PURPOSE: A hub outdoor unit in an LMDS(Local Multipoint Distribution Service) system is provided to combine the up stream signals of different sector frequency bands into a single stream signal and to carry out amplification and down frequency processing, in an LMDS system that divides a cell into 4 sectors for the management of subscribers. CONSTITUTION: A hub outdoor unit is divided into a transmitting unit and a receiving unit. The transmitting unit is comprised of a BPF(Band Pass Filter)(500), a 4way divider(510), transmitting blocks(520-550) and antenna units(560-590). The BPF(500) passes a desired signal among down stream signals modulated and outputted from a head-end unit. The 4way divider(510) divides the down stream signal passed through the BPF(500) equally and transfers the divided signals to the transmitting blocks(520-550). Each transmitting block(520-550) carries out frequency conversion and amplification for each down stream signal divided and transferred by the 4way divider(510). The antenna units(550-590) send the amplified down stream signals to wireless sections. Each antenna unit(550-590) is composed of a transmitting antenna(563-593), an isolator(561) and a bi-directional coupler(562). The transmitting antenna(563-593) radiates each amplified down stream signal. The isolator(561) is to protect each transmitting antenna and transmitting block. The bi-directional coupler(562) detects a part of the down stream signal, when the signal is radiated, in order to check whether each transmitting block is operated normally.
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