Bradly J. Cooke

S-parameter analysis of multiconductor, integrated circuit interconnect systems

The authors explore the use of S-parameter-based network techniques for the analysis of coupled, multiconductor, high-speed analog and digital integrated circuit interconnects. S-parameter-based computer-aided design (CAD) techniques, widely used in microwave network analysis, provide a powerful framework for the analysis of analog and digital integrated circuit interconnect systems. The specific additions to the existing S-parameter network analysis framework developed provide for multiport interconnect capabilities and for the use of multiconductor S-parameters derived from three categories of input parameters: (1) lossy quasi-static R,L,C and G; (2) lossy frequency-dependent (dispersive) R,L,C,G; and (3) the propagation constants, characteristic impedance, and conductor eigencurrents, derived from full-wave electromagnetic analysis. Results are compared with computed simulations and experimental measurements. >

Methodology for rapid infrared multispectral electro-optical imaging system performance analysis and synthesis

An analysis methodology and corresponding analytical tools for rapid top-down design of multi-spectral imaging systems is presented. Beginning with top- level customer-dictated system performance requirements and constraints, the critical system and component parameters in the electro-optical image chain are derived, performance analyzed, and iterated until a preliminary design that meets customer requirements is generated. System parameters and components composing the image chain for staring, scanning, pushbroom, and time-delay and integrate systems include: aperture, focal length, field of view, cold shield requirements, image plane dimensions, pixel dimensions, pixel pitch and fill factor, detection quantum efficiency, optical filter requirements, image plane dimensions, pixel dimensions, pixel pitch and fill factor, detection quantum efficiency, optical filter requirements, and temporal sampling parameters. The performance analysis is accomplished by calculating the imaging systems optical response (to a scene radiance), total noise, and imaging resolution. The noise components include photon noise due to signal, scene and atmospheric background, cold shield, out-of-band optical filter leakage and electronic noise. System resolution is simulated through cascaded optical transfer functions (OTFs) and includes effects due to atmosphere, optics, image sampling, and system motion.

Modeling the MTI electro-optic system sensitivity and resolution

We present an analysis methodology that offers efficient characterization of the Multispectral Thermal Imager (MTI) electro-optic system response to a wide range of user-specified system parameters and spectral scenarios. This methodology combines physics-based modeling of the MTI hardware with MTI prelaunch characterization data. The resulting models enable the user to generate application-specific sensitivity and resolution studies of the MTI image capture process, and aid in the development of calibration procedures and retrieval algorithms for MTI. In addition to quantifying the MTI response, the methodology developed in this paper is sufficiently general to permit the prototyping and evaluation of a variety of multispectral electro-optic systems. Finally, an example utilizing nominal orbital parameters and targeted MODTRAN scenarios that exercise the various spectral band functions is provided.

Partial removal of correlated noise in thermal imagery

Correlated noise occurs in many imaging systems such as scanners and push-broom imagers. The sources of correlated noise can be from the detectors, pre-amplifiers and sampling circuits. Correlated noise appears as streaking along the scan direction of a scanner or in the along track direction of a push-broom imager. We have developed algorithms to simulate correlated noise and pre-filter to reduce the amount of streaking while not destroying the scene content. The pre-filter in the Fourier domain consists of the product of two filters. One filter models the correlated noise spectrum, the other is a windowing function, e.g. Gaussian or Hanning window with variable width to block high frequency noise away from the origin of the Fourier Transform of the image data. We have optimized the filter parameters for various scenes and find improvements of the RMS error of the original minus the pre-filtered noisy image.

Comprehensive system model for CO2 DIAL

The Simulation and Optimization Numerics for DIAL (SONDIAL) code is described. An overview of the code structure is given consisting of individual models for the lidar hardware linked to a set of models for the natural environment through which the laser energy must traverse. The affects of the environment are contained in the field models. A detailed description of the field models is given including the effects of the atmosphere, plume and target on the return statistics of the radiation. The atmosphere attenuates and scatters the laser light. Atmospheric extinction has both spectral and temporal structure that can cause bias and correlation in the DIAL measurements. The results of FASCODE calculations utilizing the HITRAN database are used to assess the magnitude of these effects. Atmospheric turbulence spatially modulates the intensity footprint at the target and modifies the statistics of the return light collected by the receiver aperture. The roughness of the target produces speckle at the receiver, the statistics of which are given by the intensity distribution on the target surface. An albedo model that includes the effects of (macroscopic) spatial reflectivity variations of typical natural targets on the system single-shot signal-to-noise ratio is described. To address the effect of footprint size and position on effluent detection sensitivity, an overlap calculation between a Gaussian plume model and the optical footprint is performed. Validation comparisons between the model and experimental data are given.

