Stability and linearity requirements of instruments used in radioastronomy are especially severe. This thesis describes on one hand the design and construction of a continuum detector fulfilling these requirements. A theoretical study demonstrates that the Schottky diode detector can not provide satisfactory characteristics. The deetector built here, built around tunnel diodes, exhibits a noise close to the limits imposed by fundamental physics. It has nonetheless been kept simple. The following chapter describes the design and construction of the acquisition electronics for a wideband acousto-optic spectrometer and studies its characteristics under realistic operating conditions. It includes the descriptionof a simple method which allows to get rid of the differential linearity errors of analog-to-digital converters. The validation of the spectrograph performance is based on the comparison with two other, identical, filterbank spectrometers. On the scientific side, the reports presents the observations of several objects of the solar system surrounded by an atmosphere and the interpretation of the data in the case of Titan.
