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The performance of broad-band low-noise low-dc-power-consumption cryogenic amplifiers have been studied in detail with emphasis on minimizing the power consumption and optimizing the amplifier performance at cryogenic temperature. A general approach is presented for the modeling and amplifier design, which helps in minimizing the power consumption and optimizing the performance of the amplifier. A noise temperature below 9 K and 22-dB gain was experimentally obtained in the frequency range of 4-8 GHz with a total power consumption of 4 mW with commercial GaAs transistors. Index Terms--Empirical large-signal models, FET, FET noise models, modeling, noise model extraction, noise parameter.

Two types of tunable filters have been developed at 400- and 800-MHz frequency bands, respectively. These filters have been fabricated with low-temperature co-fired-ceramics multilayer technologies assisted by varactor diodes. The filter size is 5.6 x 5.6 x 3.0 mm. Each filter has approximately 11% and 13% tuning range of frequency with a controlling voltage of 1-4 V, IL < 2.0 dB, and has an attenuation over 40 dB at fo [+ or -] 30%, respectively. Temperature stability data is also discussed. Index Terms--Ceramics, multilayers, tunable filters, varactors.

Significant advances in the development of high electron mobility field-effect transistors (HEMT's) have resulted in cryogenic, low-noise amplifiers (LNA's) whose noise temperatures are within an order of magnitude of the quantum noise limit (hv/k). Further advances in HEMT technology at cryogenic temperatures may eventually lead to the replacement of maser and superconducting-insulator-superconducting (SIS) front-ends in the 1-100 GHz frequency band. Key to identification of the best HEMT's and optimization of cryogenic LNA's is accurate and repeatable device measurements at cryogenic temperatures. A cryogenic on-wafer noise and scattering parameter measurement system has been developed to provide a systematic investigation of HEMT noise characteristics. In addition, an improved parameter extraction technique has been developed to help understand the relationship between device structure and LNA performance.

The early history of the high electron mobility transistor contains a good illustration of the way a new device idea happens and develops toward commercialization. These events that took place in our laboratory are described in this paper. Index Terms--Cryogenic low-noise amplifier, depletion-mode HEMT, enhancement-mode HEMT, GaAs MESFET, GaAs MOSFET, HEMT, HEMT IC, high electron mobility transistor, inverted HEMT, radio telescope.

In this paper, we present detailed on-wafer S-parameter and noise parameter measurements and modeling of InP/InAlAs/InGaAs high electron mobility transistors (0.1-[micro]m gate length) at cryogenic temperatures. Various physical effects influencing small-signal parameters, especially the radio-frequency (RF) transconductance and RF output resistance and their temperature dependence, are discussed in detail. Accurate on-wafer noise parameter measurements are carried out from 300 to 18 K, and the variation of the equivalent noise temperatures of drain and source ([T.sub.d] and [T.sub.g]) are modeled against temperature. Based on these models, a cryogenic low-noise amplifier in the Ka-band is developed with a record-low noise temperature of 10 K. Index Terms--Cryogenic, high electron mobility transistor (HEMT), impact ionization, low-noise amplifier (LNA), noise, small-signal model.

This paper presents the measured results of a C-band 60-channel superconductive input multiplexer integrated with pulse-tube space-qualified cryocoolers. The multiplexer is developed to duplicate the requirements of the INTELSAT 8 program. The channel filters are self-equalized ten-pole high-temperature superconductor (HTS) planar structures designed with drop-in cryogenic ferrite circulators and isolators. This paper presents details on RF design, packaging, and cryocooler integration, as well as an assessment of overall reliability of using HTS equipment in a space environment. This paper demonstrates that at least 50% reduction in mass and 65% reduction in size can be achieved by replacing the INTELSAT 8 C-band dielectric-resonator input multiplexer with a superconductive multiplexer. Index Terms--Channel bank filters, cryogenics, high-temperature superconductors, satellite applications, superconductive filters.