ISSCC 2005 / SESSION 4 / TD : MIXED - DOMAIN SYSTEMS / 4 . 5 4 . 5 Towards Chip - Scale Atomic Clocks

The performance of many electronic systems is often limited by the performance of the clocks they use. For example, a receiver in the Global Positioning System (GPS) works by attempting to align an internally generated pseudorandom signal to an identical signal sent by a satellite and measuring the phase difference between the two. The receiver then calculates the time required for the satellite signal to reach the receiver, and thereby gives the distance between the satellite and the receiver. In this system, accurate timing is needed not only for precise determination of distance, but also for fast acquisition of the satellite signal and resistance against jammers. Countless other examples can be cited where timing determines the ultimate performance of a system, from parallel A/D converters, to spread-spectrum communications. In such applications, atomic clocks could greatly enhance the performance of the system. Unfortunately, however, the size and power consumption of atomic clocks has been prohibitively large for many portable applications.