Self resonant IDT as a grating reflector of surface acoustic waves

An IDT, when resonantly loaded by a pure inductance, behaves as a perfect reflector of SAWs. It is shown that this ideal condition can be approached by using the self resonance of an IDT. The reflection coefficient of the self resonant IDT is calculated to be about 0.96 and is observed to be in the range 0.93 to 0.95. It is demonstrated that the frequency of self resonance at which the reflection peak and hence the transmission null occurs can be shifted by an external capacitor connected across the self resonant reflector IDT.