Aerospace Patents 2008

A.A. Moulthrop, M.S. Muha, C.P. Silva, “Baseband Time-Domain Communications System,” U.S. Patent No. 7,321,641, Jan. 2008.

Modulated microwave signals are used to carry information in a variety of electronic communication systems. The signals may be used to transmit voice, data, or video signals from a ground transmitter through space to a satellite, and then back from the satellite to the ground receiver. The signals must then be converted into baseband, which is composed of I and Q components, and then accurately measured to meet certain qualifications. Precise measurement of communication signals is more successful when using baseband time-domain communication systems as opposed to a single-vector network-analyzer because time-domain waveforms contain all possible waveforms and therefore can create a far better signal for communication simulation. This invention is designed to provide a more accurate system for measuring imbalances in downconverters. It is a system for determining lowpass equivalencies of generated baseband signals. The invention allows for the measurement of electronic signals and devices in a time-domain signal using modulated waveforms. It will allow two sample readings of the I and Q outputs, detect and reduce any imbalances, and check for inaccuracies. The system lends itself well to nonlinear devices like amplifiers that require a communication system with a broader ability to communicate. It also allows for a decrease in imbalances and better signal reception.

E. Grayver, “Simultaneously Multithreaded Processing and Single Event Failure Detection Method,” U.S. Patent No. 7,321,989, Jan. 2008.

Radiation can be a dangerous predator for electrical equipment in space, taking its toll on electronic devices and having a negative effect on digital circuits. When electronic devices come in contact with radiation, the result can be a single event failure caused by the radiation exposure. These instances are not usually fully destructive to the equipment, but are obviously undesirable. This invention uses multithread processors with multiple worker threads running identical code and a monitor thread as a malfunction indicator. It relates to the field of concurrent parallel processing of like programs, processor voting for determining failed processes, and multithreaded processors. An advantage of this invention is that single event failures can be detected far more quickly and thus are easier to pinpoint and correct. This invention also provides a method for determining when one working program among several identical ones has failed. With parallel processing of like programs, errors can be more easily discovered and compared, and when one of the programs has been temporarily damaged by an encounter with radiation it can be more quickly detected and reset. It is unlikely that all like programs would be affected at once, so this system is fairly reliable.

G. F. Hawkins, C. H. Tang, “Force Diversion Apparatus and Methods and Devices Including the Same,” U.S. Patent No. 7,367,898, May 6, 2008.

There are many instances where it would be desirable to redirect or absorb forces during a collision. This invention provides a means of doing so through a system of machines configured to convert compression force to shear force and a layer of material that spreads the compression forces over the machines. The layer of material connected to the machines may also be configured to control the dynamic motion of the apparatus. An apparatus can be configured to impart a predetermined rotation to an object by including both a force conversion portion and a force spreading portion. Compression forces can be absorbed by converting at least some of them into shear forces while the object is in contact with the surface and simultaneously imparting a rotational force. This invention can be applied to protecting the body, protecting a vehicle (tanks, light vehicles, helicopters), or designing sports equipment (golf clubs).

M. J. O’Brien, B. A. Nelson, M. R. Hilton, “Ceramic Ball Bearing Acoustic Test Method,” U.S. Patent No. 7,370,537, May 13, 2008.

Silicon-nitride hybrid bearings, which combine ceramic balls with steel races, have been proposed for satellite use to improve momentum control wheels and flywheels; however, the silicon-nitride balls have low tensile strength, which makes them vulnerable to cracking. Current inspection methods find it difficult to differentiate between cracked and uncracked material in ceramic. This invention proposes a new, more reliable way to test these balls for flaws. To run the test, the ball is placed between platens that have hemispherical sockets with radii equal to that of the ball, but which do not completely cover the ball when pressed together. The two platens are compressed, increasing the load upon the ball until a tensile hoop stress develops at the equator that is intense enough to cause any preexisting crack or flaw to grow, generating acoustical emissions that are monitored by a microphone. If no crack growth is detected through acoustical emissions, an upper bound can be placed on the maximum possible size of a crack or flaw that might be present. The test method is specialized for testing small bearings.

R. B. Dybdal, M. A. Rolenz, “Method of Determining Communications Link Quality Employing Beacon Signals,” U.S. Patent No. 7,373,105, May 13, 2008.

This method of determining communication link quality involves providing communication satellites with beacon transmitters and users with a real-time display of link performance. The beacons transmit two types of signals — a stable, continuous wave tone that provides a reference signal level, and a coded waveform. The user’s equipment processes the two signals to provide a real-time determination of link impairments and, from this, a determination of the type and quality of service that is available to the user. The communications device determines link loss, scintillation effects, Doppler offsets, and noise and interference levels, and controls the transmitter signal level so that each user has an equitable share of the satellite’s downlink transmitter. With this added functionality, the user can understand the limitations of the existing communication capabilities and user transmission levels are controlled to reduce the dynamic range of signals received and processed by the satellite, thereby increasing system effectiveness.

