Copper Bulk General (Cu) was chosen for the pivot material on its merits of possessing good electrical conductivity and optimised flexibility and stiffness for elastic recovery. The simulation, using Intellisuite, attained a working switch design, with an ‘Air-Gap’ of 1µm between the contacts, thus providing isolation when the switch is open-circuited.
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1. INTERNATIONAL JOURNAL OF COMPUTER ENGINEERING &
International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME TECHNOLOGY (IJCET) ISSN 0976
6367(Print) ISSN 0976 6375(Online) Volume 5, Issue 7, July (2014),
pp. 73-84 IAEME: www.iaeme.com/IJCET.asp Journal Impact Factor
(2014): 8.5328 (Calculated by GISI) www.jifactor.com 73 IJCET I A E
M E SIMULATED RF MEMS DOUBLE-POLE DOUBLE-THROW SWITCH USING A NOVEL
SEESAW STRUCTURE Mohammed Al-Amin, Sufian Yousef, Barry Morris,
Hassan Shirvani Anglia Ruskin University, Bishop Hall Lane,
Chelmsford, Essex, CM1 1SQ, United Kingdom. ABSTRACT This paper
explores the modelling and simulation of a Radio Frequency Micro
Electro- Mechanical Systems (RF MEMS) switch using Finite Element
modelling and analysis (FEM and FEA) tools on a novel seesaw
design, providing Double-Pole Double-Throw (DPDT) functionality.
This optimises the capabilities of the seesaw design structure for
use in mobile communication systems and devices. After researching
other available seesaw designs, it was realised that an improvement
could be achieved by applying additional contacts within a 3D
plane. During the development of the DPDT seesaw switch, a low
electrostatic actuation voltage of 14 V was achieved. This provided
the switch with improved compatibility with voltages closer to
those used in integrated circuits for mobile systems. The switch is
a progression of existing Single-Pole Single-Throw (SPST) seesaw
switches, with an additional set of upper and lower contacts at
each end of the seesaw, offering DPDT switching capability within
the space envelope. The length, height and width of the switch is
41 m, 7.6 m and of 9 m respectively, which is a suitable size for
fabrication and conforms to the Microscale, from 1 m to 100 m.
Copper Bulk General (Cu) was chosen for the pivot material on its
merits of possessing good electrical conductivity and optimised
flexibility and stiffness for elastic recovery. The simulation,
using Intellisuite, attained a working switch design, with an
Air-Gap of 1m between the contacts, thus providing isolation when
the switch is open-circuited. Keywords: DPDT, Electrostatic, Pivot,
RF MEMS, Radio Frequency Micro Electro-Mechanical Systems, Seesaw,
Simulated, Switch,
2. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME 74 1. INTRODUCTION As
technology progresses, there is an ever increasing need for
large-scale integration of RF MEMS switching devices within mobile
communication systems. The aim of the research was to create a
switch for mobile devices to allow switching between multiple
different protocols or frequencies. The design also needed to have
low power consumption for increased battery life and direct
interfacing capabilities with mobile components, without additional
circuitry. Achieving this leads to reduced cost and high
reliability. With the use of RF MEMS switches, it is possible to
meet all the criteria in a micro space envelope. Micro
Electro-Mechanical Systems, also known as MEMS, is an emerging
technology, which is finding its way into a number of applications,
such as gyroscopes, sensors, digital imaging and mobile
communications. The properties of materials change considerably
from the macro-scale to the micro-scale. For example electrostatic
forces become more significant, while the mass to surface area
ratio becomes less significant. MEMS technology takes advantage of
these small scale properties by being able to use simple
electrostatic plates to develop actuation forces, and relatively
increased surface area (with respect to mass) for heat dissipation,
which in turn improves reliability. MEMS can be broken down into
sub-fields, which include: MOEMS (Micro-Opto Electro-Mechanical
Systems): used for optical imaging such as, digital light
projection. Bio MEMS: an example of this is Lab-on-a-Chip (LOC)
where numerous biological tests can be carried out more efficiently
