Application of Hilbert spectroscopy to pulsed far-infrared radiation

We present our results on the development and characterization of a prototype of Hilbert spectrometer, which is intended to operate with pulsed far-infrared radiation. The new prototype consists of high-T_c Josephson detector in an optical cryostat, analog electronics with the bandwidth of 14 MHz, and a DSP-based data acquisition system, controlling spectroscopic measurements. The specially developed digital data acquisition system gives a possibility to operate in two regimes - with and without integration of the pulsed signal. The tests have been carried out using pulsed 94 GHz radiation with pulse duration of 200 ns and a pulse repetition rate of 1 MHz. A measuring time of 7 ms for a data set of 512 spectral points has been realized. It has been demonstrated, that in a broadband (≈10 MHz) regime of measurements without integration the developed spectrometer has a dynamic range of external signal power of 17 dB, which can be enhanced by using integration function.