Trap circuit with two variable inductors

摘要

In a bridge T type trap circuit having CR delta connection circuit and a variable LC tank circuit, the CR delta connection circuit is connected to the LC tank circuit via a variable inductor (19; 31, 33; 40). In one embodiment, a capacitor (18) is coupled with the variable inductor (19; 31, 33) to form another LC tank circuit. In another embodiment, a variable inductor (39) used in the first-mentioned LC tank circuit has a tap which is grounded. Impedance values of the first-mentioned LC tank circuit and the variable inductor (40) are adjusted so that absolute values of real and imaginary parts thereof have a given relationship. A resistor (22) of the CR delta connection circuit is used in common in a double-trap structure having two CR delta connection circuits and two series circuits each having two LC tank circuits.