| 摘要 |
PURPOSE:To obtain flat characteristics of a passing band with sharp rising and falling characteristics, by providing a means of lowering the Q value of a resonance circuit which consists of a capacitance and an inductance element for compensating the capacitance. CONSTITUTION:A variable resistor 26 connected in parallel to an inductance element 25 operates as a damping resistance which lowers the Q value of a resonance circuit, and consequently its resonance characteristics are adjusted. The total characteristics of the whole of an SAW (surface acoustic wave) filter circuit are those obtained by mixing amplitude characteristics that the SAW filter itself has and the resonance characteristics of an LC parallel circuit. Selecting a prescribed Q value by varying the variable resistor 26 compensates the frequency characteristics of the SAW filter itself to provide the whole of the SAW filter circuit with sharp rising and falling characteristics, and flat frequency characteristics of a passing band. |
