GB1535390A - Uhf tuner - Google Patents

Abstract

1535390 Resonators MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 16 Aug 1976 [19 Aug 1975] 34072/76 Heading H1W [Also in Division H3] A UHF tuner comprises a metal plate 13 stamped to form an outer conducting portion surrounding an opening and strip portions extending from an edge of the opening into the opening to form a resonance line 14 and a coupling line 19, 64 and a variable capacitance element 38 connected between the resonance line and the outer conducting portion to form a tunable resonant circuit. As shown, this provides the input circuit to a common base RF stage 134 having AGC applied at 86 to its base. Further similar resonant circuits are provided by metal casing 13 to provide resonance lines 15, 16 and 17 and coupling lines 20 and 21 associated with an inter coupling stage 138 and a transistor oscillator 135. A mixer diode 52 provides the IF output at 84. Tuning is obtained by variable capacitance diodes 38- 41. The lengths of the one-quarter wavelength transmission lines 14-16 can be changed by moving short-circuiting plates 26, 27 and 28 by inserting an insulating rod through bores 29- 34. Adjustment of trimming capacitor plates 22-25 is obtained via holes 2-4 in the cover plate 1, Fig. 2, which holes are covered by conductive foils 5-7. Connecting lines 35 and 36 together with holes 79 and 80 function to tap down the couplings of the coupling lines 19 and 20 to the resonance lines 14 and 15. A window 18 enhances the coupling between the resonance lines 15 and 16. The metal case 8 serves as a shield to prevent external radiation of the electromagnetic field generated by the lines. The coupling portion (92, Figs. 3 and 4, not shown) is cut after the wiring operation into separate portions 90 and 91. Modified arrangements of the openings and strips forming the lines are disclosed (Figs. 6 and 7, not shown). Lines (126 and 127) form a half-wave length resonance line when coupling portions (128 and 129) are cut away after wiring.