DESIGN AND CONSTRUCTION OF ULTRA HIGH FREQUENCY YAGI UDA ANTENNA

Antennas are introduced in general then one type of the antenna is been focused on which is the YagiUda in this paper. Also this paper outlines the process of designing a four element Yagi-Uda antenna that consists of one driven element, one reflector and two directors on software called CST to achieve specific requirements which are 500MHz operation, minimum power reflected back to the source and maximum gain with minimum front-toback ratio. The effects of changing the lengths of the elements in the antenna designed will be shown. The final antenna design with simulations of the S-parameters for both CST are presented in this paper. This project ‘the design and construction of Yagi-Uda antenna for UHF reception’ was aimed at local design and fabrication of yagi antenna capable of UHF reception. This project will find application in radio broadcasting, Broadcast television, Two-way radio, communications receivers, Radar system, Cell phones. The figures were obtained by using network analyzer. The antenna usually connected to port of the network analyzer and then the scattering parameter was measured. The power sent out through port 1 was referenced to 0 dB. There are some losses of approximately 2.5 dB for frequencies 450MHz to 500MHz.The loss of about 1dB which accounts for the losses incurred prior to antenna radiation. The remaining 1.5dB loss could be due to our cabling system. In order to test for the directivity of the Antenna constructed. This antenna was designed to operate at a frequency of 500MHz which is within the bandwidth of the antenna. In this scenario, the antenna acts as a transmitter while is a receiver. By rotating the antenna through 180 degrees in 10 degrees steps and recording the received power at each instance, one is able to determine the directivity. The recorded powers are then normalized to the maximum value and plotted to show the relative variation of the received power in Db.