<s>
A	O
radio-frequency	B-Algorithm
microelectromechanical	I-Algorithm
system	I-Algorithm
(	O
RF	B-Algorithm
MEMS	I-Algorithm
)	O
is	O
a	O
microelectromechanical	B-Architecture
system	I-Architecture
with	O
electronic	O
components	O
comprising	O
moving	O
sub-millimeter-sized	O
parts	O
that	O
provide	O
radio-frequency	O
(	O
RF	O
)	O
functionality	O
.	O
</s>
<s>
Besides	O
RF	B-Algorithm
MEMS	I-Algorithm
technology	O
,	O
III-V	O
compound	O
semiconductor	O
(	O
GaAs	O
,	O
GaN	O
,	O
InP	O
,	O
InSb	O
)	O
,	O
ferrite	O
,	O
ferroelectric	O
,	O
silicon-based	O
semiconductor	O
(	O
RF	B-Device
CMOS	I-Device
,	O
SiC	O
and	O
SiGe	O
)	O
,	O
and	O
vacuum	O
tube	O
technology	O
are	O
available	O
to	O
the	O
RF	O
designer	O
.	O
</s>
<s>
Each	O
of	O
the	O
RF	O
technologies	O
offers	O
a	O
distinct	O
trade-off	O
between	O
cost	O
,	O
frequency	O
,	O
gain	O
,	O
large-scale	O
integration	O
,	O
lifetime	O
,	O
linearity	O
,	O
noise	O
figure	O
,	O
packaging	B-Algorithm
,	O
power	O
handling	O
,	O
power	O
consumption	O
,	O
reliability	O
,	O
ruggedness	O
,	O
size	O
,	O
supply	O
voltage	O
,	O
switching	O
time	O
and	O
weight	O
.	O
</s>
<s>
There	O
are	O
various	O
types	O
of	O
RF	B-Algorithm
MEMS	I-Algorithm
components	O
,	O
such	O
as	O
CMOS	B-Device
integrable	O
RF	B-Algorithm
MEMS	I-Algorithm
resonators	O
and	O
self-sustained	O
oscillators	O
with	O
small	O
form	O
factor	O
and	O
low	O
phase	O
noise	O
,	O
RF	B-Algorithm
MEMS	I-Algorithm
tunable	O
inductors	O
,	O
and	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
switched	B-Algorithm
capacitors	I-Algorithm
and	O
varactors	O
.	O
</s>
<s>
The	O
components	O
discussed	O
in	O
this	O
article	O
are	O
based	O
on	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
switched	B-Algorithm
capacitors	I-Algorithm
and	O
varactors	O
.	O
</s>
<s>
These	O
components	O
can	O
be	O
used	O
instead	O
of	O
FET	B-Application
and	O
HEMT	B-Algorithm
switches	B-Device
(	O
FET	B-Application
and	O
HEMT	B-Algorithm
transistors	O
in	O
common	O
gate	O
configuration	O
)	O
,	O
and	O
PIN	O
diodes	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
switched	B-Algorithm
capacitors	I-Algorithm
and	O
varactors	O
are	O
classified	O
by	O
actuation	O
method	O
(	O
electrostatic	O
,	O
electrothermal	O
,	O
magnetostatic	O
,	O
piezoelectric	O
)	O
,	O
by	O
axis	O
of	O
deflection	O
(	O
lateral	O
,	O
vertical	O
)	O
,	O
by	O
circuit	O
configuration	O
(	O
series	O
,	O
shunt	O
)	O
,	O
by	O
clamp	O
configuration	O
(	O
cantilever	O
,	O
fixed-fixed	O
beam	O
)	O
,	O
or	O
by	O
contact	O
interface	O
(	O
capacitive	O
,	O
ohmic	O
)	O
.	O
</s>
<s>
Electrostatically	O
actuated	O
RF	B-Algorithm
MEMS	I-Algorithm
components	O
offer	O
low	O
insertion	O
loss	O
and	O
high	O
isolation	O
,	O
linearity	O
,	O
power	O
handling	O
and	O
Q	O
factor	O
,	O
do	O
not	O
consume	O
power	O
,	O
but	O
require	O
a	O
high	O
control	O
voltage	O
