Resonators are frequency-selective electronic circuits that can produce a fixed (resonant) frequency when properly excited. The value of the resonant frequency depends on the circuit’s components. There are several basic types of resonators. Ceramic resonators are built with piezoelectric ceramic materials that have suitable mechanical resonance properties. They produce a vibrating frequency that is a function of the resonant frequency applied. Surface acoustic wave (SAW) technology generates elastic waves that propagate on the surfaces of specific materials. The energy density of the waves is confined to a depth of no more than one wavelength. Typically, SAW devices have a high frequency selectivity, low insertion loss, and can be manufactured in small size chips or dies. Resonators with quartz crystals or passive electronic components are also available. RC resonators include resistors (R) and capacitors (C). LC resonators include inductors (L) and capacitors (C).