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Based on the tapped delay-lines (TDL) wideband model, the response variation (RV) constraint is applied to improve the frequency response consistency of the wideband beamforming. The optimization criterion of the proposed algorithm is minimizing the designed sidelobe level utmost and the constraints of the sidelobe level, interference suppression and the response variation while making the direction...
The existing adaptive beamforming techniques developed for underwater sensor array usually suffer from significant performance degradation due to the mismatch between the presumed and actual steering vectors. In this paper, a novel convex optimization based robust adaptive beamforming algorithm is proposed. First, the steering vector corresponding to the desired signal is estimated by solving a convex...
Over the past decades, many phase unwrapping algorithms have been developed and formulated for overcoming the problem of phase ambiguity. In this paper, a novel ambiguity reduced phase unwrapping method is proposed, which unwraps the linear combined phases instead of the instantaneous phases, and thus substantially reduces the degrees of ambiguity. It turns out that the ambiguity-reduce phase unwrapping...
The distributed subspace pursuit (DSP) algorithm has been proposed for sparse signal detection with a sensor network. The experimental investigation on the detection probability of DSP has been provided, but the theoretical analysis on this issue is not clear yet. In this paper, a lower bound of the detection probability of DSP is theoretically analyzed. Experimental evaluations show that our theoretical...
The rotation of rotor blades of a helicopter induces a Doppler modulation around the main Doppler shift. Such a non-stationary modulation, commonly called micro-Doppler signature, can be used to perform classification of the target. In this paper a model-based automatic helicopter classification algorithm is presented. A sparse signal model for radar return from a helicopter is developed and by means...
Cognitive radar systems must decide on suitable actions based on their perception of the environment: this is the perception-action cycle. Cognitive decision-making is a challenging task and can be made more difficult if the problem is incorrectly framed. In this paper, echoic flow is proposed as the correct frame for autonomous path planning activities. It is shown that echoic flow is a natural output...
The direction of arrival (DOA) estimation and adaptive beamforming (ABF) in Four-Dimensional (4-D) antenna arrays are presented in this paper. By using time modulation technique with appropriate time sequences, multiple beams can be obtained in the 4-D antenna arrays and each of them is located at different directions. Through the analysis of the beamspace data received by the multiple beams, the...
This paper presents a joint estimator for Doppler shift and SNR in wireless communications, which is derived from the relation of level crossing rate (LCR) and signal-to-noise ratio (SNR) in mobile propagations. Computer simulations clearly show a good performance for our joint estimator in a wide range of SNRs and velocities.
An approach for adaptive beamforming (ABF) in time modulated antenna arrays (TMAAs) based on beamspace data is proposed in this paper. By using time modulation technology with appropriate time sequences, multiple beams can be obtained in the TMAAs and each of them is located at different directions. Based on the beamspace data received by the multiple beams, the optimum weighting for each beam can...
This paper investigates an improved integer frequency offset (IFO) estimator based on guard band power ratio detection (PRD) in orthogonal frequency division multiplexing (OFDM) systems, which can work with large residual fractional frequency offsets (FFOs) and therefore large inter-carrier-interference (ICIs), resulting in excellent performance in very low signal-to-noise ratio (SNR) environments...
Direction of arrival (DOA) estimation is a very important technology for smart antennas, which have been widely used in many applications such as radar, communication and sonar etc. Various techniques for DOA estimation have been proposed. The commonly used techniques for DOA estimation are subspace based methods, such as multiple signal classification (MUSIC) and its variations. However, these methods...
A novel iterative Doppler shift estimator is proposed in this letter for the Doppler shift estimation in very low signal- noise-ratio (SNR) environment. The proposed method exploits the logarithm envelope (LE) of the mobile propagation channel, and iteratively finds the minimum mean square error (MMSE) estimation of the Doppler shift. Extensive simulation results conducted under a wide range of the...
In this paper, a new approach to speech signal synthesis is proposed. The basic idea is to represent a speech signal as the impulse response of a pole-zero digital filter. The transfer function of the digital filter is obtained using the effective balanced model reduction (BMR) technique. Extensive simulations are done to demonstrate the performance of the proposed approach for speech signal representation,...
This paper presents a novel frequency synchronizator for orthogonal frequency division multiplexing (OFDM) systems over multipath fading channels. With the help of pilot chips and channel estimates in frequency domain, we can analyze the delay power spectrum (DPS) of multipath channels and estimate the integer carrier frequency offset (CFO). Furthermore, the pseudo noise (PN) pilot chips are proposed...
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