| 摘要 |
A method of, and terminal for, detecting the presence of a 2-FSK signal, the method comprising receiving (10) a 2-FSK signal, quadrature frequency down-converting (34, 35, 36) the received signal to produce quadrature related outputs, oversampling (42, 43) the quadrature related outputs to produce digital samples, differentially decoding (44) the digital samples to produce real and imaginary components, integrating (56, 58) the imaginary components and comparing (26) the integrated value with a fixed threshold value (24) and determining a signal to be present if the threshold is exceeded.
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