MEMORANDUM

To : Dave Michelson

From : EECE 380 Team L2D8

Date : 31 March 2014

Subject : Project 2 Weekly Memo 8

INTRODUCTION

This memo outlines the progress made during the last week before the project.

PROGRESS

Hardware

With the new capacitor stocks, we finished adjusting the bandwidth of our crystal filters, ~1kHz and ~3kHz approximately.

When the RF signal is passed through the crystal ladder, there was approximately a 23 dBm loss. Therefore, we chose to build a cascode which amplifies the signal by approximately 20 dBm to compensate for the loss. The cascode is chosen due to its ability to isolate both the input and output stages, high gain and slightly wider bandwidth compared to the standard common emitter amplfier.

We also built a simple peak detector which has a stable output without any ripple. This allows for a clean input into myDAQ so that the readings are more accurate.

Software

We managed to display the xy graph in Labview as well reading the input voltage. There is also a cursor on the display that displays the values.

 

GOALS  FOR NEXT WEEK

1. Test the whole circuit with the RF Amplifier, Mixer, VCO, Attenuator, switch and software

2. Start designing the PCB Board

3. Include the frequency modulation Beta into Labview.

To: David G Michelson

From: EECE 380 Team L2D8

Date: March 23 2014

Subject: Project 2 Weekly Memo 7

 

This memo outlines the progress made this week as well as goals for next week.

 

Progress

The group has identify the key parts of the project and assigned jobs to each group members.

2 members are working on the software while the other 3 are working on the hardware.

 

Hardware

We have built the peak detector as well as the two resolution bandwidth filters. Both resolution bandwidth filters has a centre frequency of 8Mhz. However, the bandwidth of the bandwidth filter is not yet adjusted because the capacitor stock ran out. We would continue with the adjustment in the following week after obtaining the appropriate capacitor values.

 

Besides that, we built an amplifier for the ramp generator because the maximum voltage output from the myDAQ is not enough to sweep through our local oscillator range from 78 Mhz to 98 Mhz.

 

Software

There has been no update to the software portion this week. All members were focusing on the hardware part of the project for now.

 

Goals for Next Week

1. Start building the transistor amplifiers

2. Assemble everything together

3. Test the circuit out with the software.

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.