Pekka Kangaslahti

Initial Results of the Geostationary Synthetic Thinned Array Radiometer (GeoSTAR) Demonstrator Instrument

The design, error budget, and preliminary test results of a 50-56-GHz synthetic aperture radiometer demonstration system are presented. The instrument consists of a fixed 24-element array of correlation interferometers and is capable of producing calibrated images with 1deg spatial resolution within a 17deg wide field of view. This system has been built to demonstrate a performance and a design which can be scaled to a much larger geostationary Earth imager. As a baseline, such a system would consist of about 300 elements and would be capable of providing contiguous full hemispheric images of the Earth with 1 K of radiometric precision and 50-km spatial resolution. An error budget is developed around this goal and then tested with the demonstrator system. Errors are categorized as either scaling (i.e., complex gain) or additive (noise and bias) errors. Sensitivity to gain and/or phase error is generally proportional to the magnitude of the expected visibility, which is high only in the shortest baselines of the array, based on model simulations of the Earth as viewed from geostationary Earth orbit. Requirements range from approximately 0.5% and 0.3deg of amplitude and phase uncertainty, respectively, for the closest spacings at the center of the array, to about 4% and 2.5deg for the majority of the array. The latter requirements are demonstrated with our instrument using relatively simple references and antenna models, and by relying on the intrinsic stability and efficiency of the system. The 0.5% requirement (for the short baselines) is met by measuring the detailed spatial response (e.g., on the antenna range) and by using an internal noise diode reference to stabilize the response. This result suggests a hybrid image synthesis algorithm in which long baselines are processed by a fast Fourier transform and the short baselines are processed by a more precise (G-matrix) algorithm which can handle small anomalies among antenna and receiver responses. Visibility biases and other additive errors must be below about 1.5 mK on average, regardless of baseline. The bias requirement is largely met with a phase-shifting scheme applied to the local oscillator distribution of our demonstration system. Low mutual coupling among the horn antennas of our design is also critical to minimize the biases caused by crosstalk of receiver noise. Performance is validated by a three-way comparison between interference fringes measured on the antenna range, solar transit observations, and the system model.

Low noise amplifier for 180 GHz frequency band

Measurement of the humidity profile of the atmosphere is highly important for atmospheric science and weather forecasting. This sounding measurement is obtained at frequencies close to the resonance frequency of water molecules (183 GHz). We have designed and characterized a MMIC low noise amplifier that will increase the sensitivity of sounding instruments at these frequencies. This study demonstrated a factor of two improvement in MMIC LNA noise temperature at this frequency band. The measured packaged InP monolithic millimeter-wave integrated circuit (MMIC) amplifier had a noise temperature of NT=390 K (NF=3.7 dB). The circuit was fabricated in 35 nm InP high electron mobility transistor (HEMT) process.

The High-Altitude MMIC Sounding Radiometer for the Global Hawk Unmanned Aerial Vehicle: Instrument Description and Performance

The Jet Propulsion Laboratorys High-Altitude Monolithic Microwave Integrated Circuit (MMIC) Sounding Radiometer (HAMSR) is a 25-channel cross-track scanning microwave sounder with channels near the 60- and 118-GHz oxygen lines and the 183-GHz water-vapor line. It has previously participated in three hurricane field campaigns, namely, CAMEX-4 (2001), Tropical Cloud Systems and Processes (2005), and NASA African Monsoon Multidisciplinary Analyses (2006). The HAMSR instrument was recently extensively upgraded for the deployment on the Global Hawk (GH) unmanned aerial vehicle platform. One of the major upgrades is the addition of a front-end low-noise amplifier, developed by JPL, to the 183-GHz channel which reduces the noise in this channel to less than 0.1 K at the sensor resolution (~2 km). This will enable HAMSR to observe much smaller scale water-vapor features. Another major upgrade is an enhanced data system that provides onboard science processing capability and real-time data access. HAMSR has been well characterized, including passband characterization, along-scan bias characterization, and calibrated noise-performance characterization. The absolute calibration is determined in-flight and has been estimated to be better than 1.5 K from previous campaigns. In 2010, HAMSR participated in the NASA Genesis and Rapid Intensification Processes campaign on the GH to study tropical cyclone genesis and rapid intensification. HAMSR-derived products include observations of the atmospheric state through retrievals of temperature, water-vapor, and cloud-liquid-water profiles. Other products include convective intensity, precipitation content, and 3-D storm structure.

Two-Port Vector Network Analyzer Measurements in the 218–344- and 356–500-GHz Frequency Bands

We discuss methods for full two-port vector network analyzer measurements in the 218-344- (using WR3) and 356-500-GHz (using WR2.2) frequency bands. Waveguide test sets (WR3 and WR2.2) utilize Oleson Microwave Laboratories Inc. frequency extenders with the Agilent 8510C network analyzer. On-wafer measurements in the 220-325-GHz band are demonstrated with GGB Industries Inc. coplanar-waveguide probes. This paper primarily reviews the performance capabilities of the WR3 test set and introduces initial calibration results of the WR2.2 test set. For WR3, calibration methods are compared, and dynamic range and frequency extender output power data are presented

A 75–116-GHz LNA with 23-K noise temperature at 108 GHz

In this paper we present the design and measurement results, both on-wafer and in package, of an ultra-low-noise and wideband monolithic microwave integrated circuit (MMIC) amplifier in the frequency range of 75 to 116 GHz. The three-stage amplifier packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology achieves a record noise temperature of 23 K at 108 GHz when cryogenically cooled to 27 K. The measured gain is 22 to 27 dB for frequency range of 75 to 116 GHz. Furthermore, the amplifier utilizes four-finger devices with a total gate width of 60 μm resulting in higher output power. Therefore, we consider that this amplifier achieves state-of-the-art performance in terms of bandwidth, noise temperature, gain, and linearity so far reported for cryogenically cooled amplifiers around W-band.

