116. A 14-BAND INDUCTOR-LESS FREQUENCY SYNTHESIZER FOR MULTI-BAND OFDM UWB
Name: Mohammad Farazian
Grad Year: 2008
This poster presents a fully integrated 14 band frequency synthesizer for Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB which is implemented in a standard CMOS technology using a digital centric design methodology. In MB-OFDM UWB standard, the unlicensed band of 3.1GHz to 10.6GHz is divided into 14 sub bands of 528MHz. MB-OFDM UWB is a frequency hopping system and based on its requirements this synthesizer must be able to switch from one band to one another in less than 9.5ns. The most important bottle neck in implementing this frequency synthesizer is the required fast frequency switching time. Conventional approaches like using a single Phase Locked Loop (PLL) would require a very high reference frequency (in the range of several gigahertz) to meet this spec which is not practical. On the other hand using one PLL for each frequency band and switching by selection is not and efficient solution, if possible to implement. It will be a very costly approach and very hardware-inefficient. This method also suffers from undesired coupling between PLLs as well as frequency pulling because of having several Voltage Controlled Oscillators in one chip. Our approach is based on using just one on-chip Quadrature PLL and two levels of Single Side Band (SSB) mixing. In this method the PLL runs at 7.128GHz and all the required frequencies for mixers are generated from PLL output by using some integer and fractional frequency dividers. To make this synthesizer compatible with standard digital CMOS technology we are avoiding using any on-chip inductor. It will reduce the active chip area and the overall cost but will bring a lot of difficulties with spurs mitigation. In this research we are trying to suppress the spurs by Linearization of mixers and using Poly-Phase Filters. This synthesizer is implemented in CMOS 0.13um technology and generates all the required center frequencies and can frequency switch in less than 6 ns while consuming 150mW from a 1.2V supply.