The Aerospace Corporation

Other

The United States of America As Represented by the Administrator of the

The United States of America As Represented by the Administrator

Rajendra Kumar

Tien M Nguyen

Ramses Diaz De Leon

Kenneth H Lau

Various embodiments described herein are directed to methods and systems for multibeam adaptive antenna architectures for recovering user signals in the coverage area of the antenna in the presence of interference sources. For example, various embodiments may utilize an architecture comprised of an array of antenna feeds, an RF to baseband conversion subsystem, a bank of digital beamformers, a channelization subsystem, a bank of weighted combiners, and a bank of demodulators for the demodulation and detection of user signals. The multiple beamformers introduce nulls in the direction of interference sources based on distinct adaptive algorithms for providing different antenna beam patterns after adaptation. Various other embodiments may utilize architecture for providing the directions of the interference sources or intentional jammers.

Systems and methods for multi-beam antenna architectures for adaptive nulling of interference signals

Various embodiments of the invention are directed to frequency hopped frequency modulation spread spectrum (FHFMSS) multiple accessing systems and methods. For example, various embodiments of the FHFMSS transmitter may utilize an architecture comprised of a baseband modulation subsystem, a code generation subsystem for generating a multiplicity M code vector sequences, a frequency synthesizer for generating a multiplicity M periodic waveforms, a frequency modulator for generation of a frequency hopped frequency modulation (FHFM) waveform , and a spread spectrum modulator. Various embodiments of the FHFMSS receiver may comprise of a subsystem for generation of the FHFM waveform, a spread spectrum demodulator, a symbol detector, and a baseband demodulation subsystem.

Frequency hopped frequency modulation spread spectrum (FHFMSS) multiple accessing communication systems and methods

Systems and methods are provided for fast and precise estimation of frequency with relatively minimal sampling and relatively high tolerance to noise.

Systems and methods for fast and precise frequency estimation

Various embodiments of the invention are directed to orthogonal frequency chirp multiple accessing (OFCM) systems and methods. For example, various embodiments of the OFCM transmitter may utilize an architecture comprised of a baseband modulation subsystem, a subsystem for generating multiplicity N orthogonal frequency chirp waveforms, and a bank of multiplicity N spread spectrum modulators. Various embodiments of the OFCM receiver may comprise of a subsystem for generating complex conjugates of multiplicity N orthogonal frequency chirp waveforms, a bank of multiplicity N spread spectrum demodulators, a symbol estimator, a symbol timing estimator, a frequency offset estimator, a carrier phase tracking loop, a multi channel estimator, and a baseband demodulation subsystem.

Orthogonal frequency chirp multiple accessing systems and methods

A blind mode adaptive equalizer system to recover the in general complex valued data symbols from the signal transmitted over time-varying dispersive wireless channels is disclosed comprising an adaptive communication receiver for the demodulation and detection of digitally modulated signals received over wireless communication channels exhibiting multipath and fading, the receiver comprising an RF front end, an RF to complex baseband converter, a band limiting matched filter, a channel gain normalizer, a blind mode adaptive equalizer with hierarchical structure, an initial data segment recovery circuit, a differential decoder, a complex baseband to data bit mapper, and an error correction code decoder and de-interleaver.

Systems and methods for adaptive blind mode equalization

Various embodiments of the invention are directed to methods and systems for multi transform OFDM transmitter and receivers with low peak to average power ratio (PAPR) signals, that have high bandwidth efficiency and are computational efficient. For example, various embodiments of the transmitter may utilize an architecture comprised of a baseband modulator, a serial to parallel converter, a bank of multiplicity Northonormal transforms unit, a bank of multiplicity Ninverse Fourier transforms unit, a dummy symbols generator, and a minimum PAPR evaluation unit for finding the optimum transform index n. Various embodiments of the receiver may comprise of a transform index detection unit for the detection of the transform index imbedded in the OFDM signal.

Multi transform OFDM systems and methods with low peak to average power ratio signals

Various embodiments are directed to systems and methods for combining a plurality of codes. The plurality of codes may be binary codes having possible logical values of &#x2212;1 and +1 and may comprise an even number of codes. An output of the combining vmay be given by:=sgn(),where vis the sum of the first plurality of codes at the first time. Embodiments for allocating different power levels among various codes are presented.

