| 摘要 |
On an upper surface of a substrate (1), conduction paths (2a, 2b, 2c) circularly extend greater than just one circle and constitute ring units of oscillation in such a manner that the two ends of each conduction path (2a, 2b, 2c) are adjacent to each other in the width direction, and those units of oscillation are concentrically multiplexed. In this way, a part where the two ends of each conduction path are adjacent to each other is caused to serve as a capacitive region; the other parts are caused to serve as inductive regions; and each conduction path is caused to serve as a half-wave path with its two ends opened. There is no need to provide any grounding electrodes to the surface of the substrate opposite to the surface where the conduction paths are provided. As a result, an oscillator can be made by use of a very small number of constituent elements. In this way, there can be obtained an oscillator, a filter, a duplexer and a communication apparatus that can be easily made small in size and exhibit a desired Q-response appropriate to the manufacturing cost.
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