All-around vehicle antenna-apparatus

Abstract: In an all-around vehicle antenna apparatus according to the present invention, a window frame (2) of a vehicle window (1) is made of metal, a thin-film conductor (5) is formed on the surface of a translucent member (e.g., glass) (3) of the vehicle window (1) to form a slot (4) between the window frame (2) and thin-film conductor (5), and the slot (4) functions as a slot antenna element. A plurality of thin-film conductor pieces (A to H, K, L) are arranged such that at least part of the pieces (A to H, K, L) is inserted into the slot (4) so as to have a specific relationship with the slot antenna element, and thus the thin-film conductor pieces (A to H, K, L) serve as a plural-wave-receivable antenna element adapted to a specific frequency.

Description: The present invention relates to a vehicle antenna apparatus mounted on a vehicle such as an automobile and, more particularly, to an improvement in an antenna apparatus constituted mainly of a slot antenna provided on a vehicle window. In a conventional windowpane antenna apparatus provided on a vehicle window, a long, narrow thin-film conductor having a predetermined pattern, which is to be formed on the window surface, is used as an antenna element. This antenna element is connected to a transmitter/receiver set via a feeder. Since, in the windowpane antenna apparatus, a metal window frame serves as a grounding conductor, its shape has influence upon antenna characteristics. Usually the shape of a metal window frame greatly varies from vehicle to vehicle; therefore, even though an antenna element is formed with great precision so as to have a given size and a given shape, the antenna characteristics are greatly varied with the type of a vehicle on which the antenna element is to be mounted, with the result that a desired antenna characteristic cannot be obtained appropriately. To mount the above windowpane antenna apparatus on a vehicle, it is necessary to form a pattern for each antenna element in order to match the shape of a window frame of every vehicle, thus causing a drawback of making it difficult to manufacture the antenna element, and increasing in manufacturing costs. It is accordingly an object of the present invention to provide a vehicle antenna apparatus, which is capable of always stably fulfilling a desired antenna characteristic without exerting influence upon the shape of a window frame though it has a fixed size and a fixed shape and is provided on a vehicle window. EP-A-0 760 537 discloses a motor vehicle having a metallic body and provided with a window opening receiving an antenna window. The antenna window has inner and outer panes bonded together by a bonding layer with an optically-transparent electrically-conductive solar central coating reducing transmission in at least a part of the solar energy range. At least one edge of the window is left free from the coating and in this region a slot antenna is formed. At least at one additional edge, the coating runs to that edge and is overlapped by the framing portion of the vehicle body and is coupled with a high-frequency coupling to the coating. The coating may be provided as a defogger. DE 4,447,134A discloses a transparent film conductor attached to a windscreen of a vehicle so that a slot is formed between the conductor and the vehicle body. Electrical power is fed to the conductor and the vehicle body. This arrangement forms a slot antenna. A space is left within the conductor area, and a windscreen heater can be installed in this space, coupled to the conductor by a capacitor. In this way the windscreen heater forms part of the antenna, reducing the area of conductor required to build the antenna. To attain the above object, the present invention provides a vehicle antenna apparatus as set out in claim 1. Preferred features are set out in the dependent claims. This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features. The invention can be more fully under stood from the following detailed description when taken in conjunction with the accompanying drawings, in which: FIG. 1 is a view of the structure of a vehicle antenna apparatus according to one embodiment of the present invention; and FIG. 2 is a block diagram of an electric system of the vehicle antenna apparatus shown in FIG. 1. (Embodiment) Referring to FIGS. 1 and 2, one embodiment of the present invention will now be described. In FIG. 1, reference numeral 1 denotes a rear window of a vehicle. The window 1 has a window frame 2 made of metal and a translucent member 3 formed of a windowpane or the like. A thin-film conductor 5 is provided on the surface of the translucent member 3. A slot 4 having a predetermined width is formed between the window frame 2 and thin-film conductor 5. The thin-film conductor 5 is constituted mainly of a defogger 5a for preventing the rear window 1 from being fogged. Between the defogger 5a and an upper frame 2b of the window frame 2, a relatively broader belt-shaped conductor 5b is formed in parallel with the upper frame 2b. The width S1 of the upper edge of the slot 4 between the defogger 5a and belt-shaped conductor 5b, is set to about 4 cm, while the width S2 of the lower edge thereof and the widths S3 and S4 of both sides thereof are each set to about 1 cm to 2 cm. Thus, a slot antenna element ANT1 mainly including the slot 4 is formed on the surface of the rear window 1. A plurality of thin-film conductor pieces A to H, K and L are arranged in such a manner that at least part of the pieces is inserted in the slot 4 so as to have a specific relationship with the slot antenna element ANT1. Of these thin-film conductor pieces, the pieces A to D are directly connected to the defogger 5a and supplied with power, and the pieces E to H, K and L are electrostatically coupled to the defogger Sa and supplied with power. Thus, each of the conductor pieces A to H, K and L functions as a plural-wave-receivable antenna element ANT2 adapted to a specific frequency. In the foregoing embodiment, the thin-film conductor pieces A to D constitute a 4-channel FM antenna element, and the thin-film conductor pieces E to H constitute a 4-channel TV antenna element. Moreover, the piece K constitutes a key-less door lock/unlock antenna element, and the piece L constitutes an AM antenna element. Small-sized slot antenna elements M and N adapted to a specific frequency are formed on the belt-shaped conductor 5b. The antenna element M constitutes a 1.5 GHz GPS (Global Positioning System) antenna element, and the antenna element N constitutes an 800 MHz portable telephone antenna element. The belt-shaped conductor 5b is provided with auxiliary devices 6, 7 and 8 including an amplifier circuit for amplifying a signal input to the antenna apparatus and a matching circuit. The antenna elements constituted of thin-film conductor pieces are connected to their respective transmitter/receiver sets via the auxiliary devices 6, 7 and 8. For example, the thin-film conductor pieces A to D for the FM antenna element and the thin-film conductor piece L for the AM antenna element are connected to an FM/AM set 11 through the auxiliary device 6 and line L1. Similarly, the thin-film conductor pieces E to H for the TV antenna element are connected to a TV set 12 through the auxiliary device 7 and line L2. The other antenna elements, i.e., the small-sized slot antenna elements M and N serving as the GPS antenna element and the portable telephone antenna element, respectively, and the thin-film conductor piece K for the key-less door lock/unlock antenna element, are connected to a portable telephone set 13, a GPS set 14, and a door actuator 15 through the auxiliary device 8 and line Lx. Matching elements I and J of slot antenna element ANT1 are inserted in the slot 4 between the window frame 2 and thin-film conductor 5. If the matching elements I and J are adjusted in advance, the impedance matching of the slot antenna element ANT1 can be obtained.

