Abstract: An angle of arrival system is configured to efficiently measure phase differences. The angle of arrival system includes a master receiver for demodulating the signal received at one antenna and for implementing a tracking loop to identify the timing of symbols within the signal. This timing information can be fed back as a synchronization signal to a despreader in the master receiver and to a despreader in each of a number of slave receivers to synchronize the timing at which each signal is despread. Because despreading is synchronized, the outputs of the despreaders can be used to directly calculate phase differences between each pair of signals. In this way, the slave receivers do not need to implement a demodulator or a tracking loop. When the received signal is a non-spread signal, the phase differences between each pair of signals can be calculated directly from the modulated samples of each pair of signals without despreading.

Abstract: Transmitting a signal from a transmitter. A method includes identifying a threshold spectral flux density for a given physical location. The method further includes, as a result of identifying the threshold spectral flux density, transmitting a signal at a power level causing the signal to be below the spectral flux density at the given physical location, the signal being transmitted at a data rate. The method further includes receiving feedback from a receiver indicating the signal-to-noise ratio of the signal at the receiver. The method further includes adjusting the data rate of the signal based on the feedback. The method further includes continuing transmitting the signal at the adjusted data rate and power level.

Abstract: Transmitting a signal from a transmitter. A method includes identifying a threshold spectral flux density for a given physical location. The method further includes, as a result of identifying the threshold spectral flux density, transmitting a signal at a power level causing the signal to be below the spectral flux density at the given physical location, the signal being transmitted at a data rate. The method further includes receiving feedback from a receiver indicating the signal-to-noise ratio of the signal at the receiver. The method further includes adjusting the data rate of the signal based on the feedback. The method further includes continuing transmitting the signal at the adjusted data rate and power level.

Abstract: An angle of arrival system can be self-calibrating. The angle of arrival system can continuously estimate imperfections caused by the analog RF components and dynamically apply corrections based on these estimates. As a result, an angle of arrival system can employ inexpensive components, will not require factory calibration, but can still perform geolocation with high precision.

Abstract: An angle of arrival system is configured to efficiently measure phase differences. The angle of arrival system includes a master receiver for demodulating the signal received at one antenna and for implementing a tracking loop to identify the timing of symbols within the signal. This timing information can be fed back as a synchronization signal to a despreader in the master receiver and to a despreader in each of a number of slave receivers to synchronize the timing at which each signal is despread. Because despreading is synchronized, the outputs of the despreaders can be used to directly calculate phase differences between each pair of signals. In this way, the slave receivers do not need to implement a demodulator or a tracking loop. When the received signal is a non-spread signal, the phase differences between each pair of signals can be calculated directly from the modulated samples of each pair of signals without despreading.

Abstract: A virtual boresight vector for an antenna array can be calculated. The virtual boresight vector defines the direction an antenna array is pointing and can be used to ensure that angle of arrival measurements are performed with high accuracy. The virtual boresighting process can include positioning a calibration node at two different locations in order to obtain different covariance matrices. With the covariance matrices and based on knowing the angle between the two locations, an angle of arrival node can perform a process to calculate a precise angle between the antenna array and the second location.

Abstract: An antenna array can be quickly and efficiently designed to meet specified performance criteria. A system can be configured to receive various performance criteria as inputs, and from these inputs, identify how elements of an antenna array should be arranged so that the antenna array will meet the performance criteria. An iterative process can be performed to identify at least one arrangement of elements that will best meet the performance criteria while also complying with specified structural constraints.

Abstract: Embodiments are directed to synchronizing time among nodes in a network. In one scenario, a first node receives a timing message which provides an indication of the current time as measured by a second node at transmission of the timing message. The first node determines the timing message propagation time between the first and second nodes using a determined transmission frequency of the timing messages, an internal clock reading of a clock that indicates the current time in the first node, and timing and frequency measurements obtained at the first and second nodes. The first node also applies a weighting factor to the current time of the first node to adjust the current time forward or backward, and combines the determined propagation time with the adjusted clock time of the first node to generate a new, synchronized time and transmission frequency, which is broadcasted to other nodes in the network.

Abstract: The presence of a hidden signal can be detected efficiently using frequency domain multiplication. A detector system can be employed to search for a hidden signal across a wide spectrum in real time. The detector system can divide multiple antenna inputs into a series of blocks and then convert these blocks to the frequency domain possibly in a parallel fashion. Corresponding blocks from each input can then be conjugate multiplied, and the results of this conjugate multiplication can then be averaged over time. If a signal is hidden in the inputs, this averaging will reduce the noise floor thereby revealing the presence of the hidden signal at a particular frequency.

Abstract: The estimated gain profile of an amplifier can be modified during operation of the amplifier utilizing detected values of the amplification level of signals produced by the amplifier. The amplification levels can be detected at a location that is remote from the amplifier. New expected amplification levels can be determined for corresponding control signal values in the estimated gain profile. Digital filtering such as Kalman filtering can be used to determine the new expected amplification levels. The estimated gain profile can be modified with the new expected amplification levels.