than traditional testing techniques. MEMS Audio: used for
microphonic sensors in commercial, studio microphones and mobile
devices. MEMS Sensors: these include the detection of movement (in
the x, y and z axes), heat, velocity and acceleration. RF MEMS:
used for mobile phones, mobile base stations, satellites and other
communication devices. Currently, MEMS devices are at a
disadvantage when it comes to size constraints, as most RF MEMS
switches are too large to be implemented into an integrated circuit
and are packaged separately. This causes difficulty when creating
smaller mobile devices. RF MEMS are commonly known for reliability
issues [7] due to the moving components. There is a high chance of
material fatigue and breakage [6], MEMS devices are also known to
have a high voltage actuation (up to 100V) [2, 8], which is due to
electrostatic actuation and design size. This requires the device
to provide a separate voltage source to be stepped up from a low
voltage to a high voltage and causes the mobile device to consume
more power than needed due the control circuitry and power
conversion inefficiency. This paper takes these challenges into
account, for the design of the RF MEMS switch, in order to overcome
them. The paper concentrates on RF MEMS, more specifically, it
addresses the use of RF MEMS switching on mobile phone devices with
the goal to operate at lower voltages than those used in existing
portable devices. The device was required to fit within the MEMS
scale of 1 m 100 m, with ease of fabrication for future integration
into microchips.
3. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME 75 Figure 1: Cross sectional
representation of the RF MEMS seesaw switch in the off-state The
research undertaken is a novel concept, using similar ideas of
seesaw theory from K. Jongseok (2007) et al [4] and J. M. Cabral
& A. S. Holmes (2006) [1]. These authors created an approach to
design, with the seesaw concept, but as a Single- Pole Single-Throw
(SPST) switch with similar voltages. The research in hand takes the
SPST concept and adds addition contacts on a 3D plane. This
provides the seesaw switch with Double-Pole Double-Throw (DPDT)
connectivity and in turn gives the device the flexibility of
selecting four protocols or frequencies. Multiple seesaw switches
can be configured and utilised to provide an extensive switching
selection of more than four configurations. This innovation has not
been attempted, to date, and quadruples the connectivity within a
reduced space envelope. The decision of using the seesaw concept
over others, such as the wobble motor principle switch, designed by
S. Pranonsatit (2006) et al [8], is that the design allows for
multiple connectivity within a reduced area. Also, with the ability
to reduce the size for lower actuation voltages. The wobble motor
does provide Single-Pole 8-Throw (SP8T) switching, but sacrifices
size and ease of fabrication, due to manually attaching the
cartwheel. The procedure for development of the RF MEMS switch
required the use of Finite Element Modelling (FEM) for designing
the switch and Finite Element Analysis (FEA) for simulation. FEM
modelling focuses on a two dimensional (2D) layout of the structure
with the intent of creating a three dimensional (3D) design model.
FEA simulation uses the FEM to provide stress, displacement and
electromagnetic outcomes of the structure, for a given voltage
input. The use of FEA software tools provides an expedient approach
to design and simulation, while reducing cost to a minimum. These
software tools can be used on a high specification computer to
provide computational data of the structure of a MEMS device,
without requiring external equipment or development time and cost.
The software tools provide high precision analysis with regular
updates. Intellisuite, created by Intellisense, was selected
because of its software capabilities. It is able to provide a
comprehensive materials database, efficient Solid and Process
modelling tools and an effective Thermo-Electromechanical analysis
tool [3] [5], with a graphical user interface (GUI) tool for users
to develop and analyse MEMS devices. The software is designed for
MEMS development only, but provides a simple CAD FEM tool with a
validation tool to detect any errors in the mesh.
4. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME Intellisuite uses an
intuitive method of designing, allowing the user to draw the shape
on a grid with a mouse. 76 The properties of the materials used in
MEMS are crucial to the functionality of the design, since the use
of inappropriate materials can cause a malfunction or damage to the
device and its peripheral components. Common materials used in RF
MEMS simulations are Silicon Bulk General (Si), Copper Bulk General
(Cu) and Aluminium Bulk General (Al) [2] [4]. The operating
principles of this RF MEMS switch relies on an electrostatic force
to close the contacts within an RF circuit (Figure 3). This force
(F) depends on the following equation: (1) Where, V = Supply
voltage = Dielectric constant of the Air Gap A = Area of the
electrostatic plates d = Distance between the electrostatic plates
F = Force between the electrostatic plates Figure 2: Graphical
representation of the force parameters The simulation takes into
account fringe capacitance, which affects the forces on the beam.
Fringe capacitance should be added to the equation as a constant
(C) to provide improved accuracy to the result. The simulation
required a voltage of 14 V to achieve a sufficient pulling force,
using a copper pivot (Figure 6), with a pivot thickness of 0.0476
m. The only parameters, which can be changed in equation 1, to
increase this force, are the area (A) and the distance (d) between
the parallel plates. As the seesaw is a symmetrical design, a
degree of flexibility is required to ensure that the contacts on
each side of the seesaw are closed simultaneously to provide
maximum contact surface area, for a low resistance [4].
5. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME 77 Figure 3: Cross sectional
representation of the activated RF MEMS seesaw switch in the
on-state The design, which has been created, incorporates most of
the research developments within one structure, these are: low
voltage actuation, reduced von-mises stress and increased switching
functionally within a space envelope of the micrometre range. To
understand the characteristics of the design, the research adopted
an empirical, simulation based approach, in order to provide
effective results, using Intellisuite software to model and
simulate the RF MEMS seesaw switch. 2. SUITABILITY OF THE DESIGN
FOR MOBILE COMMUNICATION The research conducted has concentrated on
optimising the best features of existing designs and incorporating
them into a seesaw switch structure. The dimensions of the space
envelope allows the design to be incorporated into mobile
communication devices. RF MEMS provides innate advantages over
conventional solid state switching materials; for example: Low
insertion loss, due to direct contact of low impedance materials
Low power consumption, due to voltage activation rather than
current activation Immunity to current leakage, due to no current
path High isolation, due to the Air-Gap between contacts Compared
to semiconductors, the on-state resistance of RF MEMS is innately
linear, because of its ohmic contacts. The seesaw mechanism relies
on the elastic recovery forces of the pivot and is controlled by
using two independent pull-down electrodes. 3. DESIGN AND
DEVELOPMENT To accommodate the Microscale between 1 m to 100 m, a
length of 41 m was chosen to be an appropriate value, enabling the
design to be large enough to facilitate fabrication and small
enough for increased switching speed. The distance between the beam
contacts and the fixed contacts is 1 m when in the off-state
(Figure 1). The seesaw pivot was designed using single polarity
supply voltages across each pair of electrostatic plates, which
were driven alternately with pulsed voltage waveforms. This allows
reduced external control circuitry and circuit complexity. With the
use of the DPDT switch design [1] [4], the RF MEMS seesaw device
accommodates two distinct radio frequencies, which communicate
simultaneously. By taking into account the area of the device (41 m
x 9 m or 369 m2, which is shown in Table II), this increases
functionality within the space envelope. With the use of elastic
recovery, the device is set to the off-state (Figure 1) without any
voltages being applied.
6. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME 78 The pivot is the thinnest
component of the structure, at a thickness of 0.0476 m, which
causes fabrication constraints. This restricts the design for use
only with advanced fabrication techniques, such as 32 nm
fabrication. The seesaw provides an advantage during the etching
process because of its simple design, as it allows the etching
solution to run though the structure without being held in the
gaps. Table I: Seesaw Dimensions Seesaw Dimensions Elements
Dimensions (m) Air Gap 1 Beam Length 41 Beam Height 4 Beam Width 5
The seesaw RF MEMS switch enables switching between a dual input
and output configuration, depending on the application. For primary
use, it is configured for switching between two RX (receive) and TX
(transmit) frequency bands. Other configurations may be used by
employing RF mixers at the input to the seesaw RF MEMS switch, and
provides simultaneous RX and TX for two distinct RF frequency
bands. This in turn, provides a dual RX/TX switch with a total of
four frequencies. The seesaw RF MEMS switch is designed to be used
for mobile communication devices for common protocols such as GSM,
Wi-Fi, 3G, 4G, WiMAX, Bluetooth, GPS and many other protocols.
