A Comprehensive Analysis of M-ary PSK and M-ary QAM Schemes

In the last few decades, data communication has recorded massive improvements. These improvements were brought about by advancement in digital circuitry, its availability and persistent reduction in cost. Before the advancement of digital communication technology, analogue communication was the dominant means of transmitting data. As the internet expands across the globe, the need to transfer data over long distances increases. However, the major problem with analogue communication is that the quality of signals is lost with distance. Also, it has minimal security and does not support data integration. Digital communications provided an alternative to analogue communication. Today, digital modulations have become part and parcel of the present and future communication technologies. Despite the advantages of these schemes, the traditional channel impairments, such as noise, can affect their performance. Moreover, data transmission is mostly done over wireless channels, which are very unpredictable and are characterised by multipath fading effects. This paper presents a short research article that presents a study of digital modulation schemes (M-ary QAM and M-ary PSK) using MATLAB/Simulink under Additive White Gaussian Noise (AWGN). The result shows that, among the three modulation schemes compared, QAM has the best BER performance with minimal energy consumption.

Active digital spoof plasmonics

Digital coding and digital modulation are the foundation of modern information science. The combination of digital technology with metamaterials provides a powerful scheme for spatial and temporal controls of electromagnetic waves. Such a technique, however, has thus far been limited to the control of free-space light. Its application to plasmonics to shape subwavelength fields still remains elusive. Here, we report the design and experimental realization of a tunable conformal plasmonic metasurface, which is capable of digitally coding and modulating designer surface plasmons at the deep-subwavelength scale. Based on dynamical switching between two discrete dispersion states in a controlled manner, we achieve digital modulations of both amplitude and phase of surface waves with nearly 100% modulation depth on a single device. Our study not only introduces a new approach for active dispersion engineering, but also constitutes an important step towards the realization of subwavelength integrated plasmonic circuits.