Untuned systems for the calibration of electrical noise sources

The design of untuned radiometers is demonstrated. The resulting systems allow for broader band operation. The coaxial system described is more amenable to multi-frequency operation under computer control, and in principle can measure at any frequency within the 10 MHz to 18 GHz band. Computer controlled multi-frequency operation of the mm-wave systems is limited by the unavailability of suitable tuneable band-pass filters. However, investigations are proceeding in an attempt to exploit some of the recent developments in the quasi-optical field.<>