Research On Deep Submicron CMOS RF Bandpass Filtering Technique Based On Switched-capacitor

With the evolving standards of wireless communications,the number of the subscribers are increasing dramatically.We do need transceiver schemes of low cost and high flexibility,under the urgent requirement that the standalone wireless communication device could accommodate different bands and standards as many as possible.Nowadays,the available multi-band transceiver schemes almost adopt multiple off-chip surface acoustic wave?SAW?filters of different center frequencies,which are chosen by switches.However,these kinds of schemes suffer from commercial limitation due to the cost,the weight,and the volume of the devices.There are some integrated RF bandpass filters?BPF?,for example,Q-enhanced LC BPF,Gm-C BPF,and micro mechanical BPF.However,due to the intrinsic disadvantages,the mentioned integrated BPFs can not achieve good enough performance to meet the tough requirements of multi-band multi-mode communications.Through theoretical analysis and experiment,this thesis researches highly integrated RF BPF,which is based on the switched-capacitor technique.The research is conducted with emphases placed on the key specifications of the filter,for example,center frequency,tuning flexibility,passband gain,noise performance,stopband rejection,and linearity.Aiming at the deep submicron complementary metal oxide semiconductor?CMOS?process,we propose architecturally innovative schemes.The main contributions of this thesis are briefly stated below:On the basis of comparing three kinds of analysis methods of linear periodically time-varying?LPTV?circuits and systems,this author derives the system transfer functions of multi switched-capacitor N-path filter by frequency-domain current division method,supporting the modeling of high-order N-path filter.And the author also derives that of the N-path filter with common memory effect components by the matrix form of state-space method,filling the gap of accurate derivation of this kind of filter.The thesis proposes a new structure that equips the conventional N-path filter with a passive LCR network.As is well known,conventional N-path filter does not meet the condition of input impedance matching.And it suffers from insertion loss even in the filter's passband.The stopband rejection is also limited by the nonzero on-resistance of the switches.The passive LCR network is used to make impedances matched,to boost the passband voltage gain and to improve the stopband rejection performance,without penalty on linearity.The thesis also proposes the Active-RC upconverted high order N-path filtering technique to deal with the close-in interferences and to improve the passband gain and noise performance.Taking the advantage of the superior high frequency performance of the deep submicron CMOS process,one could design wideband active amplifier with limited voltage gain.With the switched-capacitor bank being a feedback element of the inverting amplifier,the needed capacitors could be smaller for the same bandwidth thanks to the miller effect.The miller effect also relaxes the limitation of the filter's stopband rejection caused by the nonzero on-resistance of the switches.Finally,high order bandpass filter with improved passband gain flatness could be realized by placing cascaded filters in a global feedback loop.A prototype of 4-path filter is implemented in 65nm CMOS process.The filter is armed with a capacitor and a resistor,both of which are on-chip for impedance matching.And the matching inductor is off-chip.It has been demonstrated by measurement that in 1GHz center frequency mode,the LCR matching network does make the impedances matched,raise both the passband voltage gain and the ultimate rejection?Ult.Rej.?by 5dB.And the immunity to harmonic aliasing effect is improved by 3dB at least.Besides,a prototype of the Active-RC upconverted 4^th-order 4-path filter is implemented in 65nm CMOS process.The high order bandpass filtering function and frequency tunability have been demonstrated by measurement results.The detailed performances are listed below:the filter works at 1.2V supply voltage,consuming 20 to 30mW depending on the center frequency,which is tunable from 1 to2.2GHz.The voltage gain is 24 to 16dB with 13±2MHz 3dB bandwidth.The noise figure is7.7 to 9.8dB.In 1.6GHz center frequency mode,the filter achieves in-band/out-of-band input referred third order intercept point?IB/OOB-IIP3?of-19/+13dBm,and input referred 1dB compression point due to OOB blocker?B1dB_CP?of-8dBm.And the Ult.Rej.of the filter is 57dB.