arXiv subjects

Mengying Gao

Publications and source records attributed to Mengying Gao.

4 recordsLinked to original sources

arXiv2025

Construction of Self-Orthogonal Quasi-Cyclic Codes and Their Application to Quantum Error-Correcting Codes

In this paper, necessary and sufficient conditions for the self-orthogonality of t-generator quasi-cyclic (QC) codes are presented under the Euclidean, Hermitian, and symplectic inner products, respectively. Particularly, by studying the structure of the dual codes of a class of 2-generator QC codes, we derive necessary and sufficient conditions for the QC codes to be dual-containing under the above three inner products. This class of 2-generator QC codes generalizes many known codes in the literature. Based on the above conditions, we construct several quantum stabilizer codes and quantum synchronizable codes with good parameters, some of which share parameters with certain best-known codes listed in Grassl's code table.

cs.IT↗

arXiv2024

Movable Superdirective Pairs: A Phase Shifter-Free Approach to mmWave Communications

In this letter, we propose a novel Movable Superdirective Pairs (MSP) approach that combines movable antennas with superdirective pair arrays to enhance the performance of millimeter-wave (mmWave) communications on the user side. By controlling the rotation angles and positions of superdirective antenna pairs, the proposed MSP approach maximizes the received signal-to-noise ratio (SNR) of multipath signals without relying on phase shifters or attenuators. This approach addresses the limitations of traditional superdirective antennas, which are typically restricted to the endfire direction and suffer from reduced scanning bandwidth and increased complexity. An efficient algorithm based on alternating optimization and the gradient projection method is developed to solve the non-convex optimization problem of antennas' joint rotating positioning. Simulation results demonstrate that the MSP approach achieves significant performance gains over fixed-position array (FPA) employing Maximum Ratio Combining (MRC), while reducing system complexity and hardware costs.

cs.IT↗

arXiv2024

A Superdirective Beamforming Approach with Impedance Coupling and Field Coupling for Compact Antenna Arrays

In most multiple-input multiple-output (MIMO) communication systems, antennas are spaced at least half a wavelength apart to reduce mutual coupling. In this configuration, the maximum array gain is equal to the number of antennas. However, when the antenna spacing is significantly reduced, the array gain of a compact array can become proportional to the square of the number of antennas, greatly exceeding that of traditional MIMO systems. Achieving this "superdirectivity" requires complex calculations of the excitation coefficients (beamforming vector), which is a challenging task. In this paper, we address this problem with a novel double coupling-based superdirective beamforming method. In particular, we categorize the antenna coupling effects to impedance coupling and field coupling. By characterizing these two coupling in model, we derive the beamforming vector for superdirective arrays. We prove that the field coupling matrix has the unique solution for an antenna array, and itself has the ability to fully characterize the distorted coupling field. Based on this proven theorem, we propose a method that accurately calculates the coupling matrix using only a number of angle sampling points on the order of the number of antennas. Moreover, a prototype of an independently-controlled superdirective antenna array is developed. Full-wave electromagnetic simulations and real-world experiments validate the effectiveness of our proposed approaches, and superdirectivity is achieved in reality by a compact array with 4 and 8 dipole antennas.

cs.IT↗

arXiv2023

An EEP-based robust beamforming approach for superdirective antenna arrays and experimental validations

A superdirective antenna array has the potential to achieve an array gain proportional to the square of the number of antennas, making it of great value for future wireless communications. However, designing the superdirective beamformer while considering the complicated mutual-coupling effect is a practical challenge. Moreover, the superdirective antenna array is highly sensitive to excitation errors, especially when the number of antennas is large or the antenna spacing is very small, necessitating demanding and precise control over excitations. To address these problems, we first propose a novel superdirective beamforming approach based on the embedded element pattern (EEP), which contains the coupling information. The closed-form solution to the beamforming vector and the corresponding directivity factor are derived. This method relies on the beam coupling factors (BCFs) between the antennas, which are provided in closed form. To address the high sensitivity problem, we formulate a constrained optimization problem and propose an EEP-aided orthogonal complement-based robust beamforming (EEP-OCRB) algorithm. Full-wave simulation results validate our proposed methods. Finally, we build a prototype of a 5-dipole superdirective antenna array and conduct real-world experiments. The measurement results demonstrate the realization of the superdirectivity with our EEP-based method, as well as the robustness of the proposed EEP-OCRB algorithm to excitation errors.

cs.IT↗