The chapter begins with presentation of common demodulation framework for different kind of amplitude modulated systems which includes discussion of receiving system introduced in Chap. 3. In each case, received signal and noise power is calculated and signal to noise ratio (SNR) at the final stage (baseband filter) is arrived at. This gives a measure of the noise robustness of a particular modulation scheme. Another measure, called figure of merit defined as ratio of output SNR to input SNR of a receiver is also presented. For double sideband with carrier modulation we can employ convenient noncoherent techniques like square law demodulator or envelop detector. But in noisy condition both show a threshold effect under which performance starts to degrade more rapidly. It was shown that on this account square law demodulator performs relatively better. Many other practical issues that includes noise overload of amplifier are discussed under various topics.
