1. Methods of transfer of ultra-stable frequencies to radio telescope
А.Tsaruk, А. Vytnov, D. Ivanov
Institute of Applied Astronomy
of Russian Academy of Sciences
3rd International VLBI Technology Workshop
November 2014
Groningen/Dwingeloo, the Netherlands

2. Overview
Transfer methods of reference frequencies
Components
Unit forming the reference frequency
Results

3. Introduction
Estimated frequency instability which must be provided for coherence losses less than 1% on 1 hour integration time
IAA Transactions, 2006, V.15, P [Trudy IAA RAS(in russian)]

4. Transfer methods of reference frequency 100MHz to radio telescope
Transmission of the 100 MHz signal via RF cable with amplification.
Transmission of the 5 MHz signal via RF cable with amplification and multiplication.
Modulation of the optical signal by radio frequency 100 MHz and its transmission via fiber optic cable with demodulation on the radio telescope.

5. Transfer methods of reference frequency 100MHz to the radiotelescope

6. Components LOW NOISE FREQUENCY MULTIPLIERS x10 x2
Ultra-Low Phase Noise: Hz  kHz  kHz
AMPLIFIERS
DISTRIBUTION AMPLIFIER
FIXED GAIN
Low phase noise:  Hz  kHz

7. Components Laser module Optical receiver Optical isolator
Connector Type
FC/APC
Wavelength
1.55 μm
Frequency Range
MHz
Maximum optical attenuation
-25 dB
Relative Intensity Noise
-140 dB/Hz
Connector Type
FC/APC
Wavelength μm
Frequency response irregularity
±3  dB
Frequency Range
МHz
Return loss
-25 dB
Connector Type
FC/APC
Insertion loss
0.41  dB
Isolation
47.5 dB
Optical circulator

8. Reference frequency transmission via fiber optic cable

9. Cable delay compensation scheme

10. Unit forming the reference frequency signal
Ground part
Antenna part

11. Unit forming the reference frequency signal
(antenna part)
Supply stabilization
Ripple and noise
< 3mV
Temperature stabilization
The internal temperature +35˚С
at an external temperature of +5˚С...+40˚С

12. Results

13. Conclusion
The device is developed for the reference signal transmission to the radio telescope, allowing to transmit the signal of the reference frequency by optical and RF cable.
Introduced frequency instability in both methods of transfer reference frequency avoids the coherence loses greater than 1% on time interval of 1 hour.
At the moment there is an installation of the designed formation block of the reference frequency on the radio telescopes RT-13 produced by IAA RAS. Their future operation will show efficiency of the proposed methods for transmitting reference frequency on the radio telescope in real conditions.

14. Thank you!