Abstract: A system in which a sending node sends modulated waveform signals to a receiving mode can include the capability to change the waveform type of the modulated waveforms from a current waveform type to a new waveform type. The sending node can generate and send to the receiving node a variable length header that provides the receiving node sufficient information for the receiving node to demodulate modulated waveform signals modulated in accordance with the new waveform type. The variable length header can identify the parameters in a parameter set defining the new waveform type that have different values as compared to the current waveform type.

Abstract: The present invention is generally directed to using code division multiplexing (CDM) on the beacon and traffic channels while lowering the power of the beacon channel so that it rides under the traffic channel and becomes very difficult to detect. In this way, the beacon channel can contain sensitive information for decoding the traffic channel while remaining hidden from unintended recipients. By hiding the beacon channel, the CDM technique can be particularly beneficial in adaptive waveform systems where sensitive traffic channel acquisition information is regularly transmitted to the receiver.

Abstract: A digital electronic message comprising datawords to be transmitted in a communications system can be encoded prior to transmission using an asymmetric error detection coding scheme. The coding scheme is asymmetric because the coding scheme includes multiple codeword groups each with a different minimum coding distance. The codewords in a group having a greater minimum coding distance can correspond to datawords that have a relatively high susceptibility to transmission errors. The codewords in a group having a lesser minimum coding distance can correspond to datawords that have a relatively low susceptibility to transmission errors.

Abstract: A spectral sensing demodulator can include a programmable filter bank and a reconfigurable processor coupled to the programmable filter bank. The programmable filter bank can frequency demultiplex a plurality of frequency division multiplexed channels from a frequency band into a plurality of demultiplexed channels. The reconfigurable processor can include a plurality of reconfigurable resources. Each resource can be alternatively be configured to demodulate a demultiplexed channel and to monitor a demultiplexed channel.

Abstract: A spectral sensing demodulator can include a programmable filter bank and a reconfigurable processor coupled to the programmable filter bank. The programmable filter bank can frequency demultiplex a plurality of frequency division multiplexed channels from a frequency band into a plurality of demultiplexed channels. The reconfigurable processor can include a plurality of reconfigurable resources. Each resource can be alternatively be configured to demodulate a demultiplexed channel and to monitor a demultiplexed channel.

Abstract: In one exemplary embodiment of the invention, a device includes: a first frequency search engine configured to receive input values and determine a frequency of a signal to be within a first frequency band; a second delay component configured to store at least a portion of the plurality of input values; and a second frequency search engine configured to determine the frequency of the signal to be within a second band that is a subset of the first band. The first frequency search engine includes: a shift register configured to store bits of the input values; a combining circuit configured to combine bits of the plurality of input values; a first delay component configured to serially store a plurality of accumulator values; and a feedback circuit configured to add a function of the first delay component output to a next accumulator value to obtain a modified next accumulator value.

Abstract: A technique for reducing memory usage during signal processing includes storing least significant portions of a plurality of intermediate results in a first memory. Most significant portions of a subset the plurality of intermediate results are stored in a second memory having a smaller length than the first memory. A data linkage is maintained between the most significant portions and corresponding least significant portions.

Abstract: Decreased capability for detection of communications signals by an adversary is provided by applying frequency hopping, frequency chirping, and direct sequence spreading to the signals. The frequency hopping and frequency chirping can be driven by pseudo random functions. The direct sequence spreading can use a pseudo random chip sequence.

Abstract: A method of transmitting a spread spectrum signal in a single communication session between a transmitter and a receiver, stores a series of N unique waveform designs and a hopping sequence in a transmitter memory. A signal is transmitted to a receiver according to the hopping sequence using the plurality of N unique waveform designs. Preferably, each waveform design is characterized by a unique composite spreading code that is formed by at least some of a plurality of constituent code segments. Alternatively or additionally, the waveform designs may differ by any one or more of code length, symbol or chip timing or phase, frame or burst structure, chip offset, modulation, error control coding, encryption scheme, or scrambling code. A transmitter and receiver are also disclosed, as is the concept of appending chips between symbols to expand the universe of unique spreading codes without incurring an increase in processing gain.

Abstract: A method of transmitting a spread spectrum signal in a single communication session between a transmitter and a receiver, stores a series of N unique waveform designs and a hopping sequence in a transmitter memory. A signal is transmitted to a receiver according to the hopping sequence using the plurality of N unique waveform designs. Preferably, each waveform design is characterized by a unique composite spreading code that is formed by at least some of a plurality of constituent code segments. Alternatively or additionally, the waveform designs may differ by any one or more of code length, symbol or chip timing or phase, frame or burst structure, chip offset, modulation, error control coding, encryption scheme, or scrambling code. A transmitter and receiver are also disclosed, as is the concept of appending chips between symbols to expand the universe of unique spreading codes without incurring an increase in processing gain.