February 10, 2014

To: Dr. David Michelson

From: Lauren Aliman, L2C4 Team Leader

This memorandum serves as an update for progress of the EECE 380 Design Studio III team, L2C4, during the week of February 3 – February 9, 2014.

We had our weekly team meeting on Monday, February 3, where we talked about our progress in the software and hardware portions of the project from the previous week. We also talked about how each individual component of the Spectrum Analyzer works and how they all tie together. At the conclusion of the meeting, we decided on the following goals to be attained by the end of the week:

Hardware

• Develop “unit” tests for each separate block
• Simulate the entire system for integration testing of the RBW and peak detector, replacing the MyDAQ visual display block with the lab spectrum analyzer

Software

• Attain a good understanding of the theory behind the software design.
• Generate an XY-graph that acquires data from the ramp generator (y-axis) and from an analog myDAQ input (x-axis).

Updates on Hardware Portion:

Last week’s issue regarding unexpected gain at high frequencies outside of the RBW filter was solved by adding the 10.7MHz BPF in series with the RBW. It was noticed that placing this BPF at the input the crystal ladder had different effects than placing it at the output. We attempted to use the RF amplifier that was provided in our kit to add gain to our ~10MHz filtered signal, however the amplifier provided gain for frequencies that we considered noise, so the professional 10.7MHz BPF was connected after the RF amplifier to eliminate these high frequencies.

The current peak detector will be upgraded to have an op-amp to compensate for the diode voltage drop. However, the 10MHz op-amp that we purchased had major attenuation starting just below 1MHz, to the point where there was an unreadable signal at 10MHz. A proposed solution was to use a 100MHz op-amp that causes no attenuation at 10MHz. This part has been ordered and we will attempt to have a functional precision peak detector by the start of next week.

Updates on Software Portion:

During the first lab session, we spent some time talking about how the outputs from each component of the project look like, in both the time and frequency domains. By doing so, we were able to get a clear picture of what was going on, which made designing the software portion a lot more straightforward.

To display the amplitude of a signal in the y-axis of the graph, we connected a DC signal from a signal generator to one of the analog inputs in myDAQ which we then mathematically manipulated to display the corresponding power in dBm. For the x-axis, we adjusted the ramp generator to have voltages ranging from 3V to 6V. We then came up with a linear function, that simulates the behavior of a local oscillator, to convert the ramp generated voltages to corresponding frequencies between 45 MHz and 57 MHz. By the end of the second lab session, we ended up with a graph consisting of a single pulse that sweeps across the displayed frequency range (45-57 MHz). This output makes sense because we were only feeding the myDAQ input with a constant DC signal. On the other hand, the output from the peak detector would have to be a DC signal whose voltage changes along with the signal from the local oscillator; in other words, each frequency in the given range corresponds to a different output voltage from the peak detector. In theory, the display should work; however, we are yet to come up with a method to test the software portion without connecting it to the peak detector.

We will have our next weekly meeting on Tuesday, at the start of the lab session, to plan out this week’s goals.