Direct Amplitude Modulation Technique using Metamaterial Broadside Coupled Split Ring Resonator (BCSRR) Structure

Abstract

This paper introduces a novel Amplitude Modulation (AM) technique employing metamaterial Broadside Coupled Split Ring Resonator (BCSRR). The carrier wave in the range of GHz frequency is directly modulated by the signal, using a specially designed BCSRR acting as a modulation sensor. The Modulated signal is transmitted through air and receiving it from a distance, the original signal is faithfully reproduced. Resonant frequency dependence of the spacing between the two rings of the BCSRR is employed for the modulation process and it is achieved by varying the spacing between the rings in accordance with the input signal. For the effective modulation, the carrier frequency is chosen at the midpoint of the linear section of the falling/rising slope of the absorption curve of the BCSRR unit. By selecting the BCSRR with narrow bandwidth, effective modulation is obtained even for weak signals. The chances of distortions in the AM wave due to over modulation are also addressed. The distinct characteristics of this modulation process, which does not require any associated electronic components, over conventional AM process, along with its manifold possibilities in the field of communication and instrumentation are also discussed.