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Arrays deployed in antenna-array-based direct position determination (DPD) systems are conventionally placed parallel to each other with invariant orientations, which may be inappropriate. This paper proposes a novel array orientation adjustment method to achieve optimal DPD performance, in which we seek optimal array orientations that maximize the trace of the Fisher information matrix (FIM) and then minimize localization uncertainty. The optimization problem is unconstrained, multivariable, and can be converted into multiple tractable single-variable optimization problems. An exact solution can be obtained by a straightforward but computationally tedious one-dimensional exhaustive search. To reduce the computational load, we then derive an asymptotic solution in cases where the arrays consist of massive antennas. Numerical examples demonstrate the effectiveness and feasibility of the proposed method in resolution and precision enhancement, especially in a low signal-to-noise ratio (SNR).

This letter considers the direction of arrival (DOA) estimation of non-circular (NC) source using a large uniform linear array with a single snapshot. First, by utilizing the waveform characteristics of the NC signal, the proposed algorithm can enlarge the virtual array aperture that is twice the length of the physical array, and resultantly enhance DOA estimation accuracy. Moreover, by multiplying a correction matrix, the proposed algorithm can offset the NC phase error, thereby obtain further improved DOA estimation performance. Furthermore, the advocated algorithm can reduce the computation complexity by using the Newton-Raphson method instead of the traditional grid-search method. Finally, the numerical simulation results are provided to demonstrate the effectiveness and superiority of the proposed algorithm.

Compared with nested array, coprime array can significantly alleviate the mutual coupling between array sensors due to the sparser array structure. However, plenty of holes in its difference co-array extremely reduce the achievable number of uniform degrees of freedom(uDOFs). In this letter, a coprime array with prime integer 3(CAP-3) is proposed, in contrast to several well-known nested arrays, which can offer comparable number of uDOFs, and alleviate mutual coupling simultaneously. Specifically, the CAP-3 consists of three appropriately placed subarrays, and it can eradicate most of the holes in difference co-array except two at both ends. Hence a large number of uDOFs can be obtained. Furthermore, CAP-3 possesses robustness against heavy level of mutual coupling due to the reduced number of sensor pairs with small inter-element spacing. Simulations reveal the advantage of the CAP-3 in uDOF, mutual coupling robustness, and direction of arrival estimation accuracy.

Direction of arrival (DOA) estimation using new proposed array geometries named sparse nested arrays with coprime displacement (SNACD) is discussed in this paper. The SNACD has sparse subarrays with nested relationship, and the displacement between the subarrays is coprime to the inter-element spacing of the smaller subarray. This geometry can combine the properties of nested array and coprime array, which can simultaneously achieve virtual uniform array with large aperture in co-array domain and reduce the mutual coupling influence in physical-array domain. In the co-array domain, the coprime parameter estimations are separated into the virtual direction matrix and source vector, respectively. Based on this data model, several DOA estimation methods can be applied, like the spatial smooth multiple signal classification (SS-MUSIC) and atomic norm minimization based grid-less (ANM-GL) method, which both are robust to the grid mismatch problem. To further reduce the complexity, we proceed to propose a Discrete Fourier transform with offset compensation (DFT-OC) method, which requires neither eigenvalue decomposition nor sparse recovery. The final unique DOA estimation is achieved from the intersection of the coprime estimations, which are achieved with automatically pairing. Compared to coprime array and nested array based methods, the proposed scheme obtains better DOA estimation accuracy and higher angular resolution with mutual coupling influence. Multiple simulations are presented to verify the effectiveness of our approach.

The coprime array owns a sparse array structure, which can effectively alleviate mutual coupling, while the holes existing in the difference co-array(DCA) greatly reduce the number of uniform degrees of freedom(uDOFs). In this letter, we propose a new coprime array structure called hole-free coprime array (HFCA) by carefully assembling the subarrays, and the resulting HFCA can generate a hole-free DCA. Furthermore, we derive the optimal HFCA that can produce the largest hole-free DCA with a given number of sensors, which contributes to an increase of uDOFs compared with existing coprime array structures. In addition, the simulations are provided to demonstrate the superiority of HFCA in terms of uDOFs, direction of arrival estimation performance, and spatial resolution.

This article proposed a novel hybrid-connected boost converter (HCBC) with ultrahigh step-up and ultralow voltage stress. At the input part, a traditional interleaved boost converter structure is adopted based on dual coupled inductors, which can reduce the input current ripple and ease the current stress flowing through main switches and magnetic elements. Then, the voltage doubling capacitors embedded in this circuit can lift voltage and clamp the voltage stress on switches. Therefore, it will not only increase the voltage gain, but also recycle the leakage energy of coupled inductor to alleviate the voltage spikes across the power switches. At the output, the dual secondary windings of coupled inductors are connected in series and combined with a capacitor-diode to form a voltage multiplier module, which is stacked on the output for higher voltage gain. The working principle and steady-state performance of the proposed converter are analyzed in detail, and a 400-W experimental prototype based on HCBC is built to verify the correctness of theoretical analysis.

In this letter, two-dimensional (2D) direction of arrival (DOA) estimation using one-dimensional (1D) nested array motion is studied, and an improved Discrete Fourier transform (DFT) algorithm is proposed. Exploiting nested array to move vertically along its axis enables 2D DOA estimation with large-scale and hole-free difference co-array. DFT algorithm has lower complexity than multiple signal classifications(MUSIC) method, but traditional DFT algorithm still requires multiple extra searches to ensure estimation accuracy. We use DFT to obtain the initial angle estimations, and then compensate the estimation offsets via total least squares (TLS) constructed from Taylor expansion approximation. Compared with the traditional DFT search method, the proposed method has lower complexity and better performance. Multiple simulations are conducted to verify the effectiveness of our approach.

In this paper, an integrated step-up inverter without transformer is investigated for photovoltaic (PV) power generation. The proposed topology can be derived by combining a traditional boost converter with a single-phase full bridge dc–ac converter. The main features of the integrated inverter are: First, the leakage current caused by the solar cell array-to-ground parasitic capacitance can be theoretically reduced to zero due to the characteristics of the converter configuration, which can improve the efficiency and the reliability of the PV generation system; second, the output ac voltage of the proposed inverter can be higher than the input dc voltage, which is capable of connecting low voltage PV panels to the grid; third, only five active switches are used in the presented inverter, and those switching devices can be synchronously driven by various sinusoidal pulsewidth modulation methods based on the carrier; therefore, the proposed inverter is compact and with curtailed cost. The working principle and analysis of the proposed integrated inverter are elaborated. Finally, simulation and experimental results are obtained in a lab prototype, which agree well with the theoretical analysis.