A configurable sampling rate converter for all-digital 4G transmitters

This paper presents a digital interpolation chain for non-integer variable-ratio sampling rate conversion, targeted to 4G mobile 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 integer fraction of the carrier frequency. A highly configurable architecture is proposed to cope with the flexibility needed in 4G applications. The system achieves excellent ACLR of 75 dB, EVM degradation of 0.05%, and RX-band noise below −160 dBc/Hz. Digital synthesis of the circuit in a 40nm low-power CMOS process results in a core area of only 0.073 mm
²
. The estimated power consumption is between 6 and 29 mW, depending on channel bandwidth and transmission band.