Download Terahertz Integrated Circuits for Radio Astronomy Applications

Terahertz Integrated Circuits for
Radio Astronomy Applications
Sina Fathi
EUC Berlin, 2014
07.05.2014
Sina Fathi, CST European User Conference
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Agenda
 Introduction
− Radio Astronomy
− Radio telescope and atmospheric window
 KOSMA Laboratory
− Superconducting based detectors (SIS, HEB,…)
 CST Suite Software
−
−
−
−
3D design of waveguides, antennas,…
Modeling of superconducting materials
Some examples of designed circuits
Comparison between simulation result and FTS
measurement of HEB mixer at 4.7THz
 Conclusion
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Introduction
Radio Astronomy:
 Mixing sky signals (RF) to lower frequencies (IF)
 Observations begin from hundred GHz to a few THz
(~5THz)
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0.3 – 5 THz
RF
0.1 – 10 GHz
IF
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Introduction
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Pillars of Creation

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far-infrared: ESA/Herschel/PACS/SPIRE/Hill, Motte, HOBYS Key Programme
Consortium; ESA/XMM-Newton/EPIC/XMM-Newton-SOC/Boulanger; optical:
MPG/ESO; near-infrared/VLT/ISAAC/McCaughrean & Andersen/AIP/ESO
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Radio Telescope
Single Ended Receiver

Filter Spectrometer
K H Gundlach and M Schicke, IRAM, Supercond.
Sci. Technol. 13 (2000)
 Applying heterodyne receiver because
of no sufficient low noise amplifier for
electronic processing of weak signals
from 300 GHz to several THz
 Receivers with HEMT amplifier at 100
GHz
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 SMART Receiver on
Nanten 2
 Great Receiver on
SOFIA, 2010
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Atmospheric Window
Atmospheric frequency windows determine ground based
observations
 Observations especially at lower THz frequencies should be done at high altitude
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Herschel Satellite (May 2009)
 3.5 meter mirror
 480 GHz to 1910 GHz (SIS and
HEB mixers)
 Band 2 (640-800 GHz) by KOSMA
NANTEN 2 Observatory (May 2006)
ALMA observatory (2013 Inauguration)
Atacama desert Chile, 5,058 meter altitude
66 telescopes (12 meter and 7 meter)
31-950 GHz frequency range (HEMT for two
lowest bands and SIS mixers for above
84GHz)
SOFIA Observatory (First light on May 2010)
Atacama Desert, Chile, 4800 meter
1.3 - 1.4 THz / 1.9 THz / 2.5 THz / 4.7 THz (May 2014)
altitude
110 GHz to 880 GHz (SIS mixers, KOSMA) (HEB Mixers, KOSMA)
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KOSMA Laboratory
Development of superconducting based detectors working
at millimeter and sub-millimeter frequency ranges:
 Development:




Design
Micro/nano-fabrication
Cryogenic THz measurements
Waveguide machining
 Detectors:
 Nonlinear mixing devices like SIS or HEB,
 Balanced and side band separating mixers,
 Waveguides, antennas,…
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SIS and HEB Mixers
Superconductor-Insulator-Superconductor (SIS):
 The most sensitive heterodyne receivers from 100 GHz to 1.1 THz
 Two superconductors are separated by a really thin layer insulator
 Two common frequency mixers are Nb/AlOx/Nb or high current density
Nb/AlN/Nb (Tc of Nb≈9 K)
 Current passes through the junction via tunneling process
 Strong nonlinear current-voltage (I-V) characteristic
 Modelling as a parallel resistor and large junction capacitance
30𝜇𝜇
𝒉𝝂� 𝒎𝒎
𝒆
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𝒅 = 𝟎. 𝟗𝟗𝟗
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SIS and HEB Mixers
Hot Electron Bolometer (HEB):
 Not limited by energy gap of the superconductor (up to several THz)
 Required very low LO power (20-1000 nW) and unlike SIS does not
increase with frequency
 HEB is a square law mixer
 Model as a resistor (proximity effect-NbN is simulated as a normal
conductor)
At 4.2 K in He(l)
Au
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Tc = 9.3 K
Ic= 400 µA
NbN
NbN
Microbridge of
NbN, NbTiN,…
Au
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Balanced Mixer
Advantages of balanced mixer configuration over the single
ended mixer:
 Reduces a side band noise of LO
 Separates the RF and LO inputs from each other that eases integration of
several pixels in focal plane arrays configuration
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CST 3D models
Using mainly CST microwave suite to design our THz
integrated circuits
 Integrated superconducting balanced mixer working at 350-500 GHz
Port 2
12 micron
Port 3
S2,1
Port 1
S3,1
Port 4
 Nb based circuitry
 SiO2 bridges (No airbridge)
 9𝜇𝑚Silicon membrane
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

−𝟗𝟗. 𝟐𝟐𝟐
−𝟏𝟏𝟏. 𝟓𝟓
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E-Field Monitor of IBAMI
Absolute E-Field monitor of IBAMI mixer (Two antennas and a 90° branch line
coupler)
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Fabricated IBAMI
1 cm
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Receiver Noise Temperature of
prototype LF band of CHAI Receiver
 The measured receiver noise temperature over an IF bandwidth from1 to 6 GHz
for a LO frequency of 462 GHz
𝑵𝑵 = 𝟏𝟏 𝑳𝑳𝑳𝟏𝟏 (𝑻𝑻𝑻𝑻⁄𝑻𝑻 + 𝟏) = 𝟏. 𝟐𝟐𝟐𝟐
25 meter CCAT observatory,
5600 meter altitude, Cerro
Chajnantor, Chile
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Modeling of Superconducting
Materials in CST
I.
II.
III.
Analytically calculate the surface impedance using Mattis-Bardeen theory
Putting in CST via surface calculating impedance table
Fitting process
Tabulated Surface
Impedance
 Error Limit: 0.06

Error: 0.035
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180° RF Hybrid at 0.8-1.1 THz
 Applying NbTiN superconducting material in the design of a Rat-race180°RF
hybrid
 Towards designing a balanced SIS mixer from 800 GHz to 1.1 THz
𝑀𝑀𝑀 1𝐷 = arg 𝑆𝑆,1 − arg(𝑆𝑆,1)
8 um
−180°
−
−
−
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9µ𝑚 Silicon
SiO2 micro bridges
NbTiN superconductor
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E-field Monitor of Rat-Race at 0.8-1.1
THz
 Absolute E-Field monitor:
8 um
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Fitting of Gold material
•
CST model of 200 nm Gold using anomalous limit for designing HEB mixer
at 4.7 THz
Tabulated Surface Impedance
 Error Limit: 0.1

Error: 0.038
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Feedhorn / mixer-block
Mixer block with Feedhorn
Mixer block without Feedhorn
1000 µm
SMA connector
Wire bonds
671 µm
Silicon IF board
Device
zoom
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HEB for upGreat Receiver in SOFIA
 2 µm Silicon membrane
 200 nm Gold for circuitry
 3 µm Beamleads
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E-Field Monitor of 4.7 THz
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Fabricated 4.7 THz HEB
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Comparison of Simulation and
Measurement of a 4.7 THz HEB
 Good agreament between CST simulation and FTS
measurement results
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Conclusion
 Development of state-of-the-art SIS and HEB mixers in
KOSMA laboratory at Universität zu Köln
 Using CST suite as a main 3D software to design our
THz circuits
 First integrated balanced SIS mixer working at 350-500
GHz
 Very good agreement between simulation and FTS
measurement of 4.7 THz HEB is reported
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Thank You!
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