Nonstationary signals are used extensively in modern telecommunications applications. Due to their growing ubiquity, the radio spectrum gets saturated; hence the need for an equipment capable of analyzing a large band of the frequency spectrum. But, analyzing this spectrum in realtime is a complex task because we need a joint analysis in time and frequency, based on an adequate time-frequency representation (TFR). In this paper we present an architecture which computes efficiently and simultaneously the short time Fourier transform TFR of a given signal with different time-frequency resolutions. We also present the results obtained from a first prototype manufactured in 130nm CMOS.