US 4,288,794 A · Shielded loop VOR/ILS antenna system

Abstract

A VOR/ILS antenna system for rotor aircraft eliminates rotor modulation of signals without varying rotor speed. The system comprises one or more loop antennas each having one or more closed loop windings mounted on the aircraft in a generally horizontal plane and having a conductive shield covering the windings and dielectrically separated therefrom and having a small gap breaking the continuity thereof. A dual loop VOR/ILS system for helicopters is particularly disclosed wherein the pair of loop antennas are mounted in a horizontal plane on opposite sides of the central vertical helicopter mast extending upwardly between a pair of cowling members in which the antennas are disposed. Each antenna has a gap in the shield facing inboard and a connection point for the windings opposite the gap and outboard. The connection point provides a lobe in the individual radiation pattern of the respective loop antenna which is outboard relative to the mast and which compensates an otherwise null point in the composite radiation pattern of the pair of loop antennas whereby to provide an omnidirectional composite radiation pattern. The helicopter itself further compensates the otherwise null point to provide in combination with the dual loop antenna system a substantially circular radiation pattern. Antenna construction is also disclosed.

Claims21

Dependent claims

A VOR/ILS antenna system for rotary wing aircraft eliminating modulation of signals without varying speed of a mast driven rotor, comprising:

a pair of loop antennas, each having one or more closed loop windings, mounted and spaced on said aircraft in a generally horizontal plane on opposite sides of said mast;
each said antenna having a conductive shield covering said windings and dielectrically separated therefrom, each said shield having a small gap breaking the continuity thereof and facing the gap in the other shield;
and
communication means including a pair of electrical leads for each said antenna extending through said shield from said windings at a point opposite said gap.

1 more element

A helicopter VOR/ILS antenna system for a helicopter having a longitudinal body with a vertical mast extending upwardly therefrom and supporting a rotor blade having a horizontal rotary plane of motion, and a pair of exterior cowling members between which extends said mast, said cowling members being transparent to VOR/ILS frequency signals, comprising:

a pair of loop antennas each having one or more closed loop windings mounted in a horizontal plane within a respective one of said cowling members and spaced on opposite sides of said mast;
each said antenna having a conductive shield covering said windings and dielectrically separated therefrom, each said shield having a small gap breaking the continuity thereof and facing inboard relative to said mast;
communication means including a pair of electrical leads for each said antenna extending through said shield from said windings at a connection point opposite said gap and outboard relative to said mast;
each said connection point of said leads to said windings providing a lobe in the individual radiation pattern of the respective loop antenna which is outboard relative to said mast and which compensates an otherwise null point in the composite radiation pattern of the pair of said loop antennas whereby to provide an omnidirectional composite radiation pattern;
and
said helicopter itself further compensating said otherwise null point to provide in combination with said antenna system a substantially circular radiation pattern.

3 more elements

Dependencies are inferred from the claim text.

Shielded loop VOR/ILS antenna system

Life of this patent

Shielded loop VOR/ILS antenna system

Life of this patent

Abstract

Claims21