Laboratory Report Cover Sheet
DeVry University
College of Engineering and Information Sciences

Course Number: ECET350

Professor:

Laboratory Number: 3

Laboratory Title: Moving Average Digital Filters

Submittal Date: Click here to enter a date.

Objectives:

·  Design, test, and implement antialiasing and anti-imaging filters to be used with a real-time, digital filtering system using a microcontroller, ADC, and DAC.

·  Implement, test, and analyze the performance of a moving average, low-pass filter in conjunction with the filters and real-time system from the first objective.

Results: Summarize your results in the context of your objectives.

Conclusions: What can you conclude about this lab based on your results?

Student:
Name / Program / Signature

Measurements, Graphs, and Calculations

Paste your calculated design values of the resistors and capacitors, and record all values in Table 1.

Answers:

Calculated Design Values / Actual Component Values Used
R1 =
R2 =
C1 =
C2 =
-3 dB
Frequency

Table 1: Component and Cutoff Frequency Values

Paste your Excel spreadsheet data table for your second order, salley-key, low-pass filter in the space provided.

Paste your graph of the low-pass filter frequency response data into the space provided below. Please remember that graph, axes, and titles are part of the documentation and are part of the requirements to be met for grading.

Copy and paste your moving average filter response Excel data table in the space provided.

Note: The students were only asked to include the linear output, but the log magnitude has also been provided here for your reference.

Paste your graph of the linear magnitude response of the nine-point moving average filter into the space provided below. Use this graph to answer the following questions.

Sallen-Key, Low-Pass Filter Analysis Questions

Using the Vpp output at 1000 Hz as your reference, and the fact that a second order, low-pass filter attenuates a frequency at the rate of -12 dB per octave, calculate the dB attenuation per decade for the measurements indicated below.

1. dB/decade attenuation from 1000 Hz to 2000 Hz:

2. Compare the dB/octave attenuation measurement. Is it close to the expected value? Explain why or why not?

Moving Average Filter Questions

From the graph of the nine-point, moving average filter output, perform the calculations required in order to answer the following questions. Record all formulas, work done with your calculations, and all answers in the spaces provided.

3. Using the Fs/M relationship, calculate and record the first zero gain frequency point of the filter. Show your work and your answer.

4. From the graph, measure and record the first zero gain frequency of the filter. Please note that due to noise in the circuitry, the gain will not be zero, but should be an easily determined first minimum gain of the filter response.

5. Is the measured zero or minimum gain response close to what the calculated response is? Explain your answer, whether it is or isn’t close.

6. Using the 0.5Fs/M relationship, calculate and record the cutoff frequency point of the filter. Show your work and your answer.

7. From the graph, measure and record the cutoff frequency of the filter, which is determined at the 0.707 * max gain of the filter, measured at the 0 Hz (or 10 Hz actual) point.

8. Is the cutoff frequency response close to what the calculated response is? Explain your answer, whether it is or isn’t close.

Grade:

Deliverable / Points Available / Points Achieved
Data Measurements / 10
Graphs (labels, accuracy) / 10
Answers to Questions / 10
Organization (format of results and style) / 10
Total Points / 40
Comments:

______

Course Number: ECET-350 Laboratory Number: 3 Page 6 of 6