Aerospace Patents 2009

M. A. Zurbuchen, “Automated Sectioning Tomographic Measurement System,” U.S. Patent No. 7,507,145, March 2009.

There is frequently a need to image the internal structure of an object — particularly at the scale of 200 nm to 10 mm — to determine failure mechanisms. Typically, a sectioning approach is used in which successive layers are removed in very thin slices; however, this approach poses difficulties in terms of accuracy and resolution. This invention describes a tomographic measurement system that integrates the processes of grinding and polishing a 3-D cross section and imaging it in digital form so that it can be stored in a computer. The system includes a number of abrasive grinders, a wash station for washing and etching the object for improved imaging, an imaging station that captures both the object and a marker that indicates the depth of grinding, and a robot for moving the fixture between the grinder, washer, and imager. A simple edge-detection algorithm enables computer control software to recognize the marker reading in a given image; the marker can therefore be used to stop the automated serial sectioning at target depths. The system can process objects on scales as small as 2.5 nm.

A. O. Okorogu, “High Power Optical Fiber Laser Array Holographic Coupler Manufacturing Method,” U.S. Patent No. 7,551,818, April 2009.

This cost-effective method of manufacturing universal or versatile holographic optical element (HOE) couplers requires no mechanical etching or embedded micromirrors and offers easy mechanical coupling, insensitivity to misalignment of laser diodes, and high-angular and spectral filtering selectivity. The process entails simulating a laser diode or an array of diodes with varying divergence angles by placing a slit or slit array and/or an array of microlenses in the path of collimated object beams, which generate spherical wavefronts with divergence angles of various magnitudes. The position of the slits represents the lateral location of the laser diodes in the arrays that are to be coupled into the fiber. The separation of the slits is the exact separation distance of the intended diode in the fiber scheme. A computer controls the lateral position of each slit or microlens point and incrementally steps light from there to illuminate the holographic film plate where it intersects with a reference spherical beam. The intersection of the beams creates a varying fringe structure called a “chirped” grating. Creation of the chirped grating within the HOE increases the coupling efficiency of the laser diodes into a supported cladding mode of the fiber to greater than 90 percent. This would be impossible with any coupler that does not account for sources with varying divergence angles.

J. T. Dickey and T. T. Lam, “High Density Electronic Cooling Triangular Shaped Microchannel Device,” U.S. Patent No. 7,523,780, April 2009.

Cooling technology for microelectronic products is being pushed to the limit by the increasing number of components mounted on high-density electronic chips. This patent describes a pumped-fluid loop with triangular microchannels arranged in a sawtooth configuration. This orientation maximizes the absorption of thermal energy by the fluid and can increase the heat-transfer coefficient by 4.5 W/cm2/°C. The microchannels have a large heat conduction area that effectively spreads heat throughout the device, resulting in low surface temperatures. The triangular shape allows for a large number of microchannels to be packed together, thereby enabling a high flow rate of the pumped fluid. The sawtooth configuration allows for high heat conduction through an interstitial area, enabling heat to travel freely to the entire convective surface area. The reduced and uniform temperature serves to increase reliability and component life.

M. A. Rolenz, “Laser Communications Crosslink System,” U.S. Patent No. 7,526,206, April 2009.

Traditional satellite crosslinks can adversely increase the complexity and power requirements of a space system. This laser crosslink system mitigates these problems. A sigma-delta modulator converts an analog input to a binary data stream that is sent to a laser transmitter. The data stream is received by a laser receiver and sent to a digital filter that generates a digital output. Thus, the system enables direct laser modulation of binary signals. Because it combines the analog-to-digital conversion and transmission steps, the system requires fewer parts and power requirements than a comparable system based on phase-shift keying. The use of a sigma-delta modulator prior to transmission also reduces the roll-off requirements for anti-aliasing filters in the analog-to-digital converter, which in turn reduces manufacturing tolerances and required performance.