R. Kumar, “Power Controlled Fading Communication Channel System,” U.S. Patent No. 7,373,168, May 13, 2008.

Existing closed-loop power control algorithms in the Code Division Multiple Access (CDMA) and Universal Mobile Telephone System ignore the round-trip delay incurred in the measurement of the received signal power. This assumption of zero round-trip delay may be valid when the delay is negligible, but not in the case of satellite channels. Any power control algorithm based on a zero delay assumption will not have satisfactory performance, resulting in interrupted communication, and may result in a drastic reduction in the capacity of the CDMA system. This invention provides a system for improving the reception of communication signals and to maximize the system capacity by adjusting the power level of a transmitted signal by predicting the amount of fading in a fading channel. A power-control algorithm accounts for the propagation delay by including an adaptive nonlinear predictor. The fading channel power gain is modeled in terms of a parameterized nonlinear model with memory. The model parameters are adaptively estimated by a recursive least-squares algorithm, from which a power controller derives the required prediction of the channel power gain and the requisite transmitted power level.

W. E. Lillo, “Dual Code Spread Spectrum Communication System,” U.S. Patent No. 7,397,840, July 8, 2008.

Spreading codes have long been used to isolate channel signals so that only receivers with predetermined codes can receive them. This invention relates to use of multiple correlated codes for demodulating a single spread spectrum signal, allowing for different levels of access to different users. Some of the receivers get the channel signal first using one spreading code, and others get it later using a second spreading code. The first group of receivers generate a replica of the first spreading code, and the second group generate replicas of the first and second spreading code. Thus, all of the receivers correlate the first channel signal during a first time period, but only a portion of the receivers fully correlate the second channel signal during the second time period. In this manner, the first message is communicated in the first channel signal to all of the receivers, while a second message is communicated in the second channel signal to only a subset of all of the receivers. Hence, the broadcast communication system can be used for sending secret messages to certain receivers at one time and for sending public messages to the entire group at another time.

R. Kumar, “Generalized Polyphase Channelization System,” U.S. Patent No. 7,403,577, July 22, 2008.

This invention describes a digital channelizer for channelizing a broadband input signal into a number K of channel signals using a complex mixer for converting the input signal into a complex baseband signal, an analog-to-digital converter, a bank of filter blocks, and a bank of FFT (fast Fourier transform) processors. The sampling rate of the individual channels is equal to 1/M times the sampling rate of the broadband signal where M is the decimation factor. The invented architecture deals with the case wherein K is higher than M, and one is not an integer multiple of the other, and permits allocation of seamless band comprised of multiple channels to a single user while avoiding any distortion due to the channelization process. The architecture is computationally very efficient as the number of computations increases only logarithmically with K. For broadband signals, such computational requirements may be one of the dominant factors in determining the overall cost, weight, and power requirements of a satellite system.

M. H. Abraham, H. Helvajian, S. W. Janson, “Laser Assisted Chemical Etching Method for Release Microscale and Nanoscale Devices,” U.S. Patent No. 7,419,915, Sept. 2, 2008.

The global market for microelectromechanical systems (MEMS) and nanotechnology is greater than $8 billion per year. Most MEMS fabrication techniques are time-consuming and expensive, and do not lend themselves to nanoscale devices. This invention provides a method for creating buried patterned films in bulk material using a focused ion beam or a broad-area ion beam and a mask. It uses laser-assisted chemical etching for etching bulk silicon from a patterned buried film. More specifically, a laser is used to precisely heat an area about a buried film so that the localized heat enhances the chemical etching of the substrate for releasing nanoscale patterned structures that exist in or on the silicon wafer. Devices can be fabricated with microscale or nanoscale dimensions using implanted ions; resolution is defined by the ion-beam implant pattern resolution and dose. The resulting thicknesses are on the order of thousands of angstroms and may be patterned by lithography or by direct write with a focused ion beam. The method can be scaled up for mass production.

D. A. Ksienski, J. P. McKay, S. S. Osofsky, K. S. MacGowan, and G. M. Shaw, “Higher-Order Intermodulation Reduction Using Phase and Angle Smearing,” U.S. Patent No. 7,420,508, Sept. 2008.

Multiple, simultaneous antenna beams required in communication systems are often achieved using active phased arrays. A common problem encountered in these systems is the generation of intermodulation product beams due to nonlinear effects. This patent describes a method for reducing intermodulation beams. It starts by identifying one or more higher-order intermodulation beams that need to be reduced and determining acceptable degradations for the fundamental beams associated with them. Next, phase and angle beam-smearing parameters are identified that would reduce the intermodulation beams with acceptable degradation to the fundamental beams. These parameters are then used to apply a beam-smearing phase distribution to an array along with a beam-steering distribution. This invention can be used for satellite antenna arrays or any application that generates multiple simultaneous beams in the presence of nonlinear effects.

