Single Aperture Antenna Research Articles

Control of Orbital Angular Momentum Regimen by Modulated Metasurface Leaky-Wave Antennas

In this paper, we present the design procedure of modulated metasurface leaky-wave antennas (MMLWAs) to generate coaxial superposition of vortex beams with several orbital angular momentum (OAM) states. Based on the Flat Optics (FO) technique and aperture field estimation (AFE) method, an analytical framework is proposed to facilitate the implementation of MMLWAs generating multiple topological charges in the OAM regimen. Furthermore, using the spectral analysis which has been derived from the proposed model, we have shown that the symmetry of aperture shape can affect the purity of the mode. Also the perfectly symmetric circular shape is introduced as an ideal choice for high-purity vortex generation. This single aperture antenna with embedded monopole feed can be an appropriate alternative to more complex vortex beam generators such as spiral phase plates and circular antenna arrays.

Quasi-optical antennas for radiometric remote-sensing

Millimetre- and submillimetre-wave radiometers are employed for remote-sensing of the Earth's atmosphere. They must operate in several widely-spaced frequency bands which together might exceed the fundamental bandwidth of a waveguide. A wholly independent radiometer for each band would be inefficient and considerable savings in space and weight can be achieved if all bands are received via a single aperture antenna and then separated by an optical demultiplexer, the arrangement comprising a `quasi-optical' antenna. This paper discusses the requirements for, and the design of, quasi-optical antennas for radiometric remote-sensing and illustrates this with particular reference to the Advanced Microwave Sounding Unit AMSU-B, which was designed and built by Matra Marconi Space UK for the UK Meteorological Office and is due to be placed in orbit on a satellite.

Signal Acquisition Techniques for Receiving Arrays of Large-Aperture Antennas

This paper considers the signal phase acquisition problem for arrays of large-aperture steerable antennas. In particular, long-range signal acquisition is considered for those cases in which the signal-to-noise ratio in each antenna-receiver channel is too low to permit signal phase-lock in each individual receiver. Techniques are discussed which promise to extend the array acquisition sensitivity toward that of an equivalent-area single-aperture antenna. Several acquisition methods are analyzed mathematically and an approximate minimum power threshold estimated for each technique. A numerical comparison between the acquisition techniques for various assumed atmospheric conditions is presented which indicates the limitations on array sensitivity imposed by both the transmission medium and the acquisition technique.