| 摘要 |
The invention concerns a narrow- band bridge-connected crystal filter having a tunable input transformer the secondary of which is centre-tapped. One end of the secondary is connected to the branch of the bridge containing the crystal connected in series with a capacitor. The bandwidth of the transformer is at least 20 times the design bandwidth of the crystal filter. The series-connected crystal and capacitor are shunted by a fixed and a variable capacitor connected in parallel with each other. <IMAGE> |
