We review some aspects of radio telescope performance, particularly those relating to the characteristics of the feed system used for illuminating the antenna. We discuss the aperture eeciency, radiation pattern, beam width, and coupling and beam eeciencies, emphasizing the eeect of the aperture illumination on these quantities. The discussion should be useful for understanding calibration of a...

A novel type of circularly polarized broadband antenna consisting of a modified circular wideslot aperture and an L-shaped feed probe is introduced. The modified circular wide-slot is partially covered to generate circular polarization with broadband characteristics in the axial ratio. Variations in both the axial ratio and the S11 characteristics of the device are investigated and radiation pa...

Some recent advances done by the author and his collaborators in the field of antennas and antenna arrays are presented. These include: multiband systems, an infinite-wavelength antenna array series feeding network, a true time delay system allowing beam squint free scanning, a pencil-beam full-space scanning array, a beam-forming system based on active aperture discretization, a MIMO dynamic r...

We address the capacity limits of sizeconstrained multi-input multi-output (MIMO) arrays. While most work on MIMO focuses on arrays with of a small number of sufficiently spaced, low correlated antenna elements, we look at the case where a fixed small space is being filled up with antenna elements. We obtain a dense MIMO system whose rate performance is analyzed. We establish capacity limits an...

This paper presents a review of the most important features of the Shorted Annular Patch antennas. These radiators have several mechanical and electrical advantages with respect to other microstrip geometries. In particular, the presence of the short in the central zone of the antenna provides increased radiation flexibility which permits to control the antenna beam aperture. In order to demons...