Selected Applications of Tunable Materials for Microwave Components

Matthias Maasch, Onur Hamza Karabey, Sebastian Strunck and Rolf Jakoby

Mircowave Engineering, Technische Universität Darmstadt

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 2

Tunable Materials for Microwave Components

Phase shifter in antenna arrays for beam forming

Matching networks

Power amplifiers

Implementation of tunability by using

Liquid Crystal above 10GHz

Ferroelectrics (Barium-Strontium-Titanate) below 15GHz

Metamaterials

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 3

Outline

Coaxial Transmission Line for Liquid Crystal Charaterization

Thermal Effects in Interdigital Capacitors

Tunable SRR loaded Waveguide

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 4

Coaxial Transmission Line for Liquid Crystal Charaterization

Thermal Effects in Interdigital Capacitors

Tunable SRR loaded Waveguide

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 5

LC Characterization Setup

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 6

LC Characterization Setup

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 7

10 20 30 40 50-5

-4

-3

-2

-1

0

f (GHz)

|S2

1|/d

B

no EM leakage

incl. EM leakage

EM Leakage through Filling Channels

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 8

Simulated Impact of Filling Channels

Karabey et al. “Precise Broadband Microwave Material Characterization of Liquids” EuMW 2010

Error due to EM leakage: r’ : <6% r’’ : <40%

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 9

Coaxial Transmission Line for Liquid Crystal Charaterization

Thermal Effects in Interdigital Capacitors

Tunable SRR loaded Waveguide

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 10

Interdigital Capacitor on BST

r of BST is tunable by static E-field

Cheap printing technology

Better linearity compared to semiconductor varactors

High power capability ‟ thermal effects?

Alumina (250µm)

BST (10µm)

Gold (3µm)

Gold (3µm)

+VDC

-VDC

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 11

Simulated Temperature

IDC size: 200x600µm2

Gap width: 20µm

Finger width: 20µm

BST RF properties

r = 200, tan = 0.02

RF input power:50W @ 2GHz

Maximum temperature ≈ 52°C

Temperature inside BST layer ≈ 37°C

He “Heat capacity, thermal conductivity, and thermal expansion of barium titanate-based ceramics” Thermochimica Acta, 2004

BST

Alumina

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 12

Coaxial Transmission Line for Liquid Crystal Charaterization

Thermal Effects in Interdigital Capacitors

Tunable SRR loaded Waveguide

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 13

Tunable SRR loaded Waveguide

Maasch et al. “Voltage Tunable Split-Ring-Resonators for Waveguide Applications” Metamaterials 2009

Introduction of tunability to Split Ring Resonators by loading the gap

Phase shifter, filter inside a waveguide

Step towards voltage tunable 3D Metamaterial

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 14

DC-Biasing of SRR Array

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 15

Simulated Impact of Bias Elements

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 16

Simulation of Tuning

theoretical tuning range: 0.7…2.4GHz

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 17

Measurement Setup

9 SRRs with 9x9mm2

Substrate: RT/duroid 5880, t=0.38mm

Biasing Resistor

Varactor Diode

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 18

Measurement Results

measured tuning range: 0.9…2.2GHz

ETiT | Mikrowellentechnik „ Microwave Engineering | CST User Group Meeting 2010 | 19

Thank you for your attention.