Kein Folientitel

1

MEMS Tuneable Dielectric Resonator for Mobile
Communication Systems
G. Panaitov, R. Ott and N. Klein Research Center
Jülich, Germany
2
MEMS Tuneable Dielectric Resonator

• Outline
• Principle of Cellular Mobile Communication
• General
• Approach (MEMS, Slotline)
• Experimental Setup
• Results
• Summary

3
Principle of Cellular Mobile Communication
GSM Mobile System 960-935MHz 910-895MHz
GSM Network
MS mobile station
SC switching center
BS base station
4
Principle of Cellular Mobile Communication
GSM Mobile System 960-935MHz 910-895MHz

• MS mobile station
• transmitter
• receiver
• control circuitry

Receiv. Chnl. 25kHz
Transm. Chnl. 25kHz
Disadvantages - very limited number of channels
- limited propagation
5
Principle of Cellular Mobile Communication
GSM Mobile System Base Station

• Communication via BS
• MS1 BS MS2
• BS transmitter/receiver, towers
• effective retransmission
• BS coverage area hexagon
• limited to 30-40km

BS base station
30 40 km
6
Principle of Cellular Mobile Communication
GSM Mobile System Cellular Network
Series of individual cells build a Cellular
network covers the GSM area
7
Principle of Cellular Mobile Communication
GSM Mobile System Cellular Network

• Each NC with the neighbours
• cells form a kind of
• Cluster configuration
• Frequency distribution
• every cluster use the complete set of
• available frequencies (1000)
• Total Number of available channels
• Nchnl 1000Nclst

8
Principle of Cellular Mobile Communication
GSM Mobile System Switching Center

• BS SC connection
• multichannel radio or fiber-optic cables
• Flexible frequency use
• - looks for the best frequency
• connection between MS
• - change f-channel if MS moves
• out of cell while the call in
  progress
• - change of f-channel at a noise
• disturbance

Switching center
9
Principle of Cellular Mobile Communication
GSM Mobile System Switching Center

• SC and BS require f-selective
• components (filters, resonators)
• with tunagle resonance frequency
• 3G UMTS (universal mobile
• telecommunication system)
• - 1920-1980MHz uplink
• - 2110-2170MHz downlink
• - high data rate (up170kb/s mobile)
• require faster tuning time (ms)

Switching center
10
Tunable UMTS Filters based on dielectric
resonators (TUF)
Project goal Development of the tuneable
dielectric resonator at about 2 GHz (large tuning
df, high Q)

• Techniques Partners
• Ferroectric based tuning (South Bank University
  (London)
• Ferrite and ferroelectric/paraelectric (Warsaw
  University of Technology)
• Dielectric ceramic development (Institute Josef
  Stefan (Ljubljana), Filtronic Comtek (UK) Ltd)
• MEMS (Micro Electro-Mechanical Systems) tuneable
  resonator (FZJ, Jülich)

• Device Examples (Ericson)
• Tuneable reject filter (to remove narrow band
  interferer)
• t ms low load. Q gt 3000 at 2 GHz df
  up 60 MHz,
• Channel filter, 5 MHz wide
• t seconds medium load. Q gt 10000 at
  2 GHz df up 60 MHz

11
MEMS micro-electromechanical switch

• Free-standing strictures 1)micro bridges 2)
  cantilever
• Actuation 1) Electrostatic 2) Bimetal 3)
  Piezo-electric

Microstrip 1
Microstrip 2
12
MEMS micro-electromechanical switch
Technology 1) sacrificial layer
2) Si-macromachining, anisotropic
etching (RWTH, Aachen)
13
Microwave Slotlines
Slotline planar microwave resonator

• Narrow slot etched in the metallisation
• on one side of dielectric substrate
• Resonanse parameters
• Z, f, l, Q depends on h, w, er
• for thick substrate h gtgt w

h
er
w
14
Microwave Slotlines
Short End Slotline Microwave Resonator

• Resonator parameters
• f, l, Q depends on
• l-slotline length
• State of the free end of slotline
• closed/open

l
h
er
w
15
Microwave Slotlines
Short End Slotline Transmission Line Theory
Z0 - characteristic impedance b 2p/l -
propagation constant Z1, Z2 - slotline end
impedances
16
MEMS tuneable dielectric resonator
Tuning Concept
l

• 4 radial slots
• MEMS open quarter wave resonator (ll/4)
• MEMS closed half wave resonator (ll/2)
• DR TE01? ,mode coupled to slotline if fDR
  fquarterwave

