The invention relates to a method for processing a radio navigation signal originating from a satellite (SAT) and received by a radio navigation receiver comprising a plurality of receive antennas, each antenna being configured to receive signals originating from a satellite of interest (SAT), from at least one jammer and possibly from at least one other satellite (SAT) in given directions, the method comprising the following steps: detecting (E1), on the basis of the signal received by each antenna, at least one direction of a jamming signal; attenuating (E2, E2) the detected jamming signal in the detected direction; in which method detecting (E1) the direction of a jamming signal is based on determining a covariance matrix dependent on the signals received by each antenna given by (i), where Z is a matrix of size NM in which each column corresponds to the signal received by each antenna, N denoting the number of samples acquired during a fixed period T and M being the number of antennas.

An interference cancellation system (ICS) may be used with a communication system to prevent or minimize interference from one or more sources. The ICS may receive radio frequency (RF) signals comprised of one or more signals of interest (SOI) and multiple interfering signals. An interference estimation processor (IEP) may be used to estimate the one or more interfering signals. The interfering signals may be estimated using spatial and/or time diversity, which may be combined with statistical methods. The estimated interfering signals may be sent to the ICS, which may use the estimated interference signal to cancel the interference and output the SOI.

An interference removal filter that includes a combination of a first filter and a second filter, where the first filter passes signals over a frequency range of size B with a variation of less than +/3 dB, where the peak value of the impulse response of the second filter is displaced in time from the peak value of the impulse response of the first filter by at least 2/B time units, and where the combination of the first filter and the second filter produces a notch in frequency at a frequency location within the frequency range.

Systems and methods for cancelling interference from a received signal in order to properly detect a signal of interest are disclosed. A combined signal of interest plus interference signal may be received. A copy or sample of the interference signal may be determined. The interference signal and the combined signal of interest plus interference signal may be converted to the optical domain. The interference signal may be optically phase shifted by 180 degrees, which may result in an optically inverted interference signal. The optically inverted interference signal may be variably optically attenuated and/or variably optically time delayed, for example based on a detected output power of an optical subsystem of the interference cancellation system. As a result, interference cancellation of the interference signal from the combined signal of interest plus interference signal may be achieved, resulting in 50 dB or more of cancellation of the interference signal.

A method for mitigating interference in a receiver, where the received signal is transmitted in a fashion having equivalent information content in at least two distinct bands. The method compares mean power per unit bandwidth in suitably normalised sidebands and sets a rejection threshold based upon the measured levels. Bands above the threshold may be rejected from further processing. The bands may include sidebands produced by a modulation process that produces sidebands having the same informational content. The threshold may be set relative to the band having the lowest mean power per unit bandwidth or according to some other function of the bands. Also extends to a signal processor in a receiver, and a receiver. The primary focus of the application is toward the Galileo Public Regulated Service (PRS) Satellite navigation signal.

A method for waveform-enabled jammer excision (WEJE) may include performing a jammer measurement during a look-through window when no signal-of-interest (SOI) is present and obtaining a jammer signal. A SOI-plus-jammer measurement may be performed and a SOI-plus-Jammer signal may be obtained when both the jammer signal and the SOI are present. Optimal weights that maximize a SOI-to-jammer power ratio may be determined. SOI-plus-jammer signals from a number of antenna elements may be optimally weighted and combined to copy the SOI and null the jammer signal based on the determined optimal weights.

A method, computer-readable storage device and apparatus for locating a source of a communication impairment are disclosed. For example, the method detects the communication impairment, performs a sweep to locate a direction of the source of the communication impairment, wherein the sweep is performed in response to the detecting the communication impairment at the endpoint device, and generates a null in the direction of the source of the communication impairment.

Disclosed are methods, systems and devices for addressing a jammer signal transmitted by a device that effects a signal received at a receiver. In a particular embodiment, an application content signal is encoded for transmission in a wireless transmission medium to provide symbol content where the symbol content comprises at least some symbols representing the application content signal. A receiver may be selectively blanked synchronized with at least a portion of the symbol content.

A method and apparatus for improving anti-jamming performance are provided. A threshold value level estimated in a GPS (global positioning system) receiver RF/IF stage, a threshold value weight, a median value of a median value of a 28 MHz bandwidth is estimated as a threshold value with respect to a frequency component exceeding the estimated threshold value level, and an adjustable K-median threshold scheme is provided in a multi-jamming environment.

A communication network element (10) comprising: an optical path (12) for an optical communication signal (14); a monitoring port (16) arranged to output an optical monitoring signal; an optical splitter (20) provided in the optical path, the optical splitter arranged to receive the optical communication signal and to split off a part of the optical communication signal to form the optical monitoring signal; and optical isolation apparatus (22) connected between the optical splitter and the monitoring port, the optical isolation apparatus arranged to transmit the optical monitoring signal propagating towards the monitoring port and arranged to apply an attenuation, IA, to an attacking optical signal (24) propagating from the monitoring port towards the optical splitter to thereby prevent a substantial part of the attacking optical signal being transmitted to the optical path.