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UNIVERSITY OF CALIFORNIA
College of Engineering Electrical Engineering and Computer Sciences Department
EECS 145M: Microcomputer Interfacing Laboratory
Spring Midterm # Monday, April 20, 1997
- Closed book (equation sheet handed out with this midterm)
- Calculators OK
- You must show your work to get full credit
PROBLEM 1 (40 points)
Describe four A/D converter circuits in terms of the following characteristics:
- conversion accuracy (maximum number of bits)
- differential linearity
- cost (number of internal A/D circuit components)
- speed (number of steps the A/D needs to perform one conversion)
- external circuits needed for full performance
1a. (10 points) Successive approximation
1b. (10 points) Flash
1c. (10 points) Integrating (or Dual Slope)
1d. (10 points) Half flash
2d. (5 points) What is the minimum sampling frequency required to be able to handle speeds of 100 m/s?
2 e. (5 points) Considering your answer to 2d above, what value of f 1 does your low pass filter require?
2 e. (5 points) How many samples will you take for each measurement?
2 f. (5 points) If you want to record the echo signal to an accuracy of 5%, how many bits does the A/D converter need?
2 g. (5 points) What type of A/D converter would you use for this application?
2h. (20 points) After taking the necessary number of samples from the echo receiver circuit, you take the FFT. Sketch all FFT magnitudes vs. frequency index for a fluid speed of 10 m/s. You will need to use a vertical axis labeled in powers of ten. Provide an additional label for the horizontal axis in Hz. Assume that before anti-aliasing the magnitude of each Fourier coefficient contains white noise that is 10% of the Fourier magnitudes that contain the echo signal.
