A 12-b 16-GS/s RF-Sampling Capacitive DAC for Multi-Band Soft Radio Base-Station Applications With On-Chip Transmission-Line Matching Network in 16-nm FinFET

A 16-GS/s single 1.2-V supply direct RF-sampling capacitive D/A converter for soft radio base-station applications is implemented in a 16-nm FinFET technology. Due to co-integration with a wideband on-chip matching network, the D/A converter (DAC) is capable of signal synthesis between 600 MHz and 8 GHz, with a measured peak RF output power of +5.6 dBm. The linearity required by cellular base-station applications is achieved by employing several analog-domain linearization techniques, yielding a two-tone intermodulation distortion of better than -70 dBc up to the first Nyquist frequency. When transmitting a true multiband signal covering an instantaneous bandwidth of 1 GHz, an adjacent channel leakage ratio (ACLR) of better than -69 dBc is achieved. Digital segment mismatch correction is shown to improve the linearity of a segmented DAC in deep digital backoff operation. A full-rate digital pre-distortion (DPD) method with efficient model identification is experimentally demonstrated. Using DPD, the design achieves an spurious free dynamic range (SFDR) of better than 72 dBc over the entire 0.6-6-GHz frequency range.