Low-complexity digital bandwidth-configurable modulator

Bandwidth configurable modulators are required in some applications, where the systems with same modulation techniques offer multiple channel-bandwidth options. In this paper, we propose a low-complexity digital bandwidth-configurable modulator (D-BCM) based on a configurable rate conversion module at digital baseband, followed by traditional DAC and RF modules. And the configurable rate conversion module works at multiple input sampling rates and fixed output sampling rate. The ideas behind the D-BCM are: bandwidth-configurable capability is equivalent to multiple rate conversion capability; an Image-Rejection filter is required for each baseband rate conversion; the filter requirements can be reduced after pulse-shaping at up-sampling rate, and one Image-Rejection filter can fulfill the requirements of multiple rate conversions subject to some constraints. The concrete scheme of the novel D-BCM is introduced and the system is verified with the emphasis on the design of configurable rate conversion module at digital baseband.