ABSTRACT
Baseband signals are generally band-limited low-pass signals which cannot be directly transmitted over the transmission medium. This chapter discusses the conventional modulation schemes alongside modern digital modulations with high bandwidth efficiency. It analyses the receiver structures for the signal demodulation. One of the long-existing modulation schemes which is used even today is the amplitude modulation (AM) for long-distance broadcasting. In this method, the data are embedded on the amplitude of the signal, therefore it is sensitive to amplitude noise. Furthermore, we introduce circuits to demodulate AM signals. One of the applicable modulations is the phase modulation. In this modulation, the baseband data are embedded in the phase of the radio signal enabling high data rates. The chapter then discusses quadrature amplitude modulation which is one of the most applied modulation schemes in modern radios, phase modulator and demodulator. It also analyses a few special modulation schemes.
