Signal booster 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/19 MHz/ 6MHz, CDMA10MHz/DCS75MHz with compatibility between digital system and analogue system.