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IEEE 254
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IEEE 254 1963 Edition, November 15, 1963 Standard Definitions of PARAMETRIC DEVICE TERMS
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Description / Abstract:
INTRODUCTION
While the term parametric amplifier implies a device which operates by virtue of the variation of some parameter, resistive or reactive, current usage applies it to circuits in which only a reactance is varied. When applied to electron beam devices and devices employing distributed nonlinear media, the variable parameter is equivalent to a reactance in the sense that it is associated with energy storage rather than energy dissipative properties of the beam or medium. The qualifier, reactance, is more frequently applied to circuits in which the variable element is an easily identified lumped reactance. The qualifier, parametric, is more frequently applied to electron beam and distributed parameter devices, but can include the variable reactance devices as well. Thus in any of the following definitions, reactance may be used in place of parametric. These definitions are intended to exclude devices which operate by virtue of variable resistance or negative resistance.
There is some confusion as to whether a reactance amplifier operates by virtue of a nonlinear reactance or a time-varying reactance. It is recognized here that while all practical embodiments make use of nonlinear elements, the effect of the pump is to make them behave as time-varying elements. Thus in its simplest form, the concept of a reactance amplifier is based on the assumption that the pump is sufficiently large and the signals are sufficiently small that the nonlinear element can be replaced as far as the signals are concerned by an equivalent, linear, time-varying element. In these definitions the small signal restriction is assumed.
There is some past usage which has made the term amplifier apply to any device having power gain even though the input and output signals are at different frequencies. While these definitions permit this usage, it is recommended that the term amplifier be restricted to those devices having the same input and output frequency, and its application to frequency converters is deprecated.
There exist devices for which the names are composites of the following terms. No definitions have been given for such combinations where the meanings are sufficiently obvious
While the term parametric amplifier implies a device which operates by virtue of the variation of some parameter, resistive or reactive, current usage applies it to circuits in which only a reactance is varied. When applied to electron beam devices and devices employing distributed nonlinear media, the variable parameter is equivalent to a reactance in the sense that it is associated with energy storage rather than energy dissipative properties of the beam or medium. The qualifier, reactance, is more frequently applied to circuits in which the variable element is an easily identified lumped reactance. The qualifier, parametric, is more frequently applied to electron beam and distributed parameter devices, but can include the variable reactance devices as well. Thus in any of the following definitions, reactance may be used in place of parametric. These definitions are intended to exclude devices which operate by virtue of variable resistance or negative resistance.
There is some confusion as to whether a reactance amplifier operates by virtue of a nonlinear reactance or a time-varying reactance. It is recognized here that while all practical embodiments make use of nonlinear elements, the effect of the pump is to make them behave as time-varying elements. Thus in its simplest form, the concept of a reactance amplifier is based on the assumption that the pump is sufficiently large and the signals are sufficiently small that the nonlinear element can be replaced as far as the signals are concerned by an equivalent, linear, time-varying element. In these definitions the small signal restriction is assumed.
There is some past usage which has made the term amplifier apply to any device having power gain even though the input and output signals are at different frequencies. While these definitions permit this usage, it is recommended that the term amplifier be restricted to those devices having the same input and output frequency, and its application to frequency converters is deprecated.
There exist devices for which the names are composites of the following terms. No definitions have been given for such combinations where the meanings are sufficiently obvious