| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that a radio apparatus goes into a transmission mode and continues until a protector circuit functions after starting transmission operation even in an open state with no load connected to antenna terminals or a shorted state due to antenna failures, etc., so that there is possibility of damaging transmitter circuits or duplexer circuits. SOLUTION: A DC voltage is applied via a resistor to an antenna terminal line in the radio apparatus. A voltage divided by a resistance component of an external antenna connected to an antenna terminal is extracted and detected via a choke coil having no influence on high-frequency components and inputted to a microcomputer to block the transmission from startup if the resistance component connected to the antenna has a value corresponding to an open or shorted state. COPYRIGHT: (C)2003,JPO
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