Filters for RFI Suppression in AERA Radio Detection of Cosmic Rays

The Auger Engineering Radio Array (AERA), located within the Pierre Auger Observatory is the radio detector of ultra-high energy cosmic rays. The frequency range investigated by AERA radio detectors is 30 - 80 MHz. However, this frequency range can be seriously polluted by radio-transmitters and others radio frequency interferences (RFIs). RFIs should be significantly suppressed to increase a signal to noise ratio to avoid spurious triggers. Recently the 200 MW solar farm is considered to be built inside the area of the Pierre Auger Observatory, the largest groundbased Observatory of the ultra high-energy cosmic rays. A conversion of 200 MW into high-voltage current will introduce a significant noise in a measured spectrum. Reliability and stability of small cosmic rays signal with a huge background becomes a crucial issue. The paper compares several (currently in use and proposed) RFI filters used in AERA.