Null symbol detection device

摘要

In a null symbol detection device, at the time of receiving a terrestrial digital broadcast, a null symbol can be stably detected even under a fading environment. A synchronous addition buffer group is provided subsequent to an amplitude detector so as to synchronously add an OFDM signal at a null symbol repetition period. A moving average processing unit performs a moving average operation upon synchronous addition data with the number of samples corresponding to a null symbol to output a moving average value. A transmission mode determining unit detects the minimum value among the moving average values normalized in a correction processing unit and compares levels of the minimum values to determine a reception mode. A null position detector generates a synchronous pulse at a null position.