2002 University of Illinois at Chicago ECE 431 V. Goncharoff
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ECE 431 - Analog Communication Circuits
Homework #1: due at the start of class on Tuesday, 9/3/02.
Write answers in the space provided.
You are given an antenna, an RF stage, a 1.0 MHz oscillator, a frequency
divider (÷N, where N is an integer), a frequency multiplier (×M, where M is
an integer), a mixer, a 500 KHz IF stage, an envelope detector, an audio
amplifier and a loudspeaker.
(a) By interconnecting these circuits, design a superheterodyne receiver
block diagram to receive the AM broadcast station WBBM at 780 KHz.
Specify the values of N and M in your receiver. (draw on reverse side)
(b) What is the image frequency in your receiver when it is tuned to
780 KHz?
(c) What is the maximum bandwidth that your RF stage may have and still
reject another station, having 10 KHz bandwidth, that is centered at the
image frequency?
(d) Let's assume that instead of receiving 780 KHz, you with to receive the
frequency that we called the "image" in (b). What change needs to be
made in the superheterodyne receiver, from that shown in block diagram
(a), to make this possible?
(e) What will be the new image frequency for the modified receiver
described in (d)?
KHz
KHz
KHz