JP2006197528A - Folded linear inverse f-shaped antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save a space for a linear inverse F-shaped antenna, to accomplish a wide band and high sensitivity, and to promote miniaturization of a mobile communication apparatus such as a folder type mobile phone terminal. <P>SOLUTION: A linear inverse F-shaped antenna 1 of the present invention is disposed on a printed wiring board 4 in the vicinity of a flexible flat cable (FFC) 6 and folds an antenna element orthogonally with the FFC 6 in a folded portable wireless apparatus including the FFC 6 for connecting an electric signal between the printed wiring board 4 and a printed wiring board 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inverted-F antenna that is used in a folding portable wireless device or the like.

  In recent years, due to the widespread use of mobile communication devices such as mobile phones and automobile phones, there has been an increasing demand for downsizing of devices. Along with this, antennas used in communication devices are also small and have high gain and can be placed inside the housing. A type antenna is required. As an antenna suitable for such an application, there is an inverted F type antenna.

  Inverted F-type antennas can be broadly classified into linear inverted F-type antennas and plate-shaped inverted F-type antennas according to the shape of the elements, and the operating principle is the same for both. The plate-like inverted F-type antenna is a small antenna having a circumference length of about ½ wavelength, and unlike a normal dipole antenna, it is an antenna that can transmit and receive in a relatively wide range on any of XY, YZ, and ZX planes. Both vertical polarization components can be received.

  Japanese Unexamined Patent Publication No. 4-129302 has been proposed as a prior art example of a small and thin antenna that can be built into a portable wireless device body with such a plate-like inverted F-type antenna, but is used as a main antenna of a mobile communication device. For this reason, since the frequency bandwidth of the antenna is insufficient, most examples are used only for diversity reception.

  In Japanese Patent Laid-Open No. 6-314984, in order to prevent deterioration of antenna characteristics due to the approach of the human body, the antenna portion and the circuit portion inside the telephone are separated by a metal plate, and the space in the device is effectively used to reduce the size of the product. An antenna that can be designed has been proposed. However, in recent mobile communication devices, there is a strong tendency for colorization and large screens of liquid crystal display devices due to the Internet connection function and camera mounting, etc. The shape of the mobile phone terminal main body has changed from the conventional straight bar type to a large display device The mounting height of the antenna and the area of the substrate are narrowed because it has changed to a folding type that is easy to mount, and the miniaturization by the plate-like inverted F type antenna as in the above prior art exceeds the limit It has become. In particular, in the 800 to 900 MHz band having a low frequency, it is very difficult to adopt a plate-like inverted F-type antenna.

  In order to solve this problem, an antenna has been devised in which a linear inverted F-type antenna element is bent in parallel with the ground conductor plate to reduce the size. To widen the bandwidth, a sufficient height is required, and mounting a component with ground potential next to the antenna mounting surface adversely affects the antenna characteristics. Therefore, it is necessary to place a component near the antenna. There is a disadvantage that it is impossible to prevent downsizing of the product.

  Furthermore, such an antenna is practical because the antenna gain and frequency bandwidth are significantly degraded when the main body is folded in a folding-type mobile phone terminal, and there is a large difference from the antenna performance in a talking state with the main body open. is not.

  In a folding type mobile phone terminal, a circuit block divided into two parts, a display unit and an operation unit, is mainly connected by a flexible flat cable (FFC). Noise including frequency components is generated, and placing an antenna element in the vicinity of the flexible flat cable causes a significant deterioration in reception performance.

  The problem to be solved by the present invention is to realize space saving, wide band and high sensitivity of a linear inverted F-type antenna, and to promote downsizing of mobile communication devices such as a folding mobile phone terminal. is there.

  In order to solve the above-mentioned problems, the folded linear inverted F antenna of the present invention has a folding mobile phone having an electric wire or a flexible flat cable for connecting an electric signal between printed wiring boards arranged separately via a movable part. In the type wireless device, the antenna element is arranged on a printed wiring board in the vicinity of the electric wire or the flexible flat cable, and the antenna element is bent so as to be orthogonal to the electric wire or the flexible flat cable.

  The printed wiring board is electrically equivalent to a ground conductor plate, and the elements of the folded linear inverted F-type antenna are folded in the vertical direction on the printed wiring board.

  The length of the element of the folded linear inverted F-type antenna is such that the element close to the printed wiring board is short and the element far away is long.

  The width of the element of the folded linear inverted F antenna is such that the element close to the printed wiring board is narrow and the element far away is wide.

  The length of the element of the folded linear inverted F antenna is bent so as to avoid the vicinity of the electric wire or the flexible flat cable.

  According to the folded line inverted F-type antenna of the present invention, it is easy to widen the frequency bandwidth of the antenna because electrostatic and electromagnetic coupling between the flexible flat cable or printed wiring board and the antenna element can be reduced. Furthermore, the influence of noise generated by electronic components mounted on the printed wiring board can be reduced, the reception sensitivity can be improved, and the antenna arrangement can be reduced, so that the portable wireless device can be easily downsized.

  When the folded linear inverted F-type antenna of the present invention is used in a foldable mobile phone terminal, it is possible to reduce changes in antenna characteristics when the main body is opened and closed.

  The contents of the present invention will be described below by showing specific examples. FIG. 1 is an example of a linear inverted F antenna according to the present invention. In the figure, 1 is an antenna body, 2 is an antenna feeding point, 3 is a short circuit point, 4 is a first printed wiring board, 5 is a second printed wiring board, and 6 is a flexible flat cable (FFC). The configuration of FIG. 1 assumes a foldable mobile phone terminal. 4 First printed wiring board on which a transmission / reception circuit, a control circuit, etc. are mounted and 5 Second printing on which an LCD display device is mounted There is a wiring board, and these are electrically connected by 6 flexible flat cables.

