Bookmarks

Recent Publications, Papers, and Patents by the Aerospace Technical Staff

Publications and Papers

(July 2006–Feb. 2007)

E. M. Bassett, T. S. Lomheim, J. A. Lang, and T. L. Hayhurst, "Parametric Prediction of the POD and PFA for Reflective Hyperspectral Imaging Systems: Dependencies on Target, Scene, and Sensor Design Characteristics and Detection Algorithms," Proceedings of SPIE: Imaging Spectrometry XI Conference, Vol. 6302, No. 63020B (San Diego, Aug. 14–16, 2006).

R. E. Bitten, D. A. Bearden, N. Y. Lao, and T. H. Park, "The Effect of Schedule Constraints on the Success of Planetary Missions," Acta Astronautica, Vol. 59, No. 8–11, pp. 1101–1109 (Oct.–Dec. 2006).

J. B. Blake et al., "Role of Non-Adiabatic Processes in the Creation of the Outer Radiation Belts," Geophysical Research Letters, Vol. 33, No. 18, L18108.1–L18108.5 (2006).

J. B. Blake, T. Mulligan, et al., "Solar and Cosmic Ray Physics and the Space Environment: Studies for and with LISA," AIP Conference Proceedings, Vol. 873, No. 1, pp. 172–178 (Nov. 29, 2006).

R. H. Buenneke, R. L. Abramson, T. D. Shearer, and P. B. McArthur, "Best Practices for Protection of Commercial Satellite Communications Infrastructure," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5386.

J. C. Camparo, M. Huang, and J. G. Coffer, "Absorption Cross-Section Fluctuations Driven by Continuous and Discrete Laser Frequency Variations," Optics Communications, Vol. 265, No. 1, pp. 187–196 (Sept. 2006).

W. T. Cerven, "Geometric Diversity and Directional Access Analysis for Satellite and Constellation Trade Studies," Advances in the Astronautical Sciences, Part I, Vol. 123, pp. 481–497 (2006).

J. C. Chai, A. O. Britting, and S. Feng, "Comparison of On-Line Lightning Monitoring System Data with Derived EM Responses of Space Launch Systems to Lightning," 17th International Zurich Symposium and Technical Exhibition on Electromagnetic Compatibility, pp.132–135 (Singapore, Feb. 27–Mar. 3, 2006).

M. W. Chen, L. R. Lyons, et al., "Initial Simulation Results of Storm-Time Ring Current in a Self-Consistent Magnetic Field Model," Journal of Geophysical Research, Vol. 111, No. A4, pp. A04225.1–A04225.10 (2006).

H. Chew, "RF Spectrum Trade Space for U.S. Government Mobile-Satellite Service User Link," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5387.

P. A. Dafesh and E. Grayver, "Future GOES-R Global Ground Receivers," Proceedings of SPIE: Satellite Data Compression, Communications, and Archiving II Conference, Vol. 6300, No. 63000D (San Diego, Aug. 13–14, 2006).

K. D. Diamant, J. E. Pollard, R. B. Cohen, Y. Raitses, and N. J. Fisch, "Segmented Electrode Hall Thruster," Journal of Propulsion and Power, Vol. 22, No. 6, pp. 1396–1401 (Nov./Dec. 2006).

M. P. Ferringer and D. B. Spencer, "Satellite Constellation Design Optimization Via Multiple-Objective Evolutionary Computation," Advances in the Astronautical Sciences, Part I, Vol. 123, pp. 461–480 (2006).

J. E. Granata, T. D. Sahlstrom, P. Hausgen, S. R. Messenger, and R. J. Walters, "Thin-Film Photovoltaic Proton and Electron Radiation Testing for a MEO Orbit," Proceedings of the World Conference on Photovoltaic Energy Conversion (4th) (2006).

E. Grayver, "Performance of Turbo-Coded High-Order Modulations with Nonlinear Amplification," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite & Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5463.

