Design, fabrication, and demonstration of low-mass, low-power, small-volume, direct detection millimeter-wave radiometers at 92 and 130 GHz

2012 Spring.Includes bibliographical references.Advances in future ocean satellite altimetry missions are needed to meet oceanographic and hydrological objectives. These needs include accurately determining the sea surface height (SSH) on spatial scales of 10 km and larger, as well as monitoring the height of the world's inland bodies of water and the flow rate of rivers. The Surface Water and Ocean Topography (SWOT) mission was recommended by the National Research Council's Earth Science Decadal Survey and selected by the National Aeronautics and Space Administration as an accelerated Tier-2 mission to address these needs. Current surface altimetry missions use nadir pointing 18-37 GHz microwave radiometers to correct for errors in SSH due to wet-tropospheric path delay. Using current antennas at these frequencies, oceanic measurements include significant errors within 50 km of coastlines due to varying emissivity and temperature of land. Higher frequencies (90-170 GHz) can provide proportionally smaller footprints for the same antenna size. In turn, this provides improved retrievals of wet-tropospheric path delay near the coasts. This thesis will focus on the design, fabrication, and testing of two direct detection radiometers with internal calibration at center frequencies of 92 and 130 GHz. Component design, testing and integration of the radiometers using multi-chip modules are discussed. The performance of these radiometers is characterized, including noise figure, internal calibration and long-term stability. These performance parameters, along with their mass, volume, and power consumption, will be used as the basis for the development of future airborne and space-borne millimeter-wave direct detection radiometers with internal calibration

MERITXELL: the Multifrequency Experimental Radiometer with Interference Tracking for Experiments over Land and Littoral—instrument description, calibration and performance

MERITXELL is a ground-based multisensor instrument that includes a multiband dual-polarization radiometer, a GNSS reflectometer, and several optical sensors. Its main goals are twofold: to test data fusion techniques, and to develop Radio-Frequency Interference (RFI) detection, localization and mitigation techniques. The former is necessary to retrieve complementary data useful to develop geophysical models with improved accuracy, whereas the latter aims at solving one of the most important problems of microwave radiometry. This paper describes the hardware design, the instrument control architecture, the calibration of the radiometer, and several captures of RFI signals taken with MERITXELL in urban environment. The multiband radiometer has a dual linear polarization total-power radiometer topology, and it covers the L-, S-, C-, X-, K-, Ka-, and W-band. Its back-end stage is based on a spectrum analyzer structure which allows to perform real-time signal processing, while the rest of the sensors are controlled by a host computer where the off-line processing takes place. The calibration of the radiometer is performed using the hot-cold load procedure, together with the tipping curves technique in the case of the five upper frequency bands. Finally, some captures of RFI signals are shown for most of the radiometric bands under analysis, which evidence the problem of RFI in microwave radiometry, and the limitations they impose in external calibration.Peer ReviewedPostprint (published version

COMPARACIÓN DEL GRADIENTE DE TEMPERATURA EN ESPACIOS CÚBICOS CONTROLADOS CON CELDA PELTIER EN FUNCIÓN A DOS AISLANTES TÉRMICOS. (COMPARISON OF THE TEMPERATURE GRADIENT IN CUBIC SPACES CONTROLLED WITH PELTIER CELL ACCORDING TO TWO THERMAL INSULATORS.)

