DC-2 GHz low loss cryogenic InAs/AlSb HEMT switch
A DC-2 GHz InAs/AlSb HEMT MMIC single pole double throw (SPDT) switch designed for cryogenic temperature has been fabricated and characterized. This switch is suitable for low RF power applications that require low insertion loss and high isolation. At 2 GHz, the SPDT switch demonstrated a typical low insertion loss of 0.7 dB at 300K and 0.3 dB at 90K. The isolation is greater than 40dB for both temperatures. These results demonstrate the outstanding potential of ABCS HEMT technology for low loss SPDT switches for cryogenic temperature.
A 110-GHz AlSb/InAs MMIC amplifier
We describe the first demonstration of a W-band amplifier using antimonide based compound semiconductor (ABCS) device technology. The three stage CPW MMIC uses two finger 0.1-/spl mu/m AlSb/InAs HEMT with a total periphery of 40 micron per device. Biased at a total MMIC dissipation of 3.7-m W the amplifier demonstrates 11/spl plusmn/ 1 dB gain over a 80-110 GHz bandwidth. When biased at total MMIC dissipation of 9.0 mW, the amplifier demonstrates 15/spl plusmn/ 1 dB gain over 80-100 GHz bandwidth.
Evaluation and Control of Collapsible Soils
Some compacted soils wetted under certain conditions of compaction and loading may exhibit additional settlement (collapse). To investigate the effect of the soil type, compaction water content, initial dry unit weight and applied pressure at wetting on collapse potential, 138 single‐oedometer tests were conducted on eight different soils. The results indicate that well‐graded soils tend to collapse more than poorly graded ones under similar conditions. Furthermore, collapse potential decreases with an increase in (1) The difference between the sand and clay percentages; (2) compaction water content; and (3) initial dry unit weight, while it increases with pressure at wetting. A multiple regression analysis was performed on the laboratory results to provide a collapse‐predictive model that was substantiated by data reported by several researchers. A chart is presented to estimate (1) The collapse potential of soils under various conditions; and (2) the critical water content beyond which no collapse is ex...