and	O
hermetic	O
single-chip	O
packaging	B-Algorithm
(	O
thin	O
film	O
capping	O
,	O
LCP	O
or	O
LTCC	B-Algorithm
packaging	B-Algorithm
)	O
or	O
wafer-level	O
packaging	B-Algorithm
(	O
anodic	O
or	O
glass	O
frit	O
wafer	O
bonding	O
)	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
were	O
pioneered	O
by	O
IBM	O
Research	O
Laboratory	O
,	O
San	O
Jose	O
,	O
CA	O
,	O
Hughes	O
Research	O
Laboratories	O
,	O
Malibu	O
,	O
CA	O
,	O
Northeastern	O
University	O
in	O
cooperation	O
with	O
Analog	O
Devices	O
,	O
Boston	O
,	O
MA	O
,	O
Raytheon	O
,	O
Dallas	O
,	O
TX	O
,	O
and	O
Rockwell	O
Science	O
,	O
Thousand	O
Oaks	O
,	O
CA	O
.	O
</s>
<s>
A	O
capacitive	O
fixed-fixed	O
beam	O
RF	B-Algorithm
MEMS	I-Algorithm
switch	O
,	O
as	O
shown	O
in	O
Fig	O
.	O
</s>
<s>
It	O
is	O
generally	O
connected	O
in	O
shunt	O
with	O
the	O
transmission	O
line	O
and	O
used	O
in	O
X	B-Algorithm
-	O
to	O
W-band	O
(	O
77	O
GHz	O
and	O
94GHz	O
)	O
RF	B-Algorithm
MEMS	I-Algorithm
components	O
.	O
</s>
<s>
An	O
ohmic	O
cantilever	O
RF	B-Algorithm
MEMS	I-Algorithm
switch	O
,	O
as	O
shown	O
in	O
Fig	O
.	O
</s>
<s>
Switches	B-Device
typically	O
have	O
a	O
capacitance	O
ratio	O
of	O
30	O
or	O
higher	O
,	O
while	O
switched	B-Algorithm
capacitors	I-Algorithm
and	O
varactors	O
have	O
a	O
capacitance	O
ratio	O
of	O
about	O
1.2	O
to	O
10	O
.	O
</s>
<s>
The	O
loaded	O
Q	O
factor	O
is	O
between	O
20	O
and	O
50	O
in	O
the	O
X-	O
,	O
Ku	B-Algorithm
-	O
and	O
Ka-band	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
switched	B-Algorithm
capacitors	I-Algorithm
are	O
capacitive	O
fixed-fixed	O
beam	O
switches	B-Device
with	O
a	O
low	O
capacitance	O
ratio	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
varactors	O
are	O
capacitive	O
fixed-fixed	O
beam	O
switches	B-Device
which	O
are	O
biased	O
below	O
pull-in	O
voltage	O
.	O
</s>
<s>
Other	O
examples	O
of	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
are	O
ohmic	O
cantilever	O
switches	B-Device
,	O
and	O
capacitive	O
single	O
pole	O
N	O
throw	O
(	O
SPNT	O
)	O
switches	B-Device
based	O
on	O
the	O
axial	O
gap	O
wobble	O
motor	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
components	O
are	O
biased	O
electrostatically	O
using	O
a	O
bipolar	O
NRZ	B-Protocol
drive	O
voltage	O
,	O
as	O
shown	O
in	O
Fig	O
.	O
</s>
<s>
The	O
use	O
of	O
a	O
bipolar	O
NRZ	B-Protocol
drive	O
voltage	O
instead	O
of	O
a	O
DC	O
drive	O
voltage	O
avoids	O
dielectric	O
charging	O
whereas	O
the	O
electrostatic	O
force	O
exerted	O
on	O
the	O
beam	O
is	O
maintained	O
,	O
because	O
the	O
electrostatic	O
force	O
varies	O
quadratically	O
with	O
the	O
DC	O
drive	O
voltage	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
components	O
are	O
fragile	O
and	O
require	O
wafer	O
level	O
packaging	B-Algorithm
or	O
single	O
chip	O
packaging	B-Algorithm
which	O
allow	O
for	O
hermetic	O
cavity	B-Algorithm
