摘要
A low noise, high conversion gain down-conversion mixer for WLAN 802.11a applications, which adopts the high intermediate frequency （IF） topology, is presented. The input radio frequency （RF）band, local oscillator（LO）frequency band and output IF are 5.15 to 5.35, 4.15 to 4.35 and 1 GHz, respectively. Source resistive degeneration technique and pseudo-differential Gilbert topology are used to achieve high linearity, and, current bleeding technique and LC resonant loads are used to acquire a low noise figure. In addition, the mixer adopts a common-source transistor pair cross-stacked with a source follow pair（CSSF）circuit as an output buffer to enhance the mixer＇s conversion gain but not deteriorate the other performances. The mixer is implemented in 0.18 μm RF CMOS（complementary metal oxide semiconductor transistor）technology and the chip area of the mixer including all bonding pads is 580 μm×1 185 μm. The measured results show that under a 1.8 V supply, the conversion gain is 10.1 dB; the input 1 dB compression point and the input-referred third-order intercept point are-3.5 and 5.3 dBm, respectively; the single side band （SSB）noise figure （NF）is 8.65 dB, and the core current consumption is 3.8 mA.
给出了一个应用于无线局域网WLAN802.11a的中低噪声、高增益的下变频器.该下变频器采用高中频的结构,输入的射频频率(RF)、本振(LO)频率和输出的中频频率(IF)分别为5.15 ～5.35,4.15 ～4.35和1GHz.为了提高混频器的线性度,电路采用了伪差分的吉尔伯特结构和源极电阻负反馈技术;为了获得低的噪声系数,混频器采用电流源注入技术和LC谐振电路作为负载.此外,采用了一种改进的源极跟随器输出缓冲电路,在不恶化其他性能的情况下混频器可以达到较高的增益.该芯片采用0.18μm RF CMOS工艺制作,包含所有焊盘在内的芯片尺寸为580μm×1 185μm.测试结果表明:在1.8V电源电压下,消耗电流为3.8mA,转换增益为10.1dB,输入1dB压缩点为-3.5dBm,输入三阶截点为5.3dBm,单边带(SSB)噪声系数(NF)为8.65dB.
基金
The Science and Technology Program of Zhejiang Province (No.2008C16017)