F. E. Livingston and H. Helvajian, “Pulse Modulation Laser Writing System,” U.S. Patent No. 7,526,357, April 2009.

Laser processing and micro/nanomachining of materials and components are generally limited by the relative lack of precision photon flux control, particularly when the samples are in motion or constructed of multiple heterogeneous materials. This pulse-modulated laser writing system overcomes this problem by enabling the position-synchronized delivery of discrete, preprogrammed laser pulse scripts to a substrate with high fidelity during patterning and motion sequences. The laser pulse scripts are synchronized with the motion-control file so that every laser-irradiated spot within the sample will receive exactly the photon dose and intensity pulse sequence necessary, despite the evolving material properties or changes in velocity of the sample. The laser processing platform is highly versatile and can seamlessly and dynamically merge a diverse array of other process scripts, including material type, surface topography, prior photon dose history, and the desired type of material processing, along with automated calibration routines and diagnostic tests. The laser technique can be readily applied to fundamental investigations of complex laser-material interaction phenomena, and the architecture can be easily integrated into laser-material processing schemes for commercial and industrial applications.

G. L. Lui and K. Tsai, “Quaternary Precoded Continuous Phase Modulation Soft Bit Metric Demodulator,” U.S. Patent No. 7,529,323, May 2009.

A quaternary soft-bit metric (QSBM) demodulator uses the maximum-likelihood sequence estimation (MLSE) Viterbi algorithm to generate log-likelihood ratios. The demodulator can be used for precoded quaternary Gaussian minimum shift keying (GMSK) signals and, more generally, for precoded quaternary continuous phase modulation (CPM) signals. It is implemented as a streamlined MLSE Viterbi algorithm that requires no memory elements for storing the survivor path states. In a GMSK system, the bandwidth-time product of the Gaussian premodulation shaping filter is 1/3, the modulation index is 1/4, and the receiver uses three matched filters. The demodulator can be used either in a stand-alone uncoded CPM system or in a coded CPM system in conjunction with some forward error-correction scheme such as the classical rate-1/2 convolution code with MLSE Viterbi decoding. In the latter case, the demodulator can improve the signal-to-noise ratio by 3.0 decibels over hard-decision error-correction decoding.

R. B. Dybdal and D. Pidhayny, “Methods and Systems for Tracking Signals with Diverse Polarization Properties,” U.S. Patent Nos. 7,518,551 and 7,551,134, April/June 2009.

Antennas are generally designed to receive radio frequency signals with a specified polarization, but in practice, the polarization of received signals does not always conform to the specified value. The resulting polarization mismatch reduces signal strength, degrading system sensitivity; in extreme cases, the antenna tracking performance can become unstable, resulting in a loss of antenna tracking and signal reception. This invention describes a system for antenna tracking that measures and processes orthogonally polarized signal components. The processing serves two objectives. The first is to minimize polarization mismatch loss, thereby preserving full system sensitivity. The second is to avoid unstable antenna tracking and the resulting signal loss while optimizing antenna tracking performance. The antenna tracking design operates in a closed-loop manner that can dynamically follow changes in the received signal’s polarization values.

H. S. Hou, “Integrated Lifting Wavelet Transform,” U.S. Patent No. 7,552,160, June 2009.

The so-called lifting method for integer-to-integer wavelet transforms provides a powerful tool for lossless image compression — but its performance can be affected by the number of lifting steps. This wavelet transform requires fewer steps than traditional versions. It comprises four lifting stages to transform the input into a fourth highpass and a fourth lowpass output and an integrated lifting stage for processing these outputs into an integrated highpass and an integrated lowpass output. A scalar is applied to the fourth lowpass output prior to adding. When the scalar is equal to one, the integrated outputs are lossless; when it is not equal to one, the outputs are lossy. The lifting steps reduce the overall rounding errors incurred in the real-to-integer conversion process, which improves the prediction of image edges and increases the compression ratio.

