JP2006202714A - Cable and antenna assembly for signaling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and flexible signal transmission cable with desired electric characteristics. <P>SOLUTION: A ground conductor 6 is arranged on each side of a signal conductor 5 on the same plane, both of the conductors 5, 6 are coated with electric insulation thin films 7 from top and bottom, and the insulation thin films are coated with metal shielding layers 11 from top and bottom to structure a signal transmission cable 4. The metal shielding layer 11 has a plastic layer 9 made of polyethylene terephthalate or the like on one side of a metal layer 8 of copper, aluminum or the like, and a conductive adhesive layer on the other, so that sides fitted with the conductive adhesive layers 10 face each other and formed outside the electric insulation thin films 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a signal transmission cable and an antenna device using the cable as a feed line, and more particularly, a signal transmission cable that is thin, flexible, and has desired electrical characteristics, and a cellular phone and a PC (personal computer). The present invention relates to an antenna device suitable for use in an electronic device such as a PDA (Personal Digital Assistance).

  Conventionally, in electronic devices such as mobile phones, PCs, PDAs and the like, there are many cases where a coaxial cable has been used as a feed line from an attached antenna to a main board.

  In recent years, mobile phones and notebook PCs have been widely folded, and have been reduced in size and thickness. Flexibility for inserting a hinge part to be folded in the antenna feed line; Although thinning is required for wiring in a narrow space, the coaxial cable is round and has a large outer diameter, and cannot meet such requirements.

  In order to improve such a defect of the coaxial cable, a signal transmission cable as shown in FIGS. 1 to 3 has been proposed (see, for example, Patent Document 1).

  The signal transmission cable 4 includes a signal conductor 5 made of metal foil, a ground conductor 6 made of metal foil disposed on both sides of the signal conductor 5 and on the same plane as the signal conductor 5, and the signal conductor 5 and the ground conductor. 6, an electrically insulating thin film 7 covering 6, and a metal shielding layer 11 provided around the electrically insulating thin film 7.

Since the signal transmission cable 4 having such a configuration is thin and flexible, it is suitable as a power supply line for a two-fold type electronic device such as a mobile phone or a notebook personal computer.
JP 2004-289578 A (FIG. 4, paragraphs 0018 to 0023)

  However, since the electrically insulating thin film 7 of the signal transmission cable 4 is made of a material such as polyimide or polyethylene terephthalate (PET), transmission loss increases in order to achieve a desired characteristic impedance, for example, a characteristic impedance of 50Ω. There is a problem that it cannot be used as an antenna feeder for electronic equipment.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a signal transmission cable that is thin, flexible, and has desired electrical characteristics.

  Another object of the present invention is to provide an antenna device that is provided with a signal transmission cable that is thin, flexible, and has desired electrical characteristics as a feeder line.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a signal conductor made of metal foil and a ground conductor made of metal foil disposed on both sides of the signal conductor have a dielectric constant of 3.0 or less and a dielectric loss tangent. Is characterized by a cable for signal transmission in which is coated with an electrically insulating thin film of 0.002 or less and a metal shielding layer is formed around the electrically insulating thin film.

  The invention of claim 2 is characterized by an antenna device including an antenna element and the signal transmission cable according to claim 1 as a feed line to the antenna element.

  According to the first aspect of the present invention, the electrically insulating thin film is formed of a material having a dielectric constant of 3.0 or less and a dielectric loss tangent of 0.002 or less.

  For this reason, a desired characteristic impedance can be realized with a small transmission loss, and a thin and flexible signal transmission cable can be obtained.

  According to a second aspect of the present invention, the signal transmission cable is used as a feed line to the antenna element.

  Therefore, the antenna device has an electrical characteristic comparable to that of a conventional antenna device using a coaxial cable as a feed line, and is suitable for use in an electronic device such as a two-fold type mobile phone or a notebook PC. Can be obtained.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode of a signal transmission cable and antenna device of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a state in which a signal transmission cable 4 is electrically connected to the radiating section 2 and the ground section 3 of the antenna 1.

  As shown in the cross-sectional views of FIGS. 2 and 3, the signal transmission cable 4 has ground conductors 6 arranged on both sides of the signal conductor 5 on the same plane as the signal conductor 5. 6 is covered with an electrically insulating thin film 7 from both up and down directions, and the electrically insulating thin film 7 is covered with a metal shielding layer 11 from both up and down directions.

  The metal coating layer 11 is formed by providing a plastic layer 9 such as polyethylene terephthalate (PET) on one surface of a metal layer 8 such as copper or aluminum and providing a conductive adhesive layer 10 on the other surface. It is formed outside the electrically insulating thin film 7 so that the surfaces provided with 10 face each other.

  The signal transmission cable 4 is formed with a junction 12 that electrically connects the ground conductor 6 and the metal layer 8 of the metal shielding layer 11 at predetermined intervals. As shown in FIG. A part of the electrically insulating thin film 7 is removed, and the ground conductor 6 and the metal layer 8 are joined via the conductive adhesive layer 11.

  The signal conductor 5 of the signal transmission cable 4 and the radiation portion 2 of the antenna 1 are electrically connected at the connection portion 13, and the ground conductor 6 and the ground portion 3 are electrically connected at the connection portion 14. .

  In the present embodiment, both the signal conductor 5 and the ground conductor 6 are formed of a metal foil, vapor-deposited layer, or plated layer having good electrical conductivity such as copper or aluminum.

