Window glass antenna for automobiles

Abstract: A window glass antenna (1) has a plurality of elemental patterns (A1-A37) attached to a window glass (2) parallel to each other. The receiving antenna patterns (A1-A37) have ends interconnected by an end connector pattern (B). Adjacent ones of the receiving antenna patterns (A1-A37) are spaced from each other by at most about 30 mm. Some of the receiving antenna patterns (A1-A37) have different lengths. The window glass antenna (1) also includes an auxiliary pattern (C) disposed near free ends of the receiving antenna patterns (A1-A37) and extending parallel to the connector pattern (B). The window glass antenna (1) is suitable for use on an automobile and is capable of receiving radio signals in both AM and FM broadcast bands with high sensitivity.

Description: The present invention relates to a radio signal receiving antenna comprising an electric conductor attached to a sheet of window glass of an automobile. FIG. 4 of the accompanying drawings schematically shows a known window glass antenna for automobiles as disclosed in Japanese Laid-Open Utility Model Publication No. 1-146614 published on October 9, 1989. DE-U-6911585 and US-A-3771159 further disclose conventional window glass antenna. The conventional window glass antenna, generally designated by the reference numeral 101 in FIG. 4, comprises a plurality of loop-shaped receiving antenna patterns 103a, 103b, 103c attached to a sheet of window glass 102 and spaced inwardly from the outer peripheral edge thereof. The receiving antenna patterns 103a, 103b, 103c have ends connected to each other by a connector 104 that serves to pick up received radio signals. The other ends of the receiving antenna patterns 103a, 103b, 103c are spaced from the connector 104 by a gap 105. The receiving antenna patterns 103a, 103b are interrupted by respective gaps 107, 106 defined therein, so that the receiving antenna patterns 103a, 103b have different effective lengths. The loop-shaped receiving antenna patterns 103a, 103b, 103c are disposed within a limited surface area of the window glass 102. Therefore, it is difficult to increase the effective length of the window glass antenna 101. While the known window glass antenna 101 is highly sensitive to frequency-modulated (FM) broadcasts transmitted in an ultrashort wave range having frequencies ranging from 70 MHz to 110 MHz), its sensitivity is not high enough to receive amplitude-modulated (AM) broadcasts transmitted in a medium wave range with a frequency range from 500 kHz to 1.6 MHz. In view of the aforesaid problems of the conventional window glass antenna for automobiles, it is an object of the present invention to provide a window glass antenna for automobiles which is capable of receiving both AM and FM broadcast bands with high sensitivity. According to the present invention, there is provided a window glass antenna comprising a plurality of receiving antenna patterns disposed on a sheet of window glass, and an end connector pattern connecting ends of the receiving antenna patterns, wherein the window glass antenna further comprises an auxiliary pattern disposed near free ends of the receiving antenna patterns and extending parallel to the end connector. pattern, the auxiliary pattern having an end connected to the end connector pattern. An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which like reference numerals represent the same or similar objects. FIG. 1 is a schematic plan view of a window glass antenna according to the present invention; FIG. 2 is a graph showing the relationship between the pitch or spacing between adjacent ones of receiving antenna patterns of the window glass antenna shown in FIG. 1 and the sensitivity with which the window glass antenna receives the AM broadcast band; FIG. 3 is a graph showing the relationship between the frequency of the FM broadcast band and the reception sensitivity of window glass antennas; and FIG. 4 is a schematic plan view of a conventional window glass antenna. As shown in FIG. 1, a window glass antenna, generally designated by the reference numeral 1, for use on an automobile according to the present invention generally comprises 37 receiving antenna patterns A (A1 through A37) attached to a sheet of window glass 2, an end connector pattern B, an auxiliary pattern C, and a radio signal pickup area D. The patterns A, B, C and the radio signal pickup area D may be formed of a printed and baked paste material that is electrically conductive. The receiving antenna patterns A1 through A37 extend in straight lines parallel to each other, and each serve to receive radio signals in the FM broadcast band. Some of the receiving antenna patterns A1 through A37 have different lengths. The following table specifically shows the lengths of the receiving antenna patterns A1 through A37: (lengths in mm) Pattern No. Length Pattern No. Length A1 235 A26 355 A2, A3 325 A27 225 A4 ~ A6 355 A28 235 A7 ~ A15 325 A29 245 A16, A17 275 A30 255 A18 320 A31 265 A19 315 A32 245 A20 320 A33 215 A21 360 A34 210 A22 320 A35 175 A23 360 A36 150 A24 310 A37 90 A25 345 The lengths of the receiving antenna patterns A1 through A37 are selected to receive broadcasts in the entire FM broadcast band with high sensitivity. The receiving antenna patterns A1 through A37 are spaced apart by a pitch or spacing P of at most about 30 mm, preferably about 20 mm. The receiving antenna patterns A1 through A37 have ends connected to the end connector pattern B for receiving radio signals in the AM broadcast band. The end connector pattern B has one end joined to the radio signal pickup area D. The end connector pattern B is straight and runs transversely to the direction of the receiving antenna patterns A adjacent one edge, preferably the lower edge, of the window glass 2. The receiving antenna patterns A all terminate at one end on the straight end connector pattern and all extend in the same direction away therefrom towards their free ends. The auxiliary pattern C, which serves as an impedance adjusting element, is disposed near the free ends of the receiving antenna patterns A and extends parallel to the end connector pattern B. One end of the auxiliary pattern C is connected to the radio signal pickup area D by an auxiliary pattern connector CA disposed on one side of the receiving antenna patterns A. In the illustrated embodiment, the end connector pattern B has a length of 766 mm, the auxiliary pattern C has a length of 725 mm, and the auxiliary pattern connector CA has a length of 375 mm. FIG. 2 shows the relationship between the pitch or distance P between adjacent ones of the receiving antenna patterns A1 through A37 and the sensitivity with which the window glass antenna 1 receives the AM broadcast band. The graph of FIG. 2 has a horizontal axis representing the pitch P, and a vertical axis representing the radio signal reception sensitivity S (dBµV). The measurements were conducted in an electric field of 60 dBµV/m at a frequency of 1 MHz. It has been found that the radio signal reception sensitivity S of the window glass antenna 1 increases as the pitch P decreases from 80 mm to 30 mm, but does not increase substantially as the pitch P is reduced to less than 30 mm. If the pitch P of the receiving antenna patterns A1 through A37 were reduced below 10 mm, then the visibility of the window glass 2 would be impaired. FIG. 3 shows the relationship between the frequency of the FM broadcast band and the reception sensitivity of window glass antennas. The graph of FIG. 3 has a horizontal axis representing the frequency f of the FM broadcast band, and a vertical axis representing the radio signal reception sensitivity S (dBµV). The curve C1 in FIG. 3 indicates the frequency vs. sensitivity characteristics of the window glass antenna 1 according to the present invention, the curve C2 the frequency vs. sensitivity characteristics of a window glass antenna that is similar to the window glass antenna 1 except that the auxiliary pattern C is dispensed with, and the curve C111 the frequency vs. sensitivity characteristics of a comparative antenna (not shown). The comparative antenna had 37 receiving antenna patterns having the same length of 375 mm and spaced at a pitch P of 20 mm. The comparative antenna 37 had no auxiliary pattern. The measurements were conducted in an electric field of 60 dBµV/m. It has been found that an increased reception gain is achieved over a wide frequency range with the different lengths of the receiving antenna patterns A1 through A37. It has also been confirmed that the auxiliary pattern C is effective to prevent a sensitivity reduction in a middle frequency range from 94 MHz to 102 MHz of the FM broadcast band, resulting in reduced reception sensitivity variations over the entire FM broadcast band. The pitch P between adjacent ones of the receiving antenna patterns A1 through A37 is selected to be in a range, which is of at most about 30 mm, suitable for receiving radio signals in the AM broadcast band with high sensitivity. The number of receiving antenna patterns is relatively small, and hence the amount of the electrically conductive paste material used as the receiving antenna patterns is relatively small. The lengths of the receiving antenna patterns A1 through A37 are varied such that the frequency vs. sensitivity characteristic curve C1 is as flat as possible over the entire FM broadcast band. Accordingly, the window glass antenna 1 does not have any reception sensitivity peaks for particular frequencies in the FM broadcast band, but has a high reception sensitivity over the entire FM broadcast band. Therefore, the window glass antenna 1 according to the present invention is capable of receiving radio signals in both AM and FM broadcast bands with high sensitivity.

