Electromagnetic waveguides have dispersive properties, meaning the phase and group velocities change with frequency. This dispersion leads to broadening in the time-domain impulse response, which can make it difficult to separate adjacent signals if they overlap. To help address this issue, we present a dispersion-compensated algorithm for the analysis of electromagnetic waveguides. This algorithm maps signals measured in the frequency-domain to the distance-domain, and vice versa. It uses a priori information of the waveguide's propagation constant to compensate for dispersion and preserve features in the distance-domain impulse response, even over large distances. The dispersion-compensated algorithm has a variety of applications, including accurate distance-to-fault measurements and highly selective distance-domain windowing. For a simple demonstration, we show how the algorithm can be used to analyze data from a waveguide cavity resonator.

The state of development of receivers for submillimeter-wave radio astronomy is reviewed. Bolometers for continuum observation, hot-electron mixer receivers for narrowband spectral line observation, and heterodyne receivers, both Schottky diode and superconducting tunnel junction, are presented. At the lower frequency end of the submillimeter band, standard waveguide techniques, scaled from millimeter wavelengths, prevail. At wavelengths shorter than about 0.5 mm, quasioptical designs are preferred. In the case of Schottky diode receivers, corner cube designs are used almost exclusively, whereas integrated mixer designs are the focal point of research for superconductor-insulator-superconductor (SIS) receivers at these wavelengths. Although such designs are extensively reviewed, it is nevertheless the Schottky diode mixer remains the element of choice at the shortest submillimeter wavelengths.>