A study on 11 MHz ~ 1537 MHz DCO using tri-state inverter for DAB application

Digitally controlled oscillator (DCO) for digital audio broadcasting (DAB) is proposed using 0.18 ¿m CMOS process parameters with 1.8 V supply voltage. In this paper, the proposed DCO consist of tri-state inverter array and calibration block. Tri-state inverter array is 5-stage ring oscillator and each stage has 160 tri-state inverters. Calibration block is composed of 64 NMOS pass transistors and 64 metal-insulator-metal (MIM) capacitors with different values. The proposed DCO has the frequency tuning range from 10.5088 MHz to 1537.32 MHz by controlling 800 tri-state inverters. BAND-III (174.928 MHz~239.200 MHz) and L-BAND (1452.960 MHz~1492.624 MHz) are synthesized for DAB application. In order to synthesize channel frequency for DAB system, tri-state inverter array that adjusts frequency coarsely and calibration block that adjusts frequency finely have to work together and both of them are controlled by 6-bit digital word. So the proposed DCO could tune frequencies of 64 channels for DAB accurately. It has simulated phase noise of -114.93 dBc/Hz at 1 MHz offset and power consumption of 3.28 mW at 174.928 MHz. And it has simulated phase noise of -106.35 dBc/Hz at 1 MHz offset and power consumption of 25.77 mW at 1490.624 MHz.