Microwave antennas for short distance communications in cryogenic systems
Résumé
Wireless digital or analog communications are nowadays widely used in miscellaneous fields of applications. When wireless systems are used for short distance communications, the absence of cables does simplify the setup of some equipment, and is necessary for mobility. But the absence of cables also presents a strong interest for cryogenic systems. Indeed, hold times of cryostats are partly limited by heat loads due to thermal conduction between the room temperature environment and the cryogenic part. The conduction of cables that are used to transmit signals in and out of the cryogenic systems can represent a non negligible part of the thermal load for instruments that require many parallel channels. In case of cryogenerators, this load needs to be compensated by more power to run them, which puts some constraints on the instruments, especially if they need to be embarked on satellites. These constraints hold true for scientific payloads since future high frequency heterodyne or bolometric imagers for radioastronomy or Earth atmosphere studies do require several parallel data channels in the GHz to THz range. To this regard, it is valuable, for complex cryogenic systems requiring many communications channels like imagers, to feed or extract data through wireless means. In this work, we have chosen to use bow-tie antennas placed in near-field configuration to transmit data in the 8-12 GHz band. This frequency range corresponds to a typical intermediate frequency range used for Superconductor-Insulated-Superconductor (SIS) mixers cooled at 4K for radioastronomy applications. We will present results obtained in terms of transmission coefficient for elements composed of an emitting and a receiving antennas respectively placed across from each other on different thermal shields of a cryostat. We obtained transmission losses lower than 3 dB over a 1.5 GHz bandwidth. The sensitivity to slight displacements of one antenna with respect to the other one has been studied as well. Finally, we will show results concerning crosstalk between different elements composing an array of such microwave antennas.
| Origine | Fichiers produits par l'(les) auteur(s) |
|---|---|
| Licence |