Digitally Controlled Oscillator Design with Variable Capacitance XNOR Gate.

Digitally Controlled Oscillator (DCO) designs using three transistors XNOR gates as variable capacitance load are presented in this study. Two different design approaches for five- and seven-stage DCOs were reported. Output frequencies were controlled digitally with digital bits applied to delay cells. Five-bit controlled DCO using delay cell-I showed frequency and power variation of 1.5335-2.0526 GHz and 2.5906-2.4271 mW, respectively, by varying control word 00000-11111. Moreover, seven-bit controlled DCO showed frequency and power consumption variation of 1.0890-1.4764 GHz and 3.6268-3.3979 mW, respectively, with varying control word 0000000-1111111. Further, five-bit controlled DCO with delay cell-II showed frequency and power variation of 0.77891-1.3840 GHz and 6.5225-6.0320 mW, respectively, with control word variations 00000-11111. Seven-bit DCO showed frequency of 0.58322-1.0431GHz and power consumption of 9.006-8.3199 mW with control word variation 0000000-1111111. Power consumption, output frequency and Figure of Merit (FoM) of proposed circuits were compared with earlier reported circuits and the present approaches showed significant improvements. [ABSTRACT FROM AUTHOR]