Memorandum
Date: February 16th, 2014
To: Professor David G. Michelson
From: EECE 380’s L2D4 Group
Subject: Weekly Memo for Week 4
This week the software group completed the design of the display and the video filter by using myDAQ; the display has been tested and functions well, however, the video filter still needs additional testing. The hardware group completed the cascaded Common Emitter amplifier and a precision peak detector.
Hardware Sub-group
The goals of the team for the week were
- Build an amplifier which will be put after the mixer and before the peak detector
- Build and test a precision peak detector
Cascaded Common Emitter Amplifier
As the previous memo mentioned, an amplifier is needed to make the signal large enough for the peak detector. In this week, we have built a second set of cascaded Common Emitter amplifier in an attempt to have a performant gain. However, it did not function as what we expected. Then we investigated that the DC offset of the cascaded Common Emitter amplifier could give us a high enough output, related to the amplitude of the signal. Therefore, the amplifier will work well if we find the relationship between its output and the amplitude of the input signal.
Precision Peak Detector
This week we built a precision peak detector by using the high frequency op amps we received in order to enhance the accuracy. However, it does not function well at around 10MHz. Next week, we will make adjustments on the precision peak detector to solve this problem.
Video Filter
This week we built a simple RC circuit which is a low pass filter. After testing, we observed that it does not function accurately as a video filter when the signal is small. To meet our requirements, we decide to complete the video filter by using myDAQ.
The goals of hardware sub-group for this week are all achieved. Additional testing on the precision peak detector will be done. In addition, we are going to combine all parts of the project and perform testing in the next week.
Software Sub-group
The goals of the team for the week were
- Complete the display for the spectrum analyzer and perform testing.
- Complete the video filter
Display
In this week, we complete the display for the spectrum analyzer. Our display was having a problem of resetting in last week. To solve this problem we create a design block to set a range for the display and connect it to the reset port of the design block build XY graph. After testing we find out that this method solve the problem efficiently. In addition, we observed that the lowest readable signal of myDAQ is around 0.1V.
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
In this week, we have figured out how to build logarithmic amplifier by using the LabView. However, to complete this part, data collection and calculations of the relationship between DC voltage and power in dBm is needed. This task will be done in the next week.
The goals of software sub-group for this week are all achieved. We will complete the logarithmic amplifier, perform testing, and combine all parts of the project in the next week.