Optimal Design of Yagi-Udi Antenna for VHF Band Application Using Magus 2.2 Software

This paper presents an optimal design of low cost Yagi Udi antennas. The design targets the field strength in the main beam to be larger than a critical minimum value, the directivity to be large enough over the whole frequency band, the antenna’s input impedance to match the generator reasonably well over the entire band and that the VSWR be small. Nigerian Television Authority, Makurdi Network centre in Nigeria parameters was used. It transmits at VHF, operating on Channel 13 (215 218) MHz. The specification was used to calculate values for the antenna dimensions to be used for the simulation. Antenna Magus 2.2 software was used to simulate the optimal designed conditions of the Yagi-Uda antenna. For this design, the director spacing of the designed antenna was varied while maintaining the spacing between the first director and keeping the driven element constant. Optimal design was obtained at a gain of 14.37 dBi and frequency of 223.7 MHz. Peak real impedance of the antenna was attained at 134.61Ω with a corresponding frequency of 259.7 MHz and the Real impedance at zero-crossing frequency increased to 334.0 Ω at Frequency 200.9 MHz. The VSWR of as low as 1.463 was obtained at frequency of 212.8 MHz, which falls within the VHF operating frequency. These results show a significant reduction in the value of VSWR and increase in both gain and bandwidth.