| 摘要 |
1,141,087. Tuning arrangements; filter networks. HAZELTINE CORP. 25 Sept., 1967 [5 Oct., 1966], No. 43413/67. Headings H3Q and H3U. In electrical apparatus, having a variable resonant circuit 12a or 12b tunable over a given frequency band, a frequency-dependent coupling means 13<SP>11</SP> or 13<SP>1</SP> is connected to couple the input signal 10a or 10b and output load 11<SP>11</SP> to the resonant circuit so as to vary the coupling to the input signal and load inversely with respect to each other and as the resonant circuit is tuned over the range, to maintain the loading on the resonant circuit substantially constant such that the tunable bandwidth of the apparatus is maintained substantially constant. As shown the coupling means 1311 and 13<SP>1</SP> include capacitive and inductive components which vary inversely with respect to each other as the V.H.F. and U.H.F. tank circuits 12a, 12b are tuned over their ranges to maintain the loading and bandwidth substantially constant. The outputs from these circuits are connected to a transistor R.F. amplifier 11<SP>11</SP> of a television receiver which can feed a mixer. The two tank circuits 12a, 12b are mechanically coupled so that when one tuning element V.H.F. or U.H.F. is engaged the other element U.H.F. or V.H.F. is disengaged. The impedances of the capacitor 19 and inductor 22, capacitor 23 isolate the U.H.F. and V.H.F. circuits from one another when one is selected. The tank circuits can include single or double parallel connected capacitor and inductor arrangements (Figs. 2 and 3, not shown), having variable inductors. |
