JP2009212645A - Wideband antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wideband antenna for wireless communication which includes two antenna lines and nonetheless materializes wideband with only one feed point. <P>SOLUTION: The wideband antenna includes a line constituting a first antenna, a line constituting a second antenna connected to the line of the first antenna in series, and a conductor arranged parallel to the line constituting the second antenna across a dielectric. A connection point between the line constituting the first antenna and the line constituting the second antenna is used as the feed point, an end point of the second antenna is connected to an inputting part of a radio part, a switch is provided for switching whether to ground the conductor in accordance with a control signal for determining whether to operate the antenna in a high frequency or a low frequency, the antenna is configured only by the line constituting the first antenna while the conductor is grounded by the switch, and the antenna is configured by the lines of the first and second antennas while the conductor is not grounded. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a broadband antenna of a mobile terminal.

  In recent years, it has become possible to receive digital terrestrial television broadcasting (one-segment broadcasting) by a portable terminal such as a cellular phone. However, it has been difficult to receive terrestrial digital TV broadcasts with a wide band with an antenna mounted in a small casing such as a portable terminal.

  In other words, since a large number of channels are allocated over a wide band of 100 megahertz, the required antenna length differs considerably between the low frequency channel and the high frequency channel, and there is a problem in miniaturization of the apparatus.

  A configuration for using one antenna in two frequency bands apart from each other has been proposed (see Patent Document 1), and FIG. 5 shows the configuration of the proposed frequency switching antenna.

In FIG. 5, 50 is a spiral first radiation conductor, 51 is a spiral second radiation conductor, 52 and 53 are first and second feeding points, 54 is an impedance control switching unit, and 55 is switching control. Reference numeral 56 denotes a first feed line. The first radiating conductor 50 is set to an electrical length that resonates at the first frequency, and the second radiating conductor 50 and the second radiating conductor 51 are resonated at the second frequency so that the total electrical length of the first radiating conductor 50 and the second radiating conductor 51 resonates. The electrical length of the radiating conductor is determined. When the antenna is used at the first frequency, the RF signal from the radio is connected to the first feeding point 52 by the impedance control switching unit 54 via the first feeding line 56 by the control signal of the switching control unit 55. Then, the impedance of the second feeding point 53 is given by the impedance control switching unit 54 such that the impedance viewed from the first feeding point 52 to the second radiation conductor 51 side is almost open. When used at the second frequency, the RF signal is connected to the second feeding point 53 by the impedance control switching unit 54, and the first feeding point 52, which is a non-connection terminal, is almost opened by the impedance control switching unit 54. The impedance to be connected.
Japanese Patent Laid-Open No. 11-163620

  In the configuration of the frequency switching type antenna as shown in Patent Document 1, since there are two feeding points and the feeding point is switched according to a necessary frequency, there is one connecting component to the feeding point. 2 times as compared to the above, and the cost is increased, and the area for mounting the connection parts is also doubled, which makes it difficult to reduce the size of the portable terminal device.

  An object of the present invention is to provide a wideband antenna for wireless communication in a portable terminal that can realize a wideband with only one feeding point.

  The broadband antenna according to the present invention includes a line constituting the first antenna element, a line constituting the second antenna element connected in series to the first antenna element, and a line constituting the second antenna. On the other hand, conductors arranged in parallel with a dielectric in between are provided. The connection point between the line constituting the first antenna and the line constituting the second antenna is used as a feeding point, and the terminal of the second antenna is connected to the input part of the radio part to operate the antenna at a high frequency or low. A switch is provided for switching to a state of whether or not the conductor is grounded in accordance with a control signal for operating at a frequency.

  When the conductor is grounded by the switch, the antenna is configured with only the first antenna line and operates at a high frequency, and when the conductor is not grounded, the antenna is configured by the first and second antenna lines. .

  Further, the second antenna line can be constituted by a microstrip line provided on the upper surface of the dielectric, and the conductor can be provided on the lower surface of the dielectric. Further, the second antenna line operates as an impedance line when used at a high frequency, and operates as an antenna together with the first antenna line when used at a low frequency.

