There is provided a multi-mode communication
system which is operable according to different operating
modes, such as
GSM and WCDMA. The multi-mode communication
system includes first and second switching units, a
delta-sigma modulator, an analog-to-
digital converter, sequential
convolution units and a selection unit. The
delta-sigma modulator samples an
analog signal, which is inputted through the first switching unit in one mode, into 1-bit
digital signal. In another mode, the analog-to-
digital converter samples an
analog signal, which is inputted through the first switching unit into an n-bit
digital signal. The sequential
convolution units multiply filter factors with the output of the
delta-sigma modulator, which is inputted through the second switching unit at the first mode, and multiply PN codes by the output of the analog-to-
digital converter, which is inputted through the second switching unit at the second mode, to generate WCDMA output waveforms. The selection unit delays the outputs of the sequential
convolution units by a predetermined time at the
GSM mode to restore
GSM output waveforms. Accordingly, the multi-mode communication
system is operable according to multimodes, such as GSM mode and WCDMA mode.