说明：  The horn antenna is widely used in the transmission and reception of RF microwave signals. It is usually an assembly of flaring metal, waveguide and antenna. Beyond the fundamental knowledge of microwave propagation, it is essential in the design of horn antenna to understand the intricacies and design considerations at two important ends: the points of propagating microwaves and points of intercepting microwaves. Great care must be taken at the receive ends especially if it involves astronomical applications where the microwaves to be intercepted are from extra terrestrial sources extremely far away and hence very weak. This paper highlights the design considerations of a horn antenna which are fundamental principles employed in the design of a compact horn antenna that will be suitable for astronomical application at