Distributed-switch Dicke radiometers

摘要

A radiometer on an orbiting spacecraft derives high spatial resolution information from terrestrial and atmospheric regions. N elements or subapertures on the spacecraft transduce electromagnetic energy into electric signals.Many or all of the elements are simultaneously illuminated by electromagnetic energy radiated from the same region. Identical, parallel processing channels are responsive to the N elements. Each of the channels includes a variable gain amplifier responsive to the signal transduced by its corresponding array elements. The gain of each amplifier is controlled as a function of the output difference when the channel is connected periodically to each of a pair of Dicke noise sources, such as resistors maintained at predetermined temperatures. Output signals from the different channels, indicative of radiation from subregions of the terrestrial region, are combined phase- coherently to derive a further signal that is a replica of the radiant energy from the subregion and indicative of the vector sum of the energy illuminating all of the elements of the array.