  As shown in FIG. 2, a basic inverted-F antenna is an L-shaped antenna formed by bending a monopole antenna and provided with a short-circuit point for impedance matching. The total length of the antenna element needs to be adapted to the frequency to be used. However, in order to arrange the antenna in the housing, a bent type as shown in FIG. 3 has been devised.

  Next, the difference in characteristics between the linear inverted F antenna according to the present invention shown in FIG. 1 and the conventional linear inverted F antenna shown in FIG. 3 will be described. FIG. 4 shows the relative positional relationship between the linear inverted F-type antenna 1 and the flexible flat cable 6 according to the prior art. Since a part of the antenna element is parallel to the flexible flat cable 6, And electromagnetic coupling increases. Some signal currents flowing through the flexible flat cable 6 include a frequency component in the reception frequency band, and when this is mixed in the antenna 1, it causes deterioration in reception sensitivity.

  On the other hand, in the linear inverted F-type antenna 1 according to the present invention shown in FIG. 5, the flexible flat cable 6 and the antenna element are orthogonal to each other, so that electrostatic and electromagnetic coupling is reduced, and the flexible flat cable 6 is reduced. Is less affected by the signal current flowing through Further, as shown in FIGS. 6 and 7, the linear inverted F-type antenna according to the present invention is electrostatically coupled (floating capacitance 7) to the printed wiring boards 4 and 5 which are ground conductor plates as compared with the conventional one. ), The frequency bandwidth of the antenna can be widened, and the influence of noise generated by an IC or the like mounted on the printed wiring board 4 can be reduced.

  Another embodiment of the linear inverted F antenna according to the present invention will be described. FIG. 8 shows the antenna element close to the printed wiring board 4 shortened and the distant element lengthened, and the electrostatic coupling with the ground conductor plate described above is further reduced to increase the bandwidth. The noise characteristics are improved. Further, the antenna characteristics can be improved more effectively by shortening the antenna element close to the flexible flat cable 6.

  FIG. 9 shows that the width of the antenna element close to the printed wiring board 4 is narrowed and the distance of the far element is widened, and the width of the antenna element can be increased while reducing the electrostatic coupling with the ground conductor plate. A broadband antenna can be realized.

  As described above, the linear inverted F-type antenna according to the present invention is easy to increase the bandwidth compared to the conventional one because the electrostatic and electromagnetic coupling with the printed wiring board and the electronic components mounted thereon are sparse. In addition, since it has characteristics that are not easily affected by noise, there are few restrictions on mounting, and it is easy to miniaturize portable wireless devices.

Further, since the electrostatic and electromagnetic coupling between the antenna 1 and the flexible flat cable 6 is sparse, the influence of the printed wiring board 5 on which a display device or the like is mounted on the radiation pattern of the antenna is reduced. FIG. 10 is a graph showing this state, and the horizontal axis is the position when the folding mobile phone terminal is opened and viewed from the side. The radiation pattern of the linear inverted F antenna according to the present invention indicated by a solid line is less radiated on the printed wiring board 5 side than the conventional linear inverted F antenna indicated by a broken line on the graph. When radio waves are radiated from both printed wiring boards, there is a problem in practical use because the radiation pattern varies greatly due to the change in antenna characteristics when the folding cellular phone terminal is opened. The linear inverted-F antenna of the present invention has a dominant change in the radiation characteristics on the printed wiring board 4 side, so that there is little change in the antenna characteristics with respect to the shape change, and the wireless communication performance in the actual usage state of the folding mobile phone terminal is improved. To make it easier.

Example of a linear inverted-F antenna according to the present invention Basic inverted F-type antenna Example of linear inverted-F antenna according to prior art Description of characteristics of linear inverted F antenna by conventional technology Description of characteristics of linear inverted F antenna according to the present invention Description of the characteristics of the conventional linear inverted F antenna Description of characteristics of linear inverted F antenna according to the present invention Another embodiment of the linear inverted F antenna according to the present invention Another embodiment of the linear inverted F antenna according to the present invention Antenna radiation pattern graph

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reverse F type antenna main body 2 Feeding point 3 Short-circuit part 4 1st printed wiring board 5 2nd printed wiring board 6 Flexible flat cable 7 Floating capacity (coupling capacity)

Claims (5)

  In a foldable portable wireless device having an electric wire or a flexible flat cable that connects electrical signals between printed wiring boards arranged separately through a movable part, on the printed wiring board in the vicinity of the electric wire or flexible flat cable, etc. A folded linear inverted F-type antenna, wherein the antenna element is bent so as to be orthogonal to the electric wire or the flexible flat cable.   2. The folded linear inverted F antenna according to claim 1, wherein the printed wiring board is electrically equivalent to a ground conductor plate, and the antenna element is folded in a direction perpendicular to the printed wiring board.   3. The folded linear inverted F antenna according to claim 2, wherein the elements of the folded linear inverted F antenna have a shorter element closer to the printed wiring board and a longer distant element.   3. The folded linear inverted F antenna according to claim 2, wherein the elements of the folded linear inverted F antenna have narrower elements closer to the printed wiring board and wider distant elements.   2. The folded linear inverted F antenna according to claim 1, wherein the length of the folded linear inverted F antenna is bent to avoid the vicinity of the electric wire or flexible flat cable.

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