Amplitude and Phase Analysis Based on Signed Demodulation for AM-FM Signal

Guanlei Xu,Xiaotong Wang,Limin Shao,Xiaogang Xu

doi:10.4236/jcc.2014.29012

Abstract

This paper proposes a new amplitude and phase demodulation scheme different from the traditional method for AM-FM signals. The traditional amplitude demodulation assumes that the amplitude should be non-negative, and the phase is obtained under the case of non-negative amplitude, which approximates the true amplitude and phase but distorts the true amplitude and phase in some cases. In this paper we assume that the amplitude is signed (zero, positive or negative), and the phase is obtained under the case of signed amplitude by optimization, as is called signed demodulation. The main merit of the signed demodulation lies in the revelation of senseful physi- cal meaning on phase and frequency. Experiments on the real-world data show the efficiency of the method.

Highlights

In many signal processing fields such as communication, wireless navigation and machine systems, the modulation and demodulation are often used to process the amplitude component and the phase component [1]-[10]
The basic problem in processing AM-FM signals is demodulation, i.e., estimation of the information stored in the amplitude and phase signals while given the composite signal
The biggest advantage of Hilbert transform is that one can directly obtain the amplitude and phase for AM-FM components, e.g., a real signal x (t ) = a (t ) cosφ (t ), one can obtain the follows via Hilbert transform

Summary

Introduction

In many signal processing fields such as communication, wireless navigation and machine systems, the modulation and demodulation are often used to process the amplitude component and the phase component [1]-[10]. For monocomponent AM-FM signals many successful demodulation approaches have existed, ranging from standard methods such as Hilbert transform demodulation [1] or phase-locked loops (PLL’s) to the recent energy separation algorithm (ESA) that tracks and demodulates the energy of the source producing the AM-FM signal using instantaneous nonlinear differential operators [2]-[18]. While each of these monocomponent algorithms may have its advantages and disadvantages, they more or less offer a solution to the monocomponent AM-FM demodulation problem. We derive a new scheme, different from the traditional method for AM-FM signals that can obtain the signed amplitude and senseful physical meaning phase and frequency by optimization

Traditional Demodulation of Amplitude and Phase

The Proposed Signed Demodulation Method

Experiment and Discussion

Conclusion