Abstract: Provided herein are circuits and methods for processing samples of a received in-phase and quadrature (I/Q) domain signal that includes a desired signal and an interference signal that spectrally overlaps the desired signal. In the I/Q domain, a first contribution to the interference signal is removed from the samples using a first algorithm to generate first processed signal samples. Amplitudes and phases of the first processed signal samples are obtained. In an amplitude domain, a second contribution to the interference signal is removed from the amplitudes of the first processed signal samples using a second algorithm to generate second processed signal samples. A signal quality metric of the second processed signal samples is obtained. Based on the signal quality metric of the second processed signal samples, one or more parameters of the first or second algorithm are adjusted to improve the signal quality metric of the second processed signal samples.

Abstract: A narrowband AJ signaling system includes an AJ processor placed between a high precision analog-to-digital (ADC) converter and a narrowband digital receiver. In another example, the AJ processor is placed between the high precision ADC and a digital-to-analog converter (DAC). The AJ processor of either example may suppress the jammer power down to the level of the noise floor of the system.

Abstract: Provided herein are circuits and methods for processing samples of a received in-phase and quadrature (I/Q) domain signal that includes a desired signal and an interference signal that spectrally overlaps the desired signal. In the I/Q domain, a first contribution to the interference signal is removed from the samples using a first algorithm to generate first processed signal samples. Amplitudes and phases of the first processed signal samples are obtained. In an amplitude domain, a second contribution to the interference signal is removed from the amplitudes of the first processed signal samples using a second algorithm to generate second processed signal samples. A signal quality metric of the second processed signal samples is obtained. Based on the signal quality metric of the second processed signal samples, one or more parameters of the first or second algorithm are adjusted to improve the signal quality metric of the second processed signal samples.

Abstract: Cyberattacks are rampant and can play a major role in modern warfare, particularly on a widely adopted platforms such as the MIL-STD-1553 standard. To protect a 1553 communication bus system from attacks, a trained statistical or machine learning model can be used to monitor commands from a bus controller of the 1553 communication bus system. The statistical and/or machine learning model can be trained to recognize communication anomalies based at least on the probability distribution of patterns of one or more commands. The statistical model can be stochastic model such as a Markov chain that describes a sequence of possible commands in which the probability of each command depends on the occurrence of a group of one or more commands.

Abstract: Under one aspect, a method is provided for processing a received signal, the received signal including a desired signal and an interference signal that spectrally overlaps the desired signal. The method can include obtaining an amplitude of the received signal. The method also can include obtaining an average amplitude of the received signal based on at least one prior amplitude of the received signal. The method also can include subtracting the amplitude from the average amplitude to obtain an amplitude residual. The method also can include, based upon an absolute value of the amplitude residual being less than or equal to a first threshold, inputting the received signal into an interference suppression algorithm so as to generate a first output including the desired signal with reduced contribution from the interference signal.

Abstract: Under one aspect, a method is provided for processing a received signal, the received signal including a desired signal and an interference signal that spectrally overlaps the desired signal. The method can include obtaining an amplitude of the received signal. The method also can include obtaining an average amplitude of the received signal based on at least one prior amplitude of the received signal. The method also can include subtracting the amplitude from the average amplitude to obtain an amplitude residual. The method also can include, based upon an absolute value of the amplitude residual being less than or equal to a first threshold, inputting the received signal into an interference suppression algorithm so as to generate a first output including the desired signal with reduced contribution from the interference signal.

Abstract: A narrowband AJ signaling system includes an AJ processor placed between a high precision analog-to-digital (ADC) converter and a narrowband digital receiver. In another example, the AJ processor is placed between the high precision ADC and a digital-to-analog converter (DAC). The AJ processor of either example may suppress the jammer power down to the level of the noise floor of the system.

Abstract: Cyberattacks are rampant and can play a major role in modern warfare, particularly on a widely adopted platforms such as the MIL-STD-1553 standard. To protect a 1553 communication bus system from attacks, a trained statistical or machine learning model can be used to monitor commands from a bus controller of the 1553 communication bus system. The statistical and/or machine learning model can be trained to recognize communication anomalies based at least on the probability distribution of patterns of one or more commands. The statistical model can be stochastic model such as a Markov chain that describes a sequence of possible commands in which the probability of each command depends on the occurrence of a group of one or more commands.

