SCANNING ANTENNA SYSTEMS

• Main Authors: ROWATT, CHARLES, ANTHONY, CARTER, CHRISTOPHER, RALPH, GILHESPY, BERNARD, PAUL, STEPHENS, BENJAMIN, DAVID
• Format: Patent
• Language: English; French; German
• Published: 07.06.2006
• Subjects: ANTENNAS, i.e. RADIO AERIALS; BASIC ELECTRIC ELEMENTS; ELECTRICITY; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE; WAVEGUIDES

Described herein is a quasi-optic rotating joint (100) which allows circularly polarised radiation to be transmitted therethrough irrespective of the angle of rotation of the joint. The rotating joint (100) comprises a first quasi-optic lens (102) having a first axis (112), which is carried on an inner part (116, 118) of bearings (108, 110) and which shares first axis (112). An outer part (122) of bearing (110) carries a quasi-optic mirror (104) and a second quasi-optic lens (106). The second lens (106) has a second axis (114) which is orthogonal to the first axis (112) of the first lens (102) and which intersects at the mirror (104). A Gaussian beam waist is formed at the mirror (104) by the first lens (102) and the second lens (106) is matched to the reflection of the beam waist at the mirror (104). Circularly polarised Gaussian beams passing through the joint (100) suffer a phase shift of angle Psi which increases at the same rate as the increase in angle of rotation of the joint (100). If the radiation returns through the joint (100) 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 2Psi.