Depending on the capacity of the antennas, all protocols can be
implemented, as most of them use frequencies that are less than 5.8
GHz. Figure 4: Activated RF MEMS seesaw switch. An earlier
prototype simulation, of an oblique view in the on-state with
colour coded displacement The seesaw switch has the versatility of
being connected into three configurations i.e. SPST DPDT or
Single-Pole Double-Throw (SPDT) switching without any changes to
the seesaw structure. This can be achieved by selecting the
appropriate contact terminals. Using multiple RF MEMS seesaw
switches with its three configurable modes, it is possible to
achieve switching between multiple different protocols to create a
switching matrix for GSM, 2G, 3G, 4G, Bluetooth, Wi-Fi and
GPS.
7. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME 79 4. TECHNIQUES OF THE
SWITCH The RF MEMS device employs two SPDT switches, which are
mounted at each end of a beam. The beam is balanced on a fixed
central pivot to provide a seesaw mechanism. The pivot gives the
seesaw elastic recovery of the beam, to a central position, when
the switch is in the off-state. The pulling force, developed by the
electrostatic plates, need to exceed the force of elastic recovery
in order for the switch to make contact. During operation, each
electrostatic plate is activated alternately to control the seesaw
motion. Since the switches are mechanically linked via the beam,
they are inversely synchronised with each other and may be
considered as one Double-Pole Double- Throw (DPDT) switch. The
seesaw motion of the beam is controlled by two complementary,
electrostatic control signals, with a duty-cycle of 50 %, in the
form of digital voltage pulses. The electrostatic forces, generated
by these pulses, are used to alternately pull down each side of the
seesaw to activate the switches. Four pairs of contact terminals
are closed via the bridging contacts located at each end and both
sides of the beam. Two switching pairs are closed simultaneously.
This is shown in Figure 4. 5. DESIGN PROCEDURE By looking at
existing seesaw designs available, it was discovered that an
improvement could be achieved by adding additional contacts. The
SPST Seesaw switch [1] [4] could be improved to a DPDT switch by
adding a set of upper and lower contacts to each side of the
seesaw. One of the important design requirements for the seesaw
switch is the pivot, as it is necessary for the switch to be used
in three dimensions. In order to allow the beam to pivot in any
orientation, consideration was given to the effect of gravity, even
though this is relatively weak at the micro-scale. To keep in
control of the movement, it is vital that the pivot is attached to
the beam, for elastic recovery. Standard materials (silicon bulk
general, copper bulk general and aluminium bulk general) were used
from the Intellisense materials database. A number of database
materials were tried and tested. Silicon bulk general, copper bulk
general and aluminium bulk general were selected as ideal materials
for use in MEMS fabrication. Silicon bulk general was used for all
of the substrates and aluminium bulk general was used for the
contacts and the electrostatic plates, as shown in Table II. For
the pivot, two copper bulk general material thicknesses were
considered, in order to evaluate their properties. The elastic
recovery of the materials is an important property of the pivot to
enable the off-state of the switching to occur while providing
flexibility for contact. Table II: Materials and beam
specifications Materials Substrate (Si) Silicon Bulk General Pivot
width 0.048 m (Cu) Copper Bulk General Pivot width 0.053 m (Cu)
Copper Bulk General and (Al) Aluminium Bulk General Beam (Al)
Aluminium Bulk General Contacts (Al) Aluminium Bulk General
Electrostatic Plates (Al) Aluminium Bulk General
8. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME 6. METHODOLOGY OF TESTING THE
PARAMETERS 80 The technique of testing was by using Intellisense
simulation software. The parameters of the simulation provides the
electrostatic plates with controlled pulse-widths. If the beam did
not respond to the pulse, the amplitude was then increased in
increments, until the correct response in displacement was
observed. The results were displayed graphically, by the simulation
package, and the associated data exported into a Microsoft Excel
