Memorandum  5

Date:               March 2^nd, 2014

To:                  Professor David G. Michelson

From:              EECE 380’s L2D4 Group

Subject:          Weekly Memo for Week 5

This week the group focused on compiling all the parts together and testing the project by inputting a RF signal between 50-54 MgHz with power level varying between -60dbm to -20dbm.Upon testing we came upon few unforeseen issues within the software which we are currently working on.

Hardware Sub-group

The goals of the team for the week were

• All the goals for the hardware sub group have been completed.

Cascaded Common Emitter Amplifier

Upon testing with a range of signals it was decided that the current quality and quantity of the amplifiers are sufficient.

 Precision Peak Detector

 The peak detector works within the full range of power, -60 to -20 dbm. Previously we had issue with detecting the signal at -60dbm but with further adjustments we can now detect the signal at that power.

Video Filter

 From the feedback of our previous tests we have incorporated the video filter within the lab view architecture.

One issue we had last week was the transportation and movement of all the different parts of the project. This week we constructed an enclosed box to contain all the wires and circuits so that the project remains connected and operational thus increasing the efficiency. Also now the project can be transported without any interference.

 Software Sub-group

The goals of the team for the week were

• Calibrate the frequency domain on the display so it displays the correct RF frequency.
• Calibrate the power domain on the display so it displayed the correct RF power.

Display

We have resolved all the previous issues with the display but upon testing the full project it was discovered that the frequency being displayed differed by some unknown factor from the test signals frequency. To resolve the issue we have started to calibrate the frequency on MyDaq by recording the values at numerous test points onto an excel file. By drawing a graph of this data we can calculate the relationship between the actual frequency and the frequency being displayed on MyDaq.

Video Filter

 The video filter is completed by using a design block Butterworth filter and setting it to be a low pass filter. The high cut-off frequency we choose is 1.1MHZ. Testing of the video filter will be performed in the next week.

Logarithmic Amplifier

 We had the same display issue with the logarithmic amplifier as well. The power being displayed differed from the power being inputted. To resolve this issue we took the same approach as before. We recorded numerous values at various test points in order to calculate the relationship between the power and its display error.

Memorandum 

Date:               February 2^nd, 2014

To:                   Professor David G. Michelson

From:              EECE 380’s L2D4 Group

Subject:          Weekly Memo for Week 2

This week our group divided into two specialised sub-groups – Hardware and Software. The Hardware sub-group consisting of three members would work on building the peak detector, Resolution Bandwidth Filter, Video filter and the Logarithmic Amplifier. The Software sub-group consisting of two members would work on the myDAQ to build the ramp generator and displaying the results on the screen.

Hardware Sub-group

The goals of the team for the week were

• Finish the Resolution Bandwidth Filter
• Build a simple Peak Detector.

Resolution Bandwidth Filter

We were asked to utilize the crystals provided to us to build a Crystal Ladder Band Pass filter. Our group decided to build a four Pole Crystal Ladder Band Pass filter. We did a lot of reading on it and decided to create the following design for our purposes.

This design gave us a very nice band pass filter that was centered at 9.997620 MHz with a Band Width of 900Hz. After changing the capacitor values a little bit, we noticed that to have a flatter top, we need to have all the capacitors of the same value. We also learned that the higher capacitance used would give us a narrower band width but there would be a trade-off with the amount of power it would consume instead. This design we thought gave the optimum amount of Bandwidth while we lost about 10dbm of power. This is acceptable since when we put everything together, we will have amplifiers to retain the power of the signal.

Peak Detector

The Peak detector we agreed was the most vulnerable part of our circuit and also the part at which a lot of power would be lost. We first built a simple peak detector which had a design that looked similar to the following.

The time constant was chosen so that it would take 1/10^th of the frequency of the input signal. This would make sure that the capacitor does not discharge completely resulting in the DC output of the peak. When we tested the circuit we were getting a great DC offset from the signal generator. To get rid of the offset, we connected a 100Ω resistor in parallel with the above circuit to get rid of the DC waves. After that our Peak detector worked fine except that 0.4V were lost at the output due to the Schottky Diode. We realised that we would need an amplifier to rectify this loss. However, we also learned that normal Op-amps do not operate at high frequencies as high as 10MHz. So we placed an order for high frequency Op-Amp which should arrive later this week. We will then build a precision Peak Detector which will be better for our project.

Thus we finished both our goals for this week in the hardware section.

Software Sub-group

The goal of the software team for the past week was to build a ramp generator.

Ramp Generator

From Tutorial, our group had noted that the local oscillator needed to generate a frequency band between 60Mhz and 64Mhz for our project. This meant that our ramp would have to be between 3.75V and 5.5V from the linear nature of the Local Oscillator. We first introduced ourselves with the various functions of myDAQ and the features we were required to know. After a couple of sessions with the software, we were successful in creating a saw tooth function in the region that we wanted and we even tested the output with the Local Oscillator. We will now concentrate on the displaying the results part of our project requirement.

Those were our tem updates from this week. As mentioned above, we have cleared a lot of ground in terms of fulfilling project requirements. We are now looking to finish the software and the hardware part by the end of next week so that we can all work on putting all the parts together and debug the system as a whole. Rest assured, we are on good track at the moment.

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