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Message ID: 195     Entry time: Thu Jul 1 13:49:58 2010
Author: Megan 
Type: Notes 
Category: VCO 
Subject: VCO Output Amplitude Depending on Modlevel Input 

I measured the output amplitude of the VCO with different Modlevel voltage inputs (from 0 V to 5 V) by measuring the RMS voltage on the oscilloscope. While I was varying the voltage input, I discovered the sine wave is very distorted between roughly 0.8 V and 3.5 V of modlevel input. Extra peaks started appearing that disappeared or became less prominent when below or above that range. The graphs show the output of the VCO in dBm and voltage (input impedance of 50 Ohms), accounting for the 19 dBm attenuation added to the output of the VCO.

I also started measuring the phase noise of the complete, unmodified VCO so we have a reference for the noise of the modified version when we are done with that. It is all set up right now and I should be able to start recording data on the computer soon. After we have a reference of the noise of the unmodified VCO, we will modify the VCO and see how it affects the noise level - hopefully it drops.

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Output_vs_Modlevel_Voltage.png
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