A digitized group modulator using simple fractional sampling

This paper proposes a new digitized group modulator for radio base station transmitters. The group modulator can set the carrier spacing flexibly and features simple construction owing to the simple fractional sampling technique. A group modulator LSI was designed and built using 0.5-μm BiCMOS technology, and a π/4-shifted QPSK group modulator was constructed using this LSI. Experiments confirm the modulator generates multiple carriers simultaneously in a wide bandwidth without precise adjustment and there is little difference between each of the carriers in terms of BER performance