Switches for MIcrowave Cryogenic applications – SMIC

The developments of present day superconducting cryogenics integrated electronics have pushed out this technology beyond laboratories demonstration and the prospects are good for widespread future deployment in civilian and military area of wireless communication over an ultra wide frequency range.The need for extremely narrow-band, highly selective and frequency-agile filters can be well satisfied by using this technology.
Frequency tunability can be achieved by discrete frequency hopping using commutated bank of capacitance or by continuous tuning using ferro-electric or ferro-magnetic thin film associated with HTS materials. The latter solution was studied in the past pointing out the remaining problem related to dielectric losses in the tuneable material so we propose to develop first solution.
At room temperature, for discrete frequency hopping PIN diodes are used because of their low losses, high isolation and power handling. Nevertheless, due to the high DC power consumption resulting in heat, low consumption alternative solution are developed such as :
Semi conducting based Field Effect Transistor (FET) and Micro ElectroMecanical System (MEMS) switches. These solutions are well suitable for cryogenic implementation and probably unique.
Compound Semiconductor based transistors, such High Electron Mobility Field Effect Transistor (HEMT), are interesting because of their low intrinsic on-state resistance. However it is known that for the behaviour of some III-V HEMTs at cryogenic temperature can induce trapped charge carrier, resulting to strong performance degradation. Among the various III-V HEMTS, the most promising ones is AlSb/InAs Field effect Transistor. It presents one of the higher channel electron mobility which could be multiplied by a factor 3 at low temperature as well as very low ohmic contact resistance . For cryogenic switching applications, it is necessary to evaluate at cryogenic temperature the balance between the so called on-state resistance (RON) and off-state capacitance (COff) to ensure that the off capacitance is neglectible.
Ohmic MEMs metal contact switches are also very attractive due to their very low microwave losses at room temperature typically 0.3 dB and high isolation 40 dB @ 500 MHz. Here the low temperature would have a benefit effect due to the decrease of the electrical resistivity in metal contact. However the mechanical stress resulting from low temperature induced deformation of the device is not yet very clear and must be investigated.
The goal of the project is to evaluate by a large series of cryogenic characterisations these two technologies from room to cryogenic temperature and compare to Pin diodes performances.
Then a series of specific development will be performed to address precise frequency range utilisation such as : V-HUF frequency range (200-600 MHz Military communication) were Ohmic MEMs seems to be the better choice and L,S C band (2-8 GHz Military and mobile communication) were AlSb/InAs III-V HEMTS are very promising. The switching capability will be demonstrated by the hybridization of the selected switches from the project development with superconducting test vehicle in the form of a re-use of V-UHF superconducting tuneable filter developed at THALES TRT and a bank of switched superconducting resonator for the higher frequency band.