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An eighth order channel selection filter for low-IF and zero-IF DVB tuner applications

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Journal of Semiconductors 2009年第11期30卷 79-87页

作者：邹亮廖友春唐长文 ASIC & System State Key Laboratory Fudan University Ratio Microelectronics Technology Co Ltd

An eighth order active-rc filter for low-IF and zero-IF DVB tuner applications is presented, which is implemented in Butterworth biquad structure. An automatic frequency tuning circuit is introduced to compensate the cut-off frequency variation using a 6-bit switched-capacitor array. Switched-resistor arrays are adopted to cover different cut-off frequencies in low-IF and zero-IF modes. Measurement results show that precise cut-off frequencies at 2.5, 3, 3.5 and 4 MHz in zero-IF mode, 5, 6, 7 and 8 MHz in low-IF mode can be achieved, 60 dB frequency attenuation can be obtained at 20 MHz, and the in-band group delay agrees well with the simulation. Two-tone testing shows the in-band IM3 achieves -52 dB and the out-band IM3 achieves -55 dB with -11 dBm input power. This proposed filter circuit, fabricated in a SMIC 0.18μm CMOS process, consumes 4 mA current with 1.8 V power supply.

关键词： active-rc filter Butterworth frequency tuning group delay noise linearity

A low power 8th order elliptic low-pass filter for a CMMB tuner

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Journal of Semiconductors 2011年第9期32卷 82-88页

作者：龚正陈备胡雪青石寅代伐 Institute of Semiconductors Chinese Academy of Sciences Department of Electrical and Computer Engineering Auburn University

This paper presents an 8th order active-rc elliptic low-pass filter（LPF） for a direct conversion China Mobile Multimedia Broadcasting（CMMB） tuner with a 1 or 4 MHz -3 dB cutoff frequency（f_（-3dB））.By using a novel gain-bandwidth-product（GBW） extension technique in designing the operational amplifiers（op-amps）, the proposed filter achieves 71 dB stop-band rejection at 1.7f_（-3dB） to meet the stringent CMMB adjacent channel rejection（ACR） specifications while dissipates only 2.8 mA/channel from a 3 V supply,its bias current can be further lowered to 2 mA/channel with only 0.5 dB peaking measured at the filter＇s pass-band *** common-mode（CM） control circuits are applied to the filter op-amp to increase its common-mode rejection ratio （CMRR） and effectively reject the large signal common-mode *** results show that the filter has 128 dBμV_（rms） in-band IIP3 and more than 80 dB passband *** in a 0.35-μm SiGe BiCMOS process,the proposed filter occupies a 1.19 mm^2 die area.

关键词： CMMB tuner IC continuous-time filter active-rc filter low power analog filter gain-bandwidth-product extension CMRR

A baseband LPF for GSM,TD-SCDMA and WCDMA multi-mode transmitters

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Journal of Semiconductors 2011年第2期32卷 85-90页

作者：余永长韩科锋王丽芳谈熙闵昊 State Key Laboratory of ASIC & System Fudan University

This paper describes a low-pass reconfigurable baseband filter for GSM, TD-SCDMA and WCDMA multi-mode transmitters. To comply with 3GPP emission mask and limit TX leakage at the RX band, the out- of-band noise performance is optimized. Due to the distortion caused by the subthreshold leakage current of the switches used in capacitor array, a capacitor bypass technique is proposed to improve the filter＇s linearity. An automatic frequency tuning circuit is adopted to compensate the cut-off frequency variation. Simulation results show that the filter achieves an in-band input-referred third-order intercept point （IIP3） of 47 dBm at 1.2-V power supply and the out-of-band noise can meet TX SAW-less requirement for WCDMA ＆ TD-SCDMA. The baseband filter incorporates -40 to 0 dB programmable gain control that is accurately variable in 0.5 dB steps. The filter＇s cut-off frequency can be reconfigured for GSM/TD-SCDMA/WCDMA multi-mode transmitter. The implemented baseband filter draws 3.6 mA from a 1.2-V supply in a 0.13 μm CMOS process.

关键词： active-rc filter multi-mode transmitter analog baseband tuning circuit