Importance

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Abstract

This invention relates to the structure of slotted cable antennas used in end-fire glide slope systems employed in the instrument landing of airplanes. The structure is an improvement over that described in my U.S. Pat. No. 3,699,582 titled Slotted Cable Glide Slope Antenna. An air-dielectric coaxial transmission line, carrying a travelling wave of radio frequency energy, has a number of probe-fed slots along the outer conductor which leak current onto the outside surface of the line, resulting in radiation. The magnitude of the radiation from each slot is controlled by the probe coupling to the inner conductor and by a slot shunt consisting of a coaxial shorted line section. The relative phase of the radiations from adjacent slots is controlled by the electrical spacing of the slots. The electrical spacing increases with rising temperature due to the expansion coefficient of the transmission line, but this effect is compensated by the inclusion within the transmission line of a strand of polyethylene or similar dielectric having a negative temperature coefficient.

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First Claim