A programmable DSP front-end for all-digital 4G transmitters

This paper presents a digital interpolation chain for non-integer large-ratio sampling rate conversion, targeted to 4G applications. Such a system is needed in all-digital transmitters, where the sampling rate of the digital input to the RF front-end must be an exact submultiple of the carrier frequency. A highly flexible architecture is proposed to reduce system complexity when the RF requirements are more relaxed. The presented interpolation chain has been especially optimized by taking into account the requirements for LTE and LTE-A, but it can be used in multistandard applications as well. The system achieves excellent ACLR of 83 dB, EVM degradation of 0.03%, and RX-band noise below -160 dBc/Hz.