| 摘要 |
A received alternate pattern segment is demodulated by a DEM (13), and a power of a demodulated baseband signal is calculated by a power calculator (15). The calculated power is multiplied with a predetermined constant alpha by a constant multiplier (16). A power of a signal obtained by removing a frequency component (1/2) the baud rate frequency from the baseband signal output from a BEF (14) is calculated by a power calculator (15'). An adder/subtracter (17) compares the powers by subtracting the two signals, and the sign of the comparison result is discriminated by a sign discriminator (19), thereby detecting an alternate pattern segment and the start point of a pseudo pattern sequence. Furthermore, a count value of a counter (110) is monitored, and when a detection state of an alternate pattern segment continues for a predetermined period of time, it is determined that an alternate pattern segment is detected in practice. In the above arrangement, an alternate pattern signal can be reliably and precisely detected without causing an erroneous detection even when the level of a reception signal abruptly changes. Alternatively, a pseudo random sequence can be reliably and precisely detected without causing an erroneous detection even for a reception signal having a low S/N ratio.
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