Numerical Simulation of the Base Impedance of Long Wire Whisker Antennas

With increasing frequencies the whisker structures used to contact honeycomb Schottky diodes remain no longer thin compared to wavelength. Whereas the finite thickness and the detailed tip shape do not influence the antenna pattern very much the antenna base impedance depends on these parameters to a great extent. A good impedance matching between Schottky diode and whisker antenna is necessary to optimise mixer or detector performance and can only be achieved if the antenna impedance is known. Antenna base impedances have been simulated numerically and checked by means of scaled model measurements for several whisker shapes. The influence of further parts of the antenna environment, as for example reflectors, has also been investigated. Simulation results have been discussed and compared to theory. Simulation has been found out to be a reliable tool for the determination of base impedances of almost arbitrarily shaped whisker antennas.     

Submillimeter receivers for radio astronomy

The state of development of receivers for submillimeter-wave radio astronomy is reviewed. Bolometers for continuum observation, hot-electron mixer receivers for narrowband spectral line observation, and heterodyne receivers, both Schottky diode and superconducting tunnel junction, are presented. At the lower frequency end of the submillimeter band, standard waveguide techniques, scaled from millimeter wavelengths, prevail. At wavelengths shorter than about 0.5 mm, quasioptical designs are preferred. In the case of Schottky diode receivers, corner cube designs are used almost exclusively, whereas integrated mixer designs are the focal point of research for superconductor-insulator-superconductor (SIS) receivers at these wavelengths. Although such designs are extensively reviewed, it is nevertheless the Schottky diode mixer remains the element of choice at the shortest submillimeter wavelengths     

A novel planar diode mixer for submillimeter-wave applications

A mixer employing a planar GaAs Schottky diode has been designed and tested over a 300-365 GHz bandwidth. Using a planar diode eliminates the disadvantages of mechanical instability and labor-intensive assembly associated with conventional whisker-contacted diodes. The mixer design process uses scale model impedance measurements for both the design of individual components and the measurement of impedances presented to the diode terminals by the mixer mount at fundamental and harmonic frequencies. Results from these impedance measurements are used in linear and nonlinear numerical mixer analyses to predict the mixer performance     

Antenna patterns of an open structure mixer at a submillimeter wavelength and of its scaled model

To verify the enhancement in sensitivity of a Schottky barrier diode using a 90° corner reflector at submillimeter wavelength a 65∶1 scaled model of the open structure mixer was constructed and investigated at 2.8 cm wavelength. The results show clearly the advantage of a 90° corner reflector, the reality of the deviations for 45° and 60° corner reflectors found for submillimeter wavelengths, and the equality of the antenna patterns for a 90° corner reflector and a “cat-eye” (corner cube) reflector.     

基于倒扣技术的24GHz混合集成平衡混频器

介绍采用混合贴装倒扣二极管技术制造的新型24GHz平衡混频器，并对该混频器进行设计、仿真、加工和测试，它能提供中频100kMz时小于10dB的变频损耗，本振与信号之间优于35dB的隔离度，其结构特点利于大批量、低成本生产，适合汽车电子系统的需求。     

330 GHz太赫兹次谐波混频器设计

为了缓解微波频段频谱资源的日益紧张,对太赫兹频段进行探索,介绍了一款基于GaAs肖特基二极管的330 GHz次谐波混频器。设计采用了整体综合设计的方法,进行高频结构模拟器(HFSS)与先进设计系统(ADS)联合仿真。优化过程中,电路不连续性通过HFSS仿真结果表征,电路传输特性和二极管非线性特性由ADS仿真结果表征,通过优化传输线参数,实现优化电路的目的。此方法增大了仿真优化空间,降低了设计难度。仿真结果显示,在300~350 GHz频段内,混频器的变频损耗小于8 dB。     

250GHz 太赫兹谐波混频器设计

太赫兹变频组件是实现太赫兹成像和通信应用的关键器件。本文中介绍了基于hammer-head 滤波器紧凑结构, 结合肖特结二极管的三维模型和电气模型,设计低变频损耗250GHz 太赫兹谐波混频器的方法。在高倍光学显微镜的精 准测量下,建立尺寸可以跟信号波长相比拟的二极管三维模型,准确模拟二极管的高频特性以提高电磁仿真精度。为了 进一步降低太赫兹混频器的变频损耗,文中除了采用紧凑型的hammer-head 滤波器结构外,同时通过波导探针直接实现 与二极管阻抗的匹配,简化了混频器的结构降低谐波信号传输线损,从而降低太赫兹谐波混频器的变频损耗。最终仿真 结果表明,250GHz 谐波混频器在3dBm 的本振功率驱动下,在230~270GHz 射频范围内,变频损耗(SSB)均小于6.8dB, 最低变频小于6.2dB,中频带宽大于20GHz。     