ResumenEste trabajo estudia el gradiente de temperatura en espacios cúbicos de dimensiones pequeñas utilizando dispositivos de enfriamiento peltier. Se demuestra que el material, el volumen, potencia y temperatura exterior afecta la eficiencia de un elemento termoeléctrico.  Los materiales seleccionados en la construcción de los espacios cúbicos cuentan con baja conductividad térmica, a fin de evitar que la temperatura exterior afecte a la medición. Se tomaron periódicamente valores de temperatura en espacios cúbicos. El banco de prueba consiste en microcontrolador, disipadores de calor en lado frio y caliente y módulos peltier. Se realizó la comparación de los valores que obtienen en cada volumen. Se determina el uso de mayor cantidad de celdas peltier, optimizando el tiempo de enfriamiento y la potencia necesaria que se requiera. Según las ecuaciones que se obtienen el comportamiento del enfriamiento en espacios cúbicos es semejante, la eficiencia que se presenta en enfriamiento a espacios es reflejada en material, volumen, potencia de enfriamiento y temperatura externa. Palabras Claves: Peltier, Modelado, temperatura, Gradiente, Optoelectrónica.AbstractThis paper studies the temperature gradient in cubic spaces of small dimensions using peltier cooling devices. The dependency of the material, volume, power and external temperature was studied, which it affects the efficiency of a thermoelectric element. The materials selected for the cubic spaces elaboration were chosen with low thermal conductivity, since this avoid the room temperature affecting the measurement. The internal temperature of the cubic spaces was taken at periodic    intervals to observe its behavior. The characterization was carried out using a microcontroller, heat sinks on cold and hot sides, and peltier modules. The temperature was compared between each volume used to obtain an optimization as a function of peltiers cells, in a minimal time of set point of cooling temperature and the power required. The equiation obtain in According to the equations that are obtained the behavior of movement in cubic spaces is similar, the efficiency that is presented in space limitations is reflected in material, volume, cooling power and external temperature.Keywords: Peltier, Modeling, Temperature, Gradient, Optoelectronics

Design, Development, and Prelaunch Calibration of a Low Cost 118.75 GHz Temperature Sounding Radiometer for CubeSat Missions

The 118.75 GHz eight-channel, double-side-band scanning temperature sounding radiometer &ldquo;MiniRad&rdquo; for CubeSat missions is intended to serve as a demonstrator for a constellation of low cost, quick turn-around millimeter wave and higher frequency passive sounders and imagers for weather forecasting at high spatial and temporal resolution. This radiometer payload, built at the Center for Environmental Technology in partnership with the Colorado Space Grant Consortium and the National Snow and Ice Data Center at the University of Colorado at Boulder, can provide a 3D temperature map from the earth's surface to an altitude of 18~km. For precise prelaunch antenna calibration, an HE11 mode full wave electromagnetic field analysis was developed in Matlab for determination of an optimal feed horn and offset paraboloidal reflector geometry such that the main beam and spillover efficiencies of the system are maximized, and these and the antenna phase center location that maximizes phase efficiency are precisely known. Results from this analysis were also compared with HFSS and GRASP simulations of the antenna subsystem. The efficacy of employing a 3D-printed corrugated conical horn, operable between 110 and 127 GHz, as the feed for the reflector was addressed due to its very low cost and rapid manufacturability. Horn measurements indicated a reflection coefficient below -15 dB and an 89% average spillover efficiency at the main reflector subtending a 16&deg; half-angle. The need for a compact intermediate frequency spectrometer for operation between 50 MHz and 7 GHz resulted in the design and development of an eight-channel lumped element filterbank with bandwidths between 0.25 and 2.2 GHz. Laboratory experiments implemented to characterize the MiniRad helped in achieving radiometer sensitivities close to theoretical limits. Initial performance obtained from airborne measurements over Antarctica during the NASA Operation IceBridge experiment in Oct-Nov 2016 suggested a well-focused scanning antenna subsystem and good separation between the radiometer channels. After final system integration, measurements obtained from prelaunch experiments indicated the antenna 3-dB beamwidth to be broader by ~0.1&deg; compared to the idealized simulated pattern, and radiometer sensitivities that agreed to better than 0.5 K with theoretical estimates across all eight channels.</p

Design, Development, and Prelaunch Calibration of a Low Cost 118.75 Ghz Temperature Sounding Radiometer for Cubesat Missions

