| 摘要 |
Slot antenna apparatus for a motor vehicle roof made of an electrically conducting material with a central non-conducting portion comprises a horizontal sheet of electrically conducting material attached to the roof, the horizontal sheet including a looped slot adjacent the central non-conducting portion which divides the sheet into inner and outer portions, the slot having a total loop length of substantially one wavelength in the commercial FM broadcasting band. The horizontal sheet material has a comparatively high sheet resistance of 1 to 2 ohms per square to produce a maximum VSWR of 5 and preferably below 3. The material may be comprise a coating of nickel in an acrylic binder on the underside of an SMC roof panel. The horizontal sheet may be grounded at DC and commercial AM frequencies by a direct conductive connection between the outer portion thereof and the conducting portion of the roof and at commercial FM frequencies by the capacitive coupling of an overlap of substantially the complete periphery of the outer portion and the conducting portion of the roof. A common AM/FM feed point may be provided at the front center of the slot, or separate AM and FM feed points may be provided at the side center and front center, respectively, of the slot.
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