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Unambiguous tracking and multipath mitigation for Binary Offset Carrier (BOC) signals are two important requirements of modern Global Navigation Satellite Systems (GNSS) receivers. A GNSS discriminator design method based on optimization technique is proposed in this paper to meet these requirements. Firstly, the discriminator structure based on a linear-combined code is given. Then the requirements of ideal discriminator function are converted into the mathematical constraints and the objective function to form a non-linear optimization problem. Finally, the problem is solved and the local code is generated according to the results. The theoretical analysis and simulation results indicate that the proposed method can completely remove the false lock points for BOC signals and provide superior multipath mitigation performance compared with traditional discriminator and high revolution correlator (HRC) technique. Moreover, the proposed discriminator is easy to implement for not increasing the number of correlators.

Unambiguous tracking for Binary Offset Carrier (BOC) modulated signals is an important requirement of modern Global Navigation Satellite System (GNSS) receivers. An unambiguous tracking method based on combined correlation functions for even/odd order sine/cosine-BOC, Composite BOC(CBOC) and Alternate BOC(AltBOC) modulated signals is proposed. Firstly, a unitary mathematical formulation for all kinds of BOC modulations is introduced. Then an unambiguous tracking method is proposed based on the formulation and the idea of pseudo correlation function (PCF) method. Finally, the tracking loop based on the proposed method is designed. Simulation results indicate that the proposed method can remove side peaks while retaining the sharp main peak for all kinds of BOC modulations. The tracking performance for AltBOC is examined and the results show that the proposed method has better performance in thermal noise and long-delay multipath mitigation than the traditional unambiguous tracking methods.

The binary offset carrier (BOC) proposed for the global navigation satellite systems (GNSS) will enhance navigation performance and spectrum compatibility. However, the acquisition process is made more complex, due to the ambiguity in the autocorrelation function (ACF) of BOC. This paper proposes an unambiguous acquisition technique for the new cosine phased BOC (cosine-BOC) modulated signals, which will most likely be used in both European Galileo system and Chinese Compass system. The test criterion employed in this technique is based on a synthesized correlation function which completely removes major positive side peaks while keeping the sharp main peak using the concept of simultaneous perturbation stochastic approximation (SPSA). Theoretical analysis and simulation results indicate that the proposed technique completely removes the ambiguity threat in acquisition process with some performance degradation. This technique is also suitable for arbitrary order cosine-BOC signals.

A novel tracking method in the phased antenna array with a single-channel receiver for the moving signal source is presented in this paper. And the problems of the direction-of-arrival track and beamforming in the array system are converted to the power maximization of received signal in the free-interference conditions, which is different from the existing algorithms that maximize the signal to interference and noise ratio. The proposed tracking method reaches the global optimum rather than local by injecting the extra noise terms into the gradient estimation. The antenna beam can be steered to coincide with the direction of the moving source fast and accurately by perturbing the output of the phase shifters during motion, due to the high efficiency and easy implementation of the proposed beamforming algorithm based on the simultaneous perturbation stochastic approximation (SPSA). Computer simulations verify that the proposed tracking scheme is robust and effective.

Global Navigation Satellite Systems (GNSS) positioning accuracy indoor and urban canyons environments are greatly affected by multipath due to distortions in its autocorrelation function. In this paper, a cross-correlation function between the received sine phased Binary Offset Carrier (sine-BOC) modulation signal and the local signal is studied firstly, and a new multipath mitigation method based on cross-correlation function for sine-BOC signal is proposed. This method is implemented to create a cross-correlation function by designing the modulated symbols of the local signal. The theoretical analysis and simulation results indicate that the proposed method exhibits better multipath mitigation performance compared with the traditional Double Delta Correlator (DDC) techniques, especially the medium/long delay multipath signals, and it is also convenient and flexible to implement by using only one correlator, which is the case of low-cost mass-market receivers.

Because of the multiple side peaks in the Binary Offset Carrier (BOC) autocorrelation function (ACF), the probability of locking on a side peak will be generated in BOC code tracking process for next generation of global navigation satellite system (GNSS) receivers. A novel unambiguous tracking method based on an ideal reference function is proposed in this paper to remove the ambiguity problem. This method is suitable for Sine-BOC(2n, n) modulated signals, which is a specific family of BOC modulated signal for modernized GPS M-code signal and future Galileo. The theoretical and simulation results indicate that the proposed method completely removes the side-peaks from autocorrelation function while maintaining the sharp main peak, and the performance of multipath mitigation is also improved effectively with respect to the conventional BOC tracking methods.

An efficient frequency and 2-D arrival angles is essential in array signal processing. 3-D ESPRIT for joint 2-D angle and carrier frequency estimation offers an efficient way to handle the problem. Automatic pairing of the 3-D estimates is achieved via a marked subspace. This paper exploits multiple invariance matrix pencils from parallel uniform linear array to estimate a set of unknown parameters. For many frequency estimation and directions finding, all diagonal elements of invariance matrix are located on the unit circle in the complex plane. The marked subspace technique makes the set of parameter of each radiating source locate on the circle of the same radius, whereas different sources are located on different radius circle, so that several sources can automatically pair with the marker-radius. Computer simulations are shown to be in close agreement with theoretical analysis

The phase space is first constructed by various features extracted from semi-signals in the time domain, then, the two-category source samples of underground nuclear explosions and natural earthquakes are investigated and analysed in the very phase space. The theoretical analysis and numerical calculation results indicate that there are two "attractors" in the phase space: one is the attractor for an underground nuclear explosion, another is for a natural earthquake. The dimensions of the attractors yielded in the light of the correlation dimension are of fractal dimensions, and less than that of the phase space. When the dimensions of phase space increased from low to high, the dimensions of the attractors become apparently saturated, and different attractors have different fractal dimensions. A new concept, namely, the "attraction center" is proposed. Moreover, the attractor, the attractor dimension, and the attraction center with their applications to seismic pattern recognition of an underground nuclear explosion are also explored.

Based on the processing and analysis of seismic signals originating from underground nuclear explosions and natural earthquakes, it is illustrated that the seismic signals in the time domain possess the characteristics of statistical self-affine fractals, whilst the fractal dimension D yielded from logarithmic power spectrum does not serve as an effective feature for seismic pattern recognition. Moreover, it is found that the signal "energy" at each scale of the wavelet decomposition relates closely to the scale, and that an apex appeared on the "energy spectrum" of the detail signal, hence, the two kinds of features advocated are very likely to be utilized in seismic pattern recognition applications. The provided recognition results show the improvement and performance achieved by the proposed feature extraction and selection methods.