Scanning antenna systems

• Main Authors: Carter, Christopher R, Rowatt, Charles A, Gilhespy, Bernard P, Stephens, Benjamin D
• Format: Patent
• Language: English
• Published: 22.02.2005

Described herein is a quasi-optic rotating joint which allows circularly polarised radiation to be transmitted therethrough irrespective of the angle of rotation of the joint. The rotating joint comprises a first quasi-optic lens having a first axis, which is carried on an inner part of bearings and which shares first axis. An outer part of bearing carries a quasi-optic mirror and a second quasi-optic lens. The second lens has a second axis which is orthogonal to the first axis of the first lens and which intersects at the mirror. A Gaussian beam waist is formed at the mirror by the first lens and the second lens is matched to the reflection of the beam waist at the mirror. Circularly polarised Gaussian beams passing through the joint suffer a phase shift of angle Ψ which increases at the same rate as the increase in angle of rotation of the joint. If the radiation returns through the joint in the same hand of circular polarisation as it left, the overall phase shift is zero. If the hand of polarisation is swapped on return, the overall rotation dependent phase shift is 2Ψ.