Planar multibeam slotted waveguide antenna array with quasi-optical pattern-forming scheme

Abstract

Planar multibeam slotted waveguide antenna arrays are promising for creation of panoramic radiometric systems of airborne or spacebome remote sensing of the Earth surface having a wide observation swath and high spatial resolution. They are prospective also as on-board contoured-beam antennas for space TV and radio broadcasting. Besides, one can realize a number of partial beams working on different frequencies without making the antenna system more complex but using the effect of radiation pattern frequency scanning in the traveling wave slotted waveguide antennas.

A planar multibeam slotted waveguide antenna of 3 cm band with longitudinal slots in a broad face of each rectangular waveguide, which are made in the chess like order has been designed and investigated. It was shown theoretically that a planar radiation-pattern-forming scheme of quasi-optical (horn-reflector) type as a cut of a parabolic cylinder can be used to provide a multibeam radiation pattern of such an antenna. In comparison with the pattern-forming scheme based on Rothman’s lens and other similar ones, the proposed scheme has a more simple and firm construction, and a smaller loss level that is important for on-board radiometric systems. To decrease the antenna lateral size, multichannel radiator can be conveniently placed on the shadow surface of the slotted waveguide antenna array by using a waveguide U-turn.

A six-channel antenna of 16 waveguides has been manufactured and investigated experimentally. Each waveguide has 20 slots. Measurement of a gain factor, radiation patters and matching, as well as mutual coupling coefficients between the channels, were carried out both in the resonance excitation regime of slotted waveguide arrays and in the traveling wave regime.