Short Millimeter Low Local Wavelength Mixer with Oscillator Power

This paper discusses development, for the 240-GHz region, of whisker contacted diode mixers with LO powers between 10 and 50 µW. Mixer requirements for low parasitic diodes, situated in high-embedding impedance circuits are described and appropriate RF and IF circuit designs presented. A capacitive post RF matching circuit for a full-height waveguide is developed with superior bandwidth characteristics at high impedance levels and greater ease of fabrication than usual matching circuits in reduced height guide. Corroborating experimental results are presented for an X-band model and for a 235-GHz mixer.     

0.67 THz宽带谐波混频器设计

为研制太赫兹多频段高灵敏度探测仪,依靠太赫兹砷化镓平面肖特基二极管的非线性特性,结合石英薄膜工艺,设计了宽带0.67 THz谐波混频器,并分析了砷化镓平面肖特基二极管性能表征参数指标对太赫兹混频器性能的影响。0.67 THz谐波混频器采用整体综合的设计方法,结合电气仿真软件ADS和电磁仿真软件HFSS,优化电路中不连续性微带与波导之间的电磁空间耦合效率,以混频器的变频损耗为优化目标,最终实现0.67 THz谐波混频器仿真设计。0.62~ 0.72 THz射频范围内,混频器单边带最低变频损耗小于8 dB,本振功率小于4 mW,本振端口与中频端口、射频端口与中频端口之间隔离度大于-30 dB。     

微波双栅FET混频器的分析与设计

本文分析了双栅FET的混频机理,给出了双栅FET的三种非线性模型.介绍了采用三端口阻抗条件设计双栅FET混频器的方法.在S、L波段制作的两种双栅FET混频器,噪声系数略高于二极管混频器,而变频增益比二极管混频器高10dB.整机应用结果表明,它具有简化电路、降低成本和对前置中放噪声系数要求不高的优点.     

The resonant terahertz response of a slot diode with a two-dimensional electron channel

The terahertz response of a slot diode with a two-dimensional electron channel is calculated on the basis of the first principles of electromagnetism. It is shown that all characteristic electromagnetic lengths (scattering, absorption, and extinction lengths), as well as the impedance of the diode, exhibit resonances at plasmon excitation frequencies in the channel. The fundamental resonance behaves similarly to the current resonance in an RLC circuit. It has been concluded that, even at room temperature, a slot diode with a two-dimensional electron channel provides a resonant circuit at terahertz frequencies that couples effectively to external electromagnetic radiation with a loaded Q-factor exceeding unity. The diode resistance may be measured from contactless measurements of the characteristic electromagnetic lengths of the diode.     

183 GHz double diode subharmonically pumped mixer

A double diode subharmonically pumped mixer is described. A diode-whisker contacting arrangement has been developed which avoids many of the problems associated with whisker contacts. Early tests indicate that the circuit structure is rugged and capable of good electrical performance.     

Spectral Narrowing of a Varactor-Integrated Resonant-Tunneling-Diode Terahertz Oscillator by Phase-Locked Loop

Spectral narrowing of a resonant-tunneling-diode (RTD) terahertz oscillator, which is useful for various applications of terahertz frequency range, such as an accurate gas spectroscopy, a frequency reference in various communication systems, etc., was achieved with a phase-locked loop system. The oscillator is composed of an RTD, a slot antenna, and a varactor diode for electrical frequency tuning. The output of the RTD oscillating at 610 GHz was down-converted to 400 MHz by a heterodyne detection. The phase noise was transformed to amplitude noise by a balanced mixer and fed back into the varactor diode. The loop filter for a stable operation is discussed. The spectral linewidth of 18.6 MHz in free-running operation was reduced to less than 1 Hz by the feedback.     

