Parametron

an element in automation and computer technology based on the parametric excitation and amplification of electromagnetic oscillations. The simplest parametron is an oscillatory circuit tuned to a frequency f₀. When one of the energy-storing parameters is varied periodically by a pump signal at a frequency f_p approximately equal to 2/o, an oscillation is generated at a frequency f_g = f_p/2 ≈ f₀; the generated oscillation is coherent with respect to the exciting oscillation. The phase of the oscillations excited in a parametron can assume one of two values; these values differ by 180° and are conventionally designated as 0 and π. The phase can remain in this state as long as desired. The parametron’s capability to select one of two stable phases is known as the phase-quantization feature. The parametron was invented by the Japanese scientist E. Goto, who patented it as a logic element or cell in a memory unit in 1954. Parametrons have been used in constructing counters, registers, adders, memory units, and computer control systems.

Parametrons are classified according to the type of nonlinear element as inductive (using ferrite cores and magnetic films), capacitive (using parametric semiconductor diodes and ferroelectric capacitors), or resistive (using tunnel and other semiconductor diodes with a volt-ampere characteristic that has a decreasing portion). The switching rate—clock frequency f_c—of a parametron is proportional to the pump frequency, which is 20 to 50 times greater than f_c. The most reliable and inexpensive parametrons are the single-circuit inductive types that use ferrite cores, have a power requirement of 15 to 50 milliwatts, and have f_c ≤ 100 kilohertz. Capacitive parametrons using capacitors are more economical (3 to 6 milliwatts) and have a faster speed (f_c ≈ 5 megahertz). Resistive parametrons are even faster because the time needed to establish oscillations is comparable to the period of the natural oscillations in the circuit. Inductive parametrons using thin magnetic films and capacitive parametrons using semiconductor diodes have a clock frequency of up to 150 megahertz. The development of parametric light amplifiers and generators has made it possible, in principle, to work with frequencies in the optical band. Such a development should bring a substantial improvement in parametron speed.