High Doping Density Schottky Diodes in the 3MM Wavelength Cryogenic Heterodyne Receiver

The paper describes a 3mm cryogenic mixer receiver using high doping density (“room-temperature”) Schottky diodes. The measured equivalent noise temperature T_eq of the diodes is 109 K at 20 K, which is much higher than the T_eq of the low doping density (“cryogenic”) diodes. In spite of this, the double-sideband (DSB) noise temperature of the cryogenic receiver developed is 55 K at 110 GHz, owing to the low conversion loss of the mixer and ultra-low noise of the PHEMT IF amplifier. This is the lowest noise temperature ever reported for a Schottky diode mixer receiver. The results obtained are useful for the development of submm receivers in which high doping density Schottky diodes are used.     

High-Performance 94-GHz Single-Balanced Diode Mixer Using Disk-Shaped GaAs Schottky Diodes

We present a high-performance 94-GHz single-balanced monolithic millimeter-wave integrated-circuit (MMIC) mixer using the disk-shaped GaAs Schottky diodes grown on an n/$hbox{n}+$ epitaxial structure. Due to the superior characteristics of the GaAs diodes with high diode-to-diode uniformity, the mixer shows a conversion loss of 5.5 dB at 94 GHz, a 1-dB compression point $(P_{1 hbox{-}{rm dB}})$ of 5 dBm, and high local-oscillator to radio-frequency isolation above 30 dB in an RF frequency range of 91–97 GHz. To our knowledge, the fabricated mixer shows the best performance in terms of conversion loss at 94 GHz and $P_{1 hbox{-}{rm dB}}$ among the W-band MMIC mixers without amplifier circuits.      

A 10–40 GHz Broadband Subharmonic Monolithic Mixer in 0.18 $mu$ m CMOS Technology

A 10–40 GHz broadband subharmonic monolithic passive mixer using the standard 0.18 $mu$ m CMOS process is demonstrated. The proposed mixer is composed of a two-stage Wilkinson power combiner, a short stub and a low-pass filter. Likewise, the mixer utilizes a pair of anti-parallel gate-drain-connected diodes to achieve subharmonic mixing mechanism. The two-stage Wilkinson power combiner is used to excite a radio frequency (RF) and local oscillation (LO) signals into diodes and to perform broadband operation. The low-pass filter supports an IF frequency range from dc to 2.5 GHz. This proposed configuration leads to a die size of less than 1.1$,times,$ 0.67 mm$^{2}$ . The measured results demonstrate a conversion loss of 15.6–17.6 dB, an LO-to-RF isolation better than 12 dB, a high 2LO-to-RF isolation of 51–59 dB over 10–40 GHz RF bandwidth, and a 1 dB compression power of 8 dBm.      

Response Coefficients of a Double-Balanced Diode Mixer

This paper presents the results of a computer-assisted analysis of a commonly used double-balanced diode mixer circuit. It is shown that the magnitudes of some of the responses to one or more input radio frequency signals are sharply dependent on the degree to which the diodes comprising the mixer are balanced. The average rejections imparted to a particular undesired intermodulation (or spurious) response by a random sample ofsuch mixers are plotted as a function ofthe tightness ofthe control of diode characteristics of the population from wl lch the four diodes comprising a single mixer are selected. A computer program based on a Fourier-series expansion of the time-dependent coefficients of a Taylor-series representation of the four diode currents was employed to compute the response coefficients of the mixer [1H3] The response coefficients are defined as the magnitudes of the intermodulations of sinusoidal-input radio-frequency signals and the local-oscillator-frequency signal. The method treats the switching action characteristic of the large local-oscillator power levels, rather than relying on the more usual and invalid [1] assumption of " mild" nonlinearity. Orders of nonlinearity up to the tenth are treated.     

Noise and Loss in Balanced and Subharmonically Pumped Mixers: Part II--Application

The theory presented in Part I is applied here to some simple two-diode subharmonically pumped and balanced mixers. It is shown that the magnitude of the loop inductance (seen by currents circulating through the two diodes) affects the subharmonically pumped mixer much more strongly than the balanced mixer. The theory is also applied to the ideal two-diode mixer (balanced or subharmonically pumped) using exponential diodes with no series resistance and no nonlinear capacitance. It is shown that, like its single-diode counterpart, this mixer has a noise-equivalent lossy network whose physical temperature is eta T/2, where eta is the ideality factor of the exponential diodes. It follows that the ideal subharmonically pumped resistive mixer is not intrinsically less noisy than the ideal resistive fundamental mixer. This is not necessarily the case if parametric effects, due to nonlinear diode capacitance, are present.     

Microwave characterization of the properties and performance of GaAs Schottky barrier mixer diodes

Microwave measurements have been made of the equivalent circuit parameters and performance characteristics of unpackaged GaAs Schottky barrier mixer diodes. The dependence of mixer performance on series inductance, junction capacitance, and series resistance is delineated. Performance of mixer diodes in packaged and unpackaged form is compared.     