spread-sheet for numerical analysis. This empirical approach to the
research improved each area of the RF MEMS seesaw switch via
multiple iterations, which yielded lower voltages and von mises
stress levels. The waveforms have a mark-space ratio of 1:1
(equivalent to a duty cycle of 50%), which enables each side of the
seesaw to be switched in an alternating fashion. 7. EXPERIMENTAL
ANALYSIS Using Thermo Electro-Mechanical analysis, a set of dynamic
results were produced (Figures 6-8). This uses time, stress and
displacement data to provide the seesaw switch with a time based
movement. Figure 5 shows that the displacement of the beam reaches
1 m (thus enabling the contacts to close) when a voltage of 14
volts was applied across the electrostatic plates, for copper,
using static simulation for a ranged voltage analysis. Figure 5:
Static analysis of displacement vs. Voltage for copper with a width
of 0.048 m This displacement is also shown in Figure 6 and Figure 7
as a function of time with pivot widths of 0.048 m and 0.053 m,
respectively. The 0.053 m thick pivot does not allow sufficient
displacement due to its stiffness and prevents the contacts from
closing.
9. International Journal of Computer Engineering and Technology
(IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5,
Issue 7, July (2014), pp. 73-84 IAEME Figure 6: Dynamic analysis of
displacement vs. Time using a copper pivot with a width of 0.048 m
Figure 7: Dynamic analysis of displacement vs. Time using a copper
pivot with a width of 0.053 m 81 Figure 8 also shows a graph of
displacement of the beam as a function of time, using aluminium.
Although aluminium has the same pivot thickness of 0.053 m as the
copper pivot shown in Figure 7, it provided a displacement which
reached its target destination due to the innate flexibility of the
material. Figure 8: Dynamic analysis of displacement vs. Time using
an Aluminium pivot with a width of 0.053 m
10. International Journal of Computer Engineering and
Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 -
6375(Online), Volume 5, Issue 7, July (2014), pp. 73-84 IAEME 82 A
dynamic simulation was carried out using aluminium with a pivot
thickness of 0.048 m, however, the software reported that the
aluminium pivot material exceeded its boundary conditions and
failed, therefore no graph was produced. A separate experiment was
conducted for the thickness of the pivot. Figures 9 and 10 show von
mises stress and displacement vs the thickness of the aluminium and
copper materials respectively, with a pulling voltage of 3 V. The
experiments show aluminium to provide higher flexibility over
copper at a thickness of 0.05m, but compromises von mises stress
that goes beyond its ultimate yield strength, which would lead to
fracture failure. Copper provides an optimum displacement at the
same thickness, with a von mises stress under the yield strength,
which guarantees no deformity of the material during the
electrostatic pulling force. Therefore, copper bulk general was
selected as the pivot material, because of its intrinsic
properties. Figure 9: Von Mises Stress and Displacement vs
Thickness of Aluminium pivot at 3V Figure 10: Von Mises Stress and
Displacement vs Thickness of Copper pivot at 3V
11. International Journal of Computer Engineering and
Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 -
6375(Online), Volume 5, Issue 7, July (2014), pp. 73-84 IAEME 83 8.
CONCLUSION After numerous iterations of the design, the
electrostatic supply voltage was reduced significantly from typical
values exceeding 40 volts to 14 volts for copper bulk general. This
was achieved using empirical analysis to observe each area of the
structure for improvements. The maximum pulling force was achieved
by making use of the surface area of the electrostatic plates on
the beam and the base of the seesaw. Also, an improvement was made
by optimising the thickness of the pivot to operate under von mises
stress and applying the minimum voltage for increased reliability.
A working simulation was achieved without compromising the Air-Gap
between the contacts, which retained isolation when the switch was
open-circuited, with alternating pulses. By using dynamic analysis
on Intellisuite software, the seesaw action was enabled. The seesaw
RF MEMS switch is an improved concept over existing designs, which
are limited to Single-Pole Single-Throw (SPST) switching [1] [4].
