A Robust and Fast Algorithm for ALMA Local Oscillator Power Amplifiers Optimization

I present here a new algorithm for the optimization of the local oscillator power amplifiers of all receivers in use at the Atacama Large Millimeter/submm Array, ALMA. The configuration of ALMA receivers (SIS mixers) is done by applying frequency-dependent pre-defined values of voltage and current extracted from a look-up table. The bias voltage is applied to the mixer by the bias voltage controller. The bias current, instead, is optimized indirectly by adjusting the power from the local oscillator. The algorithm presented here is able to guarantee fast and reliable optimization even with noisy control and response variables. This new algorithm has been implemented in the ALMA main control software starting from Cycle-5 (October 2017).