E. Grayver and P. E. Santacruz, "Effect of Nonlinear Amplification on Turbo Coding Gain," 2006 IEEE Aerospace Conference, p. 9 (Big Sky, MT, Mar. 4–11, 2006).

T. J. Grycewicz, B. E. Evans, C. J. Florio, and T. M. Christian, "Fourier Plane and Optical Processing for Sub-Pixel Image Registration," Proceedings of SPIE: Optical Information Systems IV Conference, Vol. 6311, No. 631117 (San Diego, Aug. 16–17, 2006).

J. S. Halpine, "AC Impedance to Measure Degradation Mechanisms," 4th AIAA International Energy Conversion Conference and Exhibit (San Diego, June 26–29, 2006), AIAA Paper 2006-4111.

J. Hant, D. Lanzinger, and D. Sklar, "Assessing the Performance of Packet Retransmission Schemes over Satellite Links," 2006 IEEE Aerospace Conference, p. 13 (Big Sky, MT, Mar. 4–11, 2006).

B. S. Hardy, R. P. Welle, and R. L. Williams, "Aerodynamically Induced Fracture of Ice Shed from the Space Shuttle External Tank," 24th AIAA Applied Aerodynamics Conference (San Francisco, June 5–8, 2006).

J. H. Hecht et al., "The Application of Ground-Based Optical Techniques for Inferring Electron Energy Deposition and Composition Change During Auroral Precipitation Events," Passive Optics Aeronomy: Passive Optics Workshop (Boulder, CO, April 1–3, 2004); Journal of Atmospheric and Solar-Terrestrial Physics, ed. by J. W. Meriwether, Vol. 68, No. 13, pp. 1502–1519 (2006).

M. J. Hecht, D. Buettner, and J. Hellrung, "Risk Assessment of Real-Time Digital Control Systems," Proceedings, IEEE Annual Reliability and Maintainability Symposium, p. 7 (Newport Beach, CA, Jan. 23–26, 2006).

E. D. Jansing et al., "One-Dimensional Fractal Error for Motion Detection in an Image Sequence," Proceedings of SPIE: Automatic Target Recognition XVI Conference, ed. by F. A. Sadjadi, Vol. 6234, pp. 623412.1–623412.9 (Kissimmee, FL, Apr. 18–19, 2006).

A. B. Jenkin, "Maximum Deliverable Mass For Low-Thrust Geosynchronous Transfers Under Realistic Mission Constraints," Advances in the Astronautical Sciences, Part III, Vol. 123, pp. 2265–2284 (2006).

M. A. Johnson, "Modeling, Simulation, and Analysis of Satellite Communications in Nuclear Disturbed Environments with OPNET," Proceedings of SPIE: Modeling and Simulation for Military Applications Conference, ed. by K. Schum and A. F. Sisti, Vol. 6228, pp. 622803.1–622803.11 (Kissimmee, FL, Apr. 18–21, 2006).

J. A. Kechichian, "Optimal Altitude—Constrained Low-Thrust Transfer Between Inclined Circular Orbits," Proceedings of SUNY-Buffalo, Advances in the Astronautical Sciences; Malcolm D. Shuster Astronautics Symposium, Vol. 122 (Grand Island, NY, June 12–15, 2005) (2006).

H. I. Kim, J. R. Lince, O. L. Eryilmaz, and A. Erdemir, "Environmental Effects on the Friction of Hydrogenated DLC Films," Tribology and Lubrication Technology, Vol. 62, No. 8, pp. 38–42 (2006).

Y. Y. Krikorian, M. K. Sue, G. V. Leon, L. Cooper, S. K. Do, R. Kumar, D. Taggart, D. L. Emmons, D. J. Dichmann, and J. P. McVey, "Dynamic Proximity Communication Link Analysis Tool for Orbiting Satellites and Ground Assets on Mars," 2006 IEEE Aerospace Conference, p. 8 (Big Sky, MT, Mar. 4–11, 2006).

