
84-21Modulation
reected from nearby objects, and the reected signal is mixed with the emitted signal to produce
th
e
su
m
an
d
di
erence
of th
e
tr
ansmitted
an
d
re
ceived
fr
equencies
. If th
e
ob
ject
an
d
th
e
mi
crowave
em
itter
ar
e
in re
lative
mo
tion,
th
e
re
ected
si
gnal
re
turns
to th
e
em
itter
sh
ied
in fr
equency
by th
e
Do
ppler
sh
i
fr
equency
∆f
D
:
∆f
v
c
f
D c
=
2 cos( )
α
(8
4
.33
)
where
v
i
s
t
he
r
elative
v
elocity
o
f
t
he
s
ource
a
nd
t
he
r
eecting
o
bject
(
m/s)
c
i
s
t
he
s
peed
o
f
l
ight
i
n
a
ir
(
3
.0 × 1
0
8
m/s)
f
c
is the frequency of the microwave (carrier) source (Hz)
α
i
s
t
he
a
ngle
o
f
i
ncidence
b
etween
t
he
s
ource
a
nd
t
he
r
eector
For
K-b
and
mi
crowave
so
urces
(2 ...