MODULATION

Modulation is the process by which the communications signal that contains the information is combined with another signal. This results in a signal at frequencies more compatible with the application and in a desired part of the spectrum.  Hence, demodulation is the process of extracting or recovering the original modulating information successfully. 

With the present types of modulation technique used for transmission; like Amplitude Modulation (AM), Frequency Modulation (FM) and Phase Modulation (PM), there are several pros and cons for each of the individual techniques used, depending on the application.  In theory, AM is more noise prone (e.g.: noise or static generated by motor or circuitry) than FM and PM, the noise adds to the signal will corrupts the modulation itself which carries the useful information.  AM also wastes a lot of power on transmitting the carrier which does not contained any useful information.  As for the bandwidth, the sidebands occupy twice the spectrum that the original signal required which is also a waste of bandwidth too.

Whereas, for the both FM and PM (both having a very similar features) it offer greater noise immunity than AM, but it will require much more bandwidth. However, for this point, it’s of useful application where FM using more bandwidth to overcome the noise issue.  FM and PM need a more complex circuitry for modulation and demodulation the signal, especially on the demodulation portion as compared to AM.

In today’s modern design, the complexity circuitry of the FM could be easily available in a ICs module package.  Hence, to suit the design requirement of this project, FM Transmitter and Receiver modules are selected.  These FM Transmitter and Receiver are easily available in the market at a competitive price and yet offer very good noise resistant even at a longer range (e.g.: 300m).