A single‐layer planar end‐fire circularly polarised microstrip antenna with enhanced bandwidth is proposed by loading with a metal pin. The original antenna is designed with a shorted parallel‐plate cavity that serves as a magnetic dipole, and a double‐sided printed bowtie dipole acts as an electric dipole. Then a metal pin is loaded connecting two metal surfaces and impedance bandwidth is improved obviously. One prototype is fabricated for verification and measured 19% –10 dB impedance bandwidth and 36% 3 dB axial ratio bandwidth are achieved.

This letter studies the secrecy performance for a two-way integrated satellite terrestrial relay networks. Particularly, multiple legitimate users along with maximal user scheduling scheme are applied in the considered networks. In addition, the closed-form expression for the secrecy outage probability of the considered two-way networks is obtained. Moreover, to investigate the impacts of the system parameters on the secrecy performance in high signal-to-noise ratio regime, the asymptotic analysis for the secrecy outage probability is further derived. Finally, Monte Carlo simulation results are provided to prove the theoretical results.

This article investigates the impacts of relay selection schemes on cooperative underlay cognitive radio non-orthogonal multiple access networks, where the partial relay selection scheme, the max–min relay selection scheme and the two-stage relay selection scheme are applied in the network. Moreover, decode-and-forward protocol is used at the transmission relays. What’s more, in order to show the effect of the schemes on the considered network, the closed-form expressions and asymptotic expressions for the outage probability of the system are derived. Furthermore, the outage performance under the effect of perfect and imperfect successive interference cancellation is analysed. Numerical results are given to illustrate the impacts of the relay selection schemes, the number of relays, the residual interference factor and the power allocation factor on the outage performance. Finally, Monte Carlo simulations are presented to validate the accuracy of the numerical results.

In this article, we studied the robust security transmission design for multi-user peer-to-peer relay networks, where all users demand secure communication and the eavesdropper is passive. Although the previous researches have designed the physical-layer security schemes under perfect channel state information, this study focuses on investigating the robust transmission design in the presence of a passive eavesdropper. Our goal is to maximize the artificial noise power to confuse the passive eavesdropper and subject to the worst-case signal-to-interference-noise-ratio constraints for all users under a bounded spherical region for the norm of the channel state information error vector from the relays to the destinations and the individual power constraints of all relay nodes. Mathematically, the original robust problem is difficult to solve due to its non-linearity and non-convexity. We propose to adopt S-Procedure and rank relaxation techniques to convert it to a semidefinite programming convex problem. The numerical results show the advantage of the proposed robust method.