High resolution adaptive arrays based on random processing techniques: frequency hopping modulation

A new architecture for adaptive arrays using frequency hopping modulation is addressed. The resolution of the array and the interference rejection increase substantially applying random processing to the carrier frequency of the signals. The proposed framework is composed of two different stages. The anticipative stage, devoted to minimize the noise and fixed interferences contribution and the GSLC stage which provides cancellation of follower jammers and solves the multiuser collision problem. The developed system requires neither temporal nor spatial reference for its implementation, only the frequency sequence must be known. An adaptive approach has been implemented, allowing a fast convergence to the optimal behavior.Peer ReviewedPostprint (published version

Pointing correction in an adaptive array for communications

The authors discuss DSP procedures for pointing correction in adaptive arrays which uses a spatial reference to form the optimum beam (generalized sidelobe canceller, GSLC). The problem of adequate pointing arises from many effects on the aperture and the receiver front-end of every array channel. Component aging, channel mismatching, sensor location, etc., promote steering errors that may produce the rejection of the desired signal. Currently, highly complicated telemetry systems and monopulse radars are used for steering correction. The authors describe the existing alternatives as well as further improvements that can be achieved from the use of temporal references combined with the GSLC beamformerPeer ReviewedPostprint (published version

Adaptive array beamforming for frequency hopping modulation

A new architecture for Array Processing using Frequency Hopping (FH) modulation is addressed in this paper which takes advantage of the knowledge of the frequency sequence at the receiver, requiring neither temporal nor spatial a priori reference. Consequently, the paper deals with a Code Reference Beamformer (CRB). The proposed framework is composed of two parallel processors. The first one, the Anticipative processor, is devoted to predict the scenario at the hop frequency before this frequency is transmitted, providing a fast convergence of the second processor and avoiding the fall of the Signal to Interference plus Noise Ratio (SINR) with the frequency hops. The second one, the On-line processor, provides maximum SINR by applying the optimum beamvector which can be estimated minimizing the Mean Square Error (MSE) at the array output or, directly, maximizing the SINR.Peer ReviewedPostprint (published version

Two-stage code reference beamformer in mobile communications

This paper addresses a new architecture for blind adaptive beamforming when dealing with frequency hopping (FH) modulation in cellular mobile communications systems. The proposed code reference beamformer (CRB) takes advantage of the inherent frequency diversity to estimate beforehand the noise plus interference correlation matrix, which is employed as the first part of the framework. Then, a second stage is adaptively obtained without any a priori knowledge of either the direction of arrival or the array manifold. Using this information, the first stage is in turn readjusted and, as a result, the scheme is able to track non-stationary scenarios following the channel variations with no previous referencesPeer ReviewedPostprint (published version

The K-filter: a new architecture to model and design non-linear systems from Kolmogorov's theorem

A new architecture to model and design nonlinear transfer functions is presented using a new formulation for nonlinear systems. This approach follows the guidelines of the mapping theorem due to A. Kolmogorov and it is based on the direct Fourier transform of the transfer function. The resulting scheme is formed by two stages; the first stage contains phase modulators, which, based on random sampling concepts reported by I. Bilinskis, are duplicated with a small perturbation in the modulation factor. This stage depends on the number of diversity data and it is independent of the function. The second step reduces to Volterra systems and a direct combiner of the new diversity kernels. The reported architecture and design seem to be able to cope with both linear and nonlinear filtering problems, which can be considered as a formal framework for generalised signal processing.Peer ReviewedPostprint (published version

