Radio Communication

Propagation of Radio waves

Here we only look at the simple architecture of the radio system, a system for radio communication. The block diagram of the radio system is shown on Picture 1. As we can see from the picture, we have starting point for the signal (from its source) to the end of the radio link where this signal is received. So, the first part of the radio system is the source of signals (information). The source of signals can be anything, for example, a radio station. These primary signals are proceeded in the Radio-transmitter. Radio transmitter should process these signals in order to send them in the air (wireless) through its antenna. That means that transmitter should amplify the signal level (if needed), do the radio modulation of the signal - so the signal can be easily send in the air, and if there is need for protection of the information, it can also encrypt the signal with some pre-defined code, which is known only at the other side where this signal should be received.

After the signal is prepared for transmission, it travel through the air as EM (electro-magnetic) wave. Here we will not discuss about the propagation of the EM waves. The EM wave is exposed to disturbances in the point where it is generated (in the transmitter), all the way it travels (in the propagation environment) and in the point where it is received (in the receiver). The frequency carrier on which the modulated radio signal is transmitted is actually the transmission channel. The amount of disturbances and other critical parameters of transmission depends on the used frequency channel.

The radio receiver received the EM waves emitted from the the transmitter through its receiver antenna. This received signal is amplified, demodulated and decoded if it was previously coded, so it returns to its primary form as it was generated in the source, and finally it's send to the device for reproduction. So, on this way, the information is send through the air from point A (the transmitter) to point B (the receiver), and we can say that there is a radio communication between points A and B, which can be a miles away one from another, and the signals are send wireless (no need of cables) through the air.

Picture 1: Block diagram of radio system (propagation of radio waves)