Patent ID: 6556815
Filing Date: 2003-04-29
Classification: H04B

Abstract:
A transmitting circuit comprising:a power amplifier; a directional coupler provided between the power amplifier and an antenna to detect reflected wave reflected from the antenna side onto the power amplifier; a detector circuit for detecting a reflected wave taken out of the directional coupler; and a comparator for inputting thereto voltage detected by the detector circuit and a predetermined reference voltage and outputting voltage at a low level or at a high level, wherein the transmitting circuit is provided with a microcomputer for storing information on rating of the power amplifier and information on transmission power level, wherein the information on rating of the power amplifier and the information on the power level is utilized to calculate the predetermined reference voltage and output the predetermined reference voltage at the low level or at the high level to the comparator, wherein the comparator outputs the predetermined reference voltage, wherein the predetermined reference voltage is set as voltage corresponding to an allowable level of the reflected wave by which the power amplifier is not damaged; and wherein, when the level of the reflected wave exceeds the predetermined reference voltage, supply of power supply voltage to be applied to the power amplifier is cut off.