Patent ID: 7170929

Claim:
A signal processing unit, to which a demodulated signal and a correlation value signal from a digital signal receiver are supplied, said digital signal receiver receiving a digital signal from a digital transmitter, said digital signal including a plurality of signal units, each of said signal units having a guard interval to reduce multi-path effect, said digital signal receiver demodulating said digital signal and producing said correlation value signal from said demodulated signal, said signal processing unit comprising: a signal converter, coupled with said digital signal receiver, from which said correlation value signal is supplied, for generating at least a main wave signal level, a ghost imaging signal level corresponding to said correlation value signal, and a guard interval signal corresponding to a period of said guard interval; and a display, coupled with said signal converter, for displaying a main wave corresponding to said main wave signal level and a reflected wave corresponding to said ghost imaging signal level in each horizontal scanning period of said display, and for displaying whether said main wave and said reflected wave are placed within a period of said guard interval signal to indicate a transmission condition of said digital signal from the digital signal transmitter.