Claims: A window glass antenna (1) comprising: a plurality of receiving antenna patterns (A1-A37) disposed on a sheet of window glass (2); and an end connector pattern (B) connecting ends of the receiving antenna patterns (A1-A37), characterised in that said window glass antenna further comprises an auxiliary pattern (C) disposed near free ends of the receiving antenna patterns (A1-A37) and extending parallel to said end connector pattern (B), said auxiliary pattern (C) having an end connected to said end connector pattern (B). A window glass antenna (1) according to claim 1, wherein each of said elemental patterns (A1-A37) is straight, said ends of the elemental patterns (A1-A37) interconnected by said connector pattern (B) being adjacent one edge of said window glass (2). A window glass antenna (1) according to claim 2, wherein said elemental patterns (A1-A37) extend parallel to each other. A window glass antenna (1) according to claim 3, wherein said elemental patterns (A1-A37) include elemental patterns having different lengths. A window glass antenna (1) according to any preceding claim, wherein adjacent ones of said elemental patterns (A1-A37) are spaced from each other by at most about 30 mm. A window glass antenna (1) according to any preceding claim, wherein said auxiliary pattern (C) is connected to a radio signal pickup area (D) by an auxiliary pattern connector (CA). A window glass antenna (1) according to claim 6, wherein said auxiliary pattern connector (CA) is disposed on one side of said receiving antenna portions (A1-A37). A window glass antenna (1) according to any preceding claim, wherein said receiving antenna portions (A1-A37) are arranged in combination with said auxiliary pattern (C) to substantially prevent a sensitivity reduction in a middle frequency range from 94 MHz to 102 MHz.

Inventors: KAKIZAWA HITOSHI, KAKIZAWA, HITOSHI, KAKIZAWA, HITOSHI, NIPPON SHEET GLASS CO., LTD.
Applicants: NIPPON SHEET GLASS CO LTD, NIPPON SHEET GLASS CO., LTD.
Application year: 1991
Main classification: H01Q1
IPC codes: H01Q1, B60R11, B60R16