Analyti tic V c Veri rifica cati tion o of the P Perf rforman - - PowerPoint PPT Presentation

• J. Leema, G. S. Yuna, M. Kima, J. Leea, W. Leea,
• H. K. Parkb, J. S. Kangc, N. Itod, and A. Masee

Analyti tic V c Veri rifica cati tion o

• f the P

Perf rforman ance o ce of Notc tch f filter ters of

• f the K

KST STAR AR EC ECEI EI Sy System

KSTAR Conference 2014 Mayhills Resort, Jeongseon-gun, Gangwon-do, Korea, Feb. 24 – Feb. 26, 2014

a Pohang University of Science and Technology, Pohang, Korea bUlsan National Institute of Science and Technology, Ulsan, Korea c Korea Research Institute of Standards and Science, Daejeon, Korea d Ube National College of Technology, Ube, Yamaguchi, Japan e KASTEC, Kyushu University, Kasuga-shi, Fukuoka, Japan

Supported by

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Detection process of the ECEI system

ECEI detction system is based on “Heterodyne design” At the 1st mixing stage of ECEI detection process, detectors (mixer-type) could be exposed to stray power of the microwave heating sources or excessive radiation from the plasma Without protection, the detected signal can suffer froml modulation or saturation due to high power RF radiations. In the extreme case, the detector elements can be destroyed

Micro-strip dual dipole antenna for broadband (75-140 GHz) detection

Diode (working as a balanced mixer)

ECEI detector array

(developed by UC Davis)

KSTAR 1st ECEI system

• G. S. Yun et al., Rev. Sci. Instrum.

81, 10D930 (2010)

1st Mixing : Optical mixing (LO + ECE in the air) 2nd Mixing : RF mixing (LOs + IFs from 1st mixing process in the circuit)  divided into 8 channels depending on LO frequencies

Complete schematic of the ECE Imaging system

C.W. Domier., http://tempest.das.ucdavis.edu/mmwave/dma.html

Mini lens

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Characteristics of ECEI detector

MSG901 (similar to MA4E1310) Specification of MA4E1310 Type: GaAs Flip Chip Schottky Barrier Diode Usage: Single and double balanced mixers through millimeter wave frequencies Operating temperature: -65 ºC ~ 125ºC Maximum LO power: “+20 dBm” Maximum RF power: “+20 dBm”

ECEI dual antenna detector

Dual dipole antenna of the ECEI system

• X. Kong, C.W. Domier, and N.C. Luhmann, Jr., 33rd IRMMW, 15-19, Sep, (2008)

Sensitivity of the mini lens-based dual dipole antenna of ECEI

• X. Kong, C.W. Domier, and N.C. Luhmann, Jr., 33rd IRMMW, 15-19, Sep, (2008)

“ > 20 dB loss of antenna gain at 170 GHz” “ > 20 dB loss of antenna gain at incident angle > 10º ”

Maximum stray RF power detected by the ECEI system,

 When the stray RF power has normal incidence to the ECEI detector array  Or, the antenna is exposed directly to the stray power of ECRH

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

KSTAR 170 GHz ECH

170 GHz ECH (1 MW/20 s) 2nd ECEI & MIR 1st ECEI

KSTAR 170 GHz X2 ECH/CD SYSTEM Gyrotron system

• 1.11MW for 20 sec (40% efficiency)

Transmission line system : ~10% loss, “70m” Launcher : ~25% loss

ECE Measurement Strategy

Stray microwave power from ECH heating (170GHz, 10s of MW) - Reflected ECH power is a

particular hazard at plasma startup

• D. Johnson., Status of US ITER Diagnostic Development, Web

seminars of USBPO (2013)

“Direct stray power from the gyrotron system is negligible” Absorption power of 170 GHz ECH (estimated from the change of 𝑒𝑋

𝑞 𝑒𝑒

⁄ ) co-CD w/ 20 degree : 78 %

J.H. Jeong et al.., “Recent progress of 170 GHz Gyrotron in KSTAR - 2nd harmonic heating experiment in L-mode plasma”, Japan-Korea Workshop

• n Physics and Technology of Heating and Current Drive, 28-30, Jan, (2013)

