Telecommunication Principles Engineering

FM Modulator and Demodulator
Nor Ayu Hidayah Binti Mohd Safri (31743) Department of Electronic Engineering (Computer) Universiti Malaysia Sarawak, Malaysia Kuching, Sarawak, Malaysia Email : [e-mail]

Abstract This paper presents about FM modulator and Abstractdemodulator.In electronic and telecommunication, modulation process of varying one or more properties of a high frequency periodic waveform , called carrier signal with a modulating signal which typically contain information to be transmitted. The modulator and demodulator contain an optimized direct digital frequency synthesizer (DDFS) based on quarter-wave symmetry technique for generating the carrier frequency with spurious free dynamic range (SFDR) of more than 64 dB. 64 In this article also will have about the performance in FM. Also have an example for each demodulator and modulator for FM.

it can be processed and used on the receiver end.

II. FM Modulator Modulator
In angle modulation, the amplitude of the signal is held constant and the phase is being varied with the message.An angle modulated signal is of the form xc(t) = Ac cos(Ωct + φ(t)).......... (1) The instantaneous phase of xc(t) is given by θi(t) = Ωct + φ(t).................(2) and the instantaneous frequency is given by Ωi(t) = dθi(t)/dt = Ωc + dφ(t)/dt........... (3) Using this approach, if the message is proportional to φ(t), which is the phase deviation, then we have phase modulation. If the message is proportional to dφ(t)/dt , which is the frequency deviation, then we have frequency modulation.In order to have phase modulation, φ(t) = kpm(t).............(4) where kp is known as the deviation constant. For frequency modulation, dφ(t)/dt = kfm(t)..............(5) where kf is known as the frequency deviation constant. Consequently, an FM modulated signal is of the form xc(t) = Ac cos(Ωct + kf

I. Introduction
FM is the one of info signal is used to control the frequency of the carriers waves. The frequency of the

References: [1] R. Hussin, A. Y. M. Shakaff, N. Idris, Z. Sauli, R. C. Ismail,and A. Kamarudin, “An efficient modified booth multiplier architecture,” in Proceedings of the International Conference onElectronic Design (ICED ’08), pp. 1–4, December 2008. [2] F. Yu, “FPGA implementation of a fully digital FM demodulator,”in Proceedings of the 9th IEEE Singapore InternationalConference on Communication Systems (ICCS ’04), pp. 446–450, September 2004. [3] H. L. Lin, R. C. Chang, and M. T. Chan, “Design of a novel radix-4 Booth multiplier,” in Proceedings of the IEEE Asia-Pacific Conference on Circuits and Systems (APCCAS ’04), vol.2, pp. 837–840, December 2004. IV. Conclusion As a conclusion , we know about FM modulator and demodulator. In FM modulator , its contains varactor tuned modulation,reactance modulator and indirect FM using armstrong method. While FM demodulator contain Foster seeley discriminator, ratio detector, slope detector and PLL detector. Advantages of Frequency Modulation : � � It gives noiseless reception. Noise is a form of amplitude variation and a FM receiver will reject such signals. The efficiency of transmission is very high. [4] M. Young, The Technical Writer 's Handbook. Mill Valley, CA: University Science, 1989.