P. L. Smith, “GPS Airborne Target Geolocating Method,” U.S. Patent No. RE40,800, June 2009.

Stationary beacons, including stars, are used as reference points to geolocate targets for military operations. This invention provides a method for using GPS satellites instead of stationary beacons. In a typical implementation, a higher-altitude vehicle hosts a reference beacon pointed at a lower-altitude vehicle that serves as a sensor platform for simultaneously imaging the higher-altitude beacon and target. The beacon sensor boresight is precisely aligned with the sensor boresight on the lower-altitude sensor platform, which uses relative GPS techniques to accurately geolocate the target relative to the GPS grid. This invention can be applied to the development of very low-cost short-range terminal seekers for precision-guided bombs. The method can also be used in other applications where improved boresighting accuracy is required and relative GPS navigation techniques can be employed. This patent is a reissue of a patent issued in March 2003.

W. E. Lillo et al., “Binary Offset Carrier M-Code Envelope Detector,” U.S. Patent No. 7,555,033, June 2009.

The code-tracking loops in traditional code-division multiple-access (CDMA) spread-spectrum systems are usually based on steepest-ascent algorithms. Code-tracking loops are used to align a replica code with the incoming code of the received signal; however, the correlation envelope in a binary offset carrier (BOC) signal (such as the M code) does not result in a single correlation peak. Therefore, the phase tracking of BOC codes is subject to errors because the receiver can lock on to the incorrect peak. This invention improves the tracking and receiving of M-code signals and their modulation by singling out the peak correlation. An envelope detector receives an incoming BOC signal and generates inphase and quadraphase BOC signals, separated by an offset. The generated signals each have ambiguous correlation envelopes; combining them provides a nearly unimodal correlation function. The detector is further improved through the use of code replicas having narrow partial chip phases, such as 1/8 chip phases, for providing nearly linear code-phase error tracking.

W. H. Ailor, III, “Spacecraft Hardware Tracker,” U.S. Patent No. 7,557,753, July 2009.

Modern vehicle tracking systems collect GPS data from a vehicle and transmit it via satellite to a collection point. This invention applies this type of tracking to launch hardware such as in-line fuel stages, external fuel tanks, payload fairings, and external solid rocket boosters. A primary goal is to facilitate location of impact points of launch hardware that is not designed to reach orbit. Many different launch vehicles can be fitted with lightweight, autonomous tracking devices that require only attachment, but no other service from the launch vehicle. The tracker would include its own power supply, GPS receiver, data recorder, and transmitter, enabling it to return trajectory and other data spanning from launch to impact.

G. F. Hawkins, M. J. O’Brien, “Sound Suppression Material and Method,” U.S. Patent No. 7,565,950, July 2009.

Noise suppression generally involves either passive systems, which deflect sounds or absorb them in porous material, or active systems, which cancel sounds by generating other sounds that are out of phase with the originals. This invention describes a new approach: a sound-suppression material that selectively changes the sound passing through it and uses it to destructively cancel all sound in a large area. The material comprises a base and a flexible member coupled by a passive mechanism. The passive mechanism includes levers configured to deform longitudinally and laterally and to rotate in response to sound pressure. Thus, sound pressure at the base causes the connecting mechanism to pull portions of the flexible member toward the base, thereby shifting the phase of sound waves passing through so that they destructively interfere with sound waves passing through other portions of the flexible member. The material could be made light enough for use in weight-sensitive applications.

A. A. Moulthrop, M. S. Muha, and C. P. Silva, “Baseband Time-Domain Communications Method,” U.S. Patent No. 7,583,759, Sept. 2009.