  According to the present invention, even a configuration having a single feeding point can operate as an ideal antenna by changing the electrical length according to the required frequency, and ensure good antenna characteristics. Can do.

  In addition, it is possible to improve the wireless quality of a portable terminal such as a cellular phone, and to reduce the mounting area of components necessary for the antenna, thereby reducing the size and cost of the device.

  A schematic configuration of a broadband antenna according to the present invention is shown in FIG. In the figure, 10 is a line of the first antenna, 11 is a line of the second antenna, and 12 is a conductor arranged in parallel with an interval formed by a dielectric between the line constituting the second antenna. , 13 is a dielectric disposed between the line 11 and the conductor 12 of the second antenna, 14 is a feeding point provided at a position connecting the first antenna and the second antenna, and 15 is a second antenna. A switch (SW) for switching whether the line 11 functions as an antenna or an impedance line, 16 is a control unit, and 17 is a radio unit.

  The line 11 and the conductor 12 constituting the second antenna are configured as impedance lines, and the conductor 12 is grounded (grounded) when the switch 15 is turned on, and the line 11 functions as a simple impedance line as an antenna element. Does not work. In this case, of the first and second antenna lines, the line that functions as the antenna element is only the first antenna line 10, and the feeding point 14 has the second antenna line that functions as an impedance line. Since the power is supplied through the antenna 11 and the antenna has a short length, it can cope with a high frequency.

  In the state where the switch 15 is switched off, the conductor 12 is disconnected from the ground (ground), so that the line 11 functions not as an impedance line but as a line of the second antenna connected to the line 10 of the first antenna. However, it has a line length obtained by adding two lines, and can cope with a low frequency (low frequency range) in which the antenna length is longer than that of the first antenna.

  When a control signal for turning off the switch 15 is generated from the control unit 16 to select a low frequency (low frequency) channel, the switch 15 is turned off and the first antenna line 10 and the second antenna line are turned off. 11 is added, and the radio unit 17 receives a radio signal of a low-frequency channel from the feeding point 14. When a control signal for turning on the switch 15 to select a high frequency (high frequency) channel is generated from the control unit 16, the switch 15 is turned on, and the line 11 of the second antenna functions as an impedance line. The radio unit 17 receives a radio signal of a high-frequency channel from the feeding point 14.

  FIG. 2 shows the configuration of the embodiment, and FIG. 3 shows the configuration of the second antenna portion.

  In FIG. 2, 20 is a housing of a portable terminal that receives digital terrestrial television broadcasting, 21 is a first antenna line (corresponding to 10 in FIG. 1), and 22 is a connection portion between the first antenna and the second antenna. , Feeding devices 23 to 25 are devices constituting the second antenna, 23 is a microstrip line provided on the dielectric (corresponding to the line 11 of the second antenna in FIG. 1), and 24 is A dielectric (corresponding to 13 in FIG. 1), 25 is a conductor such as copper (corresponding to 12 in FIG. 1) provided on the lower surface of the dielectric 24, and 26 is electrically connecting the conductor 25 and ground (ground). A switch for switching whether or not, 27 is a control unit, 28 is a radio unit for receiving digital terrestrial television broadcasting, and 30 is a board on which a circuit of a portable terminal is mounted.

  FIG. 3 shows a cross-sectional configuration of the apparatus constituting the second antenna of FIG. 2, a microstrip line 23 having a constant width is provided on the dielectric 24, and a conductor made of copper on the lower surface of the dielectric 24. 25 is attached. The microstrip line 23 changes its characteristic impedance according to the dielectric constant, thickness, etc. of the dielectric 24.

  In the case of digital terrestrial television broadcasting, the necessary frequency band is 470 MHz to 770 MHz. Considering a monopole antenna, the necessary antenna length = λ / 4 is 160 mm to 97 mm. Here, assuming that the low frequency is f1 = 470 MHz and the high frequency is f2 = 770 MHz, the line 21 of the first antenna in FIG. 2 is set to 97 mm, and the length of the microstrip line 23 constituting the second antenna is set to 63 mm. Thus, the first antenna line length + the second antenna microstrip line length = 160 mm.

