3/31/2005 The Superhet Receiver.doc 1/8
The Super-Heterodyne Receiver
Note that the heterodyne receiver would be an excellent design if we always wanted to receive a signal at one
particular signal frequency (ω1 , say):
narrow-band narrow-band amplifier filter
ˆ it() G ()ω = ω T (ω = ω ) ≈ 1 1 1 1 narrow-band antenna detector/
A Fixed-Frequency demodulator
Heterodyne Receiver
No tuning is required!
Moreover, we can optimize the amplifier, filter, and detector performance for one—and only one—signal frequency (i.e., ω1 ).
Q: Couldn’t we just build one of these fixed-frequency heterodyne receivers for each and every signal frequency of interest?
Jim Stiles The Univ. of Kansas Dept. of EECS 3/31/2005 The Superhet Receiver.doc 2/8
A: Absolutely! And we sometimes (but not often) do. We call these receivers channelized receivers.
ˆ it1 () G ()ω = ω T (ω = ω ) ≈ 1 1 1 1
ˆ it2 () ω = ω G ()2 ω = ω ≈ T ( 2 ) 1 1
ˆ it3 () ω = ω G ()3 ω = ω ≈ T ( 3 ) 1 1
# # # ˆ itN () ω = ω G ()N T ω = ω ≈ 1 ( N ) 1
A Channelized Receiver
Jim Stiles The Univ. of Kansas Dept. of EECS 3/31/2005 The Superhet Receiver.doc 3/8
But, there are several important problems involving channelized receivers.