Total reflected ECH power inside the vessel (estimation) ~ 𝟐. 𝟐𝟐𝟐𝟐 × 𝟏. 𝟘 × 𝟏. 𝟖𝟖 × 𝟏. 𝟑𝟑 ~ 𝟐𝟐𝟏𝟐𝟐 Or 𝟐. 𝟐𝟐𝟐𝟐 × 𝟏. 𝟘 × 𝟏. 𝟖𝟖 ~ 𝟖𝟖𝟏𝟐𝟐 (𝐛𝐛 𝐪𝐪𝐛𝐪𝐪𝐛 𝐪𝐛𝐛𝐭𝐛𝐭𝐪) *Assume that, unabsorbed ECH power is non-uniformly distributed in the vessel. Detected power is ~ 𝐸 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 𝑔𝑔𝑔𝑒𝑒𝑒 × 750kW 110m3 ⁄ Vessel volume ×10cm3(Volume of interest for a single antenna)

80𝐸 𝑛𝑋 S𝑒𝑒𝑔𝑢 𝑞𝑒𝑞𝑞𝑒 𝑒𝑒 𝑒𝑢𝑞 𝑔𝑒𝑒𝑞𝑒𝑒𝑔 × 𝑂𝑒𝑒𝑔𝑢 𝑔𝑒𝑔𝑒𝑞𝑒 𝑒𝑞𝑠𝑞𝑔𝑒𝑒𝑒𝑒 × 7 (5𝑒𝑒, 𝐵𝑒𝑒𝑞𝑒𝑒𝑔 𝐻𝑔𝑒𝑒) < 100𝑛𝑋 (𝑁𝑔𝑁𝑒𝑛𝑒𝑛 𝑆𝑆 𝑞𝑒𝑞𝑞𝑒 𝑒𝑒 𝑒𝑒𝑒𝑒𝑞)

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Frequency Selective Surface

An array of periodic structure

• n a conducting sheet

WAVE TRANMISSION THROUGH THE STRUCTURE

𝒂𝒕 𝒂𝒑 𝒂𝒑

A single series circuit

𝑎𝑡 = Impedance of the periodic grating 𝑎𝑝 = Impedance of the free space

Depending on the geometries of the periodic structure, FSS can work as band-stop filter or band-pass filter

R = 1 2𝑎𝑡 𝑎𝑝 ⁄ + 1

2

T = 1 − R R = Reflection coefficient of the circuit T = Transmission coefficient of the circuit

Examples of Frequency Selective Surface and its equivalent circuit

• D. Singh et al., Progress In Electromagnetics Research B, Vol. 38, 2012

Structure of single-loop frequency selective surface

• Z. Shen et al., Plasma and Fusion

Research 2, S1030 (2007)

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Design of the KSTAR ECEI 170GHz notch filter

𝑎𝑝 𝑎𝑝 𝑆 𝐷 𝑀 Square-loop Frequency Selective Surface

KSTAR ECEI 170GHz notch filter and its equivalent circuit

“Different from previous work, angle insensitivity is

a critical specification in this application.

Five potential FSS structures are investigated, and the unit cell elements are the ring, square loop, square center, Jerusalem cross and double square. FSSs with

square loop and ring unit cell structures show best angle insensitivity. The square loop structure is

selected as the final model because it is easier to fabricate than the ring structure.” – Protection filter development in TEXTOR

• Z. Shen et al., Plasma and Fusion Research 2, S1030 (2007)
• 1. High rejection rate ( > 25 dB)
• 2. Frequency insensitive to the incident angle

Expected performance of KSTAR ECEI 170GHz notch filter

• N. Ito. Short report on 170GHz Notch filter for KSTAR

Measured angular performance of TEXTOR 140 GHz SL-FSS filter

• Z. Shen et al., Plasma and Fusion Research 2, S1030 (2007)

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Analytic verification of the notch filter (1)

𝒂𝒑 𝒂𝒑 𝑺 𝑫 𝑴

Equivalent circuit of square-loop FSS

Calculate R, L and C

• f the equivalent

circuit to find ZS

𝒂𝒕 𝒂𝒑 𝒂𝒑

𝑎𝑡 = 𝑆 + j 𝑞𝑀 − 1 𝑞𝐷

Calculate transmission coefficient in function of incident beam frequency

How to calculate R, L and C of equivalent circuit of square-loop FSS?  For square loop, modelling process starts with a series of infinite metallic strips  The equivalent-circuit model technique is based on the equations given by “Marcuvitz”, who first estimated the impedance of the periodic gratings R = 1 2𝑎𝑡 𝑎𝑝 ⁄ + 1

2

T = 1 − R

(a)The element geometries of a series of infinite metallic strips. (b)The element geometries of an array of square loop structure

𝑕 𝑞 𝑞 𝑕 𝑞 𝑞 𝑒

(a) (b)

