The two major classes/types of microwave radiation used in communication systems are:
Microwave Frequency Bands: Microwaves used in communication systems are part of the electromagnetic spectrum and have frequencies ranging from approximately 300 MHz (megahertz) to 300 GHz (gigahertz). They are classified into different frequency bands, each with its specific characteristics and applications. The main microwave frequency bands used in communication systems are:
a. UHF (Ultra High Frequency): This band covers frequencies from 300 MHz to 3 GHz. UHF frequencies are commonly used for television broadcasting, satellite communication, GPS (Global Positioning System), and some wireless communication systems.
b. SHF (Super High Frequency): SHF ranges from 3 GHz to 30 GHz. This band is utilized in various applications, including satellite communication, point-to-point microwave links, radar systems, and some wireless communication technologies like Wi-Fi and Bluetooth.
c. EHF (Extremely High Frequency): EHF encompasses frequencies from 30 GHz to 300 GHz. It is commonly used in high-speed wireless data transmission, satellite communication, and advanced radar systems.
Microwave Propagation Modes: In communication systems, microwaves can be transmitted and received using different propagation modes, depending on the application and distance involved. The two main propagation modes are:
a. Line-of-Sight (LOS) Propagation: In LOS propagation, microwaves travel in a straight line from the transmitting antenna to the receiving antenna without encountering significant obstacles or reflections. This mode is commonly used for point-to-point communication links, where a direct line of sight is maintained between two communicating antennas. LOS propagation is essential for microwave communication in satellite links, microwave radio links, and some wireless backhaul connections.
b. Non-Line-of-Sight (NLOS) Propagation: NLOS propagation involves microwaves that can bend or scatter around obstacles, allowing communication to occur even without a direct line of sight. This mode is commonly used in urban environments and wireless communication systems like Wi-Fi and cellular networks, where buildings and other structures may obstruct the direct path between the transmitter and receiver.
Both microwave frequency bands and propagation modes play a crucial role in various communication systems, enabling high-speed data transmission, long-distance communication, and reliable connectivity for a wide range of applications.