Hot-electron noise limitations in submillimetre-wave Schottky-barrier mixer diodes

The noise from small-area platinum gallium-arsenide Schottky-barrier mixer diodes has been measured at 4 GHz, to compare high-field (hot-electron) noise in diodes with different doping densities and anode areas. In the present state of technology, submillmmetre-wavelength mixer diodes should be fabricated from gallium arsenide with a doping density of about 1017 cm?3.     

Low-Noise Properties of Microwave Backward Diodes

This paper describes, for what is believed to be the first time, the low-noise properties of backward tunnel diodes in microwave applications. The physics of the diodes are reviewed together with some of the characteristics and equivalent circuit parameters. The diodes are then considered as mixer diodes with IF in the audio range and also the standard 30-Mc IF. Another promising application considered is the use of the backward diodes in low-level detection. The results show that the noise figure at 13.5 kMc with a 1-kc IF is around 15 db better than any commercially available mixer diodes. Using 30-Mc IF, the noise figure of backward diode mixers is without special optimum design, comparable to the best mixer diodes on the market. Of great importance, especially in micro-miniaturization, is the fact that these diodes may be used with a very low local oscillator power (50 µw or less). The high nonlinearity of the I-V characteristic at the origin and the low 1/f noise properties of these diodes are also of benefit in crystal video receivers and other low-level detector applications.     

Fully implanted GaAs millimetre-wave mixer diode using high energy implantation

Fully implanted GaAs millimetre-wave planar mixer diodes, suitable for monolithic integration, have been fabricated and tested. Multiple energy implantation, having a maximum energy of 6 MeV, was used to form the 3 ?m-thick active layer. The DC and RF characteristics were comparable to state-of-the-art GaAs mixer diodes fabricated on epitaxial layers.     

A novel technology for fabrication of beam-leaded GaAs Schottky-barrier mixer diodes

The fabrication of mixer diodes for use at millimeter-wave frequencies requires the definition of extremely small area Schottky-barrier junctions. It is not a trivial matter to fabricate such devices at low cost which simultaneously are mechanically rugged, exhibit low parasitics, and present high figures of merit. This paper presents a novel technology for accomplishing these objectives. By incorporating "shadow masked" proton bombardment and metal evaporation, planar beam-leaded devices of low capacitance are realized in the absence of the critical processing steps which have traditionally resulted in low yields. GaAs devices having zero bias capacitance of 0.06 pF are obtained with a series resistance of less than 3 Ω giving a cutoff frequency in excess of 800 GHz. Initial RF tests have resulted in a noise figure and conversion loss of 5.8 and 3.8 dB, respectively, at 10.7 GHz. This technology should result in the availability of inexpensive GaAs mixer diodes suitable for use at millimeter-wave frequencies.     

Cryogenic Millimeter-Wave Receiver Using Molecular Beam Epitaxy Diodes

A millimeter-wave cryogenic receiver has been built for the 60-90-GHz frequency band using GaAs mixer diodes prepared by molecuIar beam epitaxy (MBE). The diodes are mounted in a reduced-height image rejecting waveguide mixer which is followed by a cooled parametric amplifier at 4.5-5.0 GHz. At a temperature of 18 K the receiver has a total single-sideband (SSB) system temperature of 312 K at a frequency of 81 GHz. This is the lowest system temperature ever reported for a resistive mixer receiver. The low-noise operation of the mixer is seen to be a result of 1) the short-circuiting of the noise entering the image port and 2) an MBE mixer diode with a noise temperature which is consistent with the theoretical shot noise from the junction and the thermal noise from the series resistance.     

Schottky-Barrier Diodes for Submillimeter Heterodyne Detection

The fabrication and packaging techniques which were used to produce high-reliability mixer diodes for millimeter-wave satellite communications systems have been extended to produce Schottky-barrier mixer diodes for use in the submillimeter-wave region from 1 to 0.1 mm. The influence of material and circuit parameters on the performance of Schottky-barrier diodes as heterodyne detectors in the submillimeter-wave region has been considered. The semiconductor material parameters have been optimized and new packaging concepts have been investigated. A new diode package has been developed which incorporates both an integral stripline filter on 0.05-mm-thick quartz and a section of overmoded waveguide. The new package has the advantage of being replaceable in the mixer circuits, and yet it can provide a low-loss interface between the diode package and the mixer circuit. A new surface-oriented device has been developed in which the contact to the Schottky barrier is formed by photolithographic techniques onto the same surface as the ohmic contact. The surface-oriented devices exhibited heterodyne detection into the submillimeter region.     

