46MHz,Tunable,Linear,8th Order Gm-C Bandpass Filter Design

In the past decade, As the wireless communication system and integrate circuit with CMOS technology rapidly develops, the fully integrated RF system on chip has become a hot research file. Filters are very important block for specified frequency of signals in wireless communication systems.In this thesis the design of a Linear tunable CMOS Gm-C eight-order bandpass filter for applications in wireless communication systems is presented. The work is part of a study aimed towards the implementation of an integrated single-chip wireless receiver. The designer use Gm-C architecture to realize the filter since it has good high frequency performance. The objective of this work is to design an integrated bandpass filter capable of operation in the intermediate-high frequency range with high linearity, tunable, low noise and high frequency selectivity.Transconductor(Gm) is the most main unit of the whole Gm-C filter. Four different types of transconductor are used to study and compare the linearity of them. They have some advantages but them have more or less disadvantages which are not suitable for the rule of system. So an improved source degeneration transconductor is presented in this thesis. Several resistance and current, which can be changed by controlling switch, are employed to accurately tune the value of transconductor in large range. Four biquads bandpass filter based on new tunable integrators and capacitances was built. In order to satisfy the stringent selectivity requirements in wireless receiver system, the realization of the8th bandpass filter can be achieved by cascading4biquad stages, in this thesis.All circuit and layout are realized by TSMC0.18μm process. Simulation results of the filter by Cadence Hspice and SpectreRF are the center frequency of46MHz,-3dB bandwidth of24MHz, S-20dB of2.35,-22.18dBm of1dB compression point, a frequency tuning range from35MHz to73MHz and O tuning range of1.79to1.92. The simulation results reach the design target.The whole wireless receiver is fabricated in0.18μm process. The filter is measured in the receiver channel. By the Signal Spectrum curve after AGC (Automatic Gain Control amplifier), the center frequency and-3dB bandwidth are47MHz and24MHz which almost are same as the results of simulation.