Patent ID: 7292669
Filing Date: 2007-11-06
Classification: H04H,H04L

Abstract:
1. A null symbol detection device used for receivers for a digital broadcasting system which repeatedly transmits a null symbol with smaller transmission power than those of other symbols during a fixed period, where at least one of a null symbol repetition period and a null symbol width is different depending on at least one transmission mode, and in which the longer said null symbol repetition period becomes, the wider said null symbol width becomes, said null symbol detection device comprising: an amplitude detector operable for detecting an envelope of at least one of an intermediate frequency signal and a baseband signal; a synchronous addition buffer group having a plurality of synchronous addition buffers for synchronously adding data obtained by sampling an output of said amplitude detector at a fixed sample period during said null symbol repetition period corresponding to said at least one of transmission modes to be received; a transmission mode determination processor operable for performing a moving average operation upon all synchronous addition data rows stored in said at least one of synchronous addition buffers of said synchronous addition buffer group, and for determining a transmission mode by detecting, with respect to a transmission mode to be received, a minimum value of the moving average operation and an address of said at least one of synchronous addition buffers providing the minimum value; and a null position detector operable for detecting, in accordance with a transmission mode determined in said transmission mode determination processor, a null symbol position from the address providing the minimum value of the moving average operation, and for generating a synchronous pulse at a start point of the null symbol position.