Principles of forming backscattering signal modulation

Abstract

Lately there has been a steadily growing interest to implement data transmission systems (DTS) based on backscattering signal modulation. This is due to high energy efficiency of such systems, since there is no need for intrinsic microwave signal generator on the transmitter’s side. Such DTS are assumed to be applied for 5G network development, as well as in such data transmission systems as BLE, Wi-Fi, LoRA, WLAN and GSM.  Moreover, market rapid development of devices used within the concept of Internet of things and wireless sensor networks also drives up interest in devices using backscattering signal modulation. Yet theoretical issues of their formation are of little if any consideration despite available works describing implemented modulators of such signals. This article provides for the first time mathematical tool to describe principles of backscattering signal modulation. The article gives an expression for this purpose defining the signal in time and frequency domain scattered by antenna radio ID. Analysis of DTS operation was performed using backscattering principle in time domain during the process of deriving this expression. To form a specific type of signal the requirements are set for variation law of reflection coefficient from the time required for implementation of quadrature, amplitude, phase and frequency shift keying. Simulation results of backscattering signals with QAM-4, QAM-8, amplitude and phase shift keying are presented as an example. The simulation is performed at the frequency used by actual RFID systems.