Abstract: Disclosed is a fully digital spectrum analyzer which includes a digital frequency translator that makes it possible to effectively analyze frequency bands that do not start at zero frequency. With the translator, the available spectral lines can be within the band of interest and not wasted in the range from zero frequency to the start of the band, and as a result the band is examined at optimal resolution. The translation takes place after the signal to be analyzed has been digitized, and the translator time-shares much of the conventional circuitry of the spectrum analyzer, to thereby minimize the cost of translation. Additionally, the spectrum analyzer includes an analog network that reduces the frequency of very fast signals so they can be analyzed by a spectrum analyzer having a relatively low upper frequency limit.

Abstract: A dual slope analog-to-digital converter, which has an autozeroing circuit for cancelling out integrator and detector offset and drift, is additionally provided with a circuit for injecting a voltage of selected polarity and magnitude to offset the input voltage of the converter such that the input voltage can be measured with respect to a nonzero reference line.