Additional contacts, in the improved design, achieve DPDT
switching, and required lower actuation voltages, due to the
reduction in size. The seesaw switch may be configured into three
switching modes (SPST, SPDT and DPDT) making it a versatile
component for use within integrated circuits for mobile
communication devices. 9. ACKNOWLEDGMENT The authors acknowledgment
is given to Jianhua Mao from Intellisense for his software support
and valuable advice on Intellisuite modelling and simulation
software tools. 10. REFERENCES [1] J. M CABRAL & A.S. HOLMES,
(2006). A novel seesaw-type RF MEMS switch. Electrotechnical
Conference, 2006. MELECON 2006, IEEE Mediterranean 2006, pp. 288-
292. [2] K.HYOUK, C. DONG-JUNE, P.AE-HYOUNG, L. HEE-CHUL, P.
YONG-HEE, K. YONG-DAE, N. HYO-JIN, J. YOUNG-CHANG & B. JONG-UK
(2007). Contact materials and reliability for high power RF-MEMS
switches. Micro Electro Mechanical Systems, 2007. MEMS. IEEE 20th
International Conference on 2007, pp. 231-234. [3] H. JAAFAR, N.
FONG LI & N.A.M. YUNUS (2011). Design and simulation of high
performance RF MEMS series switch. Micro and Nanoelectronics (RSM),
2011 IEEE Regional Symposium on 2011, pp. 349-353. [4] K.JONGSEOK,
K. SANGWOOK, Y. HONG, J. HEEMOON & L. SANGHOON (2007). Variable
pivot seesaw actuated RF MEMS switch for reconfigurable system
application. Micro Electro Mechanical Systems, 2007. MEMS. IEEE
20th International Conference on 2007, pp. 775-778. [5] A.M. PASHA
& M.A. SAQIB (2009). Design optimization for low voltage DC
contact RF MEMS shunt switch. Electrical Engineering, 2009. ICEE
'09. Third International Conference on 2009, pp. 1-6. [6] H. R.
Shea (2006), Reliability of MEMS for space applications Proc. of
SPIE Reliability, Packaging, Testing, and Characterization of
MEMS/MOEMS V on 2006, vol. Vol. 6111, 61110A. [7] J. HWANG, 2007.
Reliability of Electrostatically Actuated RF MEMS Switches Radio-
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Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 -
6375(Online), Volume 5, Issue 7, July (2014), pp. 73-84 IAEME 84
[8] S. PRANONSATIT, G. HONG, A.S. HOLMES and S. LUCYSZYN, 2006.
Rotary RF MEMS Switch Based on the Wobble Motor Principle Micro
Electro Mechanical Systems, 2006. MEMS 2006 Istanbul. 19th IEEE
International Conference on 2006, pp. 886-889. [9] Anesh K Sharma,
Ashu K Gautam, CG Balaji, Asudeb Dutta and SG Singh, 2012. Shunt Rf
Mems Switch with Low Potential and Low Losson Quartz for
Reconfigurable Circuit Applications, International Journal of
Electronics and Communication Engineering & Technology
(IJECET), Volume 3, Issue 2, pp. 497 - 510, ISSN Print: 0976- 6464,
ISSN Online: 0976 6472. 11. ABBREVIATIONS 2G Second Generation 3G
Third Generation 4G Fourth Generation BIO MEMS Biological Micro
Electro- Mechanical Systems DC Direct Current DPDT
Double-Pole-Double-Throw GHz Giga-Hertz GPS Global Positioning
System GSM Global System for Mobile Communications MEMS Micro
Electro-Mechanical Systems MOMEMS Micro-Opto Electro- Mechanical
Systems ms Milliseconds SPDT Single-Pole Double-Throw SPST
Single-Pole Single-Throw SP8T Single-Pole Eight-Throw RX Receive RF
MEMS Radio Frequency Micro Electro-Mechanical Systems TX Transmit m
Micrometre Wi-Fi Wireless Fidelity WiMAX Worldwide Interoperability
for Microwave Access