sealing	O
.	O
</s>
<s>
A	O
cavity	B-Algorithm
is	O
required	O
to	O
allow	O
movement	O
,	O
whereas	O
hermeticity	O
is	O
required	O
to	O
prevent	O
cancellation	O
of	O
the	O
spring	O
force	O
by	O
the	O
Van	O
der	O
Waals	O
force	O
exerted	O
by	O
water	O
droplets	O
and	O
other	O
contaminants	O
on	O
the	O
beam	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
switched	B-Algorithm
capacitors	I-Algorithm
and	O
varactors	O
can	O
be	O
packaged	O
using	O
wafer	O
level	O
packaging	B-Algorithm
.	O
</s>
<s>
Large	O
monolithic	O
RF	B-Algorithm
MEMS	I-Algorithm
filters	O
,	O
phase	B-Algorithm
shifters	I-Algorithm
,	O
and	O
tunable	O
matching	O
networks	O
require	O
single	O
chip	O
packaging	B-Algorithm
.	O
</s>
<s>
Wafer-level	O
packaging	B-Algorithm
is	O
implemented	O
before	O
wafer	O
dicing	B-Algorithm
,	O
as	O
shown	O
in	O
Fig	O
.	O
</s>
<s>
3(a )	O
,	O
and	O
is	O
based	O
on	O
anodic	O
,	O
metal	O
diffusion	O
,	O
metal	O
eutectic	O
,	O
glass	O
frit	O
,	O
polymer	B-Language
adhesive	O
,	O
and	O
silicon	O
fusion	O
wafer	O
bonding	O
.	O
</s>
<s>
The	O
selection	O
of	O
a	O
wafer-level	O
packaging	B-Algorithm
technique	O
is	O
based	O
on	O
balancing	O
the	O
thermal	O
expansion	O
coefficients	O
of	O
the	O
material	O
layers	O
of	O
the	O
RF	B-Algorithm
MEMS	I-Algorithm
component	O
and	O
those	O
of	O
the	O
substrates	O
to	O
minimize	O
the	O
wafer	O
bow	O
and	O
the	O
residual	O
stress	O
,	O
as	O
well	O
as	O
on	O
alignment	O
and	O
hermeticity	O
requirements	O
.	O
</s>
<s>
Figures	O
of	O
merit	O
for	O
wafer-level	O
packaging	B-Algorithm
techniques	O
are	O
chip	O
size	O
,	O
hermeticity	O
,	O
processing	O
temperature	O
,	O
(	O
in	O
)	O
tolerance	O
to	O
alignment	O
errors	O
and	O
surface	O
roughness	O
.	O
</s>
<s>
Wafer-level	O
packaging	B-Algorithm
techniques	O
based	O
on	O
a	O
bonding	O
technique	O
with	O
a	O
conductive	O
intermediate	O
layer	O
(	O
conductive	O
split	O
ring	O
)	O
restrict	O
the	O
bandwidth	B-Algorithm
and	O
isolation	O
of	O
the	O
RF	B-Algorithm
MEMS	I-Algorithm
component	O
.	O
</s>
<s>
The	O
most	O
common	O
wafer-level	O
packaging	B-Algorithm
techniques	O
are	O
based	O
on	O
anodic	O
and	O
glass	O
frit	O
wafer	O
bonding	O
.	O
</s>
<s>
Wafer-level	O
packaging	B-Algorithm
techniques	O
,	O
enhanced	O
with	O
vertical	O
interconnects	O
,	O
offer	O
the	O
opportunity	O
of	O
three-dimensional	O
integration	O
.	O
</s>
<s>
Single-chip	O
packaging	B-Algorithm
,	O
as	O
shown	O
in	O
Fig	O
.	O
</s>
<s>
3(b )	O
,	O
is	O
implemented	O
after	O
wafer	O
dicing	B-Algorithm
,	O
using	O
pre-fabricated	O
ceramic	O
or	O
organic	O
packages	O
,	O
such	O
as	O
LCP	O
injection	O
molded	O
packages	O
or	O
LTCC	B-Algorithm
packages	O
.	O
</s>
<s>
Pre-fabricated	O
packages	O
require	O
hermetic	O
cavity	B-Algorithm
sealing	O
through	O
clogging	O
,	O
shedding	O
,	O
soldering	O
or	O
welding	O
.	O
</s>
<s>
Figures	O