Modulated microwave signals can transmit high-bandwidth data from a ground transmitter to a satellite and back again. Such signals must be accurately measured for optimal performance. Modulated microwave signals are also used to characterize devices (such as power amplifiers) in communication systems that must accurately receive and measure nonlinear signals. This patent describes a system for minimizing inaccuracies in time-domain measurements of microwave communications signals and for removing the effects of downconverter imbalances in communication receivers. The technique entails converting the signal to a complex baseband signal composed of I and Q components that differ by π/2 phase shifts of a carrier signal provided by a local oscillator or carrier tracking loop. The baseband signal is measured or sampled twice using different phase shifts. Any I and Q imbalances and nonlinearities are indicated by differences between the two measured or sampled signals. The imbalance errors can be reduced by averaging the measurements and by optimizing the measurement system, achieving a level of accuracy sufficient for modeling communications systems.

S. H. Raghavan, J. K. Holmes, and K. P. Maine, “Code Division Multiple Access Enhanced Capacity System,” U.S. Patent No. 7,586,972, Sept. 2009.

Code division multiple access (CDMA) communication systems have limited channel capacity due to the presence of CDMA noise. This invention allows for CDMAs to overlap codes so that they can work together and increase channel capacity. The CDMA spread-spectrum communication system uses two different signal spectra generated by two different code formats — NRZ for providing nonsplit spectra with a center peak, and Manchester for providing split spectra with a center null. The spectra are combined during transmission as a CDMA communication signal with a composite spectrum.

R. B. Dybdal and S. J. Curry, “Coherently Combined Antennas,” U.S. Patent No. 7,602,336, Oct. 2009.

The capability of an antenna to receive low-level signals is limited by the antenna gain and system noise temperature. Greater capability can be obtained through a high-gain antenna — but high-gain antennas are expensive. This invention describes a way to make many smaller separate antennas work together as one large high-gain antenna. The process involves transmitting a wide-bandwidth pseudo-random calibration code from the signal source. The system electronics use the pseudorandom code to determine time delays of signals incident upon the distributed antenna elements. The signals from each element can then be corrected for amplitude and phase imperfections and coherently combined using fixed and variable true-time delay. The source signal can be transmitted separately or modulated onto the calibration code.

D. W. Warren, “Compact, High-Throughput Spectrometer Apparatus for Hyperspectral Remote Sensing,” U.S. Patent No. 7,609,381, Oct. 2009.

The Dyson spectrometer form, comprising a concave diffraction grating and single thick lens, has the potential to deliver good imaging performance and high sensitivity in a simple, compact configuration suitable for hyperspectral remote sensing from aircraft and satellites. To have the highest sensitivity, the classical Dyson spectrometer requires the output position to be in close proximity to the lens element, complicating placement of an electronic focal plane detector. This invention, by incorporating an additional correcting lens in the optical path, provides greater relief and placement flexibility for the focal plane without sacrificing performance.

H. S. Hou, “Haar Wavelet Transform Embedded Lossless Type II Discrete Cosine Transform,” “Haar Wavelet Transform Embedded Lossless Type IV Discrete Cosine Transform,” and “Shared Haar Wavelet Transform,” U.S. Patent Nos. 7,613,761, 7,634,525, and 7,640,283, Nov./Dec. 2009.

One of the major drawbacks of discrete cosine transforms (DCTs) is that they produce floating-point coefficients that have to be converted into integers. In the process, information is discarded, resulting in highly lossy data. Moreover, DCTs are implemented as single functions, so they do not share resources with other transforms. Information loss due to rounding integers can never be retrieved; however, combining the type-II and type-IV DCTs with the Haar wavelet transform allows for lossless transformation. In one configuration, a nonlinear (lossless) type-II or type IV DCT is configured as a cascade connection of a front-end shared Haar transform having many word pair-wise rotations and a back-end appended DCT. In another configuration, a shared Haar transform (which uses fix angular word pair-wise rotations) is combined in cascade fashion with an appended Haar transform (which uses adaptive angular word pair-wise rotations) to produce an extended Haar transform with increased decorrelation power. In all configurations, the integer-to-integer transforms are integrated using nonlinear lifting stages which are reversible, making the overall transforms lossless during forward and inverse transformations.