R. Kumar, "Analysis of FM Demodulator Output Noise with Applications to the Space Lift Range System," 2006 IEEE Aerospace Conference, p. 9 (Big Sky, MT, Mar. 4–11, 2006).

R. Kumar, "Power Control Algorithm and Architectures for Fading Communication Channels," 2006 IEEE Aerospace Conference, p. 12 (Big Sky, MT, Mar. 4–11, 2006).

R. Kumar and R. Martinez, "CDMA Satellite System Capacity with Multiple-User Classes," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5392.

M. S. Leung, G. W. Stupian, et al., "Transport Study of a Single Bismuth Nanowire Fabricated by the Silver and Silicon Nanowire Shadow Masks," Applied Physics Letters, Vol. 89, No. 14, pp. 141503–141503-3 (Oct. 2, 2006).

V. S. Lin, A. Arredondo, and J. Hsu, "Efficient Modeling and Simulation of Nonlinear Amplifiers," 2006 IEEE Aerospace Conference, p. 9 (Big Sky, MT, Mar. 4–11, 2006).

K. T. Luey and D. J. Coleman, "Formation of Contaminant Droplets on Surfaces," Proceedings of SPIE: Optical Systems Degradation, Contamination, and Stray Light: Effects, Measurements, and Control II Conference, Vol. 6291, No. 62910G (San Diego, Aug. 15–16, 2006).

K. T. Luey, D. P. Taylor, D. J. Coleman, and K. A. Folgner, "Digital Imaging of Particulate Contamination," Proceedings of SPIE: Optical Systems Degradation, Contamination, and Stray Light: Effects, Measurements, and Control II Conference, Vol. 6291, No. 62910J (San Diego, Aug. 15–16, 2006).

D. K. Lynch, R. W. Russell, et al., "Mid-Infrared Ethane Emission on Neptune and Uranus," The Astrophysical Journal, Vol. 644, No. 2, pp. 1326–1333 (June 20, 2006).

V. N. Mahajan et al., "Orthonormal Polynomials for Hexagonal Pupils," Optics Letters, Vol. 31, No. 16, pp. 2462–2464 (Aug. 15, 2006).

G. M. Mason, J. E. Mazur, et al., "Solar Cycle Variations in the Composition of the Suprathermal Heavy-Ion Population near 1 AU," The Astrophysical Journal, Vol. 645, No. 1, Pt. 2, pp. L81–L84 (2006).

A. Mathur, "Rocket Plume Attenuation Model," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5323.

J. E. Mazur et al., "Heavy-Ion Elemental Abundances in Large Solar Energetic Particle Events and Their Implications for the Seed Population," The Astrophysical Journal, Vol. 649, No. 1, pp. 470–489 (2006).

J. E. Mazur et al., "Origin of Heavy Ions in Upstream Events near the Earth's Bow Shock," Geophysical Research Letters, Vol. 33, No. 18, pp. L18104.1–L18104.5 (2006).

J. E. Mazur, J. B. Blake, et al., "The Creation of New Ion Radiation Belts Associated with Solar Energetic Particle Events and Interplanetary Shocks: Solar Eruptions and Energetic Particles," Geophysical Monograph, ed. by N. Gopalswamy, R. Mewaldt, and J. Torsti, Vol. 165, pp. 345–352 (2006).

M. J. McFadden, M. Iqbal, T. Dillon, R. Nair, T. Gu, D. W. Prather, and M. W. Haney, "Multiscale Free-Space Optical Interconnects for Intrachip Global Communication: Motivation, Analysis, and Experimental Validation," Applied Optics, Vol. 45, No. 25, pp. 6358–6366 (Sept. 1, 2006).

T. A. Moore, B. B. Brady, et al., "Measurements and Modeling of SiCl4 Combustion in a Low-Pressure H₂/O₂ Flame," Combustion and Flame, Vol. 146, No. 3, pp. 407–418 (2006).

J. A. Morgan, "The Spin-Statistics Connection in Classical Field Theory," Journal of Physics A: Mathematical and General, Vol. 39, No. 42, pp.13337–13353 (2006).

