| 摘要 |
PROBLEM TO BE SOLVED: To obtain an FSK demodulator with a high dynamic range in which the presence of a signal is detected even under a lower reception electric field strength. SOLUTION: The demodulator is provided with a 1st filter 21 to pass through only a prescribed frequency component from a radio signal to extract a data signal, a 2nd filter 22 to pass through only a prescribed frequency component from the radio signal to extract a preamble signal, a signal presence detection means 50 to detect the preamble signal included in the radio signal to detect the presence of the data signal, a data extract means 40 to extract data from the radio signal, and changeover means 30, 31 receiving a switching control signal from the signal presence detection means 50 to select the 1st and 2nd filters 21, 22. |
