Detection of extensive cosmic ray air showers by measuring radio emission
So far, cosmic ray air showers have been detected using scintillation counter arrays on the ground widely. And also air Cherenkov detection method, which is limited its observation period in moonless nights, has been adopted. The detection method of radio emission from cosmic ray air showers is not new, but rather old method. Radio emission from cosmic ray air showers has not been detected with the method of self-trigger system. If the detection method of radio emission were available, there is no limit of the observation like Cherenkov counter. The developments of high radio frequency (RF) technology might make the detection of radio emission from extensive air showers possible. Antennas calibrated in laboratory are available. With those antennas, we can directly obtain the absolute intensity of radio frequency from cosmic ray air showers. Main issue to detect radio emission is that signal level is quite low. The thermal noise particularly causes background noise source. Those issues and detection method are discussed. We also describe an antenna detection method to generate self-trigger signal and a method to identify air shower events from natural and artificial noises.