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- ItemSplit-Ring Coupled Low-Cost Antenna with Electromagnetic Bandgap (EBG) Superstrates to Produce Tri-bands and High Gains(Společnost pro radioelektronické inženýrství, 2024-04) Kawdungta, S.; Torrungrueng, D.; Chou, H.-T.In this paper, a novel tri-band low-cost antenna covering the desired frequencies is presented. The architecture is formed by a printed dipole coupled by a split-ring within an electromagnetic bandgap (EBG) structure for high radiation gains. The printed dipole is placed beneath two dielectric superstrates, and the coupling split-ring is placed on its top. The proposed antenna is excited by the printed dipole with a coaxial connector. It is placed in the middle cavity formed by two dielectric superstrates and a metal reflector as the simple EBG structure. The simulation results show three resonant frequencies at 1.42, 2.39 and 5.40 GHz respectively, with uni-directional radiation patterns and high gains enhanced by the EBG structure. Experimental measurements over an antenna prototype validate the results of reflection coefficients and radiation patterns. It is found that the gains are 8.50, 6.00 and 8.10 dBi at 1.42, 2.39 and 5.00 GHz respectively, which are sufficient for L-band and WiFi applications. In addition, simulation and measurement results are in good agreement.
- ItemDesign and Performance Analysis of MCPC and P4 Waveforms for OFDM based Radar System(Společnost pro radioelektronické inženýrství, 2024-04) Huang, D.; Tang, J.; Xu, L.; Wu, Y.This study aimed to investigate the performance of Multicarrier Phase Coding (MCPC) and P4-encoded waveforms. Researchers explored the unique properties of these signals, focusing on aspects like phase distribution, autocorrelation, power spectral density for P4 encoding, and aperiodic autocorrelation and ambiguity function for MCPC signals. The findings identified optimal MCPC sequences with reduced peak-to-mean envelope power ratios (PMEPR), improving signal performance. Complementary codes based on permutation were also generated and analyzed for MCPC sequences. The study utilized an improved genetic algorithm to develop new and improved waveforms, underscoring the importance of techniques like optimal sequence permutation, complementary sequences, and classical window frequency weighting in enhancing signal performance.
- ItemMainlobe Interference Suppression Based on Compressive Sensing and Covariance Matrix Reconstruction(Společnost pro radioelektronické inženýrství, 2024-04) Zhao, X.; Ren, A.When mainlobe interference exists in space, the traditional anti-interference methods have problems such as peak offset and the performance of sidelobe interference suppression reduction. To solve the above problems, this paper proposes a mainlobe interference suppression method based on compressive sensing and covariance matrix reconstruction. Firstly, an improved compressive sensing algorithm is proposed to accurately estimate the Direction Of Arrival of sources, and then the signal steering vectors and signal subspaces can be established. The mainlobe interference can be suppressed by establishing an oblique projection operator through signal subspaces. Meanwhile, the sidelobe-interference-noise covariance matrix can be reconstructed by the steering vectors, and then the adaptive weight vector is obtained. Simulation results show that the proposed method can form a more robust beam pattern and has better output performance. The proposed method is still effective when the desired signal exists in the received signal.
- ItemCascaded Deep Neural Network Based Adaptive Precoding for Distributed Massive MIMO Systems(Společnost pro radioelektronické inženýrství, 2024-04) Ge, L. J.; Niu, S. X.; Shi, C. P.; Guo, Y. C.; Chen, G. J.In time-division duplex (TDD) distributed large-scale multiple input multiple output (DM-MIMO) systems, the traditional downlink channel precoding method is used to resist inter-user interference (IUI). However, when the Channel State Information (CSI) is incomplete, the performance loss is serious, not only the bit error rate is high, but also the complexity of the traditional precoding algorithm is high. In order to solve these problems, this paper proposes an adaptive precoding framework based on deep learning (DL) for joint training and split application deployment. First, we train a channel emulator deep neural network (CE-DNN) to learn and simulate the transmission process of the wireless communication channel. Then, we concatenate an untrained precoding DNN (P-DNN) with a trained CE-DNN and retrain the cascaded neural network to converge. The last step is to obtain the P-DNN, namely the adaptive precoding network, by dismantling the joint trained network. Simulation results show that, when CSI is imperfect, the proposed method is compared with Tomlinson-Harashima precoding (THP) and block diagonalization (BD) precoding. The proposed method has a lower mean square error (MSE) and higher spectrum efficiency, as well as a bit error rate (BER) performance close to the THP. The source codes and the neural network codes are available on request.
- ItemOptimized-Goppa Codes Based on the Effective Selection of Goppa Polynomials for Coded-Cooperative Generalized Spatial Modulation Network(Společnost pro radioelektronické inženýrství, 2024-04) Chen, C.; Yang, F. F.; Waweru, D. K.This paper proposes a novel optimized-Goppa-coded cooperative generalized spatial modulation (OGCC-GSM) scheme for short-to-medium information block transmission. In the proposed OGCC-GSM scheme, an efficient Goppa polynomial selection approach is designed to ensure that the selected Goppa codes applied in the source and relay nodes both have the largest minimum Hamming distance (MHD) and the optimal weight distribution. Compared to conventional coded cooperation (CC) with a single antenna, the proposed scheme employs the generalized spatial modulation (GSM) technique to achieve more diversity gains, where each node is equipped with multiple antennas and more than one transmit antenna (TA) is activated at each time-instant transmission. As a benchmark comparison, the OGCC spatial modulation (OGCC-SM) scheme is also investigated with a single TA active. Moreover, the reduced-complexity transmit antenna combination (RC-TAC) selection algorithm utilized in GSM is first developed with the aid of the channel state information (CSI) to reconcile computational complexity and system performance. In addition, joint decoding is conducted on the destination terminal to further enhance the performance of the proposed scheme. The simulated results indicate the performance of the proposed OGCC-GSM scheme is superior to that of its benchmark OGCC-SM scheme, with a substantial reduction in the number of TAs. Besides, Monte Carlo simulations demonstrate that the proposed OGCC-GSM scheme prevails over its counterparts by a margin of over 4.2 dB under identical conditions.