of	O
merit	O
for	O
single-chip	O
packaging	B-Algorithm
techniques	O
are	O
chip	O
size	O
,	O
hermeticity	O
,	O
and	O
processing	O
temperature	O
.	O
</s>
<s>
An	O
RF	B-Algorithm
MEMS	I-Algorithm
fabrication	O
process	O
is	O
based	O
on	O
surface	O
micromachining	O
techniques	O
,	O
and	O
allows	O
for	O
integration	O
of	O
SiCr	O
or	O
TaN	O
thin	O
film	O
resistors	O
(	O
TFR	O
)	O
,	O
metal-air-metal	O
(	O
MAM	O
)	O
capacitors	O
,	O
metal-insulator-metal	O
(	O
MIM	O
)	O
capacitors	O
,	O
and	O
RF	B-Algorithm
MEMS	I-Algorithm
components	O
.	O
</s>
<s>
An	O
RF	B-Algorithm
MEMS	I-Algorithm
fabrication	O
process	O
can	O
be	O
realized	O
on	O
a	O
variety	O
of	O
wafers	O
:	O
III-V	O
compound	O
semi-insulating	O
,	O
borosilicate	O
glass	O
,	O
fused	O
silica	O
(	O
quartz	B-General_Concept
)	O
,	O
LCP	O
,	O
sapphire	B-Application
,	O
and	O
passivated	B-Application
silicon	O
wafers	O
.	O
</s>
<s>
4	O
,	O
RF	B-Algorithm
MEMS	I-Algorithm
components	O
can	O
be	O
fabricated	O
in	O
class	O
100	O
clean	O
rooms	O
using	O
6	O
to	O
8	O
optical	B-Algorithm
lithography	I-Algorithm
steps	O
with	O
a	O
5	O
μm	O
contact	O
alignment	O
error	O
,	O
whereas	O
state-of-the-art	O
MMIC	B-Algorithm
and	O
RFIC	O
fabrication	O
processes	O
require	O
13	O
to	O
25	O
lithography	O
steps	O
.	O
</s>
<s>
Beam	O
patterning	B-Algorithm
,	O
release	O
and	O
critical	O
point	O
drying	O
(	O
Fig	O
.	O
</s>
<s>
With	O
the	O
exception	O
of	O
the	O
removal	O
of	O
the	O
sacrificial	O
spacer	O
,	O
which	O
requires	O
critical	O
point	O
drying	O
,	O
the	O
fabrication	O
steps	O
are	O
similar	O
to	O
CMOS	B-Device
fabrication	O
process	O
steps	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
fabrication	O
processes	O
,	O
unlike	O
BST	O
or	O
PZT	O
ferroelectric	O
and	O
MMIC	B-Algorithm
fabrication	O
processes	O
,	O
do	O
not	O
require	O
electron	B-Architecture
beam	I-Architecture
lithography	I-Architecture
,	O
MBE	B-Algorithm
,	O
or	O
MOCVD	B-Algorithm
.	O
</s>
<s>
Contact	O
interface	O
degradation	O
poses	O
a	O
reliability	O
issue	O
for	O
ohmic	O
cantilever	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
whereas	O
dielectric	O
charging	O
beam	O
stiction	O
,	O
as	O
shown	O
in	O
Fig	O
.	O
</s>
<s>
5(b )	O
,	O
pose	O
a	O
reliability	O
issue	O
for	O
capacitive	O
fixed-fixed	O
beam	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
.	O
</s>
<s>
Commercially	O
available	O
ohmic	O
cantilever	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
and	O
capacitive	O
fixed-fixed	O
beam	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
have	O
demonstrated	O
lifetimes	O
in	O
excess	O
of	O
100	O
billion	O
cycles	O
at	O
100	O
mW	O
of	O
RF	O
input	O
power	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
resonators	O
are	O
applied	O
in	O
filters	O
and	O
reference	O
oscillators	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
switched	B-Algorithm
