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which has a schematic layout with the layout.  The actual varactor model is in the schematic “Varactor”.  The negative resistance source is in the schematic “Negative Resistance Layout”.  It has an associated schematic layout.

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Graph “1_Linear Oscillation Conditions” shows the total admittance for the inputs of the tank circuit and the negative resistance source.  This was accomplished by creating a variable Y_total, and graphing its real (conductance) and imaginary (susceptance) parts.  Y_total is defined in the browser window “Output Equations” as the sum of the admittance of the tank circuit and the admittance of the negative resistance source.  Oscillation should occur where the susceptance is 0, as the conductance is negative. The tuner can be used to tune over the DC voltage levels for biasing the varactor.  Use the right “Vdc” parameter and watch the  0 crossing of the conductance change; i.e., the expected oscillation frequency is controlled by the varactor bias voltage.

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The resulting measurements are now explained:

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•    “Oscillation Frequency versus Tuning Voltage” - Plot showing the tuning range of the oscillator by the DC source.  The swept voltage setting is used as the x-axis for this graph.

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•    “Oscillator Spectrum” - Plot showing the output power spectrum for the oscillator.  This graph is set up to allow the tuner to change the state of the swept voltage source.  Tune on the left “Vdc” parameter and watch the spectrum change.

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•    “Output Power versus Tuning Voltage” - Plot showing the output power of the oscillator versus the tuning voltage of the oscillator.  The swept voltage setting is used as the x-axis for this graph.

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•    “Output Waveform” - Plot showing the output voltage waveform for the oscillator.  This graph is set up to allow the tuner to change the state of the swept voltage source.  Tune on the left “Vdc” parameter and watch the waveform change.

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•    “SSB Phase Noise” -   Plot showing the single sideband phase noise of the oscillator.  This graph is set up to allow the tuner to change the state of the swept voltage source.  Tune on the left “Vdc” parameter and watch the phase noise change slightly.

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The schematic “3_Varactor_CV_Setup” is used for creating the graph “Varactor Capacitance vs. Tuning Voltage”, which shows the capacitance of the varactor as the bias voltage is changed.  Note that the measurement models the load as a parallel RC circuit, and plots the (varactor) capacitance.

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