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

𝑃𝑒𝑒 𝐽𝑒

𝑴

𝑃𝑒𝑒 𝐽𝑒

𝑫

Analytic verification of the notch filter (2)

Inductive Strip Grating Capacitive Strip Grating 𝐹𝑝 𝐹𝑝 + + + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +

+ + + + + + +

• +
• +
• +
• +
• +
• +
• +
• +
• +
• +

𝐹𝑝 𝐹𝑝

Low-frequency source strikes the grating

 Free electrons in the metal are free to move along the strips and continue to move in the same direction until E-field reverses directions  Large amount of field energy is absorbed by the strips

High-frequency source strikes the grating

 The electrons wiggle back and forth  Out of phase between moving electron and E-field  Small absorption of field energy

Low-frequency source strikes the grating

 The strips are remained in the former state for large periods of time, since the E-field of a long- wavelength varies slowly  Only a small portion of the wave energy is absorbed

High-frequency source strikes the grating

 The strips are not remained in one state but switch rapidly between the two due to the E-field  Electrons in the metal are constantly

• scillating

 Large energy of the incident wave is absorbed

High-pass filter Low-pass filter

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Analytic verification of the notch filter (3)

𝑞 𝑞 𝑕

𝒍 𝑭𝒋𝒋𝒋

𝜄 𝜚 𝑁 𝑢 𝑨 Inductive Strip Grating Capacitive Strip Grating

𝑞 𝑕 𝑞 𝑕 𝑞∗ = 𝑕 𝑞∗ = 𝑞 𝑞∗ = 𝑞 𝑞∗ = 𝑞

𝑎𝑛𝑛𝑛𝑛𝑛 = 𝑌𝑀

𝑕∗ = 𝑕 𝑕∗ = 𝑞

2𝜌𝑔𝑀 𝑎𝑝 = 𝑌𝑈𝑈(𝑞∗) 𝑎𝑝 = 𝑞 cos 𝜄 𝜇 ln csc 𝜌𝑞 2𝑞 + 𝐻(𝑞, 𝑞, 𝜇, 𝜄)

TE incidence case (𝜚=0)

2𝜌𝑔𝐷 𝑍

𝑝

= 𝑒𝑈𝑈(𝑞∗) 𝑍

𝑝

= 1 𝑎𝑡𝑛𝑝𝑛𝑍

𝑝

= 4𝑌𝑈𝑈 𝑞∗ 𝑍

𝑝𝑎𝑝 2

= 4𝑌𝑈𝑈 𝑕 𝑎𝑝 = 4𝑞 cos 𝜚 𝜇 ln csc 𝜌𝑕 2𝑞 + 𝐻(𝑞, 𝑕, 𝜇, 𝜚)

From Babinet's Principle in Radiofrequency Structures

Equations of oblique angles of incidence for metallic strips LEE, C. K., LANGLEY, R. J., IEE Proceedings H - Microwaves Optics and Antennas, 1985, vol. 132, p. 395 – 399.

𝑎𝑛𝑛𝑛𝑛𝑛𝑎𝑡𝑛𝑝𝑛 = 𝑎𝑝

2

4

• 𝑎𝑛𝑛𝑛𝑛𝑛 = 𝑌𝑈𝑈 𝑞 𝑒𝑢𝑞𝑒,

𝑎𝑡𝑛𝑝𝑛 = 𝑎𝑝

2

4𝑌𝑈𝑈 𝑞

• TM incidence case (𝜄=0)

𝐻(𝑞, 𝑞, 𝜇, 𝜄(𝑈𝐹) 𝜚(𝑈𝑁)) = 0.5 1 − 𝛾2 2 1 − 𝛾2 4 𝐵+ + 𝐵− + 4𝛾2𝐵+𝐵− 1 − 𝛾2 4 + 𝛾2 1 + 𝛾2 2 − 𝛾4 8 𝐵+ + 𝐵− + 2𝛾6𝐵+𝐵− 𝐵𝑈𝑈± = 1 1 − 𝑞2 cos 𝜚 𝜇2 − 1 𝛾 = sin 𝜌𝑞 2𝑞 𝐵𝑈𝑈± = 1 1 ± 2𝑞 sin 𝜄 𝜇 − 𝑞 cos 𝜄 𝜇

2

− 1 cos 𝜄 → cos 𝜚 𝑎𝑡𝑛𝑝𝑛 = 1/𝑒𝐷

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Analytic verification of the notch filter (4)

