| 摘要 |
PROBLEM TO BE SOLVED: To detect received signal strength over a wide dynamic range with good linearlity. SOLUTION: Through a signal branching circuit 3, high frequency signal (a) having passed through an antenna 1 and a filter part 2 is branched into high-frequency signals b1, b2, and b3 which have levels suppressed in a plurality of stages. A switch 4 selects one of the high frequency signals b1, b2, and b3 and the selected high frequency signal (d) is amplified by an amplification part 5; and a reception part 6 measures the level of this amplified high frequency signal (e) to generate an RSSI voltage (f). A switching control part 7 generates a control signal (g) for making the switch 4 select the high frequency signal (b) which is one stage lower in level when detecting an excessively high RSSI voltage (f) and also generates a control signal (g) for making the switch select the high-frequency signal (b) which is one stage higher in level when detecting an excessively low RSSI voltage (f). An electric field intensity detection part 8 adds voltages corresponding to the RSSI voltage (f) and control signal (g) to generate an accurate RSSI voltage (h) with good linearlity. |
