  Proper modelling of astronomical receivers is vital: it describes the
systematic errors in the raw data, guides the receiver design process, and
assists data calibration. In this paper we describe a method of analytically
modelling the full signal and noise behaviour of arbitrarily complex radio
receivers. We use electrical scattering matrices to describe the signal
behaviour of individual components in the receiver, and noise correlation
matrices to describe their noise behaviour. These are combined to produce the
full receiver model. We apply this approach to a specified receiver
architecture: a hybrid of a continous comparison radiometer and correlation
polarimeter designed for the C-Band All-Sky Survey. We produce analytic
descriptions of the receiver Mueller matrix and noise temperature, and discuss
how imperfections in crucial components affect the raw data. Many of the
conclusions drawn are generally applicable to correlation polarimeters and
continuous comparison radiometers.
