US 4,795,990 AGranted

Trap circuit with two variable inductors

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsTakayoshi Ishikawa, Yasuhiko Yoshida

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Abstract

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.

Claims9

Dependent claims

A trap circuit comprising:

(a) a delta connection circuit having a resistor and first and second capacitors connected to said resistor, said delta connection circuit having an input terminal at a first junction, between said resistor and said first capacitor, and an output terminal at a second junction, between said resistor and said second capacitor.
(b) a first LC tank circuit having a first inductor and a third capacitor, one junction between said first inductor and said third capacitor being grounded, and
(c) a second LC tank circuit having a second inductor and a fourth capacitor, said second LC tank circuit being interposed in a series connection between a junction of said first and second capacitors of said delta connection circuit and the other junction between said first inductor and said third capacitor of said first LC tank circuit,
said series connection comprising a connection of a first junction of said second LC tank circuit to said junction of said delta connection circuit and connection of a second junction of said second LC tank circuit to said other junction of said first LC tank circuit.

1 more element

Dependencies are inferred from the claim text.