  That is, when the frequency f2 is high, the switch 26 is turned on by the control from the control unit 27 and the conductor 25 is grounded, whereby the microstrip line 23 of the second antenna is switched to the impedance line, and the first When the operation is performed only by the antenna and the frequency f1 is low, the switch 26 is turned off by the control from the control unit 27 and the microstrip line 23 of the second antenna is switched as the antenna, so that the first antenna line length + the first Operate as microstrip line length of 2 antennas. As a result, even if the bandwidth is wide, it can be seen as an ideal antenna length.

  FIG. 4 is a configuration example of a portable terminal according to the present invention. In the figure, the reference numerals 21 to 23, 25, 27, and 28 are the same as those of the same reference numerals in FIG. 2, 21 is the first antenna line, 22 is the first antenna and the second antenna. A connection point and a feeding point, 23 is a microstrip line constituting the line of the second antenna, 25 is a conductor disposed with respect to the microstrip line 23 via a dielectric, and 26-1 and 26-2 are First and second switches for switching whether or not the conductor 25 is grounded, 27 'is a CPU that performs overall control, 28 is a radio unit, 29 is a television that displays television signals and outputs audio ( TV) module. The dielectric 24 (see FIG. 2) disposed between the microstrip line 23 and the conductor 25 is not shown in FIG.

  In this configuration example, two switches 26-1 and 26-2 are provided as switches for switching antennas. When a signal designating a low frequency (low frequency) channel from the CPU 27 'is output to the television module 29 and an OFF signal is supplied to the switches 26-1 and 26-2, the conductor 25 is grounded and the second signal is output. The microstrip line 23 constituting the antenna line is connected in series with the first antenna line 21 as an antenna element. As a result, a radio signal of a low frequency channel is received, demodulated and detected by the radio unit 28, and a video reproduced by the television module 29 is displayed and audio is output.

  Further, when a signal for designating a high frequency (high frequency) channel from the CPU 27 'is output to the television module 29 and a signal for switching on is supplied to the switches 26-1 and 26-2, the conductor 25 is grounded. The microstrip line 23 that is separated from the potential and forms the second antenna only functions as an impedance line, and the antenna element is configured only by the line 21 of the first antenna.

It is a figure which shows schematic structure of the wideband antenna which concerns on this invention. It is a figure which shows the structure of an Example. It is a figure which shows the structure of a 2nd antenna part. It is a figure which shows the structural example of the portable terminal by this invention. It is a figure which shows the structure of the proposed frequency-switching type antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Line of 1st antenna 11 Line of 2nd antenna 12 Conductor 13 Dielectric 14 Feed point 15 Switch (SW)
16 Control unit 17 Radio unit

Claims (4)

A broadband antenna for a portable terminal,
A line constituting the first antenna, a line constituting the second antenna connected in series to the line of the first antenna, and a line constituting the second antenna with a dielectric interposed therebetween With conductors arranged in
A connection point between the line constituting the first antenna and the line constituting the second antenna is used as a feeding point, and the terminal end of the second antenna is connected to the input part of the radio unit,
Providing a switch for switching the state of whether or not the conductor is grounded according to a control signal of operating the antenna at a high frequency or a low frequency;
When the conductor is grounded by the switch, the antenna is configured only by the first antenna line, and when the conductor is not grounded, the antenna is configured by the first and second antenna lines. A broadband antenna for mobile terminals. In claim 1,
A broadband antenna for a portable terminal, wherein the line of the second antenna is configured by a microstrip line provided on an upper surface of a dielectric, and the conductor is provided on a lower surface of the dielectric. In claim 1,
The second antenna line operates as an impedance line when used at a high frequency, and operates as an antenna together with the first antenna line when used at a low frequency. antenna. In any one of Claims 1 thru | or 3,
The first antenna has a line length corresponding to a wavelength of λ / 4 of a high frequency channel of terrestrial digital television broadcasting, and the line length of the first antenna + the length of the second antenna is the terrestrial digital television. A broadband antenna for a portable terminal, comprising a line length corresponding to a wavelength of λ / 4 of a low frequency channel of broadcasting.

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