1. Status of KVN Instrumental Phase Calibration System Development Do-Heung Je 1, Moon-Hee Chung 1, Ji-Man Kang 1, Seung-Rae Kim 1, Min-Kyu Song 1, Sung-Mo Lee 1, Taehyun Jung 1, Seog-Tae Han 1, Do-Young Byun 1, Seog- Oh Wi 1, Bong-Won Son 1, Soo-Yeon Kim 2, and Won-Kyu Lee 3 1 Korea Astronomy and Space Science Institute 2 Korea University 3 Korea Research Institute of Standards and Science 2013. Oct. 12. 2 nd IVTW

2. 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

3. 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 WDM Optical MUX Digital E/O Down Converter Sampler WDM Optical DMUX Digital O/E Digital Filters Mk5B IF Selector Station Clock 1 pps Reference Generator RTS Antenna Module RTS Control Room Module 1.4 GHz 10 MHz 100 MHz Down Converter Sampler 86 GHz FE 129 GHz FE QO x2 P-cal (under development) RTS (3 sets installed in 2012)

4. KVN RTS(Round Trip System) Specification RTS is needed for compensating the cable length change due to temperature variations & movement H-maser frequency stability : ~ 2E-15@1000s RTS transmission stability : ~ 2E-16@1000s (10 times better than H-maser stability)

5. KVN RTS Development KASI developed KVN RTS through research cooperation 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 specification, 2E-16@1,000s. Real-time remote signal monitoring function was added.

6. 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.

7. Expectation of remote signal phase Remote signal phase can be expected from vco signal phase and round-trip signal phase.

8. laser VCO MZM Photo Diode H-maser Phase Compensation Circuit Observation Building Antenna Vertex Room laser MZM Photo Diode Vector Voltmeter Controller KVN RTS Test setup

9. Test results I (2011. June)

10. Test results II (2012. Jan.)

11. Test results III (after temperature stabilization)

12. Test results IV (after temperature stabilization)

13. Comparison of Allan deviations before and after temperature stabilization After stabilization Before stabilization

15. 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

16. KVN 4 ch Receiver (Front End)KVN 4 ch Receiver (Front End) 45 degree mirror

17. 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)

18. KVN P-cal Configuration Reference Generator Feeder Comb Generator 100 MHz 200 MHz 20-130 GHz Attenuator Quasi-Optic Injection Double-ridged feedhorn doubler Power Amp < 50 GHz

19. 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 subreflector Ellipsoidal mirror Mylar Film 45 degree mirror Double- ridged horn Mylar Film Transmission Loss 125 um 50 um 25 um

20. 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)

21. Wideband Feed Horn Development (Dr. Moon-Hee Chung) Double-ridged waveguide horn was designed and fabricated as a ultra-wide band feeder VSWR : < 2 @ 20-130 GHz Aperture size : 24 mm x 28 mm Lower return loss measured above 80 GHz

22. Timeline for KVN wideband P-cal P-cal system using commercial comb generator(< 50 GHz or 86 GHz), wideband feeder, Quasi-optic injection system –1 st injection test : 2013. Dec. –2 nd 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.

23. 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 development –Ultra wide-band feed is developed. –Quasi-optic injection –Custom designed high frequency comb generator is needed.