Abstract: A top loaded antenna is provided that is composed of a triangular-shaped resonator and a dielectric substrate. The triangular-shaped resonator is located on a first plane with its top connected a vertical rectangular strip and its bottom connected to a microstrip feed line through a smooth tapering strip. There is one grounded strip on both sides of the smooth tapering strip in parallel to the rectangular strip load, where each grounded strip is connected to a grounded metallic plate on a second plane through a plurality of via holes. The present invention utilizes the top loading technique and the smooth tapering technique to create the design of a compact and built-in antenna which will provide a planar antenna structure with broad bandwidth and high radiation efficiency. The inventive antenna has a very even radiation field on the horizontal plane and is thus ideal for the radio transceiver used in mobile communications.