Frequency Modulation The Amplitude Essay
Amplitude modulation AM is a fundamental technique used in radio communications to transmit information by varying the amplitude of a carrier wave. This modulation scheme finds extensive application in broadcasting, especially for medium wave and long wave broadcasts. To understand AM, consider an example where u, Ac, carrier amplitude fc, carrier frequency kf, modulation index fm, modulating frequency kf, frequency deviation modulation frequency therefore, fc, 6600 2π, 1050Hz. Question 38. Calculate the modulation index in an FM signal at FM modulating frequency, Hz and Δf, frequency deviation KHz. A. 1. Introduction Frequency modulation is a process of transmitting information on a carrier wave by varying its frequency. It is the most reliable and effective way to transfer information. It is the only means available to us for reliable transmission of music or speech over long distances. In frequency modulation, AM varies: In amplitude modulation, the amplitude of the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal. The time domain representation of an amplitude modulated signal is given as: st, Ac 1, combt, πf c t. st, A c π fct, A ckamt π fc t1. I have found some interesting applications for modulation for lasers. They always talk about some kind of frequency modulation, for example. FMCW AFAIK the frequency of a laser is almost stable for all affordable lasers. So the only way to modulate the laser would be to change the current, resulting in an amplitude modulation of the frequency of each side is an integer multiple of the modulation signal frequency. The amplitude of higher order side frequencies decreases rapidly and can generally be ignored. The amplitude of the carrier signal is also a function of the modulation index and under some conditions its amplitude can actually go to zero. In frequency modulation FM, the frequency of the carrier changes in accordance with the analog input signal, while the amplitude of the carrier remains the same 1,2,3,4,5. This is shown in Figure 8: mt is the input modulating audio signal. Ct is the carrier frequency. St is the FM modulated carrier frequency. The frequency modulation is often called FM. As we know, a modulating signal is the transmission of information or a message after converting it into an electronic signal. mt, A m cos ωmt, Ɵ Where mt is the modulating signal. Am is the amplitude modulating signal. ωm is the angular frequency.