Architectures and methods for code combiners

A receiver may comprise a complex mixer for converting the modulated signal to a complex modulated signal comprising a first in-phase component and a first quadrature component. The receiver may further comprise a digital demodulator. The digital demodulator may comprise at least one processor circuit programmed for applying a phase differencer for generating an output function in terms of a phase difference of the complex modulated signal. Applying the phase differencer may comprise converting the first in-phase component to a function of a phase difference of the first in-phase component expressed in digital time, and converting the first quadrature component to a function of the phase difference of the first quadrature component expressed in digital time. The at least one processor circuit of the digital demodulator may also be programmed for applying a four quadrant inverse tangent to the output function to generate the information signal.

Generalized frequency modulation

Various embodiments described herein are directed to methods and systems for blind mode adaptive equalizer system to recover complex valued data symbols from the signal transmitted over time-varying dispersive diversity wireless channels. For example, various embodiments may utilize an architecture comprised of a bank of estimation units, a normalizing gain estimator, a DSP unit and a feedback shift register providing the equalizer feedback state vector. The estimation unit may be further comprised of a multiplicity of adaptive algorithms providing various filtered estimates of the data symbol to the DSP unit or providing the joint estimate of the transmitted data symbol.

Systems and methods for blind mode adaptive equalization with multiple algorithms

Various embodiments are directed to systems and methods for processing signals comprising a first component and a second component. A bandwidth of the first component may be centered at a center frequency. A bandwidth of the second component may be offset from the center frequency by an offset frequency such that at least a portion of the bandwidth of the second component overlaps a skirt of the first component. In various embodiments, a transmitter may split a single signal to generate the first and second components, shift the frequency of the second component, recombine and transmit the two components. Also, in various embodiments, a receiver may receive the signal and derive the first and second components by correcting for cross-interference.

Increased capacity communication links with spectrum sharing

Various embodiments described herein are directed to methods and systems for blind mode adaptive equalizer system to recover complex valued data symbols from the signal transmitted over time-varying dispersive wireless channels. For example, various embodiments may utilize an architecture comprised of a channel gain normalizer, a blind mode equalizer with hierarchical structure (BMAEHS) comprised of a level 1 adaptive system and a level 2 adaptive system, and an initial data recovery subsystem. The BMAEHS may additionally be comprised of an orthogonalizer for providing a faster convergence speed. In various architectures of the invention, the BMAEHS may be replaced by a cascade of multiple equalizer stages for providing computational and other advantages. Various embodiments may employ either linear or decision feedback configurations. In the communication receiver architectures, differential encoders and decoders are presented to resolve possible ambiguities. Adaptive digital beam former architecture is presented.

Various embodiments are directed to a non-linear amplifier system comprising a reference output generator, an adaptive filter, a amplitude distortion (AM-AM) compensator, a phase distortion (AM-PM) compensator, an adaptive spectrum controller and a non-linear system. The reference output generator may receive an input signal and generating a reference output. The adaptive filter may generate a modified input signal based on the input signal and the reference output. The AM-AM compensator may act on the modified input signal to compensate for AM-AM distortion. The phase distortion (AM-PM) compensator may act on the modified input signal to compensate for AM-PM distortion. The adaptive spectrum controller may provide parameters to the adaptive filter to minimize the power spectral density (PSD) of an output of the non-linear amplifier system in a stop-band and maximize the PSD of the output of the non-linear amplifier system in a pass-band.

Systems and methods for mitigating spectral regrowth from non-linear systems

A method for pre-processing a signal prior to receipt of the signal by a non-linear device (NLD) to compensate for AM-AM distortion and AM-PM distortion of the signal by the NLD. The method includes generating a modified amplitude rbased on an amplitude xderived from a digitized envelope Rof the signal, generating a scale factor cbased on the modified amplitude rand the amplitude x, generating an AM-AM compensated signal based on the scale factor c, generating a first AM-PM phase compensation value based on the modified amplitude r, and generating an AM-AM and AM-PM compensated signal by modifying a phase of the AM-AM compensated signal based on the first AM-PM phase compensation value.

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Cerritos, CA, United States of America

Rajendra Kumar