
Homodyne Direct Conversion Receivers 355
ANTENNA
J LASER [
J
BANDPASS
'~ FILTER
Figure 18-5
BRAGG
CELL
INPUT
Bragg cell receiver.
LED
ARRAY
wavelength (hence frequency) of the applied RF signal. These lines can be sensed
and displayed, providing an instantaneous spectrum of the applied signal.
18-6 HOMODYNE DIRECT CONVERSION RECEIVERS
The homodyne receiver uses a
local oscillator
(LO) to produce a stable local signal
(F2) that has the same frequency as the incoming RF signal (F1). When these sig-
nals are mixed together in a nonlinear circuit element, such as a crystal diode (Fig.
18-6A), a set of new frequencies is created ...