
90-6 Signal Processing
ways to reduce the inductance of the ground path. is is accomplished by using ground planes, grids,
and straps to lower the inductance.
Ta
ble
90.3 gi
ves
th
e
im
pedances
fo
r
so
lid
gr
ound
pl
anes
at va
rious
fr
equencies
. In th
is
ca
se,
th
e
im
pedances
ar
e
in “o
hms
pe
r
sq
uare,”
wh
ich
is a me
asure
of im
pedance
ac
ross
a di
agonal
su
rface
. By
co
mparing
th
is
wi
th
Ta
ble
90.2, on
e
ca
n
se
e
th
at
at hi
gh
fr
equencies
(s
uch
as 10
0
MH
z)
th
e
gr
ound
pl
ane
im
pedance
ma
y
be se
veral
or
ders
of ma
gnitude
be
low
th
e
im
pedance
of a wi
re
. Fu
rthermore,
at hi
gh
fr
equencies
t
he
t
hickness
i
s
n
ot
a f
actor,
si
nce
t
he
i
mpedance
i
s
l
imited
b
y
t
he
s
kin
e
ect