A 2.4-GHz Digitally Controlled Oscillator with Capacitance Mismatch Calibration

• Main Authors: Wu, Dai-Ying, 吳岱穎
• Other Authors: Hsieh, Chih-Cheng
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/49004942851767328791

碩士 === 國立清華大學 === 電機工程學系 === 98 === Abstract In this thesis, a digitally controlled oscillator (DCO) designed for 2.4 GHz Industrial, Science, and Medical band (ISM-band) application is proposed. As the non-ideal effects due to process, supply voltage and temperature (PVT) variations, the DCO is not ideally controlled. This makes DCO open-loop operation unsuitable for most applications. By applying capacitance mismatch calibration, it is possible to accurately control the DCO frequency. Therefore, the above limit no longer exists. The proposed design consists of a digital controlled oscillator (DCO), a ripple counter, a mismatch calculator and a calibrated code generator. By adopting switched-capacitor arrays as varactor, the DCO oscillation frequency is stable and robust against analog noise. The counter estimates this oscillation frequency and feedback it to the mismatch calculator to find the capacitance variation. After variation values are obtained, the calibrated code generator could transfer the desired oscillation frequency into a best-fitted DCO control code. This design is implemented in TSMC 0.18 μm 1P6M CMOS process and the chip area is 1 × 1 mm2. According to the measurement results, the oscillating frequency is 2.28 ~ 2.42 GHz with total 140 MHz tuning range. The phase noise at 500-kHz frequency offset is less than -101 dBc/Hz. The frequency resolution is about 7 bits and the total power consumption is about 13 mW from an 1.8-V power supply.