(1) Using vestigial sideband amplitude modulation system: One of the most basic features of MMDS in technical multi-channel multi-point distribution system is the vestigial sideband amplitude modulation (VSB-AM) system that uses terrestrial television broadcasting, so down-conversion can be adopted. The cable is allocated to the household receiving mode and is viewed by the current home television receiver.
(2) Working in the 2.5GHz to 2.7GHz frequency band: The basic feature of MMDS is that it operates in the low frequency range of 2.5-2.7GHz, with small rain attenuation, direct propagation propagation properties of the microwave segment, and low diffraction capability. When the large area covers, the same frequency station spacing is allowed to be closer.
(3) Adjacent frequency multiplex transmission: Another basic feature of MMDS is a multi-channel television broadcasting service, which implements adjacent-channel multiplex transmission by wireless terrestrial transmission. Therefore, it is necessary to meet the deviation tolerance of the TV transmitter. The normal accuracy is lower than ±500Hz, and under the precision frequency control, I ±1Hz. The adjacent frequency application needs to meet the out-of-band spurious emission index of cable TV, and generally needs to meet -60dBc.