𝑌𝑈𝑈 𝑁 𝑢 𝑨 𝑭𝒋𝒋𝒋

(𝑼𝑭 𝒏𝒑𝒏𝒏) 𝒍

𝜄 𝑒𝑈𝑈

Square loop of 𝒒, 𝒉, 𝒙, 𝒏 = 𝒒 − 𝒉 Strip grating of 𝒒∗, 𝒉∗, 𝒙∗

𝑞∗ = 2𝑞 𝑞∗ = 𝑕 𝑞∗ = 𝑞 𝑞∗ = 𝑞

Inductive Strip Grating Capacitive Strip Grating

𝑕∗ = 𝑞 − 2𝑞 𝑕∗ = 𝑒 5𝑞 5𝑒 5𝑞 5𝑒 Modification for square-loop circuit

How the inductive and capacitive parts of SL-FSS can be derived in the case of TE-incidence

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Analytic verification of the notch filter (5)

Modification for square-loop circuit

2𝜌𝑔𝑀 𝑎𝑝 = 𝑌𝑈𝑈(2𝑞) 𝑎𝑝 = 𝑒 𝑞 𝑞 cos 𝜄 𝜇 ln csc 𝜌(2𝑞) 2𝑞 + 𝐻(𝑞, 2𝑞, 𝜇, 𝜄) 2𝜌𝑔𝐷 𝑍

𝑝

= 𝑒𝑈𝑈(𝑕) 𝑍

𝑝

= 𝑒 𝑞 4𝑞 sec 𝜄 𝜇 ln csc 𝜌𝑕 2𝑞 + 𝐻(𝑞, 𝑕, 𝜇, 𝜄) 𝐻(𝑞, 𝑞, 𝜇, 𝜄(𝑈𝐹) 𝜚(𝑈𝑁)) = 0.5 1 − 𝛾2 2 1 − 𝛾2 4 𝐵+ + 𝐵− + 4𝛾2𝐵+𝐵− 1 − 𝛾2 4 + 𝛾2 1 + 𝛾2 2 − 𝛾4 8 𝐵+ + 𝐵− + 2𝛾6𝐵+𝐵− TE incidence case

Equations of oblique angles of incidence for square-loop circuit

1.

• G. H. Sung, K. W. Sowerby, and A. G.

Williamson, IEEE Antennas and Propagation Society International Symposium, 4A, 400- 403, 2005.2. 2.

• B. Hooberman, Everything You Ever Wanted

to Know About Frequency-Selective Surface Filters but Were Afraid to Ask

“The thin dielectric substrate on which the arrays are printed is assumed to increase the susceptance (B)

• f the array while having a negligible effect on the

reactance(X)”

PARKER, E. A. 17th Q.M.W. Antenna Symposium, 1991 The effective permittivity of SL- FSS should be considered

𝜻𝒔 = Relative dielectric

constant of substrate (=2.20 from N. Ito. Short report on 170GHz Notch filter for KSTAR)

𝜻𝑴 = Relative dielectric

constant of copper printed circuit

𝜻𝒏𝒇𝒇 = 𝜻𝑴 + 𝜻𝒔

2𝜌𝑔𝑀 𝑎𝑝 = 𝑌𝑈𝑈(2𝑞) 𝑎𝑝 = 𝑒 cos 𝜄 𝜇 ln csc 𝜌(2𝑞) 2𝑞 + 𝐻(𝑞, 𝑞, 𝜇, 𝜄) 2𝜌𝑔𝐷 𝑍

𝑝

= 𝑒𝑈𝑈(𝑕) 𝑍

𝑝

= 𝜁𝑛𝑓𝑓 4𝑒 sec 𝜄 𝜇 ln csc 𝜌𝑕 2𝑞 + 𝐻(𝑞, 𝑕, 𝜇, 𝜄)

Revised equations considering effective permittivity of SL-FSS

• K. R. Jha, G. Singh, and R. Jyoti., Progress in

Electromagnetics Research B, 2012, vol. 45, p.165 – 185

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

The measurement set-up at KRISS

Measuring the transmittance of the 170GHz KSTAR notch filter

Overview Rotation stage

Millimeter wave VNA extender 110 ~ 170GHz Millimeter wave VNA extender 110 ~ 170GHz Notch-filter holder

Launching antenna Receiving antenna

Motion Guide

Movable (Controlled by PC) Absorber Absorber

Network analyzer

Sweeping the frequency of the launching beam and scan the received response

PC

Control the distance between launching & receiving antenna Antenna to antenna distance ~28cm