The 118.75 GHz eight-channel, double-side-band scanning temperature sounding radiometer “MiniRad” for CubeSat missions is intended to serve as a demonstrator for a constellation of low cost, quick turn-around millimeter wave and higher frequency passive sounders and imagers for weather forecasting at high spatial and temporal resolution. This radiometer payload, built at the Center for Environmental Technology in partnership with the Colorado Space Grant Consortium and the National Snow and Ice Data Center at the University of Colorado at Boulder, can provide a 3D temperature map from the earth's surface to an altitude of 18~km. For precise prelaunch antenna calibration, an HE11 mode full wave electromagnetic field analysis was developed in Matlab for determination of an optimal feed horn and offset paraboloidal reflector geometry such that the main beam and spillover efficiencies of the system are maximized, and these and the antenna phase center location that maximizes phase efficiency are precisely known. Results from this analysis were also compared with HFSS and GRASP simulations of the antenna subsystem. The efficacy of employing a 3D-printed corrugated conical horn, operable between 110 and 127 GHz, as the feed for the reflector was addressed due to its very low cost and rapid manufacturability. Horn measurements indicated a reflection coefficient below -15 dB and an 89% average spillover efficiency at the main reflector subtending a 16 degree half-angle. The need for a compact intermediate frequency spectrometer for operation between 50 MHz and 7 GHz resulted in the design and development of an eight-channel lumped element filterbank with bandwidths between 0.25 and 2.2 GHz. Laboratory experiments implemented to characterize the MiniRad helped in achieving radiometer sensitivities close to theoretical limits. Initial performance obtained from airborne measurements over Antarctica during the NASA Operation IceBridge experiment in Oct-Nov 2016 suggested a well-focused scanning antenna subsystem and good separation between the radiometer channels. After final system integration, measurements obtained from prelaunch experiments indicated the antenna 3-dB beamwidth to be broader by ~0.1 degree compared to the idealized simulated pattern, and radiometer sensitivities that agreed to better than 0.5 K with theoretical estimates across all eight channels

Stratospheric Water Vapour in the Tropics: Observations by Ground-Based Microwave Radiometry

This thesis reports on observations of tropical stratospheric water vapour by the ground-based microwave radiometer/spectrometer WaRAM2 in 2007. The 22GHz receiver is set up at Mérida Atmospheric Research Station on top of Pico Espejo, Venezuela (8°32'N, 71°03'W, 4765m above sea level). It is the only such sensor that continuously operates at tropical latitudes. The high altitude site is ideally suitable for microwave observations, because most tropospheric water vapour is located below the sensor. Water vapour plays a key role in middle atmospheric processes. Because of its large infrared resonance, it strongly participates in the radiative budget, both in terms of a greenhouse effect at lower altitudes and radiative cooling at higher altitudes. It is a source gas for the highly reactive hydroxyl radical, and exerts indirect effects on ozone destruction in the formation of polar stratospheric clouds. Due to its long lifetime, water vapour also serves as a dynamical tracer

Radio frequency interference detection and mitigation techniques for navigation and Earth observation

