Research And Design Of Adjustable Bandwidth Low Power Ultra - Bandwidth Gm - C Low Pass Filter

Filter is the most important block and plays a key role in signal processing. With the development of integrated circuit and telecommunication technologies, the design of full-integrated active filters has become one of the most important advances in analog VLSI and has attracted increasing attention of academia. Especially in recent years, the development of System-on-a-Chip has demanded urgently that the problem of full-integration of the active filters is going to be solved. As of today, the highest cut-off frequency low-pass continuous-time analog filters are in the frequency band of1to3GHz, targeting applications like UWB communications or hard disk drives. This thesis demonstrates an active low-pass filter tunable from30MHz to3GHz in0.13um CMOS.Firstly, this dissertation analyses different structures of filters and selects the fastest Gm-C structure as the basic structure. Secondly, after analysing different types of Gm unit, a modified Nauta’s trans-conductor was utilized as the OTA of the filter. Finally, a fourth-order29MHz-3.1GHz Gm-C low-pass filter with a unique auto tuning system is presented. By making parts of Gm units share the common-mode biasing circuit, about30%of power consumption was saved in the circuit. What’s more, to save the most power consumption at low frequency, Gm units are designed to be2stages adjustable. After analysis of limiting factors in the high frequency, the control voltage of MOS switch was improved. At last, the layout was accomplished with the reference of RF layout design rules.The filter is implemented in SMIC0.13um CMOS process and1.2V power supply is adopted, the active area of the chip is0.04mm2Simulation results show that the cut-off frequency of the filter can be tuned between29MHz-3.1GHz with64grades. From29MHz to610MHz, power consumption is3.36mW, SFDR reaches more than51.5dB, IIP3is19dBm. From610MHz to3.1GHz, power consumption is18.37mW, SFDR reaches more than56.5dB, IIP3is17.2dBm. The best advantage of the filter is that it realizes the ultra band-width, low power consumption and small area without reducing other performance.