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Status of KVN Instrumental Phase Calibration System Development
Do-Heung Je1, Moon-Hee Chung1, Ji-Man Kang1, Seung-Rae Kim1, Min-Kyu Song1, Sung-Mo Lee1, Taehyun Jung1, Seog-Tae Han1, Do-Young
Byun1, Seog-Oh Wi1, Bong-Won Son1, Soo-Yeon Kim2, and Won-Kyu Lee3
1Korea Astronomy and Space Science Institute2Korea University
3Korea Research Institute of Standards and Science
2013. Oct. 12.2nd IVTW
Contents• KVN Round Trip System
– Specification– Development progress– System configuration– Test results (old & new)
• KVN Wide-band phase calibration– Specification : power vs freq, reference frequency – P-cal System Configuration – Component’s design and fabrication– Timeline
KVN System Configuration
H-maser
Antenna Receiver Room
43 GHz FE
22 GHz FE
1 pps Distributor
100 MHz Distributor
10 MHz Distributor
1 pps Distributor
5 MHz
1.4 GHz
Control Room
WDMOptical
MUX
Digi-talE/O
Down Con-
verter
Down Con-
verter
Sampler
SamplerWDM
OpticalDMUX
Digital O/E
DigitalFilters
Mk5B
IF Selector
StationClock
1 pps
ReferenceGenerator
RTS Antenna Module
RTS Control Room Module
1.4 GHz
10 MHz100 MHz
Down Con-
verter
Down Con-
verter
Sampler
Sampler
86 GHz FE
129 GHz FE
QO
x2
P-cal(under de-velopment)
RTS (3 sets installed in 2012)
KVN RTS(Round Trip System) Speci-fication
• RTS is needed for compensating the cable length change due to temperature variations & move-ment
• H-maser frequency stability : ~ 2E-15@1000s• RTS transmission stability : ~ 2E-16@1000s (10
times better than H-maser stability)
KVN RTS Development
• KASI developed KVN RTS through research coop-eration with KRISS (Korea Research Institute of Standards and Science) in 2011.
• KASI installed RTS system in 3 KVN sites in 2012. • Fiber-optic reference signal transmission method
(from NICT, Dr. Fujieda, 2009)• The measured stability satisfied the stability spec-
ification, 2E-16@1,000s.• Real-time remote signal monitoring function
was added.
KVN RTS Configuration ,
,
,
.
Remote signal phase cannot be measured directly. We need any method to check remote signal phase for diagnosis of the system performance.
Expectation of remote signal phase
𝜑𝑣𝑐𝑜+𝜑 𝑓𝑖𝑏𝑒𝑟=𝜑𝑟𝑒𝑚𝑜𝑡𝑒
.
() ,
.
𝜑𝑣𝑐𝑜=𝜑𝑟𝑒𝑚𝑜𝑡𝑒−𝜑 𝑓𝑖𝑏𝑒𝑟
Remote signal phase can be expected from vco signal phase and round-trip signal phase.
laser
VCO
MZM
Photo Diode
H-maser
𝑉 𝑣𝑐𝑜
Phase Compensation Circuit
𝑉 𝑟𝑡
𝑉 𝑟𝑒𝑓
𝑉 𝑐
Observation Building
Antenna Vertex Room
laser MZM
Photo Diode
𝑉 𝑟𝑒𝑚𝑜𝑡𝑒
Vector Voltmeter
𝑉 𝑟𝑒𝑓
𝑉 𝑣𝑐𝑜
𝑉 𝑟𝑡
Controller
KVN RTS Test setup
Comparison of Allan deviations before and after temperature stabilization
After stabiliza-tion
Before stabi-lization
Contents• Round Trip System
– Specification– Development progress– System configuration– Test results (old & new)
• Wide-band phase calibration– Specification : power vs freq, reference frequency – System Configuration – Component’s design and fabrication– Timeline
KVN Wide-band Pcal Specification
• Quasi-optic injection is needed for calibrate path delays in 4 bands receivers
• Frequency band : 20 – 130 GHz– Covers KVN 4 ch receiver full bandwidth
• Reference frequency : 200 MHz– 2 tone signals are positioned in 500 MHz IF bw
• Power : ~ - 100 dBm (in front of each receiver’s horn antenna)
KVN P-cal Configuration
Refer-ence
Genera-tor
Feeder
Comb Genera-
tor
100 MHz
200 MHz
20-130 GHz
Attenua-tor
Quasi-Optic Injection
Double-ridged feed-horn
doubler Power Amp
< 50 GHz
Quasi Optic Injection
• KVN is comprised of 3 LPF, several mirrors. • Quasi optic P-cal injection is needed.• Double ridged feedhorn, ellipsoidal mirror, Mylar
sheet are used for quasi optic P-cal injection.
To subreflec-tor
Ellip-soidal mirror
MylarFilm
45 degree mirror
Double-ridged horn
Mylar Film Transmission Loss
125 um50 um25 um
Comb Generator
• Signal Generation– Step Recovery Diode: ~ 20 GHz– Tunnel Diode : ~ 40 GHz– NLTL (Nonlinear Transmission Line) Comb generator : > 100
GHz• PSPL : -30 dBm @ 50 GHz (200 MHz reference)• Agilent : -85 dBm@ 67 GHz (10 MHz reference)
Wideband Feed Horn Development (Dr. Moon-Hee Chung)
• Double-ridged waveguide horn was designed and fabricated as a ul-tra-wide band feeder
• VSWR : < 2 @ 20-130 GHz • Aperture size : 24 mm x 28 mm• Lower return loss measured above 80 GHz
Timeline for KVN wideband P-cal
• P-cal system using commercial comb generator(< 50 GHz or 86 GHz), wideband feeder, Quasi-optic injection system– 1st injection test : 2013. Dec.– 2nd injection test : 2013. March.– 3 sets installation : 2014. July (TBD)
• Further Works for full-band Phase calibration – NLTL MMIC Chip development needed.– MMIC Module loaded feeder development.
Summary
• KVN RTS development – 2E-16 @ 1000s – O(E-17) @ 1000s (after temperature stabilization) – Real time remote signal phase expectation method
was suggested.
• KVN wide-band Pcal system is under develop-ment – Ultra wide-band feed is developed. – Quasi-optic injection – Custom designed high frequency comb generator is
needed.