ABSTRACT
The main purpose of a communication system is to transmit data or information from one point to another or from a source to a destination. A general communication system is comprised of three parts: a transmitter, channel, and receiver. The channel is the medium where the data propagates and it can be wired or wireless. In this book we will only cover the wireless channel, hence in the transmitter there is an antenna to send the data to a specific distance. On the receiver side, there is an antenna to receive a signal, which normally is low in strength and needs to be further amplified. The main blocks in the transmitter of a general communication system include the coding, interleaving, modulation, digital-to-analog converter (DAC), mixer, filter, power amplifier, and antenna. In the receiver, however, there is a low noise amplifier (LNA), a band-pass filter (BPF), downconversion, demodulation, analog-to-digital conversion (ADC), decoder, and interleaver. It should be noted that for different generations of communication systems and different applications of broadband communication systems, the transmitter and receiver blocks are different than those mentioned earlier. The main concentration in this book is on the most costly device used in communication systems, the power amplifier (PA). Sometimes it is denoted with HPA, which stands for high power amplifier. This is because in current wireless communications systems the need for coverage and transmission to long distances makes it necessary to design PAs with high power.
