| 摘要 |
978,252. Amplitude modulation. STANDARD TELEPHONES & CABLES Ltd. April 5, 1963 [April 9, 1962], No. 13692/63. Drawings to Specification. Heading H3R. A double balanced transistor modulator uses only two transistors and a pair of identical output transformers with, in some cases, an input transformer, the carrier being applied to the transistor bases to render conductive the emitter/collector paths alternately and thereby short-circuit the modulation applied to each output transformer alternately with accompanying phase reversals of the modulation output in accordance with the alternate switching action of the carrier. Alternatively, a single output transformer with two symmetrical but phase-reversing half-portions, each including the emitter/collector path of a transistor, may be used, the transistors being rendered conductive alternately, with phase reversal, through each half of the output transformer. The transistors may be symmetrical or, if not, the transformer winding turns being proportionately arranged to balance the different emitter and collector currents. Also the transistors may be of opposite types (i.e. PNP and NPN). Specifications 471,548 and 808,396 are referred to. |