capacitors	I-Algorithm
and	O
varactors	O
are	O
applied	O
in	O
electronically	O
scanned	O
(	O
sub	O
)	O
arrays	O
(	O
phase	B-Algorithm
shifters	I-Algorithm
)	O
and	O
software-defined	B-Architecture
radios	I-Architecture
(	O
reconfigurable	O
antennas	O
,	O
tunable	O
band-pass	O
filters	O
)	O
.	O
</s>
<s>
Polarization	O
and	O
radiation	O
pattern	O
reconfigurability	O
,	O
and	O
frequency	O
tunability	O
,	O
are	O
usually	O
achieved	O
by	O
incorporation	O
of	O
III-V	O
semiconductor	O
components	O
,	O
such	O
as	O
SPST	O
switches	B-Device
or	O
varactor	O
diodes	O
.	O
</s>
<s>
However	O
,	O
these	O
components	O
can	O
be	O
readily	O
replaced	O
by	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
and	O
varactors	O
in	O
order	O
to	O
take	O
advantage	O
of	O
the	O
low	O
insertion	O
loss	O
and	O
high	O
Q	O
factor	O
offered	O
by	O
RF	B-Algorithm
MEMS	I-Algorithm
technology	O
.	O
</s>
<s>
In	O
addition	O
,	O
RF	B-Algorithm
MEMS	I-Algorithm
components	O
can	O
be	O
integrated	O
monolithically	O
on	O
low-loss	O
dielectric	O
substrates	O
,	O
such	O
as	O
borosilicate	O
glass	O
,	O
fused	O
silica	O
or	O
LCP	O
,	O
whereas	O
III-V	O
compound	O
semi-insulating	O
and	O
passivated	B-Application
silicon	O
substrates	O
are	O
generally	O
lossier	O
and	O
have	O
a	O
higher	O
dielectric	O
constant	O
.	O
</s>
<s>
A	O
low	O
loss	O
tangent	O
and	O
low	O
dielectric	O
constant	O
are	O
of	O
importance	O
for	O
the	O
efficiency	O
and	O
the	O
bandwidth	B-Algorithm
of	O
the	O
antenna	O
.	O
</s>
<s>
The	O
prior	O
art	O
includes	O
an	O
RF	B-Algorithm
MEMS	I-Algorithm
frequency	O
tunable	O
fractal	O
antenna	O
for	O
the	O
0.1	O
–	O
6GHz	O
frequency	O
range	O
,	O
and	O
the	O
actual	O
integration	O
of	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
on	O
a	O
self-similar	O
Sierpinski	O
gasket	O
antenna	O
to	O
increase	O
its	O
number	O
of	O
resonant	O
frequencies	O
,	O
extending	O
its	O
range	O
to	O
8GHz	O
,	O
14GHz	O
and	O
25GHz	O
,	O
an	O
RF	B-Algorithm
MEMS	I-Algorithm
radiation	O
pattern	O
reconfigurable	O
spiral	O
antenna	O
for	O
6	O
and	O
10GHz	O
,	O
an	O
RF	B-Algorithm
MEMS	I-Algorithm
radiation	O
pattern	O
reconfigurable	O
spiral	O
antenna	O
for	O
the	O
6	O
–	O
7GHz	O
frequency	B-Algorithm
band	I-Algorithm
based	O
on	O
packaged	O
Radant	O
MEMS	B-Architecture
SPST-RMSW100	O
switches	B-Device
,	O
an	O
RF	B-Algorithm
MEMS	I-Algorithm
multiband	O
Sierpinski	O
fractal	O
antenna	O
,	O
again	O
with	O
integrated	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
functioning	O
at	O
different	O
bands	O
from	O
2.4	O
to	O
18GHz	O
,	O
and	O
a	O
2-bit	O
Ka-band	O
RF	B-Algorithm
MEMS	I-Algorithm
frequency	O
tunable	O
slot	B-Algorithm
antenna	I-Algorithm
.	O
</s>
<s>
The	O
Samsung	B-Application
Omnia	I-Application
W	I-Application
was	O
the	O
first	O
smart	O
phone	O
to	O
include	O
a	O
RF	B-Algorithm
MEMS	I-Algorithm
