Study of a New GPS-Carriers Based Time Reference with High Instantaneous Accuracy

A possibility to obtain a new time reference constantly locked to the Caesium-derived GPS satellites carriers was investigated by means of a new GPS receiver architecture able to lock the two GPS carriers and mix them to obtain a reference frequency with an accuracy close to the GPS one. This is very important in Perceived Power Quality distributed measurements systems where the exact knowledge of the events on the geographic compass is strongly joined to the capability to associate them an accurate time. A simulation of the carrier tracking loop has been performed. It shows how choosing appropriately the frequency of the low-pass filter of Costas loop, a modified PLL typically used in GPS system, it is possible to recover carriers in presence of high noise to signal ratio too. The front-end of the system able to select GPS frequencies, which is the first block of the entire system, was also realized.