The Principle Of Transmission Of MMDS System

- Apr 05, 2019-

The transmission line between the transmitter and channel synthesizer of the MMDS system should be as short as possible, and the channel synthesizer waveguide output port should be at least 0.6 m from the wall. In order to protect the normal operation of the transmitter system (especially high-power transmitters), the ventilation and room temperature conditions in the equipment room should be guaranteed. The temperature of the equipment room should be between 0 and 45 °C. It is best to use air conditioning equipment to maintain the ideal temperature in the equipment room at +20 ° C ~ +27 ° C. Because the size of the channel synthesizer and the waveguide component directly affects the transmission frequency stability and the reliability of the transmitter. Overheating inside the transmitter will automatically protect and temporarily stop until the temperature recovers. In addition, low temperatures can cause condensation inside the equipment, which can affect electrical performance. In addition, the house and antenna tower of the MMDS system should be as close as possible. The MMDS room should be placed on the roof to shorten the length of the feeder; there should be fewer turns and a feeder frame. The machine room of the MMDS system should be sealed to the outdoor trenches, holes and walls, to prevent rain, wind, snow, frost and fog from entering the system room.

Considering the influence of the surrounding trees in the winter installation, the signal level is adjusted higher, leaving a margin because the signal level is weaker due to forest trees in summer. The output of the downconverter of the MMDS system can receive individual signals and can also be collectively received into the CATV (cable TV) distribution network; if the signals are to be collectively received, some systems directly enter the CATV distribution network, and some systems receive in the MMDS. After that, the local satellite receiving signal and the terrestrial television broadcasting signal are mixed into the distribution network in the CATV sub-front end. In addition, when mixing and receiving signals, we must pay attention to the problem of channel allocation, crosstalk, level equalization and so on.