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Tracking dynamics on the GPS signal is still a big challenge to the receiver designer as the operating conditions are becoming more volatile. Usually, the Phase-locked loop (PLL) is used in GPS receivers to track an incoming signal and to provide accurate carrier phase measurements. However, in high dynamic situations, the conflict between improving PLL tracking performance and the ability to track the signal necessitates some compromises in PLL design. Optimizing the stand-alone system for dynamics, generally, degrades the accuracy of measurements. The advanced signal processing techniques as maximum likelihood (ML) and extended Kalman filter (EKF) can be used to track a common trajectory exhibiting high dynamics. However, the estimated values of these algorithms can not be used directly to demodulate the signals. A combination of both inertial measurement unit (IMU) and GPS is an attractive method to deal with the problem of high dynamic tracking. Unfortunately, these units of IMU are often very expensive. In this paper, a new Kalman filter aided phase-lock loop is proposed to address this issue. Doppler derived from EKF is used to aid the carrier tracking loop for improving the performance under dynamic conditions. While the cost is significantly reduced compare with the IMU method. Simulations show that the method is feasible.

A combined codebook constructing method is proposed for beamforming in correlated Multiple-input multiple-output (MIMO) channels, where the codebook is dynamically constructed based on the transmit covariance matrix of the channel. Monte Carlo simulations show performance close to optimal beamforming. Huffman coding is used to further reduce the feedback rate in correlated MIMO system.

Perfect optical vortices (POVs) arevortex beams with infinitely narrow rings and fixed radii independent of their topological charges. Here we propose the concept of generalized POVs (GPOVs) along arbitrary curves beyond the regular shapes of circles and ellipses. GPOVs share similar properties to POVs, such as defined only along infinitely narrow curves and owning topological charges independent of scale. Using a rigorous mathematical derivation in a curvilinear coordinate, we reveal theoretically that the GPOVs have a topological charge proportional to the area of the swept sector in tracing the curve, suggesting a unique mode for optical vortex beams. Experimentally, the complex-amplitude masks to generate the GPOVs are realized by using a pure-amplitude digital micro-mirror device with the super-pixel encoding technique. The phase profiles of the generated GPOVs are retrieved experimentally through self-built interferometry and exhibit good agreement with the simulations. We also derive a properly modified formula to yield the intensity-uniform GPOVs along predesigned curves, which might find applications in optical tweezers and communications.

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