MODULATION AND DEMODULATION WITH SEMI-CONDUCTORS
MASSACHUSETTS INST OF TECH CAMBRIDGE ELECTRONIC SYSTEMS LAB
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Initial investigation of modulation and demodulation systems which employ transistors was concerned with classifying such systems in a manner which permits logical study and analysis. This work led to a classification system which considered linear, time-varying systems as first order, and nonlinear, square-law systems as second order. Further distinction was made between continuous-data systems in which the sensitivity function exhibits only discrete zero crossings, and sampled-data systems in which the sensitivity function possesses some characteristic distribution of finite intervals where the function is zero. Analyses were made of first- and second-order systems. The use of transistors as controlled-sensitivity devices was discussed for grounded-base and -emitter operation. Results derived experimentally from carrier-present and -suppressed systems which utilize transistors as time-varying parameters indicated that the transistor systems exhibit limited frequency response because of the intrinsic nature of the transistors, and that transistors offer no decided advantages over vacuum tubes with respect to linearity and distortion- free operation but are better than diodes in almost every operational aspect.
- Electricity and Magnetism