WR-06 W.G WR-06 W.G

• 1. S-parameters of the testing target

are measured by Vector Network Analyzer

• 2. The launching beam frequency

was swept in 100 MHz step from 110 GHz to 170 GHz

• 3. Measuring the transmitted power

from the launching antenna to receiving antenna with / without the SL-FSS filter TE1,0 mode is the dominant mode in rectangular waveguides TE-incidence case has been employed for analytic calculation

Rectangular waveguide TE1,0 mode

Absorber thickness ~ 5cm

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Test results and Analytic verification (1)

The frequency responses in different geometries of the filters

Scale: 𝝂𝒏

1 2 3 4

𝑀2 (𝑒) 476 488 500 512 𝑞 (w) 53 54 55 56 𝐻 − 𝑀2 (𝑕) 1102 1132 1160 1189

Unit cell of KSTAR ECEI 170GHz notch filter

• N. Ito. Short report on 170GHz Notch filter for KSTAR

The exact values of design parameters of each filter. Square length 𝑀2 𝑒 , width 𝑞 (w) and gap between adjacent unit cells 𝐻 − 𝑀2 𝑕 . All the parameters

grow together with L2 in the same rates. Incident angles are identical for all cases, 7 degrees The exact value of 𝜻𝒏𝒇𝒇 is determined as 5.95

• 0.33 𝐻𝐻𝑨 𝜈𝑛

⁄

As the cell is enlarged, the notch frequency decreases

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Test results and Analytic verification (2)

The frequency responses in various angles of incidence The exact value of 𝜻𝒏𝒇𝒇 is determined as 5.95

Angle increases, notch frequency decreases

The notch filter based on SL-FSS has an incident- angle dependence

Notch filter whose L2 is 488𝝂𝒏 was tested

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Summary

Large-aperture 170 GHz notch filters have been installed on the KSTAR ECEI system

• To protect detectors from the stray power of 170 GHz ECRH
• Based on Frequency Selective Surface technique
• Square-loop FSS has been chosen to take advantage of high rejection rate as

well as relative angle-insensitivity

Analytic calculation of the notch filter

• Equivalent circuit model of periodic gratings
• A series of infinite metallic strips  Square-loop FSS
• Calculate the transmittance of the SL-FSS

Verification of the performance of the notch filter

• Geometry = Total cell size increases, notch frequency decreases
• Incident angle = Angle increases, notch frequency decreases
• Analytic calculations are consistent with the test results

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

BACK-UP

BACK – UP SLIDES

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

How the diode works as a mixer?

I-V characteristics of a Schottky Diod

Let the diode voltage be I-V relationship in the diode LO input signal is RF input signal is Other terms except 𝜕𝑡 − 𝜕𝑀 will be filtered by the IF balun and amplifier

ECEI receiving end

Output signal from mixer ~ 𝑊

𝑡𝑊 𝑀

In log scale, ~ 𝑊

𝑡(𝑒𝑒 𝑒𝑒) + 𝑊 𝑀(𝑒𝑒 𝑒𝑒)

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Saturation?

In-situ test of ECEI system (Mar, 2013)

Install the test source inside the vessel and measure the system response for some cases of optics configurations

Mid-plane Foothold

Linear motion guide

Inside-vessel 88GHz test source w/ absorber in the front (Regarded as a point source) ~ “-15dBm”

“ All channels are saturated (over 2.5V digitizer limit) with the LO power (90 GHz BWO power) of > 35% during the test” During the operation of the ECEI system, the output power of BWO is being handled from 10% to 100%. Thus, the saturation case of the ECEI channels should be considered for the BWO of 100% power.

Detector LM guide H-port

Saturation happens (In-situ), 35 % BWO (12mW=10.8dBm, 90 GHz) + Test source (-15dBm, 88 GHz) = 100% BWO (70mW=18.4dBm, 90 GHz) + Test source (-22.8dBm, 88GHz)

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

KSTAR 170 GHz ECH system

J.H. Jeong et al.., “Recent progress of 170 GHz Gyrotron in KSTAR”, Japan-Korea Workshop on Physics and Technology of Heating and Current Drive, 28-30, Jan, (2013) J.H. Jeong et al.., “2nd harmonic heating experiment in L-mode plasma”

KSTAR Conference 2014 (Mayhills Resort, Jeongseon-gun, Gangwon-do, South Korea, Feb. 24 – Feb. 26, 2014)

Optical mixing / Typical angle of incidence

Ray trace on KSTAR 1st ECEI system