74-dBc SFDR 71-MHz Four-Stage Pipeline ROM-Less DDFS Using Factorized Second-Order Parabolic Equations

In this brief, a four-stage pipeline read only memory (ROM)less direct digital frequency synthesizer (DDFS) with equal division interpolation is proposed. To attain higher spurious-free dynamic range (SFDR) and faster clock rate, the hardware cost and delay using different segments with various interpolation equations are analyzed systematically to explore the optimal solution. The second-order parabolic equations with proper coefficients and factorized operation orders based on optimized hardware cost and delay are finally utilized to enhance SFDR. The proposed design is demonstrated by the physical implementation using the TSMC 0.18-μm CMOS technology cell library and on-silicon measurements, where the maximum SFDR is 74 dBc, 0.018-mW/MHz power dissipation, and the maximal clock frequency is 71.9 MHz.