2 - Definitions

Summary

This chapter contains the important definitions needed for the remainder of this book. Beginning at the beginning is the best way to build the foundation upon which this book is built. Topics covered include the basic physics upon which all this work stands. Definitions of important terms are presented so that understanding of discussions within the remainder of this book is clear and unambiguous. The key definitions include meanings of supply and bias, linear vs. polar signal processing, how gain must be interpreted when operating in compression, along with the concepts of power supply rejection (PSR), dynamic range, and bandwidth expansion.

All circuit performance metrics used in this book are derived from device characteristic curves, in order to build physical intuition into what the circuitry is actually doing. Device and block models are secondary in this discussion, as they inherently follow from the device physics. Mathematics always follows the physical discussions. In this book, mathematics is a tool, and not a primary window on to the material.

Physical foundations

The sinusoidal waveform used in radio communications is not an arbitrary choice, but is a consequence from Maxwell's equations of electromagnetism. Looking at this solution, we see that polar coordinates are the physically natural form of the signal equation. Ohm's Law, itself also a consequence from Maxwell's equations, shows how power dissipation happens in transmitters. Knowing how power dissipation reduces overall energy efficiency provides guidance on how to change designs to improve overall transmitter efficiency.

It is important to use models, both physical and mathematical, that not only describe well what the performance of these transmitters is, but are also descriptive of the physical operations. This joint requirement of the models used here is used consistently.

2.1.1 Maxwell's equations

All electronics, radio included, follow from electromagnetism described by Maxwell's equations (usually as reformulated by Oliver Heaviside) [2-1].