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Design Notes
Pulsed RF Source Example
This example shows how to create a pulsed RF signal in AWR Microwave Office or Analog Office (MWO/AO) by multiplying an RF signal by a pulse.
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In both cases, the RF signal is tone 1, whose frequency is set in the Circuit Options dialog box of the top level schematic that is using the signal source: in project browser, right-click on the schematic > Options... > Frequencies tab. The port impedance, peak power, pulse frequency, duty cycle (or duty factor) in percent, and rise and fall times are set as parameters on the subcircuits when they are placed. Equations inside each subcircuit uses these parameters to calculate the parameters for the sources required.
(Generally, the pulse sources in these schematics can be replaced by any amplitude-modulating signal, but this example focuses on the periodic pulse.)
Circuit Schematics
In these circuits, The pulse characteristics are controlled by variables that appear on the subcircuit when it is placed.
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"Top" is used to test the "Pulsed_RF_Inv" source.
Graphs
"Time Domain Output Voltage": the modulated RF signals presented to the ports, and control pulses generated by pulse voltage source and inverting circuit in the "Pulsed_RF_with_Inv" subcircuit. The limit on maximum number of points had to be increased in order to display the full waveforms: Circuit Options > APLAC Sim tab (> Show Secondary) > Maximum displayed time points.
"Output Power Spectrum": power spectrum at port 1. Since there are no nonlinearities, this is the spectrum of the RF pulse alone.
Considerations for harmonic balance simulation
The limits on harmonics and intermods have been removed to better present the time-domain signal (Circuit Options > APLAC Sim tab > uncheck Limit Harmonic Order). Number of harmonics for tone 1 has been reduced to 3 to reduce simulation time.
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Note that the total number of harmonics simulated is already very high (see the "Output Power Spectrum" graph). It may not be practical to perform a harmonic balance simulation of a nonlinear circuit with this many harmonics. If the higher order harmonics and intermods do not significantly affect the performance of the circuit, simulation speed can be improved considerably by reducing the number of harmonics/intermods included in the simulation. However, the time domain waveforms would then show the effect of truncating the spectrum. The alternative is transient simulation.
Schematic - Pulsed_RF
Graph - Top Time Domain Output Voltage