Patent ID: 6304611
Filing Date: 2001-10-16
Classification: H04L

Abstract:
An orthogonal frequency division multiplex modulator of such a system as to add guard intervals to a temporal waveform generated by modulating an input data train into a large number of carriers, conducting quadrature modulation, and outputting an OFDM signal, said orthogonal frequency division multiplex modulator comprising:an IFFT circuit for conducting inverse fast Fourier transform processing to modulate said input data train into a large number of carriers;a guard interval adder for adding a guard interval to each effective symbol duration of a composite carrier signal supplied from said IFFT circuit and outputting a resultant signal;a control signal generator for generating, in synchronism with each guard interval of the composite carrier signal having the guard intervals added thereto from said guard interval adder, such a control signal as to attenuate signal amplitude of said composite carrier signal having the guard intervals over an interval substantially equal in length to said each guard interval; andan amplitude controller responsive to said control signal, to attenuate an amplitude of the composite carrier signal having the guard intervals supplied from said guard interval adder and output a resultant signal, only over an interval substantially equal in length to said each guard interval, said amplitude controller outputting, in remaining intervals, said composite carrier signal having the guard intervals supplied from said guard interval adder as it is.