| Title |
A Study on RF Frequency Synthesizer for Narrow Band IoT |
| Authors |
김동식(Dong-Shik Kim) ; 채상훈(Sang-Hoon Chai) |
| DOI |
https://doi.org/10.5573/ieie.2019.56.1.48 |
| Keywords |
LoRaWAN ; Narrow band ; IoT ; Frequency synthesizer ; PLL ; Circuit design |
| Abstract |
This paper describes the implementation of a fractional N-PLL based RF frequency synthesizer which can be applied to the sensor node wireless communication part of the narrow band IoT system using 0.18 ㎛ silicon CMOS technology. A frequency synthesizer for LoRaWAN system with frequency range from 868.1MHz to 914.9MHz was designed to obtain 200KHz narrow channel spacing in Europe and the United States. In particular, to achieve good phase noise characteristics in the in-band, the charge pump current can be adjusted by 3-bit control. Phase noise was measured -56.21dBc/Hz to -72.24dBc/Hz at 1KHz offset frequency when the charge pump current varied from 0.05mA to 0.3mA. Experimental results show that the phase noise can be improved by increasing the charge pump current |