ECE 3074

Experiment: Passive Notch and Bandpass Filters

Name: ______

Date: ______

Analysis

The component values for the notch filter circuit with a center frequency of 60 Hz are:

Component / Value / Component / Value
R / R
Rp / 10 kW / Rp / 10 kW
Cp / Cp
Lp / 100 mH / Lp / 5 mH

The expected operating characteristics of the notch filters are:

Lp = 100 mH / Value / Lp = 5 mH / Value
Q / Q
B / B
fH / fH
fL / fL

The Bode plot for the notch filters when VS = 1V

Bandpass Filter

The component values for the bandpass filter circuit with a center frequency of 800 Hz are:

Component / Value / Component / Value
R / R
Rs / 100 W / Rs / 50 W
Cs / Cs
Ls / 100 mH / Ls / 5 mH

The expected operating characteristics of the bandpass filters are:

Ls = 100 mH / Value / Ls = 5 mH / Value
Q / Q
B / B
fH / fH
fL / fL

The Bode plot for the bandpass filters when VS = 1V

Modeling

Notch Filter

The Bode plot for the magnitude and phase of the output voltage for the notch filters (VS = 1V) is shown below.

The predicted operating characteristics of the notch filters from the PSpice simulations are:

Lp = 100 mH / Value / Units / Lp = 5 mH / Value / Units
fo / Hz / fo / Hz
fH / Hz / fH / Hz
fL / Hz / fL / Hz
qo / degrees / qo / degrees
qH / degrees / qH / degrees
qL / degrees / qL / degrees

Calculated Q and bandwidth for the notch filters from the PSpice simulations are:

Ls = 100 mH / Value / Ls = 5 mH / Value
Q / Q
B / B

Bandpass Filter

The Bode plot for the magnitude and phase of the output voltage for the bandpass filters (VS = 1V) is shown below.

The predicted operating characteristics of the bandpass filters from the PSpice simulations are:

Lp = 100 mH / Value / Units / Lp = 5 mH / Value / Units
fo / Hz / fo / Hz
fH / Hz / fH / Hz
fL / Hz / fL / Hz
qo / degrees / qo / degrees
qH / degrees / qH / degrees
qL / degrees / qL / degrees

Calculated Q and bandwidth for the bandpass filters from the PSpice simulations are:

Ls = 100 mH / Value / Ls = 5 mH / Value
Q / Q
B / B

Measurements

Notch Filter

The notch filter constructed is shown in Figure X below.

The Bode plot for the magnitude and phase of the output voltage for the notch filters (VS = 5V) is shown below.

The characteristics of the notch filter determined from the measurements and percent deviation from expected values are listed below.

Value / Units / % deviation
fo / Hz
fH / Hz
fL / Hz
qo / degrees
qH / degrees
qL / degrees

Calculated Q and bandwidth for the notch filters from the Bode measurements and percent deviation from expected values are:

Value / Units / % deviation
Q
B

The output voltage as a function of time when the frequency of the input voltage is equal to fH is shown below.

The phase angle calculated from the oscilloscope trace is: (Include equations to show how you arrived at the phase angle.)

Value / % deviation
qH

Bandpass Filter

The bandpass filter constructed is shown in Figure Y below.

The Bode plot for the magnitude and phase of the output voltage for the bandpass filters (VS = 5V) is shown below.

The characteristics of the bandpass filter determined from the measurements and percent deviation from expected values are listed below.

Value / Units / % deviation
fo / Hz
fH / Hz
fL / Hz
qo / degrees
qH / degrees
qL / degrees

Calculated Q and bandwidth for the bandpass filters from the Bode measurements and percent deviation from expected values are:

Value / Units / % deviation
Q
B

The output voltage as a function of time when the frequency of the input voltage is equal to fH is shown below.

The phase angle calculated from the oscilloscope trace is: (Include equations to show how you arrived at the phase angle.)

Value / % deviation
qH

Conclusions

Notch Filter

1.  Explain the reasons for the differences between the calculated and experimental results.

2.  Compare the results for the RLC notch filter as compared to the Twin T filter that you designed in the experiment on Electromagnetic Interference. Which would perform better when eliminating 60 Hz pick-up without causing significant distortion of the signals at frequencies close to the center frequency of the notch filter? Which component limits the performance of the RLC notch filter?

Bandpass Filter

1.  Explain the reasons for the differences between the calculated and experimental results.