Orthogonality in multibeam antennas is revisited. The difference between orthogonal beamforming and zero-forced beamforming is highlighted. The intriguing relation between orthogonality, reciprocity and losses is recapitulated. Different approaches on the design of orthogonal beamforming networks and implementation of zero-forced beamforming strategies are shown with various examples from the antenna-research-oriented literature. The use of orthogonal and zero-forced beamforming is discussed from the communication system perspective with relevant studies from diverse disciplines. Some of the future research challenges and potential benefits are outlined for the next generation satellite and cellular communication applications.@en

A novel analytically based synthesis technique for the design of sparse antenna arrays is presented. The proposed technique permits the synthesis of linear arrays with arbitrarily shaped patterns and it is applied here to the design of an Earth-coverage antenna featuring a shaped radiation pattern with an isoflux uniform illumination on the field of view (FOV).@en