Abstract: Circuits and methods are described herein for suppressing interference in binary offset carrier (BOC) modulated signals The BOC signal includes an upper sideband (USB) and a lower sideband (LSB). The LSB or the USB of the BOC signal is rotated from a first frequency to a second frequency. Interference in the rotated LSB or USB is reduced. An output BOC signal with reduced interference is generated based on the rotated LSB or USB from which interference has been reduced.

Abstract: An apparatus and method for generating a composite signal includes electronics configured to modulate a carrier utilizing a finite set of composite signal phases to generate a composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes a constant envelope for the phase modulated carrier, subject to constraints on desired signal power levels of the signals to be combined and either zero or one or more relative phase relationships between the signals. The apparatus and method can be extended to generating an optimized composite signal of different frequencies.

Abstract: An apparatus and method for generating a composite signal includes electronics configured to modulate a carrier utilizing a finite set of composite signal phases to generate a composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes a constant envelope for the phase modulated carrier, subject to constraints on desired signal power levels of the signals to be combined and either zero or one or more relative phase relationships between the signals. The apparatus and method can be extended to generating an optimized composite signal of different frequencies.

Abstract: An apparatus and method for generating a composite signal includes electronics configured to modulate a carrier utilizing a finite set of composite signal phases to generate a composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes a constant envelope for the phase modulated carrier, subject to constraints on desired signal power levels of the signals to be combined and either zero or one or more relative phase relationships between the signals. The apparatus and method can be extended to generating an optimized composite signal of different frequencies.

Abstract: A linear feedback shift register machine capable of generating periodic sequences and having means for detecting single point errors in the generated sequences.

Abstract: An apparatus and method for generating a composite signal includes electronics configured to modulate a carrier utilizing a finite set of composite signal phases to generate a composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes a constant envelope for the phase modulated carrier, subject to constraints on desired signal power levels of the signals to be combined and either zero or one or more relative phase relationships between the signals. The apparatus and method can be extended to generating an optimized composite signal of different frequencies.

Abstract: A linear feedback shift register machine capable of generating periodic sequences and having means for detecting single point errors in the generated sequences.

Abstract: An apparatus and method for generating a composite signal includes electronics configured to modulate a carrier utilizing a finite set of composite signal phases to generate a composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes a constant envelope for the phase modulated carrier, subject to constraints on desired signal power levels of the signals to be combined and either zero or one or more relative phase relationships between the signals. The apparatus and method can be extended to generating an optimized composite signal of different frequencies.

Abstract: An apparatus and method for generating a composite signal includes electronics configured to modulate a carrier utilizing a finite set of composite signal phases to generate a composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes a constant envelope for the phase modulated carrier, subject to constraints on desired signal power levels of the signals to be combined and either zero or one or more relative phase relationships between the signals. The apparatus and method can be extended to generating an optimized composite signal of different frequencies.

Abstract: A direct-sequence-spread-spectrum (DSSS) optical-frequency-shift-keying (OFSK) code-division-multiple-access (CDMA) communication system is adapted with optical transmitters and receivers for preferred use fiber optical communication systems where modulated data and pseudorandom noise (PRN) codes are encoded in the optical domain and communicated over optical paths for increasing system capacity in wide area optical networks.

Abstract: A civil moderate (CM) code and a civil long (CL) code are time division multiplex (TDM) as a combined code having alternating code chips that spectrum spread a transmitted signal received by a receiver tracking the spectrum spreading code using a two-level correlator operating with +1 and ?1 values to alternately correlate the received CM and CL code chips using a gating signal to gate by time the correlation of the two codes. The time gated two-level TDM correlation can be used in communication receivers, such as GPS receivers, receiving the TDM spectrum spreading codes.

Abstract: A coherent adaptive subcarrier modulation system applies subcarrier modulation to quadrature modulated signals with constant envelope modulation suitable for efficient sinewave and squarewave subcarrier modulations. The quadrature subcarrier enables the addition of new signals to the in-phase and quadrature phase signals with spectral isolation in the Global Position System while maintaining a constant envelop amplitude.