Page 105 - ExtendSim User Guide
P. 105

Areas of Application 79
Finally, the amount of the drug in the bloodstream is reduced by metabolism, calculated in the Equation block that uses the concentration of the drug in the bloodstream, the blood volume, and a metabolism constant. A Plotter I/O reports the concentration of the drug in the blood- stream.
Try changing the dosage amount and the frequency of application using the cloned dialog parameters on the left side of the model. Then observe the changes in the concentration of the drug in the bloodstream. Or, to illustrate the affects of different drugs, vary the metabolism and absorption constants.
Simulation is extensively used for modeling electronic, signal processing, control, and mechanical systems, as well as neural networks and other engineering systems. The following electronic signal processing example investigates the performance of a receiver in a digital FM system.
Noisy FM system
When designing receivers and demodulators, engineers need to balance quality and cost. Sim- ulation helps illustrate the trade-off, for example when the objective is to filter noise without reducing the quality of the reception. Fewer components can result in a product that is cheaper to produce and maintain, but a product with more components might have a better sound.
☞ The Noisy FM System model is located in the folder Examples\Continuous\Standard Block Models. The model uses blocks from the Electronics and Plotter libraries.
Model assumptions
• FM center frequency is 91.6khz
• Antenna tuner uses an elliptical filter
• Demodulator is a passive RC phase locked loop using an exclusive OR comparator
Model details
This model shows the performance
of a receiver in a digital FM trans-
ceiver system, within a noisy envi-
ronment. The Transmitter is a
hierarchical block with a submodel
containing a bitstream generator
and an FM carrier generator. The
bitstream generator is comprised of
two Voltage Controlled Oscillator
blocks (VCOs) and two Clipper
blocks: Noisy FM model
• ThefirstVCOoutputsasquare
wave that varies between -1 and +1 volt output.
• The first Clipper limits the square wave signal to 0 and +1 volt, so that it can modulate the second VCO and produce the periodic bitstream for testing.
• AsecondClipperlimitsthissquarewaveoutputfortheFrequencyModulation(FM)genera- tor.

   103   104   105   106   107