Callisto | Products: Cryogenic Low Noise Amplifiers

The photo above shows an X band unit developed for the ESA 35m Deep Space Ground Station located near Perth in Western Australia. The design of this unit incorporates a waveguide band pass filter in the input circuit in order to protect the reception chain from out-of-band RFI.

Ultra-low noise amplifiers are necessary for satellite missions where link margins are critical, for example for Deep Space Missions. The use of cryogenically cooled LNAs can provide improved ground station G/T at a fraction of the cost of increasing antenna diameter, for large antennas in particular.

Callisto, working with the Cryogenic Advisory Unit at the University of Southampton (UK), has developed cryogenic low noise amplifiers in S-, X- and Ka-bands for the European Space Agency ground station network.

Our designs use HEMT amplification devices, which are well suited for cryogenic operation.

Our LNA systems use 2 stage Helium closed cycle refrigerators, which provide for reliable unattended operation. The refrigerator maintains the HEMT amplifier, which is located within a vacuum Dewar, at a temperature of 15 Kelvin. The refrigerators are selected for continuous operation with service intervals of more than one year.

Specifications for high performance cryogenic LNAs

Specification	S-BAND	X-BAND	Ka-BAND
Frequency (GHz)	2.2 to 2.3	8.4 to 8.5	31.8 to 32.3
Gain	55 dB	55 dB	55dB
Noise Temperature	10 Kelvin	15 Kelvin	30 Kelvin
Input VSWR	1.4:1	1.4:1	1.4:1
Operating Physical Temperature	15 Kelvin	15 Kelvin	15 Kelvin
Service Interval	10000 hours	10000 hours	10000 hours

Callisto's high performance cryogenic LNAs systems can be provided with a computer based monitoring system. A central PC is used to control and monitor up to two LNAs, providing a convenient operational interface, parameter logging and alarm reporting. The monitor PC can also provide a data interface for reporting to a ground station central monitor and control system.

Callisto's high performance LNAs can be provided with a computer based monitoring system.

Features of the LNA Monitor System:

Automatic scanning analogue parameters:
Cryostat temperatures
Vacuum pressure
DC power supplies
Helium compressor status
Limits testing for alarms
Automatic data logging to file
On screen scrolling charts
Memorisation of alarm events
Remote computer interface
Compressor boost mode control

In addition to the high performance cryogenic LNAs described on the previous page, Callisto is also able to offer low cost designs with single stage refrigerators. These systems operate at a higher physical temperature, typically at 80 K, and the noise performance is correspondingly higher. An advantage of the single stage refrigerator is that the size can be made compact allowing installation in small antennas.

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