Introduction

As the domestic mobile communication industry develops rapidly,the amount of mobile communications users increases so steadily that the cell planning gets smaller and smaller while the base station positions get lower and lower.On the other hand,as city construction develops,more and more high-rise buildings are set up constantly,based on the shadow effect of the radio propagation,the mobile communications may get a signal blind spot behind or between the buildings.Moreover,in order to avoid interference from adjacent districts,the main lobe of the antenna radiation orientation of the cell mobile communication base station in construction has a bigger down-tilt obliquity,thus the signals usually can not be received effectively in the high and medium parts of the high rise buildings.Furthermore.the mobile communication signals cannot be received in tunnels,subways,underground stores,entertainment complex,parking fields,hotels.office buildings and other large-size and closed buildings.

Signal amplifier is an effective device that makes up the insufficient base station coverage in the mobile network,enlarges the coverage area of the base station and fills in the blind spots,which adopts double-ended duplex design and external power supply  with advantages of convenient mounting and high reliability.The bandwidth of the signal amplifier may cover GSM 25MHz/19MHz/6MHz.CDMA 10MHz/DCS75 MHz with compatibility between digital system and analogue system.