Delta-sigma based digital transmitters with low-complexity embedded-FIR digital to RF mixing

The focus of this contribution is to review delta-sigma based all-digital transmitters and to discuss issues related to large out-of-band quantization noise and possible coexistence problems. Low-complexity embedded-FIR filters are very interesting to relax the filtering constraints while keeping systems as digital as possible to benefit from the advanced CMOS node integration. In this paper we propose a single-bit digital to RF mixer with embedded-FIR, which provides noise level reduction at specific frequencies in order to target multi-standard coexistence. This architecture introduces simple logic operating at low frequency which enables single-bit output and avoids the use of an additional delayed DAC, thus reducing considerably the power consumption and area of the output stage. Finally, we introduce an asymmetric unbalanced FIR architecture to provide a complementary solution for out-of-band noise reduction.