高端口隔离度的太赫兹基波上混频器设计

Design of Terahertz Fundamental Up-conversion Mixer with Good Port-to-port Isolation

介绍了一种基于IHP 0.13μm SiGe BiCMOS工艺,具有高本振(Local Oscillator,LO)/射频(Radio Frequency,RF)及本振/中频(Intermediate Frequency,IF)端口隔离度的太赫兹基波上混频器.该混频器采用了吉尔伯特双平衡结构,本振信号通过共面波导(Coplanar Waveguide,CPW)传输来抑制其在传输过程中由于强寄生耦合效应造成的传输不对称性,削弱了由该不对称性造成的LO/RF端口隔离度恶化的特性.通过采用非对称性的开关互联结构降低本振信号在开关晶体管集电极端寄生耦合的不平衡性,提升本振信号在开关晶体管集电极端的对消效率,通过在版图中合理布局跨导级晶体管的位置来抑制本振信号在中频端口的泄露.后仿真结果表明:在2.2 V电源电压下,本振信号为230 GHz,中频信号为2~12 GHz,该上混频器工作在218~228 GHz时,LO/RF端口隔离度大于24 dB,LO/IF端口隔离度大于20 dB,转换增益为-4~-3.5 dB.当中频信号为10 GHz时,输出1 dB压缩点为-14.8dBm.电路直流功耗为42.4 mW,芯片的核心面积为0.079 mm2.该上混频器可应用于采用高阶正交幅度调制(Quadrature Amplitude Modulation,QAM)方式的无线发射系统.

A terahertz fundamental up-conversion mixer with a high Local Oscillator(LO)/Radio Frequency(RF)and local oscillator/Intermediate Frequency(IF)port isolation was presented based on IHP 0.13μm SiGe BiCMOS process.The mixer adopted Gilbert’s double-balanced structure,and the local oscillator signal was transmitted through the Coplanar Waveguide(CPW)to suppress the transmission asymmetry caused by the strong parasitic coupling effect in the transmission process,reducing the characteristic of LO/RF port isolation deterioration caused by the asymmetry.By adopting an asymmetric switch interconnection structure,the imbalance of the parasitic coupling of the local oscillator signal at the collectors of the switching transistors was reduced,and the cancellation efficiency of the local oscillator signal at the collectors of the switching transistors was improved.The leakage of the local oscillator signal was suppressed at the port of intermediate frequency by arranging the position of the transconductance transistors in a reasonable layout.The post-simulation results show that,under the power supply voltage of 2.2 V,the local oscillator signal is 230 GHz,and the intermediate frequency signal is 2-12 GHz.When the up-conversion mixer works at 218-228 GHz,the LO/RF port isolation is greater than 24 dB,LO/IF port isolation is greater than 20 dB,and the conversion gain is-4 dB to-3.5 dB.The output 1 dB compression point is-14.8 dBm when the intermediate frequency signal is 10 GHz.The DC power consumption is 42.4 mW,and the core area of the chip is 0.079 mm2.The up-conversion mixer can be applied to a wireless transmission system using a high-order quadrature amplitude modulation method.