(For Roel)Frequency Response of Low Pass, High Pass and Band Pass Filters
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e2w6_instructions.docxLaboratory 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, VIn = 1 VP.
3. Simulate the circuit shown for various frequencies indicated in Table 1 below. Record the output voltage, VOut, for each frequency and calculate the gain using the formula: 20 log(VOut P-P / VIn P-P).
|
Frequency, Hz |
VOut P-P |
GaindB |
Frequency, Hz |
VOut P-P |
GaindB |
|
100 |
|
|
2000 |
|
|
|
200 |
|
|
4000 |
|
|
|
400 |
|
|
8000 |
|
|
|
800 |
|
|
10000 |
|
|
|
1000 |
|
|
|
|
|
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 GaindB on the Y–axis.
5. What is the 3 dB cutoff frequency from the plot?
fC =___________________
6. Calculate the 3 dB Cutoff frequency using the formula: fC = 1/(2 π R C)
fC =___________________
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, VIn = 1 VP
3. Simulate the circuit shown for various frequencies indicated in Table 2 and record the output voltage and gain.
|
Frequency, Hz |
VOut P-P |
GaindB |
Frequency, Hz |
VOut P-P |
GaindB |
|
100 |
|
|
2000 |
|
|
|
200 |
|
|
4000 |
|
|
|
400 |
|
|
8000 |
|
|
|
800 |
|
|
10000 |
|
|
|
1000 |
|
|
|
|
|
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?
fC =___________________
6. Calculate the 3 dB Cutoff frequency using the formula: fC = 1/(2 π R C)
fC =___________________
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, VIn = 1 VP.
3. Simulate the circuit shown for various frequencies indicated in Table 3 and record the output voltage and gain.
|
Frequency, Hz |
VOut P-P |
GaindB |
Frequency, Hz |
VOut P-P |
GaindB |
|
200 |
|
|
340 |
|
|
|
250 |
|
|
344 |
|
|
|
280 |
|
|
348 |
|
|
|
290 |
|
|
355 |
|
|
|
300 |
|
|
352 |
|
|
|
320 |
|
|
356 |
|
|
|
324 |
|
|
360 |
|
|
|
330 |
|
|
|
|
|
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 fC =_____________ Low fC =_____________
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, fo of 340 Hz and a 3dB Bandwidth of 10% of fo.
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 fC =_____________ Low fC =_____________
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:
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Some useful formulas for the Constant K type band pass filter design: |
||
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fC = Filter Center Design frequency R0 = Filter Design Impedance f1 and f2 => 3 dB cutoff frequencies, Lower & Upper.. Also, f1 x f2 = fC2 Bandwidth = f2 – f1
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|
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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.
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|
11. Did the filter work as the original? YES NO
D. Breadboard Construction of 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).
1000
100
10
Freq, Hz
Loss
dB
10000
0
-2
-4
-6
-8
-10
-12
frequency response of a filter
1000
100
10
Freq, Hz
Loss
dB
10000
0
-2
-4
-6
-8
-10
-12
frequency response of a filter
L
1
L
2
C
1
C
2L
2
C
2
PI-Topology
L1
L2
L2
C1
C2
C2
PI- Topology
L
1
/2
2L
2
2C
1
C
2
/2
2C
1
L
1
/2
T-Topology
L1 /2
L1 /2
2L2
2C1
2C1
C2 /2
T- Topology
T-Topology
T- Topology
Freq, Hz
Loss
d
B
frequency response of a filter
1000
10010
10000
0
-2
-4
-6
-8
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-12
1000
100
10
Freq, Hz
Loss
dB
10000
0
-2
-4
-6
-8
-10
-12
frequency response of a filter
