Experimental investigation on the operation of SAW devices at harmonic frequencies with stepped-finger interdigital transducer

Stepped-finger IDTs operate at one desired harmonic, while suppressing fundamental and all other harmonics. However, if the IDT is used at microwave frequencies, a proper experimental study of some structural problems which may potentially have an affect on the response would be needed. This paper describes the feasibility of using the stepped-finger IDT at microwave frequencies. SAW delay lines operating at the 5th harmonic frequencies of 2.3, 3.4 and 4.6 GHz are studied. As a result, it is found that the degree of suppression of fundamental decreases as the 5th harmonic frequency is raised. This paper also describes the application of the stepped-finger IDT except for filters and delay lines. A 2-port SAW resonator operating at the 5th harmonic frequency of 1 GHz is studied and the resonator which has a loaded Q of 5000 is obtained.