John E. Oswald

The Earth observing system microwave limb sounder (EOS MLS) on the aura Satellite

The Earth Observing System Microwave Limb Sounder measures several atmospheric chemical species (OH, HO/sub 2/, H/sub 2/O, O/sub 3/, HCl, ClO, HOCl, BrO, HNO/sub 3/, N/sub 2/O, CO, HCN, CH/sub 3/CN, volcanic SO/sub 2/), cloud ice, temperature, and geopotential height to improve our understanding of stratospheric ozone chemistry, the interaction of composition and climate, and pollution in the upper troposphere. All measurements are made simultaneously and continuously, during both day and night. The instrument uses heterodyne radiometers that observe thermal emission from the atmospheric limb in broad spectral regions centered near 118, 190, 240, and 640 GHz, and 2.5 THz. It was launched July 15, 2004 on the National Aeronautics and Space Administrations Aura satellite and started full-up science operations on August 13, 2004. An atmospheric limb scan and radiometric calibration for all bands are performed routinely every 25 s. Vertical profiles are retrieved every 165 km along the suborbital track, covering 82/spl deg/S to 82/spl deg/N latitudes on each orbit. Instrument performance to date has been excellent; data have been made publicly available; and initial science results have been obtained.

Measurements on a 215-GHz subharmonically pumped waveguide mixer using planar back-to-back air-bridge Schottky diodes

This paper presents design and performance data for a 215-GHz subharmonically pumped waveguide mixer using an antiparallel-pair of planar air-bridge-type GaAs Schottky-barrier diodes. The waveguide design is a prototype for a 640-GHz system and uses split-block rectangular waveguide with a 2:1 width-to-height ratio throughout. The measured mixer noise and conversion loss are below that of the best reported whisker contacted or planar-diode mixers using the subharmonic-pump configuration at this frequency. In addition, the required local oscillator power is as low as 3 mW for the unbiased diode pair, and greater than 34 dB of LO noise suppression is observed. Separate sideband calibration, using a Fabry-Perot filter, indicates that the mixer can be tuned for true double sideband response at an intermediate frequency of 1.5 GHz. Microwave scale model measurements of the waveguide mount impedances are combined with a mixer nonlinear analysis computer program to predict the mixer performance as a function of anode diameter, anode finger inductance, and pad-to-pad fringing capacitance. The computed results are in qualitative agreement with measurements, and indicate that careful optimization of all three diode parameters is necessary to significantly improve the mixer performance. >

A novel split-waveguide mount design for millimeter- and submillimeter-wave frequency multipliers and harmonic mixers

A split-waveguide mount for millimeter- and submillimeter-wave frequency multipliers and harmonic mixers is presented. It consists of only two pieces, block halves, which are mirror images of each other. The mount provides parallel and series impedance tuning with two sliding backshorts at both the input and output frequencies while utilizing E-plane arms to provide an in-line waveguide input and output. Its fabrication is much easier than that of a traditional multifrequency waveguide mount. Waveguide losses are minimized by a very compact design with very short input and output waveguides. This mount is especially well suited for planar diodes used with microstrip or suspended stripline RF filters.<<ETX>>

Improved 240-GHz subharmonically pumped planar Schottky diode mixers for space-borne applications

Low-noise broad intermediate frequency (IF) band 240-GHz subharmonically pumped planar Schottky diode mixers for space-borne radiometers have been developed and characterized. The planar GaAs Schottky diodes are fully integrated with the RF/IF filter circuitry via the quartz-substrate upside-down integrated device (QUID) process resulting in a robust and easily handled package. A best double-sideband-mixer noise temperature of 490 K was achieved with 3 mW of local-oscillator power at 2-GHz IF. Over an IF band of 1.5-10 GHz, the noise temperature is below 1000 K. This state-of-the-art performance is attributed to lower parasitic capacitance devices and a low-loss waveguide circuit. Device fabrication technology and the resulting RF mixer performance obtained in the 200-250-GHz frequency range will be described.

An all solid-state 640 GHz subharmonic mixer

This paper reports on the first all solid-state two-diode subharmonically pumped (SHP) mixer operating at 640 GHz. The required local oscillator (LO) power is less than 4 mW at 320 GHz for optimum performance. Two approaches are used to generate the required LO power. The first approach utilizes a 107 GHz InP Gunn diode followed by a whisker-contacted tripler while the second employs an IMPATT diode at 80 GHz followed by two planar diode frequency doublers. The best measured mixer noise temperature is 2500 K double sideband with a conversion loss of 9 dB at an IF of 2 GHz. An IF-frequency scan of the mixer shows a noise temperature of no worse than 3700 K across the 1.5 to 15 GHz band. Extraneous LO noise from the IMPATT is not evident for the SHP mixer, even at those frequencies and with low IFs. This performance represents the state-of-the-art for room temperature subharmonic mixers operating at these frequencies. The mixers are being developed for NASAs Mission to Planet Earth.

