Array of coupled phase-locked oscillators at 160 GHz

A ten-channel millimeter-wave heterodyne phase measurement system is currently under construction. This system will be used for electron density measurement at the plasma experiment W7-AS. The main features are: (1) twofold usage of each 160-GHz oscillator to excite both the transmitting signal to the plasma and the local oscillator (LO) signal for downconversion and (2) the phase-locked loops (PLL's) of each oscillator are coupled in a chain. The authors describe the millimeter-wave part and the digital PLL circuits of that system. Test results of the first three channels, which are already running in the laboratory, are presented.