<title>Wideband digital autocorrelator for FIRST</title>

We are developing a wide band hybrid digital autocorrelator spectrometer suitable for the FIRST-HIFI instrument. At this time we have a prototype which is able to analyze four bands of 175 MHz each with a two bit three level digitizer clocked at 400 MHz. The correlation begins in a 64 channel Gallium Arsenide ASIC (Application Specific Integrated Circuit) clocked at 400 MHz and ends in a classical CMOS circuit at a lower frequency. The Gallium Arsenide technology presents several advantages for space applications, among which one can cite: (1) the power does not vary with the frequency of the signal analyzed, (2) the technology is very little sensitive to radiation. Our circuits are cascadable so that if several circuits are associated, we can build a versatile spectrometer with variable bandwidth and resolution. This presentation consists in a full description of this prototype spectrometer and a review of the current test results. We will also present a design of a spectrometer using the same technology and which will fit the needs of the heterodyne instrument of FIRST.