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This letter reports the performance of a novel single-stage W-band amplifier fabricated utilizing flip-chip bump-bonding. We have bump-bonded a high-speed, low-noise InP high electron mobility transistor (HEMT) device onto a separately fabricated passive circuit having a GaAs substrate.
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A number of monolithic W-band power amplifiers have been developed for local oscillators of the Far Infrared and Sub-millimeter Telescope.
We present results of developments of low noise millimeter wave receivers for space applications utilizing InP HEMT monolithic microwave integrated circuts (MMICs).
A prototype digital optical module has been constructed for use in conjuction with the AMANDA neutrino detector at the South Pole.
There are significant international efforts underway to place mobile robots (rovers) on the surface of Mars.
Significant advances in the development of HEMT technology have resulted in high performance cryogenic low noise amplifiers whose noise temperatures are within an order of magnitude of the quantum noise limit. Key to the identification of optimum HEMT structures at cryogenic temperatures is the development of on-wafer noise and device parameter extraction techniques. Techniques and results are described.
The spin-induced quadrupole moment of a rapidly rotating star changes the orbital dynamics in a binary system, giving rise to advance (or regression) of periastron and precession of the orbital plane. We show that these effects are important in the recently discovered radio pulsar/mail sequence star binary system PSR J0045-7319, and reliably account for the observed peculiar timing residuals. Precise measurements of the apsidal motion and orbital plane precession can yield valuable information on the internal structure and rotation of the star. The detection of orbital precession implies that the spin of the companion star is not aligned with the orbital angular momentum, and suggests that the supernova gave the pulsar a kick out of the original orbital plane. Excitations of g-mode oscillations near periastron (the dynamical tide) can induce measurable changes in the orbital period and eccentricity at each passage for this system. We also discuss the spin-orbit coupling effects for the accreting X-ray pulsars and the other know radio pulsar/main sequence binary, PSR B1259-63.
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We present the observations and analysis of teh spectral linewidths of neutral and ion species across teh DR21(OH) core to investigate the cyclotron interaction as a probe of magnetic fields.
We present results on an InP monolithic millimeter- wave integrated circuit (MMIC) amplifier having 10-dB gain at 235 GHz. We designed this circuit and fabricated the chip in Northrop Grumman Space Technology's (NGST) 0.07- m InP high electron mobility transistor (HEMT) process. Using a WR3 (220-325 GHz) waveguide vector network analyzer system interfaced to waveguide wafer probes, we measured this chip on-wafer for -parameters. To our knowledge, this is the first time a WR3 waveguide on-wafer measurement system has been used to measure gain in a MMIC amplifier above 230 GHz.
We describe the design and development of the Low Temperature Microgravity Physics Facility, which is intended to provide a unique environment of low temperature and microgravity for the scientists to perform breakthrough investigations on board the International Space Station.
The objective of this research is to determine the effects of thermal processing, freeze drying, irradiation, and storage time on the nutritional content of food, to evaluate the nutritional content of the food items currently used on the International Space Station and Shuttle, and to establish the need to institute countermeasures. (This study does not seek to address the effect of processing on nutrients in detail, but rather aims to place in context the overall nutritional status at the time of consumption).
In order to reduce the risk of decompression sickness associated with spacewalks, NASA is considering designing the next generation of exploration vehicles and habitats with a different cabin environment than used previously. The proposed environment uses a total cabin pressure of 52.7 to 58.6 kPa with an oxygen concentration of 30 to 34% by volume and was chosen with material flammability in mind. Because materials may burn differently under these conditions and there is little information on how this new environment affects the flammability of the materials onboard, it is important to conduct material flammability experiments at the intended exploration atmosphere. One method to evaluate material flammability is by its ease of ignition. To this end, piloted ignition delay tests were conducted in the Forced Ignition and Spread Test (FIST) apparatus subject to this new environment. In these tests, polymethylmethacylate (PMMA) was exposed to a range of oxidizer flow velocities and externally applied heat fluxes. The ultimate goal is to determine the individual effect of pressure and the combined effect of pressure and oxygen concentration on the ignition delay. Tests were conducted for a baseline case of normal pressure and oxygen concentration, low pressure (58.6 kPa) with normal oxygen (21%). Future work will focus on low pressure with 32% oxygen concentration (space exploration atmosphere - SEA) conditions. It was found that reducing the pressure while keeping the oxygen concentration at 21% reduced the ignition time by 17% on average. It was also noted that the critical heat flux for ignition decreases in low-pressure conditions. Because tests conducted in standard atmospheric conditions will underpredict the flammability of materials intended for use on spacecraft, fire safety onboard at exploration atmospheres may be compromised.
