rf mems ppt

1. RF MEMS : A REVIEW
ON STATE OF ART
Preetam Chandan Mohapatra
School Of Mechanical And Materials Engineering
Washington State University
Pullman, WA, USA
Preetam.mohapatra@email.wsu.edu
Arun Tapan Dash
Department of Mechanical Engineering (1st Year)
IGIT, Saranga, OR, INDIA
aruntapan1992@gmail.com

2. WHAT IS MEMS?
The whole system of micro scaled mechanical
instruments pertaining to the relevant electrical
circuitry are defined as micro electromechanical
system. MEMS is an interdisciplinary area which is
incorporate both ME and EE
WHAT IS RF?
•It refers to radio frequency i.e. the frequency
ranged within 3khz to 300ghz.
•All kind of wireless based communication (sensing
& actuating) uses RF to transmit and receive
signals.

3. WHAT IS RF MEMS?
RF MEMS can simply be categorized to be a
special application area of MEMS in the
field.
RF is one of the important sectors in CE
where MEMS proved its worth
RF MEMS holds the rein of Communication
Engineering which is an important sector for
silicon industries

4. WHY MEMS?
Miniaturized Version of machines for
different critical application and where
traditional machines are not able to work .
Due to following constrains the traditional
machines are not able to work
•Size
•Weight
•Power requirement
•Efficiency

5. HOW MEMS WORKS?
•Miniaturization of machines needs special
electrical circuitry for functionalization
•Following things are different in micro scale
for which we use special circuitry
•To receive power in micro scale for actuating
and sensing
•Operation is done by special algorithm
followed by programed logic

6. How RF works?
RF functionality consists of two basic concepts:
1. Transmitting and receiving signals
2. Generation of such high frequency
 Transmission and receiving signal is done by
antennas
 Generation of such high frequency is done by
different RF technologies like
1. RF COMS
2. RF MEMS
3. FERRO electric
4. Vacuum tubes

7. WHY RF MEMS IS POPULAR ?
•Specific range of operations
•Cost efficiency
•Reduction of noise level at output
•Less power requirement
•Better function ability and performance
•Light weight

8. DEVIECE USED IN MEMS?
Following devices are used by using
MEMS technologies
1. Oscillators
2. Clock generators
3. Resonators
4. RF switches
5. Switched capacitors
6. Tunable inductors
7. Varactors

9. Oscillators and clock generators and resonators are timing devices
Oscillators vibrate at some higher frequency called reference frequency
for
1. Operate further electronic manage data transfer rate
2. Control RF
3. Calculate time gap between operating cycles in circuitry.
4. Crystal oscillators are replaced by MEMS oscillators due to small
size , low power requirement, self sustainability
5. RF resonators- A part of oscillator that resonate at a definite
frequency
6. Q factor 10000 at GHz level
7. Clock generators are timing generates which generate clock pulse
on micro scale to feed the electronic cct.
8. RF switches, switched capacitors and varactors are actuating
devices
9. Switched capacitors ->basically micro scaled capacitors used to
brake charge in and out when closed and opened respectively.
Used in capacitive filtration.
10. RF switches are micro level switches used as capacitor for smooth
operation.
11. Varactors: also called varicap. Micro scaled diodes having
capacitance which is directly a function of voltage applied across
the ends of this diode.

10. Terms used in RF MEMS
•Resonating Frequency is the frequency at which kinetic as
well as potential energy resonates.
•Q, the quality factor is the ratio of the energy stored in the
system (passive components) to the energy dissipated in
the reactive components of the system per cycle. In simple
words it is the ratio of the imaginary part to the real part of
the electrical impedance.
•Equivalent Series Resistance is the resultant of all the
reactive and passive element resistances included in series.

11. •Linearity of a RF MEMS switch is its characteristics to
retain the independence of the device impedance from the
input power of the RF signals.
•Isolation is refers to the separation of Input and Output
signal at Radio Frequency level.
•Return loss is the Radio Frequency loss which is returned
back by the RF switches while transmitting the signal.
•Insertion loss is defined to be the radio frequency loss
dissipated inside the MEMS device while the switch is in
pass-through or closed circuit state in a series connection.
This insertion loss consists of resistive loss due to the
surface contact at the low frequency operation and loss
due to skin depth effect at higher frequency.

12. •Tenability is the ratio of the difference between maximum and
minimum inductance to the minimum inductance in the RF MEMS
tunable inductors.
•FET is the field effect transistor.
•PIN diode is a diode having a lightly doped intrinsic
semiconductor between the P-type and N-type semiconductors
which are heavily doped.
•Packaging is fundamentally the bonding of the micro mechanical
switches to the chip or board where electrical circuit is
encompassed with. This is the most critical and expensive part of
micro manufacturing process. Because it is done in a Hermitic
environment to prevent contamination of the RF MEMS switches
with water vapor or dust. They are carefully fitted on to the surface
of the substrate with required connection to the electrical circuit so
that there won’t be any interference or exposure of the moving parts
of the devices to external atmosphere when put to operation.

13. Common use types:
R and D sectors
1. Defense
2. Secret service communication
3. Secured encrypted data transfer
4. Space exploration research
5. Global sensing
6. Anti jam frequency operation
7. Ultra clean transmission

14. Commercial use:
1.All wireless communication
2.DCS
3.PCS
4.GSM
5.EGSM
6.CDMA
7.WCDMA
8.GPS
9.WIFI

15. POPULARITY OF RF SWITCHES:
•Incredible advantage over Si and GaAs switches where
H.F micro wave is concerned.
•Following advantage of the switch
1. Low insertion loss
2. Achieve extreme linearity
3. Very good for multi mode band switching
4. High data transfer rate
5. Less power consumption when used in electrical
circuitry.
6. More efficiency
7. Incredible isolation with air gaps.
8. Lower cost of manufacture than pin diode and FETs

16. Use of MEMS devices in single chip based
frontends:
Compatible for IC technology. following
are the reasons
1. Low loss filtration
2. Switching
3. Wide range frequency generation
4. Mixing
5. Low power consumption
6. Very less interference with external
atmosphere.

18. Similarly this 5 pole tunable filter made
with RF MEMS capacitive switches
shows ideal behavior along with
incredible linearity.
RF MEMS inductors developed at Tokyo
Institute of Technology, Japan, are
capable of changing Real and Imaginary
parts separately. This variable inductor is
suitable for wideband RF frontend. The
importance of MEMS inductor over
traditional ones are its wide range of
inductance, tenability for wideband
operation, higher Quality factor to lower
the loss and higher self-resonating
frequency for higher available frequency.
Conventional variable inductor is
operated with MOS switch with 187%
tenability but the MEMS inductors are
governed by actuators with only 18%
tenability. MEMS inductors are useful for
critical RF use due to their thick metal
film, highly resistive substrate and air
suspended structure. For different
wireless application researchers are
trying to integrate CMOS with MEMS
technology for high performing RF
frontend.

19. Lacuna of RF SWITCHES:
1. Reliability issues
2. High voltage and current drive
3. Packaging cost
4. Technology cost
Instead of these little challenges RF
MEMS market is growing much
faster which can be depicted as
follows;

20. (Worldwide MEMS market in two
different years 2004 and 2009)

21. (pie chart showing worldwide MEMS manufacturers)