To: David G Michelson
From: EECE 380 Team L2D8
Date: March 16 2014
Subject: Project 2 Weekly Memo 6
This memo summarizes the progress from the first tutorial to the thrid tutorial. In time span, it includes the material from March 7th to March 14th.
What we learned so far
In the first tutorial, we familiarized ourselves with the spectrum analyzer and the signal generator. We also learned to set up NI myDAQ, data acquisition device. The first tutorial was pretty preliminary. In the second tutorial, we were asked to test different components. We found out that the gains of components are as follows:
Frequency Mixer
-7 dB
RF Amplifier
22 dB
Band Pass Filter
-0.7 dB
Attenuator
-10 dB
In theory, the signal right after the RBW filter will have a very small gain of 4.3 dB. We connected everything with a 0 dBm 50 MHz signal and the peak value was observed to be around 5 dBm which is very close to the theoretical value. Particularly, we noticed that the output signal of VCO is 0 dBm instead of typical 10 dBm on the datasheet, and the final experiment also proved us right. In the third tutorial, we spent most of our time finishing up the second tutorial, but it clearly showed us what we need to do next week.
Problems Identified
The problem is that the local oscillator can only produce signals between 40MHz and 80MHz due to the voltage output limit of myDAQ. The most likely solution is to build an amplifier to amplify the voltage of ramp signal to the desired range. The other problem is that the high frequency band pass filter we have right now is centered at 10.7 MHz. To get 8 MHz center frequency, we need to find some solutions.
Work Ahead
Try thinking about solution for measuring modulation index or frequency deviation.
Try searching the solutions to adjust the center frequency of band pass filter to 8MHz.
Hardware wise: Two sets of crystal filters are needed. Two sets of high frequency peak detectors are needed. One transistor amplifier with gain around 1.4 is needed.
Software wise: In the LABVIEW, use block diagram to plot the data acquired from ramp generator and peak detector. Try to add the switch for the crystal filter.