M. J. O'Brien, G. F. Hawkins, et al., "Damping Composite Materials by Machine Augmentation," Journal of Sound and Vibration, Vol. 294, No. 4–5, pp. 828–840 (2006).

T. P. O'Brien et al., "Correlation Between the Inner Edge of Outer Radiation Belt Electrons and the Innermost Plasmapause Location," Geophysical Research Letters, Vol. 33, No. 14, pp. L14107.1–L14107.4 (2006).

I. A. Palusinski and I. Ghozeil, "Space Qualification of Silicon Carbide for Mirror Applications: Progress and Future Objectives I," Proceedings of SPIE: Novel Optical Systems Design and Optimization IX Conference, Vol. 6289, No. 628903 (San Diego, Aug. 15–16, 2006).

R. P. Patera, "Collision Probability for Larger Bodies Having Non-Linear Relative Motion," Advances in the Astronautical Sciences, Part I, Vol. 123, pp. 887–900 (2006).

T. J. Paulitz et al., "Constant Force Restraints for Frontal Collisions," Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automobile Engineering, Vol. 220, No. 9, pp. 1177–1189 (2006).

G. S. Peng, M. de la Torre-Juarez, R.W. Farley, and J. E. Wessel, "Impacts of Upper Tropospheric Clouds on GPS Radio Refractivity," 2006 IEEE Aerospace Conference, p. 6 (Big Sky, MT, Mar. 4–11, 2006).

J. Poklemba and D. Wenzel, "Turbo-Product-Coded QVSB," IEEE Transactions on Broadcasting, Vol. 52, No. 4, pp. 579–584 (Dec. 2006).

G. Radhakrishnan, P. M. Adams, and L. S. Bernstein, "Room-Temperature Deposition of Carbon Nanomaterials by Excimer Laser Ablation," Thin Solid Films, Vol. 515, No. 3, pp. 1142–1146 (Nov. 23, 2006).

S. H. Raghavan and J. K. Holmes, "Inter-BOC Signal Interference-Tracking Loop Performance," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5320.

S. H. Raghavan, M. Shane, and R. Yowell, "Spread Spectrum Codes for GPS L5," 2006 IEEE Aerospace Conference, p. 7 (Big Sky, MT, Mar. 4–11, 2006).

K. Richardson, Z. Petrosyan, R. Abbott, D. Scott, M. Hajianpour, S. Ghantiwala, K. Marabyan, A. Quan, R. Crawford, and D. Nystrom, "STARS (Spacelift Telemetry Acquisition and Reporting System) Limit Checking System," 2006 IEEE Aerospace Conference, p. 8 (Big Sky, MT, Mar. 4–11, 2006).

P. Rousseau and J. Kemp, "Report on AMTA 2005," IEEE Antennas and Propagation Magazine, Vol. 48, No. 1, pp. 177–179 (Feb. 2006).

R. J. Rudy, D. K. Lynch, S. M. Mazuk, C. C. Venturini, et al., "Early Spectral Evolution of Nova Sagittarii 2004 (V5114 Sagittarii)," Astronomy and Astrophysics, Vol. 459, No. 3, pp. 875–883 (Berlin, 2006).

P. M. Schubel, J. J. Luo, and I. M. Daniel, "Through-Thickness Characterization of Thick Composite Laminates," Proceedings of the 2006 SEM Annual Conference and Exposition on Experimental and Applied Mechanics, Vol. 4 (Saint Louis, June 4–7, 2006).

R. S. Selesnick, "Source and Loss Rates of Radiation Belt Relativistic Electrons During Magnetic Storms," Journal of Geophysical Research, Vol. 111, No. A4, pp. A04210.1–A04210.8 (2006).

Y. Y. Shprits, R. M. Thorne, R. Friedel, G. D. Reeves, and J. F. Fennell, "Radial Diffusion as a Potential Source and Loss Mechanism of Relativistic Electrons in the Outer Radiation Belt," Report No. TR-2006(8570)-3/SMC-TR-06-10 (The Aerospace Corporation, El Segundo, CA, Feb. 15, 2006).