Infrared imaging spatial heterodyne spectrometer (IRISHS) experiment effort

We present the Infrared Imaging Spatial Heterodyne Spectrometer (IRISHS) experiment. IRISHS is a new hyperspectral imaging spectrometer for remote sensing being developed by Los Alamos National Laboratory for use in identifying and assaying gases in the atmosphere when viewed against the Earths background. The prototype instrument, which can operate between 8 and 11.5 micrometers (although the current IR camera operates from 8 - 9.5 micrometers), will be described. Imaging spatial heterodyne spectrometer technology is discussed in four companion papers also presented at this symposium.

Analysis and design methodology for the development of optimized direct detection CO2 DIAL receivers

The analysis methodology and corresponding analytical tools for the design of optimized, low-noise, hard target return CO2 differential absorption lidar (DIAL) receiver systems implementing both single element detectors and multi-pixel imaging arrays for passive/active, remote-sensing applications are presented. System parameters and components composing the receiver include: aperture, focal length, field of view, cold shield requirements, image plane dimensions, pixel dimensions, pixel pitch and fill factor, detection quantum efficiency, optical filter requirements, amplifier and temporal sampling parameters. The performance analysis is accomplished by calculating the systems CO2 laser range response, total noise, optical geometric form factor and optical resolution. The noise components include speckle, photon noise due to signal, scene and atmospheric background, cold shield, and electronic noise. System resolution is simulated through cascaded optical transfer functions and incudes effects due to atmosphere, optics, image sampling, and system motion. Experimental results of a developmental single-element detector receiver designed to detect 100 ns wide laser pulses (10 - 100 kHz pulse repetition rates) backscattered from hard- targets at nominal ranges of 10 km are presented. The receiver sensitivity is near-background noise limited, given an 8.5 - 11.5 micrometer radiant optical bandwidth, with the total noise floor spectrally white for maximum pulse averaging efficiency.

Measurement strategies for remote sensing applications

Remote sensing has grown to encompass many instruments and observations, with concomitant data from a huge number of targets. As evidenced by the impressive growth in the number of published papers and presentations in this field, there is a great deal of interest in applying these capabilities. The true challenge is to transition from directly observed data sets to obtaining meaningful and robust information about remotely sensed targets. We use physics-based end-to-end modeling and analysis techniques as a framework for such a transition. Our technique starts with quantified observables and signatures of a target. The signatures are propagated through representative atmospheres to realistically modeled sensors. Simulated data are then propagated through analysis routines, yielding measurements that are directly compared to the original target attributes. We use this approach to develop measurement strategies which ensure that our efforts provide a balanced approach to obtaining substantive information on our targets.

Laser Field Imaging Through Fourier Transform Heterodyne

We present a detection process capable of directly imaging the transverse amplitude, phase, and Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LADAR systems, Fourier Transform Heterodyne incorporates transverse spatial encoding of the reference local oscillator for image capture. Appropriate selection of spatial encoding functions allows image retrieval by way of classic Fourier manipulations. Of practical interest: (1) imaging may be accomplished with a single element detector/sensor requiring no additional scanning or moving components, (2) as detection is governed by heterodyne principles, near quantum limited performance is achievable, (3) a wide variety of appropriate spatial encoding functions exist that may be adaptively configured in real-time for applications requiring optimal detection, and (4) the concept is general with the applicable electromagnetic spectrum encompassing the RF through optical.

Analysis and System Design Framework for Infrared Spatial Heterodyne Spectrometers

We present a preliminary analysis and design framework developed for the evaluation and optimization of infrared, Imaging Spatial Heterodyne Spectrometer (SHS) electro-optic systems. Commensurate with conventional interferometric spectrometers, SHS modeling requires an integrated analysis environment for rigorous evaluation of system error propagation due to detection process, detection noise, system motion, retrieval algorithm and calibration algorithm. The analysis tools provide for optimization of critical system parameters and components including: (1) optical aperture, f-number, and spectral transmission, (2) SHS interferometer grating and Littrow parameters, and (3) image plane requirements as well as cold shield, optical filtering, and focal-plane dimensions, pixel dimensions and quantum efficiency, (4) SHS spatial and temporal sampling parameters, and (5) retrieval and calibration algorithm issues.