A SiGe 8-Channel Comparator for Application in a Synthetic Aperture Radiometer

We present a high-speed low-power 8-channel comparator tailored for the application of sampling antenna signals in a cross-correlator system for space-borne synthetic aperture radiometer instruments. Features like clock return path, per-channel offset calibration and bias current tuning make the comparator adaptable and gives the possibility to adjust the comparator for low power consumption, while keeping performance within the requirements of the cross-correlator system. The comparator has been implemented and fabricated in a 130-nm SiGe BiCMOS process. Measurements show that the comparator can perform sampling at a rate of 4.5 GS/s with a power consumption of 48 mW/channel or 1 GS/s with a power consumption of 17 mW/channel

A Cross-Correlator for the Remote Sensing of Earth by Synthetic Aperture

In light of our changing climate and the unpredictability of severe weather; a better understanding of our climate and increased weather forecast accuracy are in high demand. Humidity and temperature distribution profiles with high temporal resolution can significantly increase our knowledge of highly dynamic weather phenomena and improve weather forecasts.Microwave sounding from low earth orbit is extensively used for humidity and temperature measurements in the atmosphere because of its much better cloud penetrating properties compared to visible and infrared light. Performing these observations from geostationary earth orbit (GEO) would give the additional advantage of large coverage and no revisiting times. Microwave sounding from GEO is however demanding, this because of the large aperture required to reach acceptable spatial resolution. Synthetic aperture interferometry, widely used in ground based radio astronomy, has been proposed as a solution to overcome this obstacle.Cross-correlation is a signal processing algorithm that is a central and highly calculation-intensive part of aperture synthesis. CMOS process technology scaling, and the decreasing power per performance figures that have followed, has finally reached a point where these kinds of instruments are viable for space deployment.This thesis presents a cross-correlator chip that has been designed, fabricated and extensively evaluated, paving the way for larger correlator systems based on similar design concepts. Routing and synchronization schemes were developed for the purpose of handling the massively parallel calculations and the signal distribution and timing issues specific to synthetic aperture cross-correlators. The chip presented shows significant improvements over previous correlators in power per performance evaluations

1.6 GHz Low-Power Cross-Correlator System Enabling Geostationary Earth Orbit Aperture Synthesis

We present a 64-channel cross-correlator system for space-borne synthetic aperture imaging. Two different types of ASICs were developed to fit into this system: An 8-channel comparator ASIC implemented in a 130 nm SiGe BiCMOS process technology performs A/D conversion, while a single 64-channel digital cross-correlator ASIC implemented in a 65 nm CMOS process performs the signal processing. The digital ASIC handles 2016 cross-correlations at up to 3.6 GS/s and has a power dissipation of only 0.13 mW/correlation/GHz at a supply voltage of 1 V. The comparator ASIC can handle sample rates of at least 4.5 GS/s with a power dissipation of 47 mW/channel or 1 GS/s with a power dissipation of 17 mW/channel. The assembled system consists of a single board measuring a mere 136 x 136 mm(2) and weighing only 135 g. The assembled system demonstrates crosstalk of 0.04% between neighboring channels and stability of 800 s. We provide ASIC and system-board measurement results that demonstrate that aperture synthesis can be a viable approach for Earth observation from a geostationary Earth orbit

Cross-Correlator Implementations Enabling Aperture Synthesis for Geostationary-Based Remote Sensing

An ever-increasing demand for weather prediction and high climate modelling accuracy drives the need for better atmospheric data collection. These demands include better spatial and temporal coverage of mainly humidity and temperature distributions in the atmosphere. A new type of remote sensing satellite technology is emerging, originating in the field of radio astronomy where telescope aperture upscaling could not keep up with the increasing demand for higher resolution. Aperture synthesis imaging takes an array of receivers and emulates apertures extending way beyond what is possible with any single antenna. In the field of Earth remote sensing, the same idea could be used to construct satellites observing in the microwave region at a high resolution with foldable antenna arrays. If placed in a geostationary orbit, these could produce images with high temporal resolution, however, such altitudes make the resolution requirement and, hence, signal processing very demanding. The relentless development in miniaturization of integrated circuits has in recent years made the concept of high resolution aperture synthesis imaging aboard a satellite platform viable.The work presented in this thesis addresses the challenge of performing the vital signal processing required aboard an aperture synthesis imager; namely the cross-correlation. A number of factors make the application challenging; the very restrictive power budgets of satellites, the immense amount of signal processing required for larger arrays, and the environmental aspects of in-space operation. The design, fabrication and evaluation of two cross-correlator application-specific integrated circuits (ASICs), one analog-to-digital converter (ADC) ASIC and one complete cross-correlator back-end is presented. Design concepts such as clocking schemes, data routing and reconfigurable accuracy for the cross-correlators and offset compensation and interfacing of the ADCs are explained. The underlying reasons for design choices as well as ASIC design and testing methodologies are described. The ASICs are put into their proper context as part of an interferometer system, and some different cross-correlator back-end architectures are explored.The result from this work is a very power-efficient, high-performance way of constructing cross-correlators which clearly demonstrates the viability of space-borne microwave imaging interferometer back-ends