Claims: A vehicle antenna apparatus comprising: a vehicle window (1) having a metal window frame (2) in which a translucent member (3) is fitted; a thin-film conductor defogger (5a) for defogging the vehicle window, the defogger being provided on the translucent member (3) of the vehicle window (1) with a gap serving as a slot (4) having a width between an outer circumference of the defogger (5a) and an inner circumference of the metal window frame (2); first means for causing the slot (4) to function as a slot antenna element (ANT 1); a plurality of thin-film conductor pieces (A to H, K, L) arranged in such a manner that at least part of each conductor piece (A to H, K, L) is inserted into the slot (4); and second means (6, 7, 8) for causing the plurality of thin-film conductor pieces (A to H,K,L) to function as plural-wave-receivable antenna elements (ANT 2) having a specific relationship with the slot antenna element (ANT 1) and excited in response to radio waves of plural specific frequencies; characterised by a straight, belt-shaped thin-film conductor (5b) formed between the defogger (5a) and the metal window frame (2) and in parallel with the metal window frame (2) wherein the straight, belt-shaped thin-film conductor (5b) includes a plurality of small-sized slot antenna elements (M, N) excited in response to a radio wave having a specific frequency. A vehicle antenna apparatus according to claim 1, wherein the second means (6, 7, 8) feeds power to the plurality of thin-film conductor pieces (A to H, K, L), and connects a specific one or some of the thin-film conductor pieces (A to H, K, L) to a corresponding transmit/receive set (11-15). A vehicle antenna apparatus according to claim 1 or 2, wherein the plural-wave-receivable antenna elements (ANT2) include an FM antenna element (A to D) having a plurality of channels, a TV antenna element(E to H) having a plurality of channels, a key-less door lock/unlock antenna element (K), and an AM antenna element (L). A vehicle antenna apparatus according to any preceding claim, wherein the slot(4) includes a thin-film conductor piece (I, J) for impedance-matching of the slot antenna element (ANT 1). A vehicle antenna apparatus according to any preceding claim, wherein the plurality of small sized slot antenna elements (M, N) include at least a portable telephone antenna element (N) and a GPS antenna element (M). A vehicle antenna apparatus according to any preceding claim, wherein the belt-shaped conductor (5b) includes an auxiliary device (6, 7, 8) having at least an amplifier circuit. A vehicle antenna apparatus according to any preceding claim, wherein the belt-shaped conductor (5b) is formed at an upper side of the window (1).

Inventors: ENDO HIROSHI, SAITO MASATOSHI, TACHIHARA HIROYUKI, ENDO, HIROSHI, SAITO, MASATOSHI, TACHIHARA, HIROYUKI
Applicants: HARADA IND CO LTD, HARADA INDUSTRY CO., LTD.
Application year: 1998
Main classification: H01Q1
IPC codes: H01Q1, H01Q21, H01Q13, H01Q5