  The electrically insulating thin film 7 is formed of a plastic material having a dielectric constant of 3.0 or less and a dielectric loss tangent of 0.002 or less, so that the signal transmission cable 4 having a desired specific impedance and low transmission loss can be obtained. Obtainable.

  Examples of the plastic material for forming the electrically insulating thin film 7 include liquid crystal polymer (LCP) and polytetrafluoroethylene (PTFE).

  FIG. 4 shows the measurement results of characteristic impedance and transmission loss of the signal transmission cable 4 when polyimide, polyethylene terephthalate (PET), liquid crystal polymer (LCP), and polytetrafluoroethylene (PTFE) are used as the electrical insulating thin film 7. It was.

  FIG. 4 also shows, for reference, the measurement results of a coaxial cable using a fluororesin as an insulator, which is used as a feeder line for an electronic device antenna.

  The coaxial cable has a low dielectric constant and low dielectric loss tangent because the insulator is made of fluororesin, and exhibits sufficient performance as a power supply line. Is 36 AWG, the cable outer diameter becomes as large as 0.81 mm.

  Sample No. 1 and no. 2 uses polyimide as the electrically insulating thin film 7. As shown in FIG. 1, when the thickness of the copper foil (signal conductor 5 and ground conductor 6) is 0.035 mm, which is a general thickness, and the thickness of the electrically insulating thin film 7 is 0.05 mm, the characteristic impedance is 50Ω. It is far below that impedance matching cannot be achieved. As shown in FIG. 2, when the thickness of the copper foil and the thickness of the electrically insulating thin film 7 are adjusted so that the characteristic impedance is 50Ω, the transmission loss increases, and the performance of the antenna feeder line becomes insufficient. End up.

  Sample No. 3 is one using PET as the electrically insulating thin film 7. Similar to 2, the transmission loss is large, and the performance of the antenna feed line is insufficient.

  Sample No. 4 and sample no. No. 5 uses LCP and PTFE as the electrically insulating thin film 7 in which both the dielectric constant and the dielectric loss tangent are within the ranges specified in the present invention (dielectric constant: 3.0 or less, dielectric loss tangent: 0.002 or less). A signal transmission cable having a characteristic impedance of 50Ω with a transmission loss comparable to that of a coaxial cable can be realized.

  In addition, in this case, a signal transmission cable having a thickness of 0.5 mm or less can be realized even when the outer diameter of the coaxial cable is about 0.81 mm and the metal shielding layer 11 is included. It can be said that it is suitable for wiring in a space.

  Further, even when the antenna portion is located on the liquid crystal display screen side, such as a mobile phone or a notebook PC, the signal transmission cable that is thin and flexible as in this embodiment is a hinge. It can sufficiently withstand the wiring to the main board via the part.

  A method for manufacturing a signal transmission cable in the present embodiment will be described. A copper-clad laminate in which a copper foil is laminated on one side of an electrically insulating thin film 7 is prepared, and the signal conductor 5 and the ground conductor 6 are etched by etching the copper foil. Form.

  Next, an electrically insulating thin film 7 is laminated on the surface where the signal conductor 5 and the ground conductor 6 are exposed, and further, a plastic layer 9 is formed on one side of the metal layer 8 on the upper and lower sides of the electrically insulating thin film 7, and the other surface is electrically conductive. A signal transmission cable is manufactured by heat-pressing the metal shielding layer 11 provided with the adhesive layer 10 so that the surfaces provided with the conductive adhesive layer 10 face each other.

  Similarly, for the radiating portion as an antenna element, a copper-clad laminate in which a copper foil is laminated on one side of an electrically insulating thin film is prepared, and the antenna pattern is formed by etching the copper foil to expose the antenna pattern. It is manufactured by laminating an electrically insulating thin film on the surface.

  The antenna device of the present invention may be produced by individually manufacturing a signal transmission cable and an antenna element, and electrically connecting them. However, the signal transmission cable and the antenna element are integrally manufactured. It may be what you did.

  An antenna device in which a signal transmission cable and an antenna element are integrated is prepared by preparing a copper-clad laminate in which a copper foil is laminated on one side of an electrically insulating thin film, and etching the copper foil to produce a signal conductor, a ground conductor, and an antenna. The pattern is integrally formed, and an electrically insulating thin film is laminated on the exposed surface of the signal conductor, ground conductor, and antenna pattern, and punched into a predetermined shape while maintaining the integrated shape of the signal conductor, ground conductor, and antenna pattern. Thereafter, a metal shielding layer is formed on the signal conductor and the ground conductor portion.

  Although the best embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not depart from the gist of the present invention are possible. Are included in the present invention.

  It is the perspective view explaining the signal transmission cable and antenna device of the best embodiment of the present invention, and the conventional signal transmission cable.   It is the XX sectional view taken on the line of FIG.   It is the YY sectional view taken on the line of FIG.   It is a table | surface explaining the structure and electrical property of the signal transmission cable of the best embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Radiation part 3 Grounding part 4 Signal transmission cable 5 Signal conductor 6 Grounding conductor 7 Electrical insulating thin film 8 Metal layer 9 Plastic layer 10 Conductive adhesive layer 11 Metal shielding layer

Claims (2)

  A signal conductor made of a metal foil and a ground conductor made of a metal foil disposed on both sides of the signal conductor are covered with an electrically insulating thin film having a dielectric constant of 3.0 or less and a dielectric loss tangent of 0.002 or less, A signal transmission cable comprising a metal shielding layer formed around an electrically insulating thin film.   An antenna device comprising: an antenna element; and the signal transmission cable according to claim 1 as a feed line to the antenna element.

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