Detection of Undesired Carriers in OFDM by the use of FFT output signal before equalization

Abstract

One of the factors which degrade the receiving margin of digital terrestrial broadcasting, is disturbances which exist in the same channel. They can be easily detected, if they are large enough to be visible from OFDM waveform when they are observed with a spectrum analyzer. However, as for the disturbances which are totally invisible, it is difficult to detect their existence, or get hold of their D / U ratio, unless OFDM radiation is cut out.. Then, we have devised a technique by which we can presume the frequency of the disturbances and their D / U ratio by utilizing FFT output signal from a digital-broadcasting receiver before equalization. Furthermore, we have implemented this technique and also have conducted its operational test.