JPS54102942A - Antenna circuit - Google Patents

Abstract

PURPOSE:To obtain a balun device which features excellent insulating performance, the reduced number of component parts and the low cost by forming the lines for matching of 300OMEGA and 75OMEGA on the both surfaces of the insulator panel via the print wiring and based on the logic of the 4-wire balun system. CONSTITUTION:The balun device, which functions as the impedance balance- unbalance converter of the antenna input circuit in the TV receiver or the like, is formed with insulator panel (e). Both input-side 300OMEGA line (f) and output-side 75OMEGA line (g) are formed on the surface and the back of panel (e) via the print wiring. The connection to the external circuit of the antenna circuit is given via terminal 2 and 3, and the connection to the internal circuit of the tuner or the like is secured via terminal 1 and 4 respectively. The circuit constant such as the length, width, etc. of the wiring is set for the circuit based on the logic of the 4-wire balun system. Thus, the good insulation is obtained via the insulator panel between the primary and secondary sides. And the protective circuit such as the capristor and the like and the DC cut-off capacitor can be omitted, thus reducing the production cost.