E. J. Simburger and W. L. Bunselmeyer, "Long-Term Storage of the Solar Arrays for the Defense Meteorological Satellite Program (DMSP) 5D3 Spacecraft," Report No. TR-2006 (1550)-1/SMC-TR-06-09 (The Aerospace Corporation, El Segundo, CA, Feb. 10, 2006).

Y. Sin, N. Presser, M. S. Mason, and S. C. Moss, "Characteristics and Reliability of High Power Multi-Mode InGaAs Strained Quantum Well Single Emitters with CW Output Powers of over 5 W," Proceedings of SPIE: High-Power Diode Laser Technology and Applications IV Conference, ed. by M. S. Zediker, Vol. 6104, pp. 61040H.1–61040H.12 (San Jose, CA, Jan. 23–25, 2006).

K. Siri, M. A. Willhoff, and K. A. Conner, "Uniform Voltage Distribution Control for Series Connected DC-DC Converters," 4th AIAA International Energy Conversion Conference and Exhibit (San Diego, June 26–29, 2006), AIAA Paper 2006-4133.

K. Siri, M. A. Willhoff, C. Truong, and K. A. Conner, "Uniform Voltage Distribution Control for Series-Input Parallel-Output, Connected Converters," 2006 IEEE Aerospace Conference, p. 12 (Big Sky, MT, Mar. 4–11, 2006).

G. W. Stupian, "High Pressure Studies on Silane to 210 GPa at 300 K: Optical Evidence of an Insulator-Semiconductor Transition," Journal of Physics: Condensed Matter, Vol. 18, No. 37, pp. 8573–8580 (2006).

D. Taggart, R. Kumar, S. H. Raghavan, G. Goo, N. Wagner, J. Chen, and Y. Y. Krikorian, "Modeling and Simulation of Amplifier Nonlinearities for Single 8-ary PSK Modulated Signal Input," 2006 IEEE Aerospace Conference, p. 16 (Big Sky, MT, Mar. 4–11, 2006).

L. J. Vandergriff, "Unified Approach to Agile Knowledge-Based Enterprise Decision Support," VINE, Vol. 36, No. 2, pp. 199–210 (2006).

S. Virji, R. B. Kaner, and B. H. Weiller, "Hydrogen Sensors Based on Conductivity Changes in Polyaniline Nanofibers," Journal of Physical Chemistry B, Vol. 110, No. 44, pp. 22266–22270 (2006).

R. L. Walterscheid and G. Schubert, "A Tidal Explanation for the Titan Haze Layers," Icarus, Vol. 183, No. 2, pp. 471–478 (2006).

C. C. Wang, L. Xu, and S. Lim, "Hierarchical Modulations for Unequal Protection," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5372.

C. C. Wang, L. Xu, and S. Lim, "Providing Unequal Protection for Compressed Data Using Hierarchical Modulations," Proceedings of SPIE: Satellite Data Compression, Communications, and Archiving II Conference, Vol. 6300, No. 63000A (San Diego, Aug. 13–14, 2006).

F. D. Wicker, "QoS for Space Based Routers Serving Downlinks with Time Varying Data Rates," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5360.

A. H. Zimmerman and M. V. Quinzio, "Impedance Changes in Li-Ion Cells During Life Cycling," 4th AIAA International Energy Conversion Conference and Exhibit (IECEC) (San Diego, June 26–29, 2006), AIAA Paper 2006-4112.

Patents

(July 2006–Nov. 2006)

David A. Ksienski and Gwendolyn M. Shaw, "Phased Array Antenna Intermodulation Suppression Beam Smearing Method," U.S. Patent No. 7,098,848, Aug. 2006.