Radio-Frequency Interference (RFI) signals are undesired signals that degrade or disrupt the performance of a wireless receiver. RFI signals can be troublesome for any receiver, but they are especially threatening for applications that use very low power signals. This is the case of applications that rely on the Global Navigation Satellite Systems (GNSS), or passive microwave remote sensing applications such as Microwave Radiometry (MWR) and GNSS-Reflectometry (GNSS-R). In order to solve the problem of RFI, RFI-countermeasures are under development. This PhD thesis is devoted to the design, implementation and test of innovative RFI-countermeasures in the fields of MWR and GNSS. In the part devoted to RFI-countermeasures for MWR applications, first, this PhD thesis completes the development of the MERITXELL instrument. The MERITXELL is a multi-frequency total-power radiometer conceived to be an outstanding platform to perform detection, characterization, and localization of RFI signals at the most common MWR imaging bands up to 92 GHz. Moreover, a novel RFI mitigation technique is proposed for MWR: the Multiresolution Fourier Transform (MFT). An assessment of the performance of the MFT has been carried out by comparison with other time-frequency mitigation techniques. According to the results, the MFT technique is a good trade-off solution among all other techniques since it can mitigate efficiently all kinds of RFI signals under evaluation. In the part devoted to RFI-countermeasures for GNSS and GNSS-R applications, first, a system for RFI detection and localization at GNSS bands is proposed. This system is able to detect RFI signals at the L1 band with a sensitivity of -108 dBm at full-band, and of -135 dBm for continuous wave and chirp-like signals when using the averaged spectrum technique. Besides, the Generalized Spectral Separation Coefficient (GSSC) is proposed as a figure of merit to evaluate the Signal-to-Noise Ratio (SNR) degradation in the Delay-Doppler Maps (DDMs) due to the external RFI effect. Furthermore, the FENIX system has been conceived as an innovative system for RFI detection and mitigation and anti-jamming for GNSS and GNSS-R applications. FENIX uses the MFT blanking as a pre-correlation excision tool to perform the mitigation. In addition, FENIX has been designed to be cross-GNSS compatible and RFI-independent. The principles of operation of the MFT blanking algorithm are assessed and compared with other techniques for GNSS signals. Its performance as a mitigation tool is proven using GNSS-R data samples from a real airborne campaign. After that, the main building blocks of the patented architecture of FENIX have been described. The FENIX architecture has been implemented in three real-time prototypes. Moreover, a simulator named FENIX-Sim allows for testing its performance under different jamming scenarios. The real-time performance of FENIX prototype has been tested using different setups. First, a customized VNA has been built in order to measure the transfer function of FENIX in the presence of several representative RFI/jamming signals. The results show how the power transfer function adapts itself to mitigate the RFI/jamming signal. Moreover, several real-time tests with GNSS receivers have been performed using GPS L1 C/A, GPS L2C, and Galileo E1OS. The results show that FENIX provides an extra resilience against RFI and jamming signals up to 30 dB. Furthermore, FENIX is tested using a real GNSS timing setup. Under nominal conditions, when no RFI/jamming signal is present, a small additional jitter on the order of 2-4 ns is introduced in the system. Besides, a maximum bias of 45 ns has been measured under strong jamming conditions (-30 dBm), which is acceptable for current timing systems requiring accuracy levels of 100 ns. Finally, the design of a backup system for GNSS in tracking applications that require high reliability against RFI and jamming attacks is proposed.Les interferències de radiofreqüència (RFI) són senyals no desitjades que degraden o interrompen el funcionament dels receptors sense fils. Les RFI poden suposar un problema per qualsevol receptor, però són especialment amenaçadores per les a aplicacions que fan servir senyals de molt baixa potència. Aquest és el cas de les aplicacions que depenen dels sistemes mundials de navegació per satèl·lit (GNSS) o de les aplicacions de teledetecció passiva de microones, com la radiometria de microones (MWR) i la reflectometria GNSS (GNSS-R). Per combatre aquest problema, sistemes anti-RFI s'estan desenvolupament actualment. Aquesta tesi doctoral està dedicada al disseny, la implementació i el test de sistemes anti-RFI innovadors en els camps de MWR i GNSS. A la part dedicada als sistemes anti-RFI en MWR, aquesta tesi doctoral completa el desenvolupament de l'instrument MERITXELL. El MERITXELL és un radiòmetre multifreqüència concebut com una plataforma excepcional per la detecció, caracterització i localització de RFI a les bandes de MWR més utilitzades per sota dels 92 GHz. A més a més, es proposa una nova tècnica de mitigació de RFI per MWR: la Transformada de Fourier amb Multiresolució (MFT). El funcionament de la MFT s'ha comparat amb el d'altres tècniques de mitigació en els dominis del temps i la freqüència. D'acord amb els resultats obtinguts, la MFT és una bona solució de compromís entre les altres tècniques, ja que pot mitigar de manera eficient tots els tipus de senyals RFI considerats. A la part dedicada als sistemes anti-RFI en GNSS i GNSS-R, primer es proposa un sistema per a la detecció i localització de RFI a les bandes GNSS. Aquest sistema és capaç de detectar senyals RFI a la banda L1 amb una sensibilitat de -108 dBm a tota la banda, i de -135 dBm per a senyals d'ona contínua i chirp fen un mitjana de l'espectre. A més a més, el Coeficient de Separació Espectral Generalitzada (GSSC) es proposa com una mesura per avaluar la degradació de la relació senyal a soroll (SNR) en els Mapes de Delay-Doppler (DDM) a causa del impacte de les RFI. La major contribució d'aquesta tesi doctoral és el sistema FENIX. FENIX és un sistema innovador de detecció i mitigació de RFI i inhibidors de freqüència per aplicacions GNSS i GNSS-R. FENIX utilitza la MFT per eliminar la interferència abans del procés de correlació amb el codi GNSS independentment del tipus de RFI. L'algoritme de mitigació de FENIX s'ha avaluat i comparat amb altres tècniques i els principals components de la seva arquitectura patentada es descriuen. Finalment, un simulador anomenat FENIX-Sim permet avaluar el seu rendiment en diferents escenaris d'interferència. El funcionament en temps real del prototip FENIX ha estat provat utilitzant diferents mètodes. En primer lloc, s'ha creat un analitzador de xarxes per a mesurar la funció de transferència del FENIX en presència de diverses RFI representatives. Els resultats mostren com la funció de transferència s'adapta per mitigar el senyal interferent. A més a més, s'han realitzat diferents proves en temps real amb receptors GNSS compatibles amb els senyals GPS L1 C/A, GPS L2C i Galileo E1OS. Els resultats mostren que FENIX proporciona una resistència addicional contra les RFI i els senyals dels inhibidors de freqüència de fins a 30 dB. A més a més, FENIX s'ha provat amb un sistema comercial de temporització basat en GNSS. En condicions nominals, sense RFI, FENIX introdueix un petit error addicional de tan sols 2-4 ns. Per contra, el biaix màxim mesurat en condicions d'alta interferència (-30 dBm) és de 45 ns, el qual és acceptable per als sistemes de temporització actuals que requereixen nivells de precisió d'uns 100 ns. Finalment, es proposa el disseny d'un sistema robust de seguiment, complementari als GNSS, per a aplicacions que requereixen alta fiabilitat contra RFI.Postprint (published version