Planar diode solid-state receiver for 557 GHz with state-of-the-art performance

The design and performance of a subharmonically pumped (SHP) 557-GHz mixer driven by a solid-state local oscillator (LO) are reported. Whisker contacts are not required as both the mixer and LO utilize planar Schottky devices. A measured mixer noise temperature of 2100-K double sideband (DSB) with a conversion loss of 8.9 dB has been achieved at room temperature. The mixer exhibits broad intermediate frequency (IF) bandwidth with measured DSB noise temperatures below 3400 K in the band from 1.5 to 17 GHz. An external 6-18-GHz amplifier has been added to the output of the mixer, and measured receiver noise temperatures below 7300 K have been measured across the IF band. The results are believed to represent state-of-the-art performance for a room-temperature broad-band solid-state receiver at this frequency.

600 GHz planar-Schottky-diode subharmonic waveguide mixers

We report on the first planar two-diode subharmonic mixer operating at 600 GHz. The measured mixer noise temperature of 4200 K DSB is only a factor of 2 worse than the best single diode (whisker-contacted or planar) fundamental mixers and a factor 1.5 worse than the best ever single diode (whisker-contacted) harmonic mixer at similar frequencies. The measured conversion loss is /spl ap/12 dB and a noise temperature between 4200-5300 K can be maintained with a fix tuned circuit over a 1-18 GHz IF bandwidth. The anodes are made via a trilayer direct e-beam write process that results in extremely low parasitic devices with high cutoff frequencies. The mixers are being developed for NASAs Mission to Planet Earth.

Observations of tropical cyclones with a 60, 118 and 183 GHz microwave sounder

The Jet Propulsion Laboratorys High Altitude MMIC Sounding Radiometer (HAMSR) is a 25 channel microwave sounder with channels near the 60 GHz and 118 GHz oxygen lines and near the 183 GHz water vapor line. It participated in three hurricane field campaigns, CAMEX-4, TCSP and NAMMA The absolute calibration of the HAMSR brightness temperatures is shown to be better than 1.5 K. A non-linear iterative optimal estimation based retrieval algorithm is developed to retrieve atmospheric temperature and absolute humidity profiles. Comparisons of the retrieved profiles with coincident dropsonde profiles during NAMMA show excellent agreement at all altitudes, with the exception of a 30% residual dry bias in the absolute humidity profile above 4 km. The warm core structure of Hurricane Erin in 2001 and Hurricane Emily in 2005 is retrieved. The 60/118 GHz channels which have matched clear air weighting functions are used to assess convective intensity in the eye wall through the relative scatter darkening between the two channels.

Heterodyne radiometer development for the Earth Observing System Microwave Limb Sounder

NASAs Mission to Planet Earth attempts to address issues related to environmental change through extensive scientific investigation and global monitoring. As part of this effort, the Earth Observing System Microwave Limb Sounder (EOS-MLS), Joe W. Waters principal investigator, was proposed and is currently in development. The Submillimeter-Wave Radiometer Development group at JPL along with collaborators at the Rutherford Appleton Laboratory in the United Kingdom and a small number of US laboratories are developing space-borne radiometer components to satisfy the detection requirements for EOS-MLS from 200 to 650 GHz with possible extension up to 2.5 THz (119 micrometers ). This conference paper summarizes the development that has been ongoing, with emphasis on the millimeter- and submillimeter-wave mixers. Detailed design and performance data for a subharmonically pumped antiparallel-pair planar-diode mixer are presented including computational simulations and measured mixer noise and conversion loss at 215 and 640 GHz. Results from a modest test program comparing the performance at 215 GHz of planar GaAs antiparallel-pair mixer diodes, planar In53Ga47As devices, GaAs planar-doped-barrier diodes and a GaAs millimeter-wave integrated circuit (MMIC) mixer are also presented. Finally, current and future development efforts in the areas of submillimeter-wave local oscillators, integrated planar-diode mixers, IF amplifiers, and THz radiometers are outlined.

Subharmonic mixer with planar Schottky diodes in a novel split-block at 200-240 GHz

A broadband subharmonic mixer utilizing a planar antiparallel Schottky barrier diode pair has been developed for 220 GHz. The mixer is based on a novel split-waveguide block design consisting of only two central pieces and two tuner drivers which provide series and parallel tuning elements at both the local oscillator and signal frequency. The single sideband noise temperature is just below 2000 K from 210-235 GHz when an IF at 1.5 GHz is used. The conversion loss is 9.5-10 dB. A fixed-tuned useable IF bandwidth of more than 10 GHz was achieved with the new block design.<<ETX>>