A Cross-Correlator for the Remote Sensing of Earth by Synthetic Aperture

In light of our changing climate and the unpredictability of severe weather; a better understanding of our climate and increased weather forecast accuracy are in high demand. Humidity and temperature distribution profiles with high temporal resolution can significantly increase our knowledge of highly dynamic weather phenomena and improve weather forecasts.Microwave sounding from low earth orbit is extensively used for humidity and temperature measurements in the atmosphere because of its much better cloud penetrating properties compared to visible and infrared light. Performing these observations from geostationary earth orbit (GEO) would give the additional advantage of large coverage and no revisiting times. Microwave sounding from GEO is however demanding, this because of the large aperture required to reach acceptable spatial resolution. Synthetic aperture interferometry, widely used in ground based radio astronomy, has been proposed as a solution to overcome this obstacle.Cross-correlation is a signal processing algorithm that is a central and highly calculation-intensive part of aperture synthesis. CMOS process technology scaling, and the decreasing power per performance figures that have followed, has finally reached a point where these kinds of instruments are viable for space deployment.This thesis presents a cross-correlator chip that has been designed, fabricated and extensively evaluated, paving the way for larger correlator systems based on similar design concepts. Routing and synchronization schemes were developed for the purpose of handling the massively parallel calculations and the signal distribution and timing issues specific to synthetic aperture cross-correlators. The chip presented shows significant improvements over previous correlators in power per performance evaluations

Correlators for Interferometric Radiometry in Remote Sensing Applications, A Scaling Perspective

Correlators are extensively used in the field of radio interferometry. Two different types are considered for two applications; autocorrelators for spectrometry and cross-correlators for aperture synthesis. We concentrate on satellite-based applications where power budgets are very restrictive. Several satellites are already employing correlators for interferometric measurements, and future projects are targeting even larger systems in terms of spectral channels in the case of spectrometry and baseline counts in the case of aperture synthesis. Thus, it is important to develop correlators with increasing channel count, either using ASIC technology scaling or by constructing larger systems from several ASICs. Building on earlier ASIC designs, we examine how larger correlator systems can be constructed and the implications this has, in terms of power dissipation, system complexity, and ASIC count. Our findings indicate that, for large systems, having a very high channel count per ASIC is indeed of interest for keeping system complexity and power dissipation down by reducing both ASIC and I/O count, especially for cross-correlators

Millimeter-wave and terahertz imaging techniques

This thesis presents the development and assessment of imaging techniques in the millimeterwave (mmW) and terahertz frequency bands. In the first part of the thesis, the development of a 94 GHz passive screener based on a total-power radiometer (TPR) with mechanical beamscanning is presented. Several images have been acquired with the TPR screener demonstrator, either in indoor and outdoor environments, serving as a testbed to acquire the know-how required to perform the research presented in the following parts of the thesis. In the second part of the thesis, a theoretical research on the performance of near-field passive screeners is described. This part stands out the tradeoff between spatial and radiometric resolutions taking into account the image distortion produced by placing the scenario in the near-field range of the radiometer array. In addition, the impact of the decorrelation effect in the image has been also studied simulating the reconstruction technique of a synthetic aperture radiometer. Guidelines to choose the proper radiometer depending on the application, the scenario, the acquisition speed and the tolerated image distortion are given in this part. In the third part of the thesis, the development of a correlation technique with optical processing applicable to millimeter-wave interferometric radiometers is described. The technique is capable of correlating wide-bandwidth signals in the optical domain with no loss of radiometric sensitivity. The theoretical development of the method as well as measurements validating the suitability to correlate radiometric signals are presented in this part. In the final part of the thesis, the frequency band of the imaging problem is increased to frequencies beyond 100 GHz, covering the THz band. In this case the research is centered in tomographic techniques that include spectral information of the samples in the reconstructed images. The tomographic algorithm can provide detection and identification of chemical compounds that present a certain spectral footprint in the THz frequency band.Postprint (published version

Hardware Considerations for Signal Processing Systems: A Step Toward the Unconventional.

As we progress into the future, signal processing algorithms are becoming more computationally intensive and power hungry while the desire for mobile products and low power devices is also increasing. An integrated ASIC solution is one of the primary ways chip developers can improve performance and add functionality while keeping the power budget low. This work discusses ASIC hardware for both conventional and unconventional signal processing systems, and how integration, error resilience, emerging devices, and new algorithms can be leveraged by signal processing systems to further improve performance and enable new applications. Specifically this work presents three case studies: 1) a conventional and highly parallel mix signal cross-correlator ASIC for a weather satellite performing real-time synthetic aperture imaging, 2) an unconventional native stochastic computing architecture enabled by memristors, and 3) two unconventional sparse neural network ASICs for feature extraction and object classification. As improvements from technology scaling alone slow down, and the demand for energy efficient mobile electronics increases, such optimization techniques at the device, circuit, and system level will become more critical to advance signal processing capabilities in the future.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116685/1/knagphil_1.pd

SSTAC/ARTS review of the draft Integrated Technology Plan (ITP). Volume 8: Aerothermodynamics Automation and Robotics (A/R) systems sensors, high-temperature superconductivity

Viewgraphs of briefings presented at the SSTAC/ARTS review of the draft Integrated Technology Plan (ITP) on aerothermodynamics, automation and robotics systems, sensors, and high-temperature superconductivity are included. Topics covered include: aerothermodynamics; aerobraking; aeroassist flight experiment; entry technology for probes and penetrators; automation and robotics; artificial intelligence; NASA telerobotics program; planetary rover program; science sensor technology; direct detector; submillimeter sensors; laser sensors; passive microwave sensing; active microwave sensing; sensor electronics; sensor optics; coolers and cryogenics; and high temperature superconductivity

3.6-GHz 0.2-mW/ch/GHz 65-nm Cross-Correlator for Synthetic Aperture Radiometry

A high-speed low-power cross-correlator ASIC has been implemented in a 65-nm CMOS process for the purpose of synthetic aperture radiometry from geostationary orbitingearth observation satellites. The chip performs cross-correlation on all individual signal pairs from 64 digital 1-bit inputs, which amounts to 2016 individual cross-correlation products. The experimental evaluation, using a specially developed PCB, demonstrates that the 3-mm2 chip has a top performance of 3.6 GHz at a 1.2 V supply, at which it dissipates 790 mW