W-Band cryogenic InP MMIC LNAs with noise below 30K

In this paper, we describe two monolithic millimeter-wave integrated circuit (MMIC) low noise amplifiers (LNAs) for W-Band which have a noise temperature of 30K or better over a wide bandwidth when cryogenically cooled. The LNAs were designed and fabricated in NGCs InP HEMT MMIC process having 35 nm gate length and employing an InAs Composite Channel (IACC). A two-stage amplifier exhibits room temperature S21 gain of 15–18 dB, and cryogenic gain of 20 dB with minimum noise temperature of 25K at 95 GHz, and less than 40K noise temperature between 75–105 GHz. A three-stage amplifier exhibits 29 dB of S21 gain, and a cryogenic noise temperature below 30K over the range of 94–109 GHz. We discuss the design of the amplifiers, measured and simulated S-parameters, and cryogenic measurements. To our knowledge, these are the highest frequency and lowest noise temperatures ever reported for InP cryogenic LNAs covering W-Band.

Planar Polarimetry Receivers for Large Imaging Arrays at Q-band

The characterization of the intensity fluctuations of the cosmic microwave background (CMB) will be followed by the mapping of the polarization fluctuations of the CMB. Measurement of the polarization fluctuations requires highly sensitive instruments that are only possible by increasing the number of receivers. We are developing a large receiver array for the Q, U imaging experiment (QUIET) by building individual receivers that have noise temperatures close to the physical limit and that are simple, and low cost to build and operate. We developed these planar polarimetry receivers for Q-band by designing InP MMIC amplifiers with noise below 20 K, low loss and highly balanced phase switches and an entirely planar hybrid thin film circuit for the detection of the Stokes parameters Q and U. Our receivers achieve 25 K noise temperature over 8 GHz bandwidth and provide the I, Q and U parameters simultaneously. These planar modules have a simple plug in architecture that enables automated production of a large number of receivers and simple integration of large arrays of receivers

Low noise amplifier receivers for millimeter wave atmospheric remote sensing

We currently achieve 3.4 dB noise figure at 183GHz and 2.1 dB noise figure at 90 GHz with our MMIC low noise amplifiers (LNAs) in room temperature. These amplifiers and the receivers we have built using them made it possible to conduct highly accurate airborne measurement campaigns from the Global Hawk unmanned aerial vehicle, develop millimeter wave internally calibrated radiometers for altimeter radar path delay correction, and build prototypes of large arrays of millimeter receivers for a geostationary interferometric sounder. We use the developed millimeter wave receivers to measure temperature and humidity profiles in the atmosphere and in hurricanes as well as to characterize the path delay error in ocean topography altimetry.

160-270-GHz InP HEMT MMIC Low-Noise Amplifiers

We present two low-noise amplifiers for the frequency range of 160 to 270 GHz. The amplifiers were fabricated using a 35-nm InP HEMT technology and designed for room temperature and cryogenic operation. A four-stage amplifier in a common-source topology and a three-stage amplifier utilizing a cascode stage at the output achieve 15 to 25-dB on-wafer measured gain from 160 to 270 GHz. When packaged in WR5 waveguide housings the amplifiers exhibit room temperature measured noise of 600 to 760 K from 160 to 220 GHz. When cryogenically cooled the three-stage amplifier shows a noise of 80 to 115 K over the range of 164 to 220 GHz. Furthermore, our initial room temperature measurements show a noise figure of 7-8 dB over the 220 to 252 GHz range for a four-stage amplifier packaged in a WR3 waveguide housing.

Cryogenic indium-phosphide HEMT low-noise amplifiers at V-band

Indium-phosphide (InP) high electron-mobility transistors potentially have the lowest noise at frequencies below 100 GHz, especially when cryogenically cooled. We have designed monolithically integrated InP millimeter-wave low-noise amplifiers (LNAs) for the European Space Agency (ESA) science Planck mission. The Planck LNAs design goal for noise temperature is 35 K at the ambient temperature of 20 K. The operation bandwidth is over 20% at 70 GHz. The maximum allowable power consumption for a Planck LNA (gain 20 dB) is P/sub be/=5 mW at 20 K. The chosen foundry for these LNAs was DaimlerChrysler Research, Ulm, Germany. The DaimlerChrysler 0.18-/spl mu/m InP process was used. This process is well suited for V-band LNA design, giving sufficient gain with very low noise. Several one-, two-, and three-stage amplifiers were designed. The best of them exhibited a noise figure lower than 5.5 dB with a gain higher than 14 dB over the 50-68-GHz range at room temperature. The best single-stage amplifier demonstrated a noise figure of 4.5 dB and a gain higher than 5 dS from 50 to 60 GHz at room temperature. On-wafer measurements on these monolithic-microwave integrated circuits (MMICs) have been done at MilliLab, Espoo, Finland. For the module fabrication, MMIC chips will be mounted in a WR-15 waveguide split-block housing.