 2b. The arm 2a and the arm 2c are bent so as to face each other. The arm 2b and the arm 2d are bent so as to face each other. The arm 2 d is bent so as to extend along the outer edge of the ground plate 4.

  By using the two first radiating elements 1 and 2, two resonances can be generated. By using the first radiating element 1, the fundamental mode and the higher order mode on the low frequency side are controlled, and by using the second radiating element 2, the fundamental mode on the high frequency side can be adjusted. Further, the interval between the fundamental mode and the higher order mode can be adjusted at the position of the bent portion of the first radiating element 1 and the second radiating element 2, and the interval between the resonance frequencies can be controlled. It is. By using two arms, it is possible to add a higher-order mode on the low frequency side and a fundamental mode on the high frequency side, and the bandwidth on the high frequency side can be widened.

The arm 2 d at the other end of the second radiating element 2 is bent at a point close to the ground plate 4, and the bent tip is disposed substantially parallel to the outer edge of the ground plate 4. As described above, it is preferable that the arm 2 d at the other end of the second radiating element 2 is disposed at a point close to the ground plate 4. The longer the length of the arm 2d (the symbol L _2d shown in FIG. 3), the higher the resistance due to coupling with the ground plate 4, and the stronger the capacitance characteristics. For example, the resistance is increased to about 200Ω, and the capacitance characteristic is about 70Ω. At this time, the length L2d of the arm _2d is adjusted so that the antenna impedance is up to 50Ω. In the case of the second radiating element 2, by providing the protruding arm 2d, the current flowing through the second radiating element 2 can be increased, and matching can be adjusted along with the adjustment of the frequency on the high frequency side.

The short-circuit portion 3 is bent and includes two arms 3a and 3b. The two arms 3 a and 3 b are arranged in the order of the arms 3 a and 3 b from one end of the short-circuit portion 3. The arm 3 a is connected to the ground plate 4, and the arm 3 b is connected to the power feeding arm 5. The arm 3a extends in parallel with the arm 2c. The arm 3b is opposed to the arm 2b. The impedance can be adjusted by adjusting the distance of the arm 3b from the ground plate 4. For example, the impedance can be lowered by shortening the length of the arm 3a (the symbol L _3a shown in FIG. 3).

  The antenna according to the embodiment was evaluated. FIG. 2 is a bird's-eye view showing the shape and design parameters of the antenna according to the present embodiment. FIG. 3 is a top view showing the shape and design parameters of the antenna according to the present embodiment. FIG. 4 shows the detailed values of the design parameters. FIG. 5 shows the voltage standing wave ratio characteristics of the antenna according to the example. The resonance frequency of the first radiating element and the second radiating element shifts the triple resonance frequency of the first radiating element to the low frequency side, and the GSM, DCS, and PCS bands in the target frequency band indicated by the broken line It can be seen that two resonances occur. Assuming that VSWR (Voltage Standing Wave Ratio) <3.5 is the standard, the bandwidths of the 900 MHz band (centered at 930 MHz) and the DCS and PCS bands (here centered at 1830 MHz) were 96.1 MHz and 307.2 MHz. It was.

Specifically, on the basis of VSWR <2.5, the bandwidth was 60.3 MHz from 897.1 MHz to 957.7 MHz and 192.5 MHz from 1737.5 MHz to 1930.0 MHz.
Based on VSWR <2.8, the bandwidth was 72.7 MHz from 890.9 MHz to 963.6 MHz and 228.2 MHz from 1721.8 MHz to 1950.0 MHz.
Using VSWR <3.0 as a reference, the bandwidth was 80.0 MHz from 887.0 MHz to 967.0 MHz and 251.2 MHz from 1712.1 MHz to 1963.3 MHz.
Based on VSWR <3.5 as a reference, the bandwidth was 98.1 MHz from 878.3 MHz to 974.4 MHz and 307.2 MHz from 1690.3 MHz to 197.2 MHz.

FIG. 6 illustrates a matching state of the antenna according to the embodiment. Resistance and reactance of 930 MHz and 1830 MHz were resistance R _{in 930 MHz} = 52.04Ω, resistance R _{in 1830 MHz} = 32.36Ω, reactance X _{in 930 MHz} = 29.95Ω, and reactance X _{in 1830 MHz} = −9.35Ω, respectively. .

