Laboratory Procedures 

DeVry University

College of Engineering and Information Sciences

I.                   OBJECTIVES

1.      To analyze a RC Low Pass Filter using simulation and circuit measurement.

2.      To analyze a RC High Pass Filter using simulation and circuit measurement.

3.      To analyze a LC Band Pass Filter using simulation and circuit measurement.

II.        PARTS LIST

Equipment:

            IBM PC or Compatible                      

                             Function Generator 

                        Dual Channel Oscilloscope

Parts:   

1 – 50 Ω Resistor                     1 – 470 nF, 50 V Capacitor

            1 – 330 Ω Resistor                   4 – 47 µF, 35 V Capacitor

                                4 – 4.7 mH Inductor                 2 – 100 µF, 25 V Capacitor

                        1 – 470 mH, Inductor

Software:

            MultiSim 11

III.       PROCEDURE

A.                Simulation of RC Low Pass Filter |

1.      Enter the circuit shown in Figure 1 in MultiSim.

Figure 1 – Low Pass Filter

2.      Set the function generator voltage, V_In = 1 V_P.

3.         Simulate the circuit shown for various frequencies indicated in Table 1 below. Record the output voltage, V_Out, for each frequency and calculate the gain using the formula: 20 log(V_{Out P-P} / V_{In P-P}).

Table 1 – Low Pass Filter Frequency Response Simulation Data

Low

4.      Determine the voltage “Gain/Loss” in dB for the frequency response plot. Plot the simulation data of on the semi-log graph sheet below. The frequency must be on the X axis and the Gain_dB on the Y–axis.

5.      What is the 3 dB cutoff frequency from the plot?

f_C =___________________

6.      Calculate the 3 dB Cutoff frequency using the formula: f_C = 1/(2π R C)

f_C =___________________

7.      Does the simulated measurement agree with the theoretical calculation?

Yes ______ No ______

B.        Simulation of RC High Pass Filter

1.      Enter the circuit shown in Figure 2 in MultiSim.

Figure 2 – High Pass Filter

2.      Set the function generator voltage, V_In = 1 V_P

3.      Simulate the circuit shown for various frequencies indicated in Table 2 and record the output voltage and gain.  

Table 2 – Low Pass Filter Frequency Response Simulation Data

4.      Determine the voltage “Gain/Loss” in dB for the frequency response plot. Plot the simulation data of on the semi-log graph sheet below.

5.      What is the 3 dB cutoff frequency from the plot?

f_C =___________________

6.      Calculate the 3 dB Cutoff frequency using the formula: f_C = 1/(2π R C)

f_C =___________________

7.      Does the simulated measurement agree with the theoretical calculation?

Yes ______ No ______

C.        Simulation of LC Band Pass Filter

1.      Enter the circuit shown in Figure 3 in MultiSim.

Figure  3 – LC Band Pass Filter

2.      Setup the function generator voltage, V_In = 1 V_P.

3.      Simulate the circuit shown for various frequencies indicated in Table 3 and record the output voltage and gain.

Table 3 – Band Pass Filter Frequency Response Simulation Data

4.      Determine the voltage “Gain/Loss” in dB for the frequency response plot. Plot the simulation data of on the semi-log graph sheet below.

5.      What are the 3 dB cutoff frequencies from the plot?

Upper f_C =_____________   Low f_C =_____________  

6.      The LC band pass filter is PI- Section filter which has been designed using the website:

http://www.raltron.com/cust/tools/band_pass_filters.asp

The filter has been designed to operate at a center frequency, f_o of 340 Hz and a 3dB Bandwidth of 10% of f_o.

Log in to the above website; feed the data of center frequency and the bandwidth desired. Verify if the design values chosen for the lab experiment are close enough.

7.      What are the calculated 3 dB cutoff frequencies?

Upper f_C =_____________   Low f_C =_____________   

8.      Do the simulated measurements agree with the theoretical calculations?

Yes ______ No ______

9.      Increase or decrease the center frequency by 5 and recalculate the element values. Note and record the new design parameters. What can you comment on the new design values when compared with the original values?

10.  The filter can be reconfigured to a T–type using the transformation shown below:

Source for the above formulas: “HANDBOOK OF LINE COMMUNICATIONS”, A Royal Signals Pub., 1947.

Using the suggested transformation, change the original PI type filter to T-type and simulate to verify if it works as the original. Include the new filter topology below here.

11.  Did the filter work as the original?        YES             NO

D.        BreadboardConstructionof the three Filters

1.      Build the three filters simulated above on a breadboard, one at a time

2.      Use a Function Generator to excite the filters and check for the pass band and the cut off frequencies.

3.      Submit a photograph of each of your working circuits (online) or have your instructor sign-off each circuit (onsite).