Digital Microwave can be classified as follow;
Trunk Microwave Communication Equipments
Trunk microwave equipment means that all the units including RF, IF, signal processing and multiplexing/demultiplexing are placed indoors and only the antenna feeder system is outdoor. The indoor part and the outdoor part are connected by a waveguide tube.
The structure of trunk microwave equipment.
- Branch RF Unit (BRU), which completes the function of combining and splitting RF signals
- Main Signal Transmission Unit (MSTU), which completes signal sending, receiving and modulation/demodulation, SDH electrical signal access and lossless switching
- Supervision, Control and Switching Unit (SCSU), which supervises and controls the entire system
- Baseband Interface Unit (BBIU), which implements the access of STM-1 optical signals and C3 PDH signals
Trunk microwave equipment features high cost, large transmission capacity and more stable performance.
It is suitable for long-haul transmission and trunk transmission.
All Outdoor Microwave Equipment
The equipment is consisted of four parts;
- Outdoor part including the antenna and RF processing unit. The antenna completes directional transmitting and convergence receiving of RF signals and enlarges the transmission distance. The RF processing unit transmits and receives RF signals and converts RF signals into IF signals.
- Intermediate frequency (IF) cable, which connects the RF processing unit with the IF and baseband processes unit and supplies power to the RF processing unit.
- IF and baseband processing unit, which processes IF and baseband signals.
- Service and power cable, which completes service access and supplies power to the whole equipment.
The installation is easy and the equipment room is saved, but transmission capacity is generally small.
Split-Mount Microwave Equipment
The equipment is composed of four parts;
- Antenna; Focuses the RF signals transmitted by ODUs and increases the signal gain
- Outdoor Unit (ODU); RF processing to realize IF/RF conversion of signals
- IF cable; Transmits IF signals and IDU/ODU communication signals and also supplies power to ODUs
- Indoor Unit (IDU); Performs access, grooming, multiplexing/demultiplexing and modulation/demodulation of services.
The ODU can either be directly mounted onto the antenna or connected to the antenna through a short soft waveguide to avoid feeder loss.
The split-mount microwave equipment generally used in small capacity, easy installation and maintenance, and fast network construction. It is currently the most widely applied microwave equipment
IDU is generally installed in a cabinet. Outdoor installation includes installing the antenna and ODU. There are two types, each having two methods.
- One ODU using one antenna
- Directly mounted to the antenna.
- Separately mounted to the antenna using a soft flexible wave guide
- Two ODUs sharing one antenna – For protection of link
- Directly mounted to the antenna.
- Separately mounted to the antenna using a soft flexible wave guide
In this configuration antenna is coupled to the two ODUs using a Hybrid Coupler. The Hybrid Coupler is a passive device used in radio and telecommunications. It is a type of directional coupler where the input power is equally divided between two output ports.
In Direct mounting method avoid the loss caused by the soft waveguide. Separately Mounted method is used when there is little installation space on the tower.
