| 摘要 |
PURPOSE: A duplication low noise amplifier of a receiver front end unit is provided to minimize an abnormal state in a receiving path by using a redundancy low noise amplifier. CONSTITUTION: A filter unit A(30) and a filter unit B(40) are formed with directional couplers(31,41) for transmitting a received signal from antennas(1,2) to a rear end and band pass filters(32,42) for restricting bands of the remaining signals excepting desired signals, respectively. The first and the second low noise amplifiers(61,62) remove noises of output signals of the filter unit A(30) and the filter unit B(40), amplifies the output signals, and outputs an alarm signal. A redundancy low noise amplifier(63) is used when one of the first and the second low noise amplifiers(61,62) is in an abnormal state. An RF control portion(70) outputs a command for switching an inferior low noise amplifier to a normal low noise amplifier when the first, the second, and the redundancy low noise amplifiers(61,62,63) is in the abnormal state. A switch unit(50) performs a path switching operation among the filter units A,B(30,40) and the first, the second, and the redundancy low noise amplifiers(61,62,63). In addition, the switch unit(50) performs the path switching operation among the first, the second, and the redundancy low noise amplifiers(61,62,63) and a frequency down conversion portion.
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