Serum Phospholipids Fatty Acids and Breast Cancer Risk by Pathological Subtype

This study evaluates whether serum phospholipids fatty acids (PL-FAs) and markers of their endogenous metabolism are associated with breast cancer (BC) subtypes. EpiGEICAM is a Spanish multicenter matched case-control study. A lifestyle and food frequency questionnaire was completed by 1017 BC cases and healthy women pairs. Serum PL-FA percentages were measured by gas chromatography-mass spectrometry. Conditional and multinomial logistic regression models were used to quantify the association of PL-FA tertiles with BC risk, overall and by pathological subtype (luminal, HER2+ and triple negative). Stratified analyses by body mass index and menopausal status were also performed. Serum PL-FAs were measured in 795 (78%) pairs. Women with high serum levels of stearic acid (odds ratio (OR)T3vsT1 = 0.44; 95% confidence interval (CI) = 0.30-0.66), linoleic acid (ORT3vsT1 = 0.66; 95% CI = 0.49-0.90) and arachidonic to dihomo-γ-linolenic acid ratio (OR T3vsT1 = 0.64; 95% CI = 0.48-0.84) presented lower BC risk. Participants with high concentrations of palmitoleic acid (ORT3vsT1 = 1.65; 95% CI = 1.20-2.26), trans-ruminant palmitelaidic acid (ORT3vsT1 = 1.51; 95% CI = 1.12-2.02), trans-industrial elaidic acid (ORT3vsT1 = 1.52; 95% CI = 1.14-2.03), and high oleic to stearic acid ratio (ORT3vsT1 = 2.04; 95% CI = 1.45-2.87) showed higher risk. These associations were similar in all BC pathological subtypes. Our results emphasize the importance of analyzing fatty acids individually, as well as the desaturase activity indices

Source reference in CIR beamforming

This paper presents a procedure for CIR beamforming that avoids SVD-like proceduresm and is derived from the classic CINR solution. The resulting nulls along the direction of the impinging interferers are of the same degree as those used in noise subspace procedures. The method is based on both the use of a temporal reference, available in the satellite payload, and on the spatial steered beamvector (the Applebaum solution). The resulting procedure is a valuable alternative to the classic covariance loading methods, as further matrix inversion is not required, and the noise estimate is derived from the existing hardware. Some results corresponding to a data relay satellite (DRS) scenario are reported.Peer ReviewedPostprint (published version

Simultaneous DOA estimation based on Kolmogorov's theorem

The design of a new architecture for signal processing, based on the Kolmogorov's theorem (1957), is addressed. This architecture is applied to solve the problem of source separation. Particularly, an adaptive algorithm is proposed to separate simultaneously all the unknown impinging sources on an aperture of sensors. The implemented framework is composed of two different stages: the first one is the inhibition stage, which turns the problem of estimating simultaneous DOAs (directions of arrival) into problems of a single source DOA estimation; and the second one is the optimisation stage which estimates the required parameter in a single signal context easier than the initial one with a multiple signal. A high order rule for learning is described, it improves the behaviour of the system assuring independence of the outputs.Peer Reviewe

High resolution adaptive arrays based on random processing techniques: frequency hopping modulation

A new architecture for adaptive arrays using frequency hopping modulation is addressed. The resolution of the array and the interference rejection increase substantially applying random processing to the carrier frequency of the signals. The proposed framework is composed of two different stages. The anticipative stage, devoted to minimize the noise and fixed interferences contribution and the GSLC stage which provides cancellation of follower jammers and solves the multiuser collision problem. The developed system requires neither temporal nor spatial reference for its implementation, only the frequency sequence must be known. An adaptive approach has been implemented, allowing a fast convergence to the optimal behavior.Peer Reviewe

Adaptive array beamforming for frequency hopping modulation

A new architecture for Array Processing using Frequency Hopping (FH) modulation is addressed in this paper which takes advantage of the knowledge of the frequency sequence at the receiver, requiring neither temporal nor spatial a priori reference. Consequently, the paper deals with a Code Reference Beamformer (CRB). The proposed framework is composed of two parallel processors. The first one, the Anticipative processor, is devoted to predict the scenario at the hop frequency before this frequency is transmitted, providing a fast convergence of the second processor and avoiding the fall of the Signal to Interference plus Noise Ratio (SINR) with the frequency hops. The second one, the On-line processor, provides maximum SINR by applying the optimum beamvector which can be estimated minimizing the Mean Square Error (MSE) at the array output or, directly, maximizing the SINR.Peer Reviewe