| 摘要 |
PURPOSE:To form a trap at UHF band, by providing a coil in resonance at the UHF band with the capacitance of a PIN diode at back-bias on a signal line, at the attenuation of gain. CONSTITUTION:Coils 23, 24, 25 are added to a conventional attenuator circuit. The inductance of the coil 23 is selected so that parallel resonance at the UHF band can be made with a capacitor 18, lead inductors 21, 22 of a diode, and inductance of the coil 23, and an impedance between the input and output is increased and an impedance is provided between grounds with the coils 24, 25, allowing to form a trap at the UHF band and to obtain a large attenuation. In this case, the impedance between input and output is decreased at the VHF band, but the impedance between the coils 24, 25 and ground is small and the effect of a parallel resonance circuit is small and the deterioration at the VHF band is less. The attenuation of a pi type attenuator using a PIN diode at the VHF band is sufficiently greater, and the deterioration of attenuation more or less at the VHF band gives no hindrance. |
