| 摘要 |
633,397. Impedance networks. ANDREWS, E. F. Aug. 19, 1947, No. 23030. Convention date, April 10, 1941. [Class 40 (viii)] [Also in Group XL(c)] A filter network 76 ... 83, Fig. 1, for producing a restraining voltage for a radio tuning device (see Group XL (c)), comprises two coupled tank circuits tuned to the intermediate frequency and arranged so that at the intermediate frequency the electrostatic and electromagnetic couplings are equal and opposite to give zero coupling at resonance. The first circuit comprises elements 76, 78, 79, 80, 81, 83 and the second comprises elements 79, 81<1>, 82, 83. The coupling through condenser 79 is inversely proportional to the frequency while the coupling through inductance 81<1> is proportional to the frequency. These are made to cancel at the intermediate frequency and resistor 80 is selected to give correct phase opposition. This gives substantially zero voltage across condenser 82 at resonance. Fig. 5 shows the physical arrangement of the filter elements 76 ... 83. Windings 76, 76<1> and 81<1> are carried on an H-shaped insulating member 201 carried by a grounded metal plate 200, to the upper side of which is fixed an insulating plate 202 carrying adjustable condensers 81, 82. Condensers 79, 83 and resistance 80 are supported by their conductors, and the whole unit is enclosed in a screen 106. Fig. 6 shows a modified form of filter circuit for producing the restraining voltage. It comprises a first tank circuit constituted by winding 76, adjustable condenser 220, inductance 222, 223, condenser 224 and condenser 78. The second tank circuit is constituted by condenser 224, inductance 226 and adjustable condenser 228. Both circuits are tuned to the intermediate frequency and are coupled inductively by coils 222, 223, 226, and capacitatively by condenser 224. These couplings are equal and opposite at resonance, and phase adjustment is carried out by resistance 230 and a small condenser 232. |
