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ECE 473/TAM 413
Homework Assignment #9
Due: Friday, November 7, 2008
For your information
Hour Exam 2: Thursday, November 20, 2008, 7:008:30 pm, 163 EL
Hour exams are open book (the text for the course) with one sheet of notes (you can use
both sides). Your class notes and lecture notes are not permitted. You can use calculators.
1. A baffled circular piston source with a radius of 10 centimeters operates in air (20˚C).
a) For an operating frequency of 10 kHz, what is the distance to the far field?
b) For an operating frequency of 1 kHz, what is the distance to the far field?
c) For an operating frequency of 4 kHz, what is the zerotozero beamwidth?
d) For an operating frequency of 8 kHz, what is the – 6 dB beamwidth?
e) For an operating frequency of 10 kHz, what is the radiation impedance of the air acting on
the piston? The answer should be nonzero values for both the real and imaginary parts.
Express answer in rectangular form.
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This note was uploaded on 09/19/2009 for the course ECE 473 taught by Professor Obrian during the Fall '08 term at University of Illinois at Urbana–Champaign.
 Fall '08
 OBRIAN

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