Ultra High Frequency (UHF) is a electromagnetic radiation. Especially its frequency is between 300 MHz and 3 GHz (3,000 MHz). Because of short wavelength, UHF has strong directivity and it has small area. UHF is commonly used for television signals. It is strong enough to be protected from other signal, but because of its strong directivity, receiving error by an obstacle occurs more. Hence it needs sensitive sensors.