| 摘要 |
PROBLEM TO BE SOLVED: To provide a FSK (frequency shift keying) modulator which eliminates an external element, simplifies an oscillation circuit constitution by reducing the number of a switching circuit element, and reduces the influence of a transient phenomenon by an operation of a SW circuit, at the switching frequency. SOLUTION: The FSK modulator 10 has two oscillation states for a piezoelectric substrate, IDTs of a main IDT, a gate IDT and a sub IDT and a pair of reflectors are arranged at both sides of the IDT, a two-modes-and-two-ports type SAW resonator 101, an amplifier 100 and the switching circuit 102 are provided. A SAW oscillation circuit is constituted, by connecting a primary input side terminal pair of the two-modes-and two-ports type SAW resonator 101 to the amplifier 100 of an oscillator. Spaces of a secondary output side terminal pair of the two-modes-and-two-ports type SAW resonator 101 are connected via a single piece of the switching circuit 102, and a first oscillation frequency fL or a second oscillation frequency fH, which is slightly different from the first oscillation frequency fL is generated by opening and closing the switching circuit 102. COPYRIGHT: (C)2008,JPO&INPIT
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