# Communication Systems/Analog Modulation Introduction

## Analog Modulation Overview

Let\'s take a look at a generalized sinewave:

$$x\left( t \right) = A\sin \left( {\omega t + \theta } \right)$$ It
consists of three components namely; amplitude, frequency and phase.
Each of which can be decomposed to provide finer detail:

$$x(t) = A s(t) \sin ( 2 \pi [f_c + kf_m(t)] t + \alpha \phi(t) )$$

## Types of Analog Modulation

We can see 3 parameters that can be changed in this sine wave to send
information:

-   $A s(t)$. This term is called the \"Amplitude\", and changing it is
    called \"Amplitude Modulation\" (AM)
-   $kf_m(t)$ This term is called the \"Frequency Shift\", and changing
    it is called \"Frequency Modulation\"
-   $\alpha \phi (t)$. this term is called the \"Phase angle\", and
    changing it is called \"Phase Modulation\".
-   The terms frequency and phase modulation are often combined into a
    more general group called \"Angle Modulation\".

## The Breakdown

Each term consists of a coefficient (called a \"scaling factor\"), and a
function of time that corresponds to the information that we want to
send. The scaling factor out front, A, is also used as the transmission
power coefficient. When a radio station wants their signal to be
stronger (regardless of whether it is AM, FM, or PM), they \"crank-up\"
the power of A, and send more power out onto the airwaves.

## How we Will Cover the Material

We are going to go into separate chapters for each different type of
modulation. This book will attempt to discuss some of the mathematical
models and techniques used with different modulation techniques. It will
also discuss some practical information about how to construct a
transmitter/receiver, and how to use each modulation technique
effectively.
