Frequency conversion circuit in television tuner

Abstract

Abstract PURPOSE:To obtain the optimum matching conditions for each band, by varying the value of an inductance, provided between the input electrode of a frequency converting transistor (TR) and a preceding circuit, according to band switching. CONSTITUTION:Coils L1 and L2 are interposed in series between the gate G1 of a field effect transistor Q1 which constitutes a VHF mixer and UHF-IF amplifier, and a preceding circuit 3 between VHF stages, and a coil L3 is interposed between the connection point (a) between the L1 and L2 and an UHF intermediate filter 15. The conductances of those coils are so assumed as L3+ L2>L1+L2>L2. For this purpose, switching diodes DS1 and DS2 are turned on and off to select one of low and high VHF bands and an UHF.IF band, and then the connection relation among the coils is as shown in the 1st table, so that inductances increase until the frequency decreases, thus obtaining the matching between the preceding circuit and the gate G1 of the FETQ1.

Inventors

• 👤 Masakazu Teraoka
• 👤 正和 寺岡
• 👤 Akira Usui
• 👤 晶 臼井
• 👤 Masakazu Aya
• 👤 綾　眞和
• 👤 Akihisa Wada
• 👤 昭久 和田
• 👤 Kenji Katayama
• 👤 片山　賢「じ」
• 👤 Tadaaki Nishiguchi
• 👤 西口　忠昭

Bibliographic Details