Modulation
Analog Modulation Procedure:The idea of analog modulation involves the continuous alteration of the carrier wave. Analog modulation does not play any role to play in mobile radio solutions. Instead digital modulation is used. Howebver analog modulation is used in the radio and TV sector.
Amplitude Modulation (AM): This form of modulation is used for our medium-waveband radio (MW), which is also often referred to as "AM". Here a specific carrier frequency is transmitted. Additionally the actual frequency data of the radio transmitter needs to be transmitted. To achieve this, the frequency information of the carrier wave is transformed by allowing the deflections (in other words the amplitudes) of the carrier wave to be higher or lower. In turn the edges of these carrier waves now form a wave, corresponding to the frequency information to be transmitted.
Frequency Modulation (FM): This is used by the ultra-short waveband radio (VHF). Here the carrier wave frequency varies. As a result, the carrier wave no longer transmits exclusively on a specific frequency but uses a definded frequency range.
Digital Modulation Procedure:
The idea here involves altering the carrier wave in defined very small steps (discrete steps). This is used above all in the mobile radio sector but is also used with satellite TV. The advantage of digital modulation is the possibility of clearly representing individual bits, which are digital as well. If instead of transmitting continuous data (such as analog radio transmission) you wish to transmit digital information via bits, then digital modulation procedures are preferable. Instead of using the term modulation we often refer to shift keying instead.
Amplitude Shift Keying (ASK): Similar to analog amplitude modulation, the amplitude of the carrier wave is altered but now into a number of discrete values (step by step) instead of continuous values.
Frequency Shift Keying (FSK): Here the frequency is altered, similar to analog frequency modulation. In effect we are working here with a set of different carrier waves which have very similar but slightly different frequencies. The switching pattern between these carrier waves with different frequencies transmits the desired information.
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