antenna	O
.	O
</s>
<s>
RF	O
bandpass	O
filters	O
can	O
be	O
used	O
to	O
increase	O
out-of-band	B-Protocol
rejection	O
,	O
in	O
case	O
the	O
antenna	O
fails	O
to	O
provide	O
sufficient	O
selectivity	O
.	O
</s>
<s>
Out-of-band	B-Protocol
rejection	O
eases	O
the	O
dynamic	O
range	O
requirement	O
on	O
the	O
LNA	O
and	O
the	O
mixer	O
in	O
the	O
light	O
of	O
interference	O
.	O
</s>
<s>
Off-chip	O
RF	O
bandpass	O
filters	O
based	O
on	O
lumped	O
bulk	O
acoustic	O
wave	O
(	O
BAW	O
)	O
,	O
ceramic	O
,	O
SAW	O
,	O
quartz	B-General_Concept
crystal	O
,	O
and	O
FBAR	O
resonators	O
have	O
superseded	O
distributed	O
RF	O
bandpass	O
filters	O
based	O
on	O
transmission	O
line	O
resonators	O
,	O
printed	O
on	O
substrates	O
with	O
low	O
loss	O
tangent	O
,	O
or	O
based	O
on	O
waveguide	O
cavities	O
.	O
</s>
<s>
They	O
can	O
be	O
implemented	O
using	O
III-V	O
semiconducting	O
varactors	O
,	O
BST	O
or	O
PZT	O
ferroelectric	O
and	O
RF	B-Algorithm
MEMS	I-Algorithm
resonators	O
and	O
switches	B-Device
,	O
switched	B-Algorithm
capacitors	I-Algorithm
and	O
varactors	O
,	O
and	O
YIG	O
ferrites	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
resonators	O
offer	O
the	O
potential	O
of	O
on-chip	B-Architecture
integration	O
of	O
high-Q	O
resonators	O
and	O
low-loss	O
bandpass	O
filters	O
.	O
</s>
<s>
The	O
Q	O
factor	O
of	O
RF	B-Algorithm
MEMS	I-Algorithm
resonators	O
is	O
in	O
the	O
order	O
of	O
100	O
–	O
1000	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
switch	O
,	O
switched	B-Algorithm
capacitor	I-Algorithm
and	O
varactor	O
technology	O
,	O
offers	O
the	O
tunable	O
filter	O
designer	O
a	O
compelling	O
trade-off	O
between	O
insertion	O
loss	O
,	O
linearity	O
,	O
power	O
consumption	O
,	O
power	O
handling	O
,	O
size	O
,	O
and	O
switching	O
time	O
.	O
</s>
<s>
Passive	O
subarrays	O
based	O
on	O
RF	B-Algorithm
MEMS	I-Algorithm
phase	B-Algorithm
shifters	I-Algorithm
may	O
be	O
used	O
to	O
lower	O
the	O
amount	O
of	O
T/R	O
modules	O
in	O
an	O
active	B-Architecture
electronically	I-Architecture
scanned	I-Architecture
array	I-Architecture
.	O
</s>
<s>
6	O
:	O
assume	O
a	O
one-by-eight	O
passive	O
subarray	O
is	O
used	O
for	O
transmit	O
as	O
well	O
as	O
receive	O
,	O
with	O
following	O
characteristics	O
:	O
f	O
=	O
38GHz	O
,	O
Gr	O
=	O
Gt	O
=	O
10	O
dBi	O
,	O
BW	O
=	O
2GHz	O
,	O
Pt	O
=	O
4	O
W	O
.	O
The	O
low	O
loss	O
(	O
6.75	O
ps/dB	O
)	O
and	O
good	O
power	O
handling	O
(	O
500mW	O
)	O
of	O
the	O
RF	B-Algorithm
MEMS	I-Algorithm
phase	B-Algorithm
shifters	I-Algorithm
allow	O
an	O
EIRP	O
of	O
40	O
W	O
and	O
a	O
Gr/T	O
of	O
0.036	O
1/K	O
.	O
</s>
<s>
The	O
number	O
of	O
antenna	O
elements	O
per	O
subarray	O
should	O
be	O
chosen	O
in	O
order	O
to	O
optimize	O
the	O
EIRP	O
or	O
the	O
EIRP	O
x	B-Algorithm
Gr/T	O
product	O
,	O
as	O
shown	O
in	O
Fig	O
.	O
</s>
<s>
The	O
radar	B-Application
range	O
equation	O