GaAs Schottky diodes for THz mixing applications

The operation of GaAs Schottky barrier diodes, the critical mixer element used in heterodyne receivers for a variety of scientific applications in the terahertz frequency range, is reviewed. The constraints that the receiver system places on the diodes are considered, and the fundamental guidelines for device optimization are presented. The status of ongoing research, both experimental and theoretical, is examined. Emphasis is placed on investigations of the various effects that can limit diode performance at these high frequencies. Investigations of planar diode technology are summarized, and the potential replacement of whisker-contacted devices with planar structures is considered     

Improvement of responsivity of high-speed infrared detector using hot carriers in semiconductors

A room temperature, high-speed and high-sensitive infrared hot carrier detector using p-type Ge has been investigated at 10.6 μm. The detector is composed of a whisker antenna and a diode contact forming an ohmic contact on p-type Ge. This detector has the merit that one can easily have impedance matching between the antenna and the diode contact without any matching section, so that high sensitivity can be obtained. A voltage sensitivity 16 dB higher than that of metal-insulator-metal (MIM) point contact diode has been observed from this detector.     

Investigation of a Single-Sideband Mixer Anomaly

Measurements on a 6-GHz single-sideband (SSB) balun-coupled mixer revealed a feedthrough of RF signals between the two mixer sections that caused the IF outputs to be unbalanced at the +-90° local oscillator (LO) phase differences when using a ring diode quad. Using a bridge diode quart in this same mixer eliminated this IF output unbalance. These measurements also give conclusive evidence that the balun-coupled mixer has a short-circuited image frequency voltage with the ring diode quad and an open-circuited image frequency voltage with the bridge diode quad. These two image frequency impedance conditions are independent of circuit terminating impedances and solely depend on the image frequency current path being completed or interrupted by the ring or bridge diode quads, respectively.     

Conversion Loss Limitations on Schottky-Barrier Mixers (Short Papers)

A new set of criteria involving diode area, material parameters, and temperature is introduced for the Schottky-barrier mixer diode that must be considered if its usage is to be extended to the submillimeter wavelength region or cryogenically cooled to reduce the noise contribution of the mixer. It has been well established that, in order to reduce the parasitic loss as the frequency is increased, it is necessary to reduce the area of the diode. What has not been analyzed heretofore is the effect that a reduction in diode area can have on the intrinsic conversion loss L/sub 0/ of the diode resulting from its nonlinear resistance. This analysis focuses on the competing requirements of impedance matching the diode to its imbedding circuit and the finite dynamic range of the nonlinear resistance. As a result, L/sub 0/ can increase rapidly as the area is reduced. Results are first expressed in terms of dimensionless parameters, and then some respresentative examples are investigated in detail. The following conclusions are drawn: a large Richardson constant extends the usefulness of the diode to smaller diameters, and hence, shorter wavelengths; cooling a thermionic emitting diode can have a very detrimental effect on L/sub 0/; impedance mismatching is found, in generaI, to be a necessity for minimum conversion loss; and large barrier heights are desirable for efficient tunnel emitter converters.     

Simulated performance and model measurements of an SIS waveguide mixer using integrated tuning structures

A three-port approximation of the quantum mixer theory is employed to perform mixer gain calculations at 230 GHz for SIS junctions with integrated tuning structures. In addition, the embedding impedance range of a waveguide mixer mount has been obtained from model measurements and has been included in the gain calculations. The results show that even moderately small junctions can perform well in a waveguide environment when an integrated tuning structure is used. A three-element tuning circuit is presented that would allow broad band operation with a fixed embedding impedance which is important for applications using a planar antenna structure.     

High-performance quasi-optical GaAs monolithic mixer at 110 GHz

A novel GaAs monolithic integrated circuit mixer has been fabricated which is impedance matched to fundamental waveguide. It consists of a slot coupler, coplanar transmission line, surface-oriented Schottky-barrier diode, and RF bypass capacitor monolithically integrated on the GaAs surface. At 110 GHz, a monolithic mixer module mounted in the end of a waveguide horn has an uncooled double-sideband (DSB) mixer noise temperature of 339 K and conversion loss of 3.8 dB.     

Microwave Diode Cartridge Impedance

In any application of a semiconductor microwave diode, the impedance of the diode cartridge plays a very important role. Two commonly made assumptions, which are quite erroneous, are that 1) the impedance of the diode cartridge consists simply of a shunt capacitance and whisker inductance, and 2) the metal-to-semiconductor junction at microwave frequencies behaves approximately as it does at 10 mc. In this paper it is shown that the impedance of the diode cartridge at microwave frequencies can be measured accurately by substituting a carbon die for the semiconductor.