Active-transmit phased-array antennas have multiple directional elements that use beam steering; however, the transmission of the multiple communication signals creates unwanted intermodulation products in power amplifiers. Current techniques for reducing intermodulation products reduce amplifier power efficiency or require costly development work. Physically partitioning the array into subarrays and then physically separating the subarrays suppresses unwanted grating lobes in the field of view, but this approach suppresses only intermodulation grating lobe beams and does not suppress all undesirable intermodulation product beams, such as the intermodulation main beams. This beam smearing method for intermodulation suppression includes angle smearing and phase smearing. In the preferred form, the antenna beam includes two primary main beams and two intermodulation product beams. Phase smearing uses uniform phase shifts through subarray elements and angle smearing uses gradient phase shifts. Beam smearing provides an increased 6- to 10-decibel intermodulation beam suppression at the cost of a minor 1-decibel degradation of the desired primary main beams and can be retrofitted into existing phased-array antenna systems.

Heinrich G. Muller, "Side-Pumping Laser and Optical Fiber System," U.S. Patent 7,099,074, Aug. 2006.

High-power fiber lasers are being developed for remote sensing, target identification, high-power directed-energy applications, and long-distance free-space optical communications. Light pumping is a key step for reaching higher output power levels. When laser light is directed into the fiber from any side, the laser light will pass across the fiber and not be guided through it. Hence, redirecting the laser light along the fiber is necessary. Current systems use various methods, all with some limitations, including end pumping, groove pumping, directional side pumping, and amplifier fibers. This system uses the difference in optical refraction between the semiconductor material of the laser and an amplifier fiber, by providing the laser with an angled facet and bringing it in direct contact with the fiber to redirect the beam along the length of the fiber. Optical amplifier systems can be substantially simplified using these side-pumping lasers by having direct contact and eliminating free-space optical elements. Very high coupling efficiencies and robust operational products are enabled with low fabrication cost.

Hsieh S. Hou, "Merge-and-Split Generalized Block Transform Method," U.S. Patent No. 7,099,908, Aug. 2006; "Merge-and-Split Fast Fourier Block Transform Method," U.S. Patent No. 7,099,909, Aug. 2006.

Conventional transforms have been used for some time to compress and decompress data using radix-2 transforms. While the traditional methods do separate and combine data in the transform domain, they can not perform true merge and split. Thus, for example, while video composing is substantially sped up by performing the operations in the fast transform domain with the transform coefficients being quantized into integers, the quantization process degrades image quality. This invention provides a true direct split-and-merge transform processing of equal-sized data halves in the transform domain for such conventional transforms as the fast Fourier, fast Hartley, discrete cosine, discrete sine, and discrete Karhunen-Loeve. It processes new class-block transforms that enable true successive and back-and-forth merge and split forward transformations without data degradation. Temporal or spatial domain input data can be transformed into the transform domain in the form of split halves or merged wholes, which can then be recursively split or merged without having to inversely transform domain data back into the temporal or spatial domain and without resulting data degradation.

Philip A. Dafesh and Tien M. Nguyen, "Quadrature Product Subcarrier Modulation System," U.S. Patent No. 7,120,198, Oct. 2006.

This system uses both quadrature-product subcarrier modulation (QPSM) and coherent adaptive subcarrier modulation (CASM) to add new signals in timing, telemetry, and command links within the existing spectral allocation. QPSM enables the transmission of a quadrature-multiplexed carrier modulation with one or more subcarrier signals in the same constant-envelope waveform. It can be applied to both direct and spread-spectrum quadrature-multiplexed communication systems, including those employing quadrature-phase-shift keying or minimum-shift keying. QPSM can augment existing two-code spread-spectrum systems while maintaining a constant-envelope signal with spectral separation between existing signals and new signals with high efficiency. CASM is a flexible, efficient GPS modulation approach that can be tailored to different modes of operation to provide high efficiency without altering the basic modulation architecture. It employs a subcarrier to phase-modulate new M-code signals on the same carrier as the current ranging codes. It uses cross-product intermodulation terms as new ranging communication signals, and, with subcarrier modulation, interprets cross-product terms as signals and not as losses.

