A method of determining characteristics of a signal and an apparatus using the method. The apparatus for determining characteristics of a signal includes: a level detector receiving sample values of a radio frequency (RF) signal and binary data obtained by binarizing the RF signal, generating selection signals based on the binary data, classifying each of the sample values of the RF signal into one of a plurality of levels using the selection signals, and outputting average values of sample values of each level; and a signal characteristics determiner determining a characteristics value that indicates the characteristics of the RF signal using the average values of the sample values belonging to each level.