Patent ID: 7873123
Filing Date: 2011-01-18
Classification: H01Q

Abstract:
1. A null detector, comprising: a power detector for outputting a power level signal according to the power level of a received signal; a smoother coupled to the power detector for determining according to the power level signal whether the received signal is transmitting a null symbol, the smoother outputting a null detection signal at a first state value or a second state value indicating the result of the determination; and an overlapper coupled to the smoother for providing the duration and position of the null symbols transmitted by the received signal according to the null detection signal wherein the smoother comprises a plurality of stages, the first stage is coupled to the power detector for receiving the power level signal, each of the other stages is coupled to the previous stage for receiving the output of the previous stage, the last stage is coupled to the overlapper for outputting the null detection signal, and each of the stages comprises a calculator for receiving the input of the stage and providing a calculated signal proportional to a sum of a first predetermined number of consecutive values of the input of the stage; and a comparator coupled to the calculator for comparing the calculated signal and a first threshold value, outputting the first state value if the calculated signal is greater than the first threshold value, and outputting the second state value if the calculated signal is lesser than the first threshold value, wherein the output of the comparator is provided as the output of the stage.