Charles C. Wang and Dean J. Sklar, "Turbo Decoding System Using nth Root Metrics for Non-Gaussian Communication Channels," U.S. Patent No. 7,127,000, Oct. 2006.

Conventional turbo-decoding algorithms are based on the assumption that the input sequence to the turbo decoder has been disturbed by a noise process that has a Gaussian distribution. Conventional turbo-decoding algorithms are optimized for Gaussian channels for reducing the bit-error rate. But when the actual channel statistics of the input sequence to the decoder varies significantly from the Gaussian distribution assumption, the turbo decoder performance will degrade. This invention matches non-Gaussian statistics to turbo-decoding Gaussian metric processing by an nth root transformation prior to turbo decoding. Conventional turbo decoding can then be used to communicate over a fading channel communicating differential coherent phase-shift-keying signals. That is, the nth root transformation provides near-Gaussian turbo-decoding metrics for conventional turbo decoding.

Albert M. Young, Samuel S. Osofsky, Keven S. MacGowan, and David A. Ksienski, "Hybrid Active Combiner and Circulator," U.S. Patent No. 7,129,783, Oct. 2006.

The active devices that combine signals use amplifiers to provide gain. A common active combiner uses several field-effect transistors (FETs) connected as transmission gates, but this design does not provide the reciprocity in the signal paths required in some applications, like source-pull measurements. Circulators that translate signals from one port to another are often used at the front end of a transceiver system that contains only one antenna port. Modern circulator architectures sacrifice both output power and noise figure to optimize circulator function; such circulators operate with high noise figures and low output signal levels, are heavy, and have large profiles. The hybrid active combiner and circulator serves as a coupler and a three-port network that integrates a directional coupler topology with active devices placed in the coupling paths to synthesize a low-loss active combiner circuit or a circulator device with minimal insertion losses. The coupler can have multiple-stage amplifiers with transconductance values set according to Pascal's triangle for improved performance, and it can function as a low-cost and low-weight transceiver for various communications systems.

Rouh T. Bow and Philip A. Dafesh, "Gated Time-Division-Multiplexed Spread-Spectrum Correlator," U.S. Patent No. 7,130,326, Oct. 2006.

The GPS modernization effort to provide a second civilian signal on the L2 carrier frequency has added a time-division-multiplexed (TDM) combined civil-moderate and civil-long code. The new configuration increases power consumption, making it unsuitable for cell phones and small personal digital assistants. Moreover, the chip-interleaved composite code requires a three-level correlator more complex than the two-level correlator used in existing GPS receivers. This two-level correlator uses a gating signal to alternately gate-code the chips of both civil spreading codes and interleave them into a composite L2CS code. The correlator retains the reduced complexity for commercial GPS receivers. The gated correlation process is a computationally efficient approach for the reception of the new TDM L2CS GPS signals. In general, the gated TDM spread-spectrum correlator may be applied to any number of TDM spreading codes. The correlation process uses modified gating that can be generally applied to spread-spectrum systems employing chip-by-chip time multiplexing of a composite code.

Srinivasa H. Raghavan, Jack K. Holmes, Kris P. Maine, et al., "Code Division Multiple-Access Enhanced-Capacity System," U.S. Patent No. 7,139,302, Nov. 2006.

In code division multiple-access (CDMA) communications, data are formatted and the signal spectrum is spread using CDMA spreading codes for sending signals to multiple receivers. Increasing the channel capacity increases the number of users that can be served by a CDMA communication system; but the exclusive use of nonreturn-to-zero, Manchester, and binary-offset carrier-formatted CDMA communication systems has limited channel capacities. This new system combines spread spectra generated by both a nonreturn-to-zero code that formats a nonsplit spectrum with a center peak and a Manchester or binary-offset carrier code that formats a split spectrum with a center null. Two different digital symbol formats on two groups of spreading codes produce two different signal spectra with minimal overlapping. Together, these form the composite communication signal spectrum that enables increased channel capacity.

To Spring 2007 Table of Contents