Unique features of the CHILL radar system

The University of Chicago and Illinois State Water Survey (CHILL) has been in operation since 1972 and has proven valuable in a number of ways. It has been utilized in a variety of atmospheric projects in Colorado, Illinois, Oklahoma, and Michigan. Primary attention is devoted to the coherent data processing and the coherent receiver. Certain difficulties frequently associated with the use of conventional coherent receivers are avoided in the CHILL with the aid of a special scheme. The instantaneous power received in a particular range gate is used to control variable attenuators which are in front of the linear receiver. There are 3 attenuators with attenuation of 6, 12, and 24 db. The linear receiver has a dynamic range of about 35 db. The net result of the configuration is two digital numbers in 'floating point' format.