0.45 THz次谐波混频器优化设计

采用ACST公司准垂直结构混频二极管对0.45 THz次谐波混频器进行优化设计。提出一种电路拓扑结构,使得电路结构紧凑且易于匹配。在对二极管结构分析与建模的基础上,利用射频电路仿真软件ADS及电磁场仿真软件HFSS对混频器电路及结构进行整体优化设计,得到理想情况下单边带变频损耗最小值6 dB,三分贝带宽大于30 GHz,所需本振驱动功率3.8 mW。仿真结果表明,该电路拓扑结构适用于采用反向并联肖特基二极管对实现次谐波混频器设计。     

Theoretical and Experimental Studies of Gain Compression of Millimeter-Wave Self-Oscillating Mixers

A general theory for a heterodyne Gunn self-oscillating mixer is developed to explain the experimentally observed phenomenon of "beat output power compression," i.e., an increase of down conversion gain with a decrease of millimeter injected power. Adler's general differential equation has been used, with some pertinent modifications and proper boundary conditions. This differential equation has been modified to allow the self-oscillating mixer to be frequency modulated. The solution of the new equation has been obtained through a perturbational technique, where the frequency of the self-oscillating mixer is assumed to be outside the locking range of the injected signal. The theory has been based on the fact that, owing to the bias perturbation of the (voltage tunable) self-oscillating mixer, the oscillator is modulated, both in amplitude and in angle. The functional dependence obtained depends, primarily, on the order of magnitude of the "induced" frequency of modulation. This semi-quantitative theory agrees quite well with experiments performed with both InP and GaAs Gunn diodes in the frequency range 75-100 GHz.     

340GHz 四次谐波混频器的研制

太赫兹波是电磁波谱中最后一个未被全面研究开发的频率窗口,它的开发和利用具有重大的科学价值。介绍了一种太赫兹频段内340GHz基于肖特基势垒二极管的四次谐波混频器设计。应用高频场仿真软件(HFSS)以及谐波平衡仿真软件(ADS),对反向并联二极管对进行3D建模及阻抗频率特性分析,并在此基础上对混频器进行优化。最后,对该混频器进行加工和测试,结果表明,在327~343GHz频带范围内,变频损耗小于15dB,最优值为12.7dB。     

4H-silicon carbide Schottky barrier diodes for microwave applications

In this paper, physical models for vertical 4H-silicon carbide (4H-SiC) Schottky diodes are used to develop a design method, where a maximum cutoff frequency for a given punch-through is achieved. The models presented are also used to extract microwave simulator computer-aided design (CAD) models for the devices. A device process was developed and Schottky diodes were fabricated in-house. Characterization of the devices was performed and compared to the theoretical models with good agreement. A demonstrator singly balanced diode mixer was simulated using the developed models. The mixer was fabricated using the in-house developed diodes, and measurements on the mixer show good agreement with the CAD simulations. A conversion loss of 5.2 dB was achieved at 850 MHz, and an excellent IIP/sub 3/ of 31 dBm at 850-MHz RF was measured, at 30-dBm P/sub LO/. These results verify the enhanced properties of the SiC Schottky diode compared to other nonwide bandgap diodes.     

Noise reduction in sputtered W/GaAs Schottky junctions

The noise characteristics of sputtered W/GaAs Schottky diodes, annealed at temperatures up to 700°C, have been investigated. A useful figure of merit for such millimeter and submillimeter mixer diodes is the noise performance at an RF where accurate measurements are available. Noise temperatures measured at a typical mixer intermediate frequency of 4GHz under DC biased conditions have been reduced significantly by rapid thermal annealing. The best noise data have been obtained with an annealing time of 2 minutes at 600°C and are consistent with good mixer performance.     

Subharmonically Pumped Millimeter-Wave Mixers

The two-diode subharmonically pumped stripline mixer has a pair of diodes shunt mounted with opposite polarities in a stripline circuit between the signal and local oscillator inputs. The circuit has low noise and conversion loss and substantial AM local oscillator noise cancellation.The local oscillator frequency is about half the signal frequency. A novel diode chip, the notch-front diode, which has ohmic contacts on the chip faces adjacent the face containing the diode junctions, was developed for these circuits. The notch-front diode permits the low parasitic reactance of the waveguide diode mount to be achieved in stripline circuits. The best performance for a two-diode subharmonically pumped mixer with notch-front diodes was a 400 K mixer noise temperature, obtained at 98 GHz which is comparable to the best fundamental mixers in this frequency range. The performance over a 47-110-GHz frequency range for this circuit with commercial beam-lead diodes is also presented.     

Low-parasitic, planar Schottky diodes for millimeter-waveintegrated circuits

The design and fabrication of air-bridged, ultra-low-capacitance Schottky barrier diodes are described. Mott diodes, for mixer applications, and varactor diodes, for use in frequency multipliers, have been produced simultaneously on epitaxial wafers grown by molecular beam epitaxy. Typical mixer diodes have a nominal anode contact area