Systems and methods are provided in which a direction of arrival of a radio frequency (RF) signal received by a plurality of antennas is determined. A plurality of first converter receives RF signals from the plurality of antennas and outputs a minimum of a first optical signal and a second optical signal each modulated by their corresponding RF signal. A plurality of second converters receives a minimum of the first optical signal via a first optical channel that introduces a first delay and the second optical signal via a second optical channel that introduces a second delay. The second converter outputs a first RF signal that corresponds to the RF modulation on the first optical signal and a second RF signal that corresponds to the RF modulation on the second optical signal. A switch serially receives, from the second converter outputs, the first RF signal and the second RF signal. A direction finding subsystem determines a direction of arrival using a phase difference between the first RF signal and the second RF signal.

Systems and methods are provided in which a direction of arrival of a radio frequency (RF) signal received by a plurality of antennas is determined. A plurality of first converter receives RF signals from the plurality of antennas and outputs a minimum of a first optical signal and a second optical signal each modulated by their corresponding RF signal. A plurality of second converters receives a minimum of the first optical signal via a first optical channel that introduces a first delay and the second optical signal via a second optical channel that introduces a second delay. The second converter outputs a first RF signal that corresponds to the RF modulation on the first optical signal and a second RF signal that corresponds to the RF modulation on the second optical signal. A switch serially receives, from the second converter outputs, the first RF signal and the second RF signal. A direction finding subsystem determines a direction of arrival using a phase difference between the first RF signal and the second RF signal.

A radio communication apparatus includes an estimating unit that estimates directions of arrival of signals transmitted by a plurality of respective users, a calculating unit that calculates a map as a trigonometric function of an angle representing each of the directions of arrival estimated by the estimating unit, a grouping unit that groups the users based on the maps calculated by the calculating unit, and a determining unit that determines a weight coefficient for forming a directional beam steered to a user belonging to a group, for each group resultant of grouping performed by the grouping unit.

Systems and methods for determining a location of one or more user equipment (UE) in a wireless system can comprise receiving reference signals via a location management unit having two or more co-located channels, wherein the two or more co-located channels are tightly synchronized with each other and utilizing the received reference signals to calculate a location of at least one UE among the one or more UE. Embodiments include multichannel synchronization with a standard deviation of less than or equal 10 ns. Embodiments can include two LMUs, with each LMU having internal synchronization, or one LMU with tightly synchronized signals.

A method for direction finding is described wherein incoming signals are scanned and analyzed. The bearing value and its quality of the incoming signals are determined by using a direction finding method. A covariance matrix is generated from the incoming signals by using a multiple-wave detector unit. The dimension of the covariance matrix is reduced in order to obtain a reduced covariance matrix. The eigenvalues of the reduced covariance matrix are determined. Then, it is determined whether more than one signal, a single signal or no signal is detected by using the eigenvalues and the quality determined by using the direction finding method. Further, a direction finder is described.

A method for direction finding is described wherein incoming signals are scanned and analyzed. The bearing value and its quality of the incoming signals are determined by using a direction finding method. A covariance matrix is generated from the incoming signals by using a multiple-wave detector unit. The dimension of the covariance matrix is reduced in order to obtain a reduced covariance matrix. The eigenvalues of the reduced covariance matrix are determined. Then, it is determined whether more than one signal, a single signal or no signal is detected by using the eigenvalues and the quality determined by using the direction finding method. Further, a direction finder is described.

A system and method for rank estimation of electromagnetic emitters is provided. One exemplary feature of the system and method includes the use of a Fixed Sigma Gaussian Mixture Model (FSGMM) to determine a rank estimation of electromagnetic emitters. Another exemplary feature of the system and method includes the use of a Gaussian Mixture Model (GMM) clustering approach in conjunction with an Akaike Criterion Information (AIC) to determine a number of clusters and associated statistics of emitters.

A method is provided for use of a segmented aperture communications system to determine a direction of arrival of a radio signal in which the system includes a receiver plane having equally spaced and planar aligned radio frequency ports. Computation of the aperture segments depends on the port coordinates where the geometric relationship of the segments is used to determine a time delay and direction of arrival of the signal. The ports receive at least two orthogonal polarizations that characterize the incoming signals. A central port is used as reference to determine a phase difference associated at each port. Two angles are calculated by a simultaneous solution of two phase difference measurements to determine the direction of arrival solution. A mean direction of arrival solution is obtained by averaging solution estimates that are obtained by repeating the direction of arrival determination using random port pairs.

A method is provided for use of a segmented aperture communications system to determine a direction of arrival of a radio signal in which the system includes a receiver plane having equally spaced and planar aligned radio frequency ports. Computation of the aperture segments depends on the port coordinates where the geometric relationship of the segments is used to determine a time delay and direction of arrival of the signal. The ports receive at least two orthogonal polarizations that characterize the incoming signals. A central port is used as reference to determine a phase difference associated at each port. Two angles are calculated by a simultaneous solution of two phase difference measurements to determine the direction of arrival solution. A mean direction of arrival solution is obtained by averaging solution estimates that are obtained by repeating the direction of arrival determination using random port pairs.

A radio analysis apparatus includes: a processor that calculates a modulation index of a radio signal generated by performing frequency shift keying on a baseband signal, based on phase shift amounts of the radio signal; and a memory that holds information in which bit patterns of the baseband signal are associated with correction values for correcting the phase shift amounts that have dropped by band limitation on the baseband signal. The processor restores the bit patterns of the baseband signal based on the phase shift amounts of the radio signal, corrects the phase shift amounts of the radio signal by using the correction values corresponding to the restored bit patterns, and calculates the modulation index based on the corrected phase shift amounts.