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We present the TRW 0.1 pm InP HEMT MMIC production technology that has been developed and used for state-of-the-art cryogenic LNA applications. The 0.1 pm InP HEMT devices typically show cutoff frequency above 200 GHz and transconductance above 1000 mS/mm. Aspects of device design and fabrication are presented which impact important parameters including the InP HEMT device gain, gate leakage current, and parasitic capacitance. One example of state-of-the-art cryogenic MMIC performance is a W-band cryogenic MMIC LNA operated at 20 degrees Kelvin that shows above 23 dB gain and a noise temperature of 30 to 40 K (0.45 to 0.6 dB noise figure) over the band of 80-105 GHz.

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Exploration of the Solar System with automated spacecraft that are more than ten astronomical units fiom earth requires very large antennae employing extremely sensitive receivers.A key figure of merit in the specification of the spacecraft-to-earth telecommunications link is the ratio of the antenna gain to operational noise temperature (G/Top) of the system. The Deep Space Network (DSN) receivers are cryogenic, low-noise amplifiers (LNAs) which address the need to maintain Top as low as technology permits.Historically, the extra-ordinarily sensitive receive systems operated by the DSN have employed cryogenically cooled, ruby masers as the LNA. Recent advances in the development of indium phosphide (InP) based high electron mobility transistors (HEMTs) combined with cryogenic cooling have made this technology competitive with standard DSN maser technology. InP HEMT LNA modules are demonstrating noise temperatures less than ten times the quantum noise limit (10hfk) from 1 to 100 GHz. To date, the lowest noise LNA modules developed for the DSN have demonstrated noise temperatures of under 4 K at 8.4 GHz and 11 K at 32 GHz. Front-end receiver packages employing these modules demonstrated operating system noise temperatures of 17 K at 8.4 GHz (on a 70m antenna at zenith) and 39.4 K at 32 GHz (on a 34m antenna at zenith).The development and demonstration of cryogenic, InP HEMT based front-end amplifiers for the DSN requires accurate component and module characterization, and modeling from 1 to 100 GHz at physical temperatures down to and below 12 K, because of the broad band frequency response of InP HEMTs.The characterization and modeling begins with the HEMT chip, proceeds to the multi-stage HEMT LNA module, and culminates with the complete front-end cryogenic receiver package for the antenna.This paper presents an overview of this development process with emphasis on comparison between modeled and measured results at 8.4 GHz. Results will be shown for devices, LNA modules, front-end receiver packages employing these modules, and antennae employing these packages.

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