A quasi-"Isotropic" antenna in the microwave spectrum

The general problem of radiation by apertures on spherical surfaces was first considered theoretically by Stratton and Chu in 1941. More recently, the problem was again considered by Bailin and Silver, and Mushiake and Webster. All numerical and experimental efforts to date have been restricted to the special case of a very small sphere as measured in wavelengths. This paper is in effect an extension of the previous results to the case of large spheres uniformly excited by an equatorial slot of varying size. The detailed numerical and experimental results are restricted to the first TM and TE modes. In general, it is possible to show that the large spherical slot antenna can be made unusually "isotropic" with a far-field coverage factor of over 98 per cent.