ECE432 532 Quiz 1 Study Guide 17 April 07
Section 1 Introduction to modern filter theory--frequency and impedance scaling
Design a 3 dB ripple 5th order Chebychev low-pass filter with cutoff frequency fo and
50 ohm termination impedance. Show all your work. Do the complete design before
simulating the response. Then do an AC analysis of your design using LTSpice, and
show both S11 and S21 on a single plot. Explain the relationship between S11 and
S21 for a lossless filter.
Design a 3rd order Butterworth High-Pass filter with 3 dB frequency fo and 50 ohm
termination impedance. Show all your work. Complete the design before simulating
the response. Do an LTSpice simulation and show both S11 and S21 on a single plot.
Discuss the use of fixed 5% tolerance chip components for this filter, and show the ef-
fect of component variations.
Section 2 Transformation
Step 1: Calculate your personal frequency: Write the last two digits of your student
number here ______ add 100 and divide by 2. This is the frequency fo in MHz that
you will use for all of the exercises. Confirm that it is between 50 and 100 MHz before
proceeding.
Section 3 Practical Bandpass Filter Design
Design a 5% bandwidth 3rd order bandpass filter centered on fo. Use a 0.5 dB ripple
Chebychev pi-network low-pass prototype. Design a lossless filter for an impedance of
1000 ohms, and use impedance inverters to transform the center element into a paral-
lel tuned circuit. Show all work, and use the simulator to check your work as you prog-
ress. Use the simulator for fine tuning of the design, and indicate which elements will
need to be tunable in the completed filter. After you obtain a successful design at 1000
ohms, transform the end elements to 50 ohms using taps (autotransformers) on the
inductors. Now assume an inductor Q of 300 and show the effect on the simulated S11
and S21 response. Discuss parasitic inductance and component tolerance. Discuss
breakdown voltages of the components.
This study guide is a Filter design homework assignment in preparation for the ECE
432/532 quiz 1 on April 24. The homework assignment will be turned in with the quiz.
The quiz will consist of questions from the following design exercises, and you may re-
fer to your homework during the quiz. You are encouraged to assist the other students
with understanding of the assigned exercises and simulations, but each student is ex-
pected to complete and simulate his/her own designs. The quiz will be graded, and the
homework examined to validate the quiz grade.
Note: The following three designs represent several days work for a professional Filter
designer. Start working on them NOW.
