| The size of oscillators affects not only operating frequency, but noise levels as well. Thermal noise and nonequilibrium noise both are inversely proportional to size, while 1/f noise is proportional to size at quartz sizes below the phonon coherence length. The size limit for a specific sensor design is then limited by 1/f, thermal, and nonequilibrium noise. As the size of the resonator sensor decreases the normally dominant 1/f term decreases until it is not the limiting term. The ultimate lower size limit for any given BAW, SAW, or MEMS sensor design can thus be calculated for the first time from first principles based on the quantum 1/f formulas. Device design criteria are very important as the sizes and frequency domains of sensors become smaller and larger respectively. |
