| 摘要 |
PURPOSE: An apparatus for automatically controlling forward and backward attenuations of a radio frequency(RF) repeater is provided to automatically control output values of a forward attenuator and a backward attenuator according to strength and weakness of an inputted signal, so as to obtain an optimum noise figure and an inter-modulation distortion(IMD) value. CONSTITUTION: A signal strength sensor(10) is connected to an output side of a radio frequency(RF) amplifier(20a). An analog to digital(A/D) converter(10a) converts an output of the signal strength sensor(10) into a digital value. A CPU(12a) processes a signal strength value inputted from the A/D converter(10a), and controls a forward attenuator(13) and a backward attenuator(13a). If the strength of an input signal of the RF amplifier(20a) is not bigger than an input permissible threshold value of the RF amplifier(20a), an attenuation value of the forward attenuator(13) is set up as '0' to minimize a noise figure. An attenuation value of the backward attenuator(13a) sets up an amplification degree, to appropriately output signals of an RF repeater(16). If the strength of the input signal is bigger than the threshold value, the attenuation value of the forward attenuator(13) gets bigger as the input signal strength gets bigger. The attenuation value of the backward attenuator(13a) gets smaller as the input signal strength gets bigger, to increase inter-modulation distortion(IMD) characteristics of the RF repeater(16). An output of the RF repeater(16) is regularly maintained by a sum of the attenuation values of the forward/the backward attenuators(13,13a), under control of the CPU(12a).
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