An Overview of System-Level Macromodeling Using Virtual Blocks
An Introduction to Macromodeling in RF.Spice A/D
RF.Spice A/D provides an extensive library of black-box virtual blocks that allow you to quickly test and verify new system concepts without getting into the details of particular circuit realizations. A virtual block typically has one or more input pins and one or more output pins. It models a system-level function or behavior in the form of a relationship between the input and output voltages. For example, a multiplier block takes two input voltages and outputs their product. An analog frequency doubler takes a single sinusoidal input voltage and produces a sinusoidal output voltage whose frequency is twice as large as the input frequency. A real practical frequency doubler typically involves a sophisticated circuit either with discrete components or in the form of an integrated circuit. In many situations like system design, you simply need a "black box" that exhibits the behavior of a frequency doubler just to try out and verify a system concept. You would worry about the hardware implementation of your block at a later time after the proof of concept has been established.
The Stages of a Macromodel Virtual Block
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Example 1: Analog Signal Differentiation
The simplest voltage differentiator can be made based on the basic properties of a capacitor:
[math] i(t) = C \frac{dv}{dt} [/math]
where v(t) and i(t) are the voltage and current of the capacitor and C is it capacitance. Similarly for an inductor, one can write:
[math] v(t) = L \frac{di}{dt} [/math]
where L is the inductance.
It is important to note that in virtual blocks we only care about the functional behavior, completely ignoring the practical realization of a particular circuit. In the above equations, if we set C = 1F or L = 1H (regardless of the actual physical devices), we will get a derivative relationship between the voltage and current.
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