What is the Comparison of frequency modulation and amplitude modulation?

Answer 1

I will answer this in the simplest way I know in the application I use it in; this would be in audio applications. Amplitude modulation is modulation of a carrier source's loudness; Frequency modulation is modulation of a carrier source's pitch; and Phase modulation is modulation of a carrier source's duty cycle/symmetry/timbre. One can often notice that all 3 modulation types relate in some way with another in that when frequency rises and falls it typically makes it favorable for either a rise in loudness or timbre. The most analog way to understand it in nature is typically your small vowel sounds like "iiiiiiiiiiiiii" as in the American-English word 'easy' and 'eeeeeeeeeeee' as in 'edge' are easier to say with loudness at higher pitches; medium vowel sounds like 'uuuuuuuuuuu' as in 'Utter' or 'sOn' and 'aaaaaaaaaaaa' as in 'Awe' *chuckles* are easier to say with loudness at medium pitches; large vowel sounds like 'ooooooooooo' as in 'Oh' and 'uuuuuuuuuuuu' as in 'rUne' are easier to say with loudness at lower pitches. AM is often known as 'tremolo'; FM is often known as 'vibrato'; PM is often known as 'wow'; AM/FM is 'vibremelo' and fill in the blanks for the other sub-variants. Maikel Stellerfield

Answer 2

Frequency Modulation:

1. Freq of carrier is varied in accordance with instantaneous values of modulating signal

2. f=fc(1+kVmcosWmt)

Phase Modulation :phase of carrier is varied in accordance with instantaneous values of modulating signal

Answer 3

"The essential distinction [between PM & FM] being the integration of the message in FM. Moreover, nomenclature notwithstanding, both FM and PM have both time-varying phase and frequency. These relations clearly indicate that, with the help of integrating and differentiating networks, a phase modulator can produce frequency modulation and vice versa."

Dr. Paul C. Crilly

An excerpt from "Communication Systems: An intro. to signals and noise in electrical communication"

Answer 4

Additionally, digital signals usually require an intermediate modulation step for transport across wideband, analog-oriented networks. Amplitude Modulation (AM) Amplitude Modulation occurs when a voice signal's varying voltage is applied to a carrier frequency. The carrier frequency's amplitude changes in accordance with the modulated voice signal, while the carrier's frequency does not change. When combined the resultant AM signal consists of the carrier frequency, plus UPPER and LOWER sidebands. This is known as Double Sideband - Amplitude Modulation (DSB-AM), or more commonly referred to as plain AM. The carrier frequency may be suppressed or transmitted at a relatively low level. This requires that the carrier frequency be generated, or otherwise derived, at the receiving site for demultiplexing. This type of transmission is known as Double Sideband - Suppressed Carrier (DSB-SC). It is also possible to transmit a SINGLE sideband for a slight sacrifice in low frequency response (it is difficult to suppress the carrier and the unwanted sideband, without some low frequency filtering as well). The advantage is a reduction in analog bandwidth needed to transmit the signal. This type of modulation, known as Single Sideband - Suppressed Carrier (SSB-SC), is ideal for Frequency Division Multiplexing (FDM). Another type of analog modulation is known as Vestigial Sideband. Vestigial Sideband modulation is a lot like Single Sideband, except that the carrier frequency is preserved and one of the sidebands is eliminated through filtering. Analog bandwidth requirements are a little more than Single Sideband however. Vestigial Sideband transmission is usually found in television broadcasting. Such broadcast channels require 6 MHz of ANALOG bandwidth, in which an Amplitude Modulated PICTURE carrier is transmitted along with a Frequency Modulated SOUND carrier. Frequency Modulation (FM) Frequency Modulation occurs when a carrier's CENTER frequency is changed based upon the input signal's amplitude. Unlike Amplitude Modulation, the carrier signal's amplitude is UNCHANGED. This makes FM modulation more immune to noise than AM and improves the overall signal-to-noise ratio of the communications system. Power output is also constant, differing from the varying AM power output. The amount of analog bandwidth necessary to transmit a FM signal is greater than the amount necessary for AM, a limiting constraint for some systems.

Answer 5

phase angle = delay time*frequency*360degree