ALMA | ... In this section, we explain why we need to correct phase fluctuations and ALMA's strategy to do this. Rapid fluctuations will be corrected with water vapour radiometers (WVRs). The Cavendish Astrophysics Group was also a leading contributor to the ALMA prototype WVRs, which were put through their paces in tests at the Submillimeter Array (SMA). ... The Cavendish Astrophysics Group in partnership with the Onsala Space Observatory built two prototype WVRs for the ALMA project. ...

... The design employs a differential structure. ... The input is adapted to 100 differential, and the outputs use standard Low Voltage Differential Signaling (LVDS). ... T/H SINGLE T/H Single Input T/H Single Output 1.35 0.15 0.2 T/H DIFFERENTIAL Input T/H Output T/H 0.1 1.3 0.05 volts volts Figure 5: Digital part and digital gate 0 1.25 -0.05 -0.1 1.2 Integrated Test System A test system is integrated on chip to evaluate the transmission to the data acquisition card (fig: 7). ...