A voltage controlled oscillator for obtaining a frequency reference constantly locked to L1 GPS carrier for Power Quality assessment applications

The need to correlate as accurately as possible Time to the power quality events pushes towards the necessity to develop circuits able to yield a time reference that is referable to International Time Standards. Moreover, the necessity to deploy distributed power quality monitoring systems requires these time references to be easy to disseminate, making them available on specific monitoring sites. In this paper, the possibility to obtain a time reference continuously traceable to a Cs133 atomic standard is proposed, by locking the Cesium-derived L1 GPS satellites carrier by means of a specifically designed GPS receiver. Such time reference would simply require visibility of one GPS satellite in order to be operative. In particular, the overall architecture of such receiver will be first outlined and then attention will be focused on the design and realization of the VCO which is one of its fundamental building blocks. Measurements carried out on a prototype of the proposed VCO show that its performances are adequate for the aim.