The signal path is outlined in Fig. 5.3. It shows the signal and LO paths for one antenna and one receiver band. The high frequency part (receiver) was described in Chapter 3. The amplified first IF output (1275-1775 MHz) is down-converted to the 100-600 MHz band and transported to the central building in a high-quality cable. Before down-conversion, the band shape is modified by a low-pass filter; since the LO2 is at a higher frequency than the IF2, the bandpass will be reversed in the conversion, and this by anticipation compensates for the frequency dependent attenuation in the cable (which is of course higher at the high-frequency end of the bandpass).
The 100-600 MHz band arriving in the central building is directed to the correlator analog IF processor inputs (with a division by 6 since there are 6 identical correlator units) and to total power detectors which are used for the atmospheric calibration and for the radiometric phase correction.