H. S. Hou, “Merge and Split Discrete Cosine Block Transform Method,” U.S. Patent No. 7,437,394, Oct. 2008.

Fast transform methods for the compression and decompression of data entail separating and combining data blocks in the transform domain and inversely transforming them back to the spatial or temporal domain. In the process, however, the quality of the transformed data is degraded. This invention is aimed at decreasing the degradation caused by the fast forward process. Input data in the temporal or spatial domain during either the split or merge radix-2 forward processing step first undergoes transform processing followed by combinational processing. In the split transform process, whole transformed data are split into two halves using combinational processing in the transform domain. In the merge transform process, these two halves are merged using combinational processing in the transform domain. The combinational processing enables true recursive splits and merges in the transform domain without data degradation.

G. L. Lui, K. Tsai, and M. K. Sue, “Automatic Gain Control 16-ary Quadrature Amplitude Modulation Subsystem,” U.S. Patent No. 7,450,670, Nov. 2008.

In a digital data transmission system that uses amplitude and phase modulation, such as the 16-ary quadrature amplitude modulation (16-QAM), the performance of the receiver is essential. However, if the receiver is not catching the large signal-to-noise ratios accurately enough, communication is compromised. The invention concerns a baseband automatic-gain-control subsystem that tracks the amplitude of signals with large signal-to-noise ratios as a subset of all of the signals in the constellation space. This information helps determine the amount of automatic gain control needed to uniformly improve reception of all received signals. By averaging only the signals with large signal-to-noise ratios, a demodulator can provide automatic gain control up to 1.0 dB better than a demodulator that averages all of the amplitudes of all of the received signals. The technique can be implemented with only modest modifications to an error detector in a conventional design.

T. Nguyen, J. Yoh, A. Mathur, and G. Goo, “Random Walk Filter Timing Recovery Loop,” U.S. Patent No. 7,469,026, Dec. 2008.

In a communication receiver, a received RF signal is tracked and demodulated to generate a baseband signal waveform that contains bit transitions to help the demodulator lock on to the data bit stream; however, channel noise can corrupt the bit transition timing and cause the demodulator to lose track of the bit stream. Timing recovery loops are used to track bit transitions and reacquire the bit stream, but most conventional algorithms are still subject to long reacquisition time and frequent bit timing lock drop in multipath environments. This invention uses a random-walk filter with a settable error threshold that allows for adaptive synchronization in the timing recovery loop. When the filter’s lead/lag counter output exceeds the threshold, the estimated bit transition time can be adjusted, allowing for its continued synchronization to the signal waveform. As such, the random-walk filter continuously adjusts the estimated bit transition time to maintain an accurate bit timing lock. This timing recovery loop can be used with low-power technology and is applicable to a wide range of modulation schemes for enhanced mobile communications.

A. O. Okorogu, “High Power Optical Fiber Laser Array Holographic Couplers,” U.S. Patent No. 7,469,082, Dec. 2008.

Current methods of launching high-power pump or laser light into fibers can adversely affect the mechanical integrity, power requirements, and system complexity, which would require redesigning the fiber coupling structure, especially for coupling an array of laser diodes. This patent describes a novel method of coupling high-power laser light or an array of laser diodes into double-clad Yb and co-doped Er-Yb fibers for much higher levels of light amplification. It is based on the application of mature volume holographic optical element (HOE) technology, which can be fabricated in any of the commercially available high-efficiency photosensitive holographic recording materials. This HOE coupler does not require mechanical etching of coupling structures or embedding of micromirrors within the fiber cladding. It consists of stripped double-clad fiber sandwiched between transmitting and reflecting HOEs. The device offers advantages over current coupling schemes, especially ease of coupling, high angular and spectral selectivity (filtering), high optical power (concentration), light weight, thin aspect (~15 mm), low cost, high coupling efficiency, insensitivity to misalignment, and simplicity of direct coupling into fibers with minimum perturbation of fiber structure and manufacturability. It has a unique advantage of being a truly universal coupling scheme for all types of inner cladding shapes, sizes, and designs.

W. E. Lillo, K. J. Scully, and C. D. Nealy, “Multitarget Tracking Antispoofing Receiver,” U.S. Patent No. 7,471,238, Dec. 2008.

This GPS receiver improves tracking in the presence of jamming or spoofing signals by coupling the GPS signal with an inertial navigation system that has an inertial measurement unit (IMU). When it encounters an interfering signal, the receiver maintains track on the target signal by tracking the code phase, carrier frequency, and power. Conventional multitarget tracking algorithms are used to distinguish among the competing signals. When signal tracks have been sufficiently resolved, the tracking information is fed to a prefilter and ultimately to the navigation filter. The IMU information allows for a narrow gate for the true signal. The crossing of tracks can be anticipated and resolved without losing track on a desired object. The greater power of the spoofer is a distinguishing characteristic and actually hinders its ability to interfere. Therefore, the multitarget tracking receiver can maintain a lock on a target signal, even in the presence of crossover spoofing signals.