Skip to Main content Skip to Navigation
Theses

Elisa, une référence de fréquence ultrastable pour l'Agence Spatiale Européenne

Abstract : Elisa is a cryocooled sapphire oscillator (CSO) intented for the new Deep Space Network ground station of the ESA. This oscillator is required to achieve a frequency stability σy (τ) ≤ 3 × 10−15 for τ ∈ [1 − 1000s] and a phase noise Sφ (1Hz) = −96dBc/Hz with scheduled maintenance of 2 years. This frequency standard must include a frequency synthesis with outputs at 10GHz, 100MHz and 5MHz showing identical CSO's stability. Elisa consists of a sapphire resonator (monocristal Al2 O3 puck) excited on whispering gallery modes (WG) and cooled down at 4.2K in a cryocooler. At this temperature unloaded Q-factors are around 1 × 109 . From our knowlege and the literature, W GH15,0,0 mode was chosen. Its resonant frequency was definied to simplify the frequency synthesis conception and to avoid frequency transitions of paramagnetic impurities. It was fixed at 10GHz - D where D is a confidence interval of 10MHz taking into account the manufactering tolerances. It can be easily compensated with the use of a Direct Digital Synthesizer (DDS) included in the frequency synthesis in order to reach 10GHz. The dimensions of the resonator were calculated by finite elements method. Different coupling methods were tested to achieve an efficient modal selection. Every component needed for constructing Elisa was analysed in detail. An original method of diode detector amplitude noise measurement, the design of low noise electronics, the principle of a frequency synthesis based on the use of a DDS and the description of two cryogenic technologies are shown. In the last case, we focused our study on the low mechanical vibration cryocooler. The performances demonstrated by Elisa achieve the specifications of the ESA. A frequency stability better than 3 × 10−15 for τ ∈ [1 − 1000s] was measured. A minimum value of 1.4 × 10−15 at τ = 20s was achieved. The phase noise measurement shows Sφ (1Hz) = −101dBc/Hz. Moreover, the frequency synthesis enables the transfer of the Elisa stability at 10GHz and 100MHz. The long term stability of 4.5 × 10−15 /day classifies Elisa at the state-of-the-art in the cryogenic sapphire oscillator category.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00563658
Contributor : Serge Grop <>
Submitted on : Monday, February 7, 2011 - 10:20:55 AM
Last modification on : Thursday, November 12, 2020 - 9:42:08 AM
Long-term archiving on: : Sunday, May 8, 2011 - 2:53:07 AM

Identifiers

  • HAL Id : tel-00563658, version 1

Citation

Grop Serge, Pierre-Yves Bourgeois, Vincent Giordano, Yann Kersalé. Elisa, une référence de fréquence ultrastable pour l'Agence Spatiale Européenne. Physique [physics]. Université de Franche-Comté, 2010. Français. ⟨tel-00563658⟩

Share

Metrics

Record views

615

Files downloads

879