Saman Mokhtabad
Marzieh Chaharboor - Graduate student of Electrical and Electronics Engineering, Hadaf University, Sari
Hojat Ghonoodi - PhD. Electrical and Electronics Engineering, NIT University, Babol

A Digitally Controlled Oscillator (DCO) which is presented in this paper is a main part of an All-Digital PLL because of their critical role in ADPLL foundation. Since some challenges are available such as quantization noise and the limitations in LC oscillators that they cause to dither the frequency control word make the DCO’s operation undesirable. But in the proposed method, problems removed due to high performance by the solution of employing a delta-sigma modulator and a Voltage Controlled Oscillator. The proposed idea focused on LC oscillator performance to reach the better structure of ADPLL using CMOS process. In this architecture, a modified delta sigma modulator and a custom voltage controlled LC oscillator topology is used. By using a 4th order of band pass delta-sigma modulator and PMOS LC Voltage Controlled Oscillator with good phase noise characteristic, the effects of noise on quantization decreased and the output signal improved respectively. The LC oscillator and delta-sigma modulator were implemented by using TSMC 0.18μm technology. As it can be seen, the employed oscillator causes to increase the ability of ADPLL’s operation. Improvement in output parameters is the key point of this paper. The simulation results confirm the proposed idea.

Digitally Controlled Oscillator (DCO), All-Digital PLL (ADPLL), Delta-Sigma Modulator, Voltage Controlled Oscillator (VCO), LC Oscillator, Band Pass Modulator, Complementary Metal Oxide Semiconductor (CMOS)