Ultra Stable Centralized FEE Voltage Reference Unit (RU) - 2011

The RU is developed during the GRS technology demonstrator project for ESA, in order to achieve an ultra stable centralized voltage reference with the stability of 1 ppm/sqHz at 0.1 mHz.

The main functions of the RU are as follows:
[1] Biasing the Test Mass (TM) with the tunable AC voltage via injection electrodes
[2] Biasing the TM caging mechanism plunger with the ON/OFF switchable AC voltage
[3] Providing the DC voltage references to the Front-End Electronics (FEE) ADC and DAC circuits
[4] Providing the House Keeping information to the Sensing Actuation Unit (SAU)

The main design concept of the RU to achieve 1 ppm/sqHz stability at 0.1 mHz is to stack n pieces of stable voltage references, so that the total noise could be reduced by square root of n.