Simulation Practices for Electronics and Microelectronics
Engineering
Dr. Graciano Dieck Assad / Ing. Matías Vázquez Piñón
Capstone Projects
EC-03. Low Pass and High Pass Noise Filters
Instrumentation and biomedical engineers require reliable electronic circuits to reject noisy signals
coming from working environments, HVAC systems and other electronic equipment. Data acquisition
systems, signal converters and common mode noise filtering devices in power plants, factories,
hospitals, commercial buildings, houses and laboratories use low pass and high pass filters. Electronic
noise filters can be designed using both, passive and active components. Also DSP (Digital Signal
Processors) can be used with software programs to perform the task. With this design project we
seek to establish the fundamental principles in developing passive low pass and high pass noise filters
for a wide variety of applications using resistors and capacitors.
The objective of this capstone project is to design and simulate a low pass noise filter that
rejects noise signals higher than 5 KHz, and to design and simulate a high pass filter that rejects noise
below 50KH. These are the specifications:
a.
b.
c.
d.
e.
For the low pass filter: a -3dB low frequency cut-off of 5000 Hz.
For the high pass filter: a -3dB high frequency cut-off of 50000 Hz.
Neglected source resistances.
Load resistances of 100 K.
Resistors from 100  to 20 K, and capacitors from 100 pF to 10 F in your design.
Figure EC-03.1 shows the required frequency response of the low pass filter in magnitude,
|Vo/Vi|, and phase according to the specifications of the filter. Figure EC-03.2 illustrates the required
frequency response of the high pass filter in magnitude an phase.
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Simulation Practices for Electronics and Microelectronics
Engineering
Dr. Graciano Dieck Assad / Ing. Matías Vázquez Piñón
Figure EC-03.1. Low pass filter frequency response
Figure EC-03.2. Required frequency response of the high pass filter in magnitude an phase
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D . R . © I n s t i tu t o T e c no l ó g ic o y d e E s t u d i o s S u p er i o re s d e M o n te rr e y , M é x i c o 2 0 1 2
Simulation Practices for Electronics and Microelectronics
Engineering
Dr. Graciano Dieck Assad / Ing. Matías Vázquez Piñón
Report.
1. Provide the circuit schematic and analytical solution for both, low pass and high pass designs.
2. Describe the loading effects that the circuit may have while selecting the resistor values.
3. Include the frequency domain simulation of the circuit using an AC analysis in magnitude and
phase of the transfer characteristic of each filter.
4. Include the measurement of the -3dB frequency cut-offs for both filters. Here, you must measure
magnitude and phase of the transfer characteristic.
5. Include measurement of magnitude and phase of the response at the low frequency, about 1 KHz
for the low pass, and at high frequency, about 1 M for the high pass.
6. Compare the simulated response to the analytical solution in magnitude and phase for both
frequency responses.
7. What parameters are desirable to change if we want to change the specified cut-off frequencies?
8. Discus the possible sources of errors, loading effects and personal observations when performing
the analysis and the simulation experiment.
9. Include references.
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