Abstract: A digital broadcast transmitting device and an exciter have an AGC function. In a level adjusting unit which receives an input of a baseband digital signal from a modulation processing unit, a comparator generates an error signal from a difference between a level signal obtained by digitizing a feedback signal from a power amplifier by A/D converter and a reference voltage generated by a reference generating unit, and an AGC multiplier/divider carries out digital multiplying/dividing coefficient to the baseband digital signal with or by a gain coefficient such that the error signal becomes 0. Thereby, AGC which controls transmission output from the power amplifier at a fixed level is carried out.

Abstract: According to an embodiment, a digital broadcast transmitting device and an exciter have an AGC function. In a level adjusting unit which receives an input of a baseband digital signal from a modulation processing unit, a comparator generates an error signal from a difference between a level signal obtained by digitizing a feedback signal from a power amplifier by A/D converter and a reference voltage generated by a reference generating unit, and an AGC multiplier/divider carries out digital multiplying/dividing coefficient to the baseband digital signal with or by a gain coefficient such that the error signal becomes 0. Thereby, AGC which controls transmission output from the power amplifier at a fixed level is carried out.

Abstract: A vestigial sideband (VSB) modulation apparatus includes a signal processing unit which extracts an I-axis data signal component and a Q-axis data signal component from a baseband signal with symbol data superimposed thereon, a band-limiting filter which frequency-shifts the I-axis data signal component and the Q-axis data signal component, extracted by the signal processing unit, by only a specific frequency smaller than a rate of the symbol data and limits a passband width by a frequency width smaller than the rate of the symbol data, and a quadrature modulating unit which obtains a VSB modulation signal by quadrature-modulating the I-axis data signal component and the Q-axis data signal component output from the band-limiting filter.

Abstract: A vestigial sideband (VSB) modulation apparatus includes a signal processing unit which extracts an I-axis data signal component and a Q-axis data signal component from a baseband signal with symbol data superimposed thereon, a band-limiting filter which frequency-shifts the I-axis data signal component and the Q-axis data signal component, extracted by the signal processing unit, by only a specific frequency smaller than a rate of the symbol data and limits a passband width by a frequency width smaller than the rate of the symbol data, and a quadrature modulating unit which obtains a VSB modulation signal by quadrature-modulating the I-axis data signal component and the Q-axis data signal component output from the band-limiting filter.