Design and development of an airborne microwave radiometer for atmospheric sensing

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 103-105).Satellite-based passive microwave remote sensing is a valuable tool for global weather monitoring and prediction. This thesis presents the design and development of a low-cost airborne weather sensing instrument to independently validate a satellite-based sensor platform. The NPOESS Aircraft Sounder Testbed - K-band (NAST-K) is a passive microwave radiometer operating over approximately 200 MHz bandwidth centered at 23.8 GHz and 31.4 GHz, whose data can be used to find surface water, humidity, and temperature conditions. NAST-K flies along with the existing NAST-M instrument at an altitude of 18 km in the NASA ER-2 high altitude aircraft. The primary function of NASTK is to provide coverage of channels 1 and 2 of the Advanced Technology Microwave Sounder (ATMS) aboard the NPOESS Preparatory Project (NPP) satellite, scheduled to be launched in October 2011. The combined NAST-M/K system can validate the performance of ATMS on all channels with data products up to 17km, by underflying the satellite along the same ground track and collecting correlated data. NAST-K has fullwidth at half maximum beamwidths of 7.4° and 6.8° for the two channels respectively, which is approximately consistent with NAST-M. The effective spot size of NAST-K is 2.3km in diameter for the wider 23.8GHz channel at nadir, providing an areal resolution approximately 1000 times greater than ATMS. The major contributions of this thesis include the system-level design of NAST-K, the development of the video amplifier and embedded environmental monitor, and the analysis of the antenna system.by Michael P. Scarito.M.Eng