Reconfigurable RF Frontends Technologies for Tunable …Reconfigurable RF Frontends Technologies for...

19.09.2012 | Institute of Microwave Engineering and Photonics | Holger Maune

Technologies for Tunable Antennas Holger Maune

Technische Universität Darmstadt Institute of Microwave Engineering and Photonics [email protected]


Agenda

Reconfigurable RF Frontends Technologies for Tunable Antennas Ferroelectrics

Liquid Crystal

Tunable Antennas Pattern Engineering

Impedance Tuning

Conclusion

Today‘s Technology for Radio-Frontends


Radio Frequency Frontend Digital Backend Antenna

Mixer Oscillator Amplifier

Matching Network Filtering

Switch Diplexer

Matching Network

Digital - Analog

Converter Signal

Processing

FFDA

DA

HPA

LNA

VCODSP

A wide range of incompatible, hardware-related inflexible systems, operating on a variety of carrier frequencies, modes and standards.

Towards Frequency-Agile, Software-Defined, and Cognitive Radios


Digital Backend

Digital - Analog

Converter Signal

Processing

Reconfigurable RF-Frontend with tunable passive components

Smart Antennas



Switch Diplexer

Matching Network

FFDA

DA

HPA

LNA

VCODSP Φ

Baseband (software) reconfiguration for multi-standard operation Reconfigurable RF frontends with reconfigurable/tunable analog

RF components for multi-band (and multi-standard) operation

Fundamentals of Antenna Arrays


I = +++ ΘαΘαα cos22

cos10

210 kdjjjkdjj eeIeeIeI ... = ∑−

=

⋅⋅⋅⋅1

0

cosN

n

dknjjn eeI n Θα

ζn = n⋅k⋅d⋅cos(Θ) for n= 0, 1, 2, 3...

a0

a1

Attenuators Phase shifters

+

0α

1−Nα

1α

Wavefronts

Receiver

00

jE e ξ⋅

10

jE e ξ⋅

10

NjE e ξ −⋅

d

Θ

Radiating elements

Combiner

aN-1

Phase difference at n-th element

Sum-Signal

Example: Linear Dipole Array

19.09.2012 | Institute of Microwave Engineering and Photonics | Holger Maune Br

oads

ide Θ

0=90

°

Endfire Θ0=0°

Pattern changes during scanning

Applications for Steerable Antennas


Technologies for Reconfigurable RF-Hardware


Thin Film Thick Film

Technologies for Reconfigurable Systems

MEMS LC

ACTIVE PASSIVE

FE Semiconductors MMIC RFIC

Thick Film

LC

Low cost technologies Low power consumption High linearity High power application High FoM possible Compact by using MetaMaterial structures

Ferrites

Liquid Crystal as Tunable Material for Microwave Applications


Solid

Nematic

Liquid

Temperature

z

x

n

ε⊥ε

uniaxial anisotropy

Isotropic Not Tunable

Anisotropic Tunable

Anisotropic Not Tunable

Liquid Nematic Soild

εr,

εr,

Anisotropy ∆εr= εr,-εr,

Liquid Crystal as Tunable Material for Microwave Applications


DC

RF

V

0

2( ) ( )rU Uπβ ελ

Φ = ⋅ = ⋅

( ) ' '( ) ( )U U Uj L Cγ ω µ ε≈ ∝ ⋅

0

2( ) ) ( )0(r rU Uπ ε ελ

∆Φ = − ⋅

Barium-Strontium-Titanate as Tunable Material for Microwave Applications


Large dipole moment by Ti4+ & O2-

Permittivity can be changed by an electrostatic field

Change limited by breakdown Fast Tuning ps-range Passive Tuning electrostatic field

Dielectric Tunability

εr

|E|

∆εr(E)

Barium-Strontium-Titanate as Tunable Material for Microwave Applications


3D Structures

Deposition on Si,MgO,LaAlO3,Pt… (400…650°C)

εr ≈ 100 … 600 h ≈ 70 … 500 nm

Thin-Films

Planar Structures

Screen-printing on Al2O3

Sintering (≈ 1200°C) εr ≈ 200 … 700 h ≈ 1 … 30 µm

Thick-Films

Printing of BST on various materials Sintering

h ≈ 70 … 500 nm

Inkjet-Printing


Planar Antennas

Planar Phased Array Antennas based on Liquid Crystal Technology


Planar Phased Array Antennas based on Liquid Crystal Technology


@ 17.5 GHz

Phase Shifter Topologies


Phase shifters are usually based on:

Simple design & fabrication Wide bandwidth Change of line impedance mismatching

Artificial transmission line (LH) Conventional transmission line (RH)

Phase Shifter Topologies


Larger absolute phase constant LH Line can be physically shorter

More compact phase shifter LH

RH

Phase constant with higher sensitivity to a capacitance change

Planar Phased Array Antennas based on BST Thick Film Technology


Phase Shifters for Differential Signals


Tunable differential phase shifter

Phase Shifters for Differential Signals


Performance @ 10 GHz Phase shift = 225° FoM = 38°/dB

Insertion loss = -12dB Leakage current < 0.2 nA

@ 10 GHz


Volumetric Antennas

Tunable Antennas for Inter-Satellite Communications


Tunable Antennas for Inter-Satellite Communications


-20-15-10-50

26 28 30 32 34 36 38 40

|S| [

dB]

050

100150200

26 28 30 32 34 36 38 40f [GHz]

FoM

| [°/

dB]

100225350475600

∆Φ

[°]

Tunable Antennas based on LTCC


Reflectarray Antennas


1

k0 Rn r n r 0 n 2 Nn

1

2

Functional principle Energy radiated by the feed Reradiated and phase-adjusted at

each element

Phase compensation



16x16 elements All patches in a row connected Beam steering in one plane



Gain: 20.3 dB Directivity: 24 dB Efficiency: 42%


Impedance Tuning

Towards Frequency-Agile, Software-Defined, and Cognitive Radios


Digital Backend

Digital - Analog

Converter Signal

Processing

Reconfigurable RF-Frontend with tunable passive components

Smart Antennas



Switch Diplexer

Matching Network

FFDA

DA

HPA

LNA

VCODSP Φ

Baseband (software) reconfiguration for multi-standard operation Reconfigurable RF frontends with reconfigurable/tunable analog

RF components for multi-band (and multi-standard) operation

Frequency Tunable Antenna


Ext.DC source

40 kΩ

z

y

x

Using varactors to tune compact antennas to cover several bands ( e.g. 0.99 ~ 1.11 GHz with varactors‘ tunability of 30% )

Low operation current (e.g. ~ nA) allows very low DC power consumption

0.9 1.0 1.1 1.2

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 V

50 V

90 V Refle

ctio

n Co

effic

ient

(dB)

Frequency (GHz)

Equivalent Bandwidth

Tunable Dual-Band Antenna


0

-3

-6

-9

-12

-15

-18

-21

-24

-27

-30

0.65 0.95 1.25 1.55 1.85

Frequency (GHz)

By tuning Varactor 1

0

-3

-6

-9

-12

-15

-18

-21

-24

-27

-30

0.7

Frequency (GHz)

1.1 1.5 1.9 2.3

By tuning Varactor 2

Varac. 1

Varactor 2

Application Example for Tunable Antennas


Conclusion

Concepts for tunable antennas Technologies for tunable microwave devices Prototype realizations


FE

LC

Die

lect

ric L

osse

s

Frequency

Reconfigurable RF Frontends Technologies for Tunable …Reconfigurable RF Frontends Technologies for...

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