17
MEMS tuneable dielectric resonator
Simulation with CST Microwave Studio E-field

• MEMS open
• strong intermode coupling
• f 1.878 GHz Q6,700

• MEMS closed
• weak intermode coupling
• f 1.945 GHz Q21,500

tuning range 67 MHz (3)
18
MEMS tuneable dielectric resonator
Simulation E-field of the single slotline
MEMS open Quarterwave resonator
MEMS closed Halfwave resonator
19
MEMS tuneable dielectric resonator
Piezo Actuator based Experimental Setup

• Actuator parameters
• size 32 x 7.8 x 1.2 mm3
• max deflection 325µm
• voltage 100V or 0-200V
• switching time 1,5ms
• force at the end 2,25N

20
Piezo Actuators
Piezo Effect
(e.g.
PZT)

• dL Edij L0 dij V single layer
• small dij 0.5 µm/kV
• dL n dij V multilayer
• max displacement up to 5µm
  

L0dL
V
Bimorph Piezo Actuator (Benders)

• similar to bimetal thermoexpan.
• perpendicular piezo effect
• Expansion contraction layers
• movement up to 1000 µm
• up to 109 cycles

21
MEMS tuneable dielectric resonator
Piezo actuator assembly

• Actuator parameters
• size 32 x 7.8 x 1.2 mm3
• max deflection 325µm
• voltage 100V or 0-200V
• switching time 1,5ms
• force at the end 2,25N

Thin film slotlines 19x1x0.001mm3
22
MEMS tuneable dielectric resonator
Experimental results Bulk slotlines
19x0.4x0.5mm3
Tuning Parameters
Piezo actuator assembly
Bulk slotlines 19x0.4x0.5mm3

• Variation of frequency mean discret value
  df 3.5MHz/switch
• No strong intermodular coupling betveen
  slotlines
• digital tuning possible

23
MEMS tuneable dielectric resonator
Digital frequency tuning
N - number of tuning elements (slots) df -
frequency step (digitalisation unit) dFn n
df , 0 lt n lt N
dFn n1df1 n2df2 df2 kdf1

df0.2MHz N25 Tuning
5x0.2MHz
df10.2MHz df21MHz N8
24
MEMS tuneable dielectric resonator
Experimental results digital tuning

• Optimisation of the frequency step
• slotline width, w
• slotline length, l
• DR/Slotline distance, h

25
MEMS tuneable dielectric resonator
Experimental results Bulk slotlines 20x1x0.5mm3
Tuning Parameters
Piezo actuator assembly
Bulk slotlines 20x1x0.5mm3
df 7 MHz/switch Tuning df 14MHz Q
6000 - 10000
26
MEMS tuneable dielectric resonator
Exp. Results Frequency step as the function of
slotline length
Bulk slots width1mm thickness0.5mm h
2mm
Analyse of df(l) dependence df
0.2exp(l/3.43) 0.12
27
MEMS tuneable dielectric resonator
Exp. results Frequency step, df as the function
of the h-distance between DR and slots (w0.4 and
1mm)
28
MEMS tuneable dielectric resonator
Experimental results digital tuning df
0.25MHz
Tuning Parameters Bulk slotlines 19x0.4x0.5mm3
DR/Slots distance h12mm
Frequency step, df, versus h
df 0.26MHz/switch df 1.06MHz Q 25000
29
MEMS tuneable dielectric resonator

• Conclusion
• Novel high Q fast digital tuning concept for DR
  developed
• Concept was proved by piezo-bimorph actuator
  design
• Wide range digital tuning with 7 and 3.5MHz
  steps can be realised at high Qs up to 10000
• Optimisation design, coupling parameters,
  stability etc.

30
MEMS tuneable dielectric resonator
Experimental results optimisation of actuating
voltage
Frequency and Q-data versus Piezo/Slot Distance
Strong capacitive coupling
Weak capacitive coupling
31
Cylindrical dielectric resonator
TE01d mode
a
L
a radius L length (height) er dielectric
constant f resonant frequency
32
MEMS tuneable dielectric resonator
Micromachined MEMS cantilever in flip-chip design
4 micromachined cantilever on Si-subtrate are
mounted flip-chip to control the slotline state
Resonator assambly with MEMS cantilever
33
MEMS tuneable dielectric resonator
Idea of the approach

• compact
• low power consumption
• low weight
• fast tuning time t ms