0.34 THz无线通信收发前端

描述了一种基于肖特基二极管技术的0.34 THz无线通信收发前端。该前端采用超外差结构,由0.34 THz谐波混频器、0.17 THz本振8倍频链和偏置电路组成。0.34 THz谐波混频器基于反向并联肖特基二极管,可以实现信号的上变频发射和下变频低噪声检测。0.17 THz本振8倍频链由三级二倍频及驱动放大链路组成,可将20~22.5 GHz信号倍频至0.16~0.18 THz,为混频器提供5~10 dBm左右的本振信号。实验测试结果表明:该前端用于信号发射时,在0.34 THz频点的饱和输出功率为-14.58 dBm;用于信号检测时,最低单边带(SSB)变频损耗为10.0 dB,3 dB中频带宽约30 GHz。限于测试条件,未能测试前端接收噪声温度,仿真得到的双边带噪声温度数值低于1000 K。在该前端基础上,完成了首次基于16QAM 数字调制体制的0.34 THz无线通信实验,传输速率达3 Gb/s。     

微波混频器高功率微波效应等效电路建立及仿真

 利用先进设计系统软件设计并制作了单端混频器电路。开展了高功率微波注入效应实验,获得了一组损伤程度不同的混频器。通过测试二极管的伏-安特性曲线和分析失效机理,用拟合方法建立了损伤二极管的等效电路模型。基于此模型建立了损伤混频器等效电路,并对其被高功率微波损伤前后的输入输出特性进行了仿真计算,其变频损耗与混频器损伤后的实验测试结果相吻合。结果表明：损伤二极管的等效电路模型为在正常二极管结电阻两端并联一损伤等效电阻,其阻值大小反应了混频器的损伤程度,阻值越小,损伤越严重。     

基于CSMRC结构和容性肖特基二极管的220GHz三倍频器

设计了基于容性肖特基二极管的220 GHz非平衡三倍频器。首先对容性肖特基二极管进行测试和关键参数提取,建立了肖特基二极管的等效电路模型,以此为基础进行三倍频电路设计;在倍频电路设计中通过引入紧凑悬置微带谐振单元(CSMRC)滤波结构来减小信号传输损耗;由于三倍频电路设计中难以实现全波阻抗匹配,因此采用了整体电路结构谐波平衡调匹配方法设计倍频电路,最后对制备出的倍频器进行测试和分析;实验测试结果表明:倍频器在213.1~221.6 GHz范围内输出功率大于10 mW,倍频效率大于5%,最高输出功率为18.7 mW@218.6 GHz,最高倍频效率为8.24%@217.9 GHz。     

方环结构的宽频可调超材料滤波器

采用微控制电路加载技术控制超材料的等效介电常数和等效磁导率在不同时间的空间分布形式,实现空间滤波器中心频率的可调.设计了一种方环缝隙结构超材料滤波器,单元结构尺寸为18.5mm×18.5mm,通过在单元结构上加载变容二极管实现X波段内的连续可调.当变容二极管电容值从0.15pF增大到0.70pF时,仿真结果表明滤波器的中心频率从11.8GHz逐渐减小到10.5GHz,工作带宽为16.3%(10.2~12.0GHz),通带内的回波损耗最小值为22dB,插入损耗最大值为0.6dB.测试结果表明滤波器的中心频率从11.7GHz逐渐减小到10.3GHz,工作带宽为17.2%(10.1~12.0GHz),且通带内的回波损耗最小值为25dB,插入损耗最大值为0.5dB.     

用于Ka波段行波管的反射式预失真线性化器

采用幂级数法分析得到了线性化器与行波管放大器相反的非线性特性,并建立了预失真放大器的幂级数模型。根据反并联二极管对电路能够产生奇次谐波的特点,利用反并联肖特基二极管对、正交混合电桥、二极管电路的匹配网络等结构,通过对各结构的分析优化,设计了用于Ka波段行波管的预失真线性化器。实验结果表明:该线性化器在29~31 GHz频段范围内能为行波管放大器的载波交调比带来最大19 dB的改善。     