can	O
be	O
used	O
to	O
calculate	O
the	O
maximum	O
range	O
for	O
which	O
targets	O
can	O
be	O
detected	O
with	O
10dB	O
of	O
SNR	O
at	O
the	O
input	O
of	O
the	O
receiver	O
.	O
</s>
<s>
RF	B-Algorithm
MEMS	I-Algorithm
phase	B-Algorithm
shifters	I-Algorithm
enable	O
wide-angle	O
passive	B-Algorithm
electronically	I-Algorithm
scanned	I-Algorithm
arrays	I-Algorithm
,	O
such	O
as	O
lens	O
arrays	O
,	O
reflect	O
arrays	O
,	O
subarrays	O
and	O
switched	O
beamforming	B-Algorithm
networks	O
,	O
with	O
high	O
EIRP	O
and	O
high	O
Gr/T	O
.	O
</s>
<s>
The	O
prior	O
art	O
in	O
passive	B-Algorithm
electronically	I-Algorithm
scanned	I-Algorithm
arrays	I-Algorithm
,	O
includes	O
an	O
X-band	B-Algorithm
continuous	O
transverse	O
stub	O
(	O
CTS	O
)	O
array	O
fed	O
by	O
a	O
line	O
source	O
synthesized	O
by	O
sixteen	O
5-bit	O
reflect-type	O
RF	B-Algorithm
MEMS	I-Algorithm
phase	B-Algorithm
shifters	I-Algorithm
based	O
on	O
ohmic	O
cantilever	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
an	O
X-band	B-Algorithm
2-D	O
lens	O
array	O
consisting	O
of	O
parallel-plate	O
waveguides	O
and	O
featuring	O
25,000	O
ohmic	O
cantilever	O
RF	B-Algorithm
MEMS	I-Algorithm
switches	B-Device
,	O
and	O
a	O
W-band	O
switched	O
beamforming	B-Algorithm
network	O
based	O
on	O
an	O
RF	B-Algorithm
MEMS	I-Algorithm
SP4T	O
switch	O
and	O
a	O
Rotman	O
lens	O
focal	O
plane	O
scanner	O
.	O
</s>
<s>
The	O
usage	O
of	O
true-time-delay	O
TTD	O
phase	B-Algorithm
shifters	I-Algorithm
instead	O
of	O
RF	B-Algorithm
MEMS	I-Algorithm
phase	B-Algorithm
shifters	I-Algorithm
allows	O
UWB	O
radar	B-Application
waveforms	O
with	O
associated	O
high	O
range	O
resolution	O
,	O
and	O
avoids	O
beam	O
squinting	O
or	O
frequency	O
scanning	O
.	O
</s>
<s>
TTD	O
phase	B-Algorithm
shifters	I-Algorithm
are	O
designed	O
using	O
the	O
switched-line	O
principle	O
or	O
the	O
distributed	O
loaded-line	O
principle	O
.	O
</s>
<s>
Switched-line	O
TTD	O
phase	B-Algorithm
shifters	I-Algorithm
outperform	O
distributed	O
loaded-line	O
TTD	O
phase	B-Algorithm
shifters	I-Algorithm
in	O
terms	O
of	O
time	O
delay	O
per	O
decibel	O
NF	O
,	O
especially	O
at	O
frequencies	O
up	O
to	O
X-band	B-Algorithm
,	O
but	O
are	O
inherently	O
digital	O
and	O
require	O
low-loss	O
and	O
high-isolation	O
SPNT	O
switches	B-Device
.	O
</s>
<s>
Distributed	O
loaded-line	O
TTD	O
phase	B-Algorithm
shifters	I-Algorithm
,	O
however	O
,	O
can	O
be	O
realized	O
analogously	O
or	O
digitally	O
,	O
and	O
in	O
smaller	O
form	O
factors	O
,	O
which	O
is	O
important	O
at	O
the	O
subarray	O
level	O
.	O
</s>
<s>
Analog	O
phase	B-Algorithm
shifters	I-Algorithm
are	O
biased	O
through	O
a	O
single	O
bias	O
line	O
,	O
whereas	O
multibit	O
digital	O
phase	B-Algorithm
shifters	I-Algorithm
require	O
a	O
parallel	O
bus	O
along	O
with	O
complex	O
routing	O
schemes	O
at	O
the	O
subarray	O
level	O
.	O
</s>
