Transmitting equipment MMDS MultiSegment
Transmitting equipment MultiSegment is intended for organisation of wireless broadcasting networks MMDS in a frequency band 2,0 … 3,0 GHz with service area 5...50 km by transmission 24 analog or more quantity of digital television channels, fig.1
Fig.1 MMDS MultiSegment headend transmitting equipment
The construction of transmitter represents by itself a lot connected original engineering solutions, based on general idea - joining of up convertor, amplifier and transmitting antenna in the uniform device.
As a source of a multichannel television signal can to be used the group signal from an output of any communication station of cable TV in UHF range and level 85....91 dBµV.
Main components of transmitting station are: The integrated transmitting unit (ITU) MultiSegment
The integrated transmitting unit MultiSegment converts an input multichannel group television signal of ultra high frequency to a radio-frequency signal 2 … 3 GHz, amplify it and broadcast in the air. Thus, ITU is placed on tubular derrick, but crossover - directly near communication station.
The amplifier ITU is constructed on modularity and has a very high linearity, that contributes for widening of service area and reduction of distortions of intermodulation signal.
The antenna ITU is manufactured as cylindrical phased array and is directly connected with amplifying modules. Thus the power losses in an output path of amplifying modules do not exceed 5 %. In normal arrangement of a transmitting station these losses can up 30 % because of mismatching and losses in a feeder line.
The Crossover is necessary for joining of a multichannel television signal of communication station with signals of control and diagnostics, and providing of a distant supply of ITU MultiSegment.
Such off-gauge approach to construction of transmission systems is basically new in well-known practice, allows getting high technical exploitation factor and gives a series of distinguish advantages of a system in general:
- Allows to refuse of usage expensive cable or waveguide feeder, to improve mobility of all system.
- Removes limits on an admissible altitude suspension of transmitter, that widening radius of a service area.
- Gives possibility to change in a wide range radiation pattern of the antenna, operatively to configurates a service area, depending on concrete conditions and wishes of the customer.
- Improves reliability and vitality of a system MMDS in general by modular design of ITU.
- Allows to realize free choice of a type of communication station type for usage in a system MMDS.