Direct Digital Synthesizer With Sine-Weighted DAC at 32-GHz Clock Frequency in InP DHBT Technology

A direct digital synthesizer (DDS) implemented in InP double heterojunction bipolar transistor (DHBT) technology is reported. This DDS uses a sine-weighted digital to analog converter (DAC) architecture that eliminates the need for a ROM. This enables operation at high frequencies with lower power consumption compared to traditional approaches. The phase accumulator is 8-bits wide and the sine-weighted DAC uses the five most significant bits (MSBs) for phase to amplitude conversion. The DDS operates up to a 32-GHz clock frequency for all frequency control words (FCWs) and can synthesize sine-wave outputs from 125 MHz to 16GHz in 125-MHz steps. The spurious free dynamic range (SFDR) is measured over the Nyquist bandwidth to be 31.00 dBc for the fundamental output frequency of 125 MHz. Over the full range of FCWs, the worst case SFDR is 21.56 dBc at an FCW of 95, and the average SFDR is 26.95 dBc. The circuit is implemented with 1891 transistors and consumes 9.45 W of power.