FIG. 7 shows radiation characteristics in the GSM band of the antenna according to the example, where (a) shows the xy plane, (b) shows the yz plane, and (c) shows the zx plane. The peak gain, minimum gain, and average gain in the xy plane were 0.52 dBi, −0.18 dBi, and 0.18 dBi, respectively, with a center frequency of 920 MHz.
8A and 8B show radiation characteristics in the DCS band of the antenna according to the example. FIG. 8A shows the xy plane, FIG. 8B shows the yz plane, and FIG. 8C shows the zx plane. The peak gain, minimum gain, and average gain in the xy plane were −0.24 dBi, −9.02 dBi, and −2.86 dBi, respectively, with a center frequency of 1795 MHz.
9A and 9B show radiation characteristics in the PCS band of the antenna according to the example. FIG. 9A shows the xy plane, FIG. 9B shows the yz plane, and FIG. 9C shows the zx plane. The peak gain, minimum gain, and average gain in the xy plane were −2.48 dBi, −9.52 dBi, and −4.62 dBi, respectively, with a center frequency of 1920 MHz.
And it turns out that the radiation directivity in each frequency band has the characteristic close | similar to a monopole, as shown in FIG.7, FIG.8, FIG.9.

  INDUSTRIAL APPLICABILITY The present invention can be used for a multi-frequency small antenna incorporated in an information terminal device such as a notebook personal computer, a PDA (Personal Digital Assistant) terminal, a mobile phone, or a VICS.

It is a schematic block diagram of the antenna which concerns on this embodiment. It is a bird's-eye view which shows the shape and design parameter of the antenna which concern on a present Example. It is a top view which shows the shape and design parameter of the antenna which concern on a present Example. Shows detailed values of design parameters. The voltage standing wave ratio characteristic of the antenna which concerns on an Example is shown. The matching state of the antenna which concerns on an Example is shown. It is a radiation characteristic in the GSM band of the antenna which concerns on an Example, (a) shows xy plane, (b) shows yz plane, (c) shows zx plane. It is a radiation characteristic in the DCS band of the antenna which concerns on an Example, (a) shows xy plane, (b) shows yz plane, (c) shows zx plane. It is a radiation characteristic in the PCS band of the antenna which concerns on an Example, (a) shows xy plane, (b) shows yz plane, (c) shows zx plane.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st radiating element 1a, 1b, 1c arm 2 2nd radiating element 2a, 2b, 2c, 2d arm 3 short circuit part 3a, 3b arm 4 ground board 5 feeding arm 6 feeding point 7 flexible printed circuit board

Claims (3)

A ground plate,
A feeding arm connected to the outer edge of the ground plate and fed with high-frequency power;
A short-circuit portion connecting the ground plate and the feeding arm;
A first radiating element in which one radiating conductor is composed of a plurality of arms bent on the same plane as the ground plate, and one end of which is connected to the feeding arm;
It is arranged on the side facing the one end of the first radiating element with respect to the power supply arm, one radiating conductor is composed of a plurality of arms bent on the same plane as the ground plate, and one end is A second radiating element connected to the feeding arm,
The first radiating element is connected to the feeding arm at a position closer to the ground plate side than the second radiating element,
The short-circuit portion is connected to the feeding arm at a position closer to the ground plate side than the first radiating element,
The arm that constitutes the one end of the first radiating element and the arm that constitutes the second radiating element are provided in a direction opposite to the feeding arm,
A part of the arm constituting the other end of the first radiating element is substantially parallel to any arm constituting the second radiating element ,
The antenna is characterized in that the other end of the second radiating element is bent at a point close to the ground plate, and the bent tip is disposed substantially parallel to the outer edge of the ground plate. The fundamental resonance frequency of the second radiating element, the antenna according to claim 1, characterized in that 3 times the resonant frequency and is substantially the same of the first radiating element. Wherein both ends of the feeding arm, respectively, antenna according to claim 1 or 2, characterized in that it is connected to the ground plate and the second radiating element.

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