Antenna And Wave propagation

There are more “radios” being built than ever before
‎
‎1. Telephony ‎
‎ 1.‎Cellular ‎
‎ 2.‎Public Cabinets System (PCS) ‎
‎ 3.‎Global Satellite Systems ‎
‎ 4.‎Microwave Links ‎
‎2. Broadcasting ‎
‎ 1.‎AM radio, FM radio, VHF/UHF TV ‎
‎ 2.‎Satellite Links ‎
‎ 3.‎Direct Broadcasting ‎
‎3. Networking ‎
‎ 1.‎LAN
‎ 2.‎WiFi
‎ 3.‎WiMAX
‎ 4.‎LiFi ‎
‎4. Radar and Navigation ‎
‎ 1.‎Global Positioning System (GPS) ‎
‎ 2.‎Radar detection, tracking and imaging ‎
‎ 3.‎Radio Frequency Identification (RFID)‎

Q: Just what is a radio? ‎
A: A device that transfers information to a distant site, by means of unbounded ‎electromagnetic propagation. ‎

There are five main components of a transmitter: ‎
‎1) The signal a(t) – This is the information we are trying to transmit. It may be in either digital ‎or analog form. It also may have been encoded to remove redundancy, in a process ‎known as source coding. ‎
‎2) RF source – Generates electromagnetic energy at RF/microwave frequencies that are ‎suitable for electromagnetic propagation (subject to FCC restrictions !). ‎
‎3) Modulator – Places signal a(t) (i.e., the information) onto the RF signal, known as the ‎carrier. Accomplished by modulating some parameter of the carrier signal – e.g., ‎magnitude, phase, frequency, or some combination thereof. In general, this process is ‎called channel coding. Its goal is to maximize the rate at which information is sent, while ‎minimizing the effect of unknown channel parameters. ‎
‎4) Power Amplifier – Increases the power (i.e., energy flow) of the modulated carrier signal, ‎without (hopefully) distorting it. ‎
‎5) Antenna – Acts as the coupling mechanism between the bounded e.m. wave of a ‎transmission line and the unbounded propagating wave in space. Often, an antenna is ‎required to launch the unbounded wave in a specific direction.‎