In certain aspects, the invention features methods for forming crystalline membranes (e.g., a membrane of a framework material, such as a zeolite) by inducing secondary growth in a layer of oriented seed crystals. The rate of growth of the seed crystals in the plane of the substrate is controlled to be comparable to the rate of growth out of the plane. As a result, a crystalline membrane can form a substantially continuous layer including grains of uniform crystallographic orientation that extend through the depth of the layer.
Power amplifiers comprising InP-based high-electron-mobility transistors (HEMTs) in coplanar-waveguide (CPW) circuits designed for operation at frequencies of hundreds of gigahertz, and a test set for onwafer measurement of their power levels have been developed. These amplifiers utilize an advanced 35-nm HEMT monolithic microwave integrated-circuit (MMIC) technology and have potential utility as local-oscillator drivers and power sources in future submillimeter-wavelength heterodyne receivers and imaging systems. The test set can reduce development time by enabling rapid output power characterization, not only of these and similar amplifiers, but also of other coplanar-waveguide power circuits, without the necessity of packaging the circuits.
Recent developments in semiconductor technology have enabled advanced submillimeter wave (300 GHz) transistors and circuits. These new high speed components have required new test methods to be developed for characterizing performance, and to provide data for device modeling to improve designs. Current efforts in progressing high frequency testing have resulted in on-wafer-parameter measurements up to approximately 340 GHz and swept frequency vector network analyzer waveguide measurements to 508 GHz. On-wafer noise figure measurements in the 270-340 GHz band have been demonstrated. In this letter we report on on-wafer power measurements at 330 GHz of a three stage amplifier that resulted in a maximum measured output power of 1.78mW and maximum gain of 7.1 dB. The method utilized demonstrates the extension of traditional power measurement techniques to submillimeter wave frequencies, and is suitable for automated testing without packaging for production screening of submillimeter wave circuits.
To increase the usefulness of monolithic millimeter-wave integrated circuit (MMIC) components at submillimeter-wave frequencies, a chip has been designed that incorporates two integrated, radial E-plane probes with an MMIC amplifier in between, thus creating a fully integrated waveguide module. The integrated amplifier chip has been fabricated in 35-nm gate length InP high-electron-mobility-transistor (HEMT) technology. The radial probes were mated to grounded coplanar waveguide input and output lines in the internal amplifier. The total length of the internal HEMT amplifier is 550 m, while the total integrated chip length is 1,085 m. The chip thickness is 50 m with the chip width being 320 m. The internal MMIC amplifier is biased through wire-bond connections to the gates and drains of the chip. The chip has 3 stages, employing 35-nm gate length transistors in each stage. Wire bonds from the DC drain and gate pads are connected to off-chip shunt 51-pF capacitors, and additional off-chip capacitors and resistors are added to the gate and drain bias lines for low-frequency stability of the amplifier. Additionally, bond wires to the grounded coplanar waveguide pads at the RF input and output of the internal amplifier are added to ensure good ground connections to the waveguide package. The S-parameters of the module, not corrected for input or output waveguide loss, are measured at the waveguide flange edges. The amplifier module has over 10 dB of gain from 290 to 330 GHz, with a peak gain of over 14 dB at 307 GHz. The WR2.2 waveguide cutoff is again observed at 268 GHz. The module is biased at a drain current of 27 mA, a drain voltage of 1.24 V, and a gate voltage of +0.21 V. Return loss of the module is very good between 5 to 25 dB. This result illustrates the usefulness of the integrated radial probe transition, and the wide (over 10-percent) bandwidth that one can expect for amplifier modules with integrated radial probes in the submillimeter-regime (>300 GHz).