VOLTAGE CONTROLLED OSCILLATOR

摘要

PROBLEM TO BE SOLVED: To vary the VHF through SHF bands in a wide range and also to secure the high stability for a voltage controlled oscillator by forming a lead zilconate titanate(PZT) thin film or a piezoelectric thin film of lead titanate(PT) on a monocrystal substrate and using a piezoelectric resonator obtained by forming a conductive film on the piezoelectric thin film. SOLUTION: A voltage controlled oscillator uses a 1-port or 2-port type surface acoustic wave resonator having a comb-line electrode consisting of a piezoelectric thin film formed on a monocrystal substrate and a conductive film formed on the piezoelectric thin film. The piezoelectric thin film consists of a PZT thin film or PT. For instance, a buffer layer(BST thin film) 52 of 0.2μm thickness, a PZT thin film 53 of 0.8μm thickness and Al electrodes 54 of 1500Åthickness are formed on a sapphire(monocrystal) substrate 51 of 500μm thickness to obtain a piezoelectric substrate 50. Then a gap W is set at 2μm (1/2 surface acoustic wave lengthλ) between Al electrodes 54 (a repeller 54A, a comb-line electrode 54B).