约瑟夫逊结基波和谐波混频器的模拟实验

采用约瑟夫逊结RSJ模拟器,对约瑟夫逊结的基波和谐波混频器进行了研究。用辅助电路和微型计算机系统在不同工作参数下测量了混频器中频输出(V_(IF))和结微分电阻(R_D)值,得到了谐波混频器的最大变频效率(η)与谐波次数(N)、本振电流(i_(LO))变化的关系。文中还给出了基波和二次谐波的最大变频效率随归一化本振频率(Ω(LO))变化的关系。实验结果表明,约结谐波混频器的工作状态取决于N是偶数还是奇数,偶次谐波混频器可以工作在零偏置和一定偏置这2种状态,而奇次谐波混频器仅能工作在一定偏置状态。在Ω(LO)≤0.36区域,二次谐波混频器的零偏置状态比一定偏置状态有较大的变频效率;而对Ω(LO)≤0.31,零偏置状态的二次谐波混频器比基波混频器有较大的变频效率。     

一体化VCO混频器组件的研制

介绍一体化VCO混频器组件的研制,在有限的体积中集成低噪声放大器、混频器、VCO等几个功能模块,实现射频到中频便捷变换。VCO电路采用反馈型介质稳频场效应管振荡器,通过介质和变容管,实现机械及电压调谐功能,混频器采用一级低噪声放大器和单片混频器来满足低损耗和低驻波的变频要求。该组件在X波段,实现噪声小于2.3dB、驻波小于1.19,隔离度大于50dB,自频调带宽大于±50MHz,机械调谐范围大于±93MHz,本振频率温度系数小于0.22MHz/℃的指标。     

基于EMSIW的互补裂缝环多频带谐振天线设计

文中设计了一个谐振频率在17.1GHz、27.6GHz和30GHz的多频带天线.该天线加载在八分之一基片集成波导(EMSIW)上,在EMSIW进行金属银过孔并在表面金属薄片上蚀刻一个互补裂缝环.天线尺寸占传统基片集成波导(SIW)的12.5%.利用HFSS软件进行仿真,获得了它的回波损耗、驻波比及三维增益图等参数.在谐振频率为17.1GHz时,回波损耗小于-10dB的相对带宽达到了1.9%,增益最高达到了4.4dB;在谐振频率为27.6GHz处和30GHz处,回波损耗小于-10dB的两个有效频带出现了无缝衔接,使得总相对带宽达到了15.2%,最大增益可达7.68dB.     

同轴转弯波导的设计与实验研究

提出了一种同轴转弯波导。介绍了该同轴转弯波导的基本原理,设计并数值模拟了中心频率为4.0 GHz的同轴转弯波导,并对此同轴转弯波导进行了实验研究。实验结果表明:同轴转弯波导在中心频率4.0 GHz下,传输损耗约为0.17 dB,驻波系数为1.2;在3.8~4.2 GHz的频率范围内传输损耗小于0.2 dB,驻波系数小于1.25。同轴转弯波导内部无介质支撑,且体积小,结构简单,易于实现,适用于高功率微波馈线系统中的同轴波导的转弯和连接。     

高温超导混频器变频效率的特性分析

我们研究了基于YBCO/MgO,YBCO/YSZ约瑟夫森超导结的谐波混频器.利用小型脉冲管制冷机以及小型G-M制冷机的高温超导混频测量系统,进行了亚毫米波段谐波混频的实验研究.通过实验,测量和分析了高温超导谐波混频器的变频效率的特性及其与耦合系数、本征信号功率、直流偏置和谐波次数等参数的关系.     

Ka Band Broadband Fourth Harmonic Image Rejection Mixer

This paper presents the design and implementation of Ka band broadband hybrid integrated image rejection mixer with a fourth harmonic mixer as unit mixer. Detailed design and analysis have been carried out. The mixer was fabricated by hybrid microwave integrated circuit (HMIC) process based on the thin film ceramic substrate which can reduce the cost compared to monolithic microwave integrated circuit (MMIC). The measured results showed conversion loss less than 11.2 dB and image rejection ratio (IRR) more than 20 dB in 4 GHz RF bandwidth. It can also play the role of up-converter from the test data.     

Operational Features of a Millimeter-Wave Balanced Mixer with a Broadband Intermediate-Frequency Output

We consider operational and structural features of a millimeter-wave balanced mixer with a broadband intermediate-frequency (IF) output. In this case, the heterodyne frequency is in the close vicinity of the IF band. The problem is reduced to an increase in isolation in the heterodyne-IF circuit along with the decrease in the mixer conversion loss in the broad IF band. As a result, we realized the mixer design with the following parameters: mixer input band 26-40 GHz, IF output band 0-18 GHz, conversion loss 6-8 dB, and heterodyne-IF isolation is 10-20 dB. The mixer circuit based on a combination of waveguide-slotted, coplanar, and microstrip transmission lines is studied.     

Measured mixer noise temperature and conversion loss of a cryogenic Schottky diode mixer near 800 GHz

We accurately measured the noise temperature and conversion loss of a cryogenically cooled Schottky diode operating near 800 GHz, using the UCB/MPE Submillimeter Receiver at the James Clerk Maxwell Telescope. The receiver temperature was in the range of the best we now routinely measure, 3150 K (DSB). Without correcting for optical loss or IF mismatch, the raw measurements set upper limits ofT _M=2850 K andL _M=9.1 dB (DSB), constant over at least a 1 GHz IF band centered at 6.4 GHz with an LO frequency of 803 GHz. Correction for estimated optical coupling and mismatch effects yieldsT _M=1600 K andL _M=5.5 dB (DSB) for the mixer diode itself. These values indicate that our receiver noise temperature is dominated by the corner cube antenna's optical efficiency and by mixer noise, but not by conversion loss or IF mismatch. The small fractional IF bandwidth, measured mixer IF band flatness from 2 to 8 GHz, and similarly good receiver temperatures at other IF frequencies imply that these values are representative over a range of frequencies near 800 GHz.     

A 119 GHz planar Schottky diode mixer for a space application

A planar single-ended GaAs Schottky diode mixer has been designed, built, and tested at 119 GHz. The mixer front end includes also a waveguide filter for image rejection, and a temperature compensated ring filter. Measurements at room temperature showed a conversion loss of 7 dB and a noise temperature of 900 K (SSB). At 100 K the measured noise temperature of the mixer was 500 K (SSB).     

High performance MM-wave balanced mixers for Ka band down converters

The design and development of mm-wave fin-line and crossbar suspended stripline balanced mixer with GaAs beamlead diodes for Ka-Band downconverters is described. A conversion loss of 5.9±0.6 dB over the frequency band 32 to 36 GHz has been achieved in a crossbar stripline structure, and 6.5±0.7 dB over the frequency band 26.5 to 40 GHz in a fin-line with suspended stripline structure. Integrated circuit components, such as suspended stripline filters and transitions were also developed.     

A Broad-Band Low-Noise Schottky Diode Full-Height Waveguide Mixer from 80 to 115 GHz

The RF matching problem in the input circuit of the mm-wavelength whisker contacted Schottky diode mixer is studied. The experimental results, obtained on the 3mm wavelength mixer mounts in the broad band of frequencies from 80 to 115 GHz are presented. It is shown that advantage in the receiver noise temperature may be realized by the use of a full-height instead of 1/4-reduced-height waveguide because of reduction loss in the mixer input circuit even beginning from the 3mm-wavelength. With a full-height waveguide mixer the double sideband (DSB) receiver noise temperature is 300 divided by 350K over the 85 to 110 GHz band. Input bandwidth of the fullheight waveguide mixer (cap delta f _S/f _SO greater than 30%) is equal to 1/2-and close to 1/4-reduced-height waveguide mixers.     

Measurements of the sideband conversion gain ratio of a millimeter-wave heterodyne sub-harmonic mixer using a fourier transform spectrometer

A Fourier transform spectrometer, based on a Martin-Puplett polarisation rotation interferometer and using broad-band blackbody noise sources, has been used to study the sideband response i.e., conversion gain, of a room temperature Schottky diode sub-harmonic mixer operating at 300 GHz. The technique enables the response of the mixer to be characterised and preferentially tuned to one sideband, thereby improving the rejection of unwanted spectral components which can be present in the mixer image sideband.     

A high isolation W-band MMIC drain type cascode single balanced mixer

We present a high isolation W-band MMIC drain type cascode single balanced mixer of high LO-to-RF isolation and wide band with conversion characteristic using the high directivity monolithic tandem couplers and 0.1 μm GaAs-based metamorphic high electron mobility transistors (MHEMTs). The fabricated mixer consists of two cascode MHEMT mixers and two tandem couplers using the air-bridge crossovers. We establish a drain type cascode mixer structure where the LO signal is applied to the drain port in the mixing component of common source MHEMT circuit. The tandem coupler exhibits good couplings (2.92-3.8 dB), low return losses (−32.7 dB), and isolations (15.4-39.2 dB) in a wide bandwidth of 75-110 GHz. The mixer shows a conversion loss of 9.8 dB at 94 GHz, an output P1dB of −14.8 dBm at LO frequency of 94.542 GHz, and LO-to-RF isolations of 29.5-39.5 dB at 94-100 GHz.