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Vehicle slot antenna with passive ground element

  • US 4,769,655 A
  • Filed: 05/14/1987
  • Issued: 09/06/1988
  • Est. Priority Date: 05/14/1987
  • Status: Expired due to Fees
First Claim
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1. An FM antenna for a vehicle having a body and a substantially rectangular, horizontal roof supported above the body by substantially vertical pillars at the front and rear corners thereof, the roof and pillars comprising a ground plane of conducting material with ground currents therein, the antenna comprising, in combination:

  • a side fed, looped, annular slot antenna in the roof, the slot antenna having a loop length of substantially a wavelength in the commercial FM broadcasting band and being displaced from the center of the roof toward one of the front and rear of the roof;

    an opening in the ground plane adjacent the slot antenna and somewhat smaller in size but displaced therefrom toward the other of the front and rear of the roof;

    a narrow finger of the ground plane projecting into the opening from the center of the edge adjacent the slot antenna toward the other of the front and rear of the roof, the antenna with the opening and narrow finger having reduced directionality in its vertically polarized FM radiation/reception pattern.

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