A 5 GHz direct digital synthesizer MMIC with direct modulation and spur randomization

This paper presents a low power, ultra high speed and high resolution SiGe DDS MMIC with 24-bit phase and 10-bit amplitude resolution. The DDS MMIC has the capabilities of direct frequency and phase modulations with 24 bit and 12 bit resolution, respectively. It is the first reported mm-wave DDS with direct digital frequency and phase modulation capabilities. Utilizing a 13-bit built-in ultra high speed pseudorandom binary sequence (PRBS) generator, the DDS MMIC can perform least significant bit (LSB) dithering for spur randomization.With more than twenty thousand transistors, the DDS MMIC includes a 24-bit ripple carry accumulator for phase accumulation, a 12-bit ripple carry adder for phase modulation, an LSB dithering block for spur randomization and a 10-bit segmented sine-weighted DAC for phase to amplitude mapping and digital to analog conversion. The DDS core occupies 3.0 times 2.5 mm² and consumes 4.7 W power under a single 3.3 V power supply. The Nyquist band SFDR is measured as 38 dBc with 469.360351 MHz output under 5.0 GHz maximum clock (FCW = 0 x 180800). With 1.246258914 GHz output frequency (FCW = 0x3FCFE7), the narrow band SFDR is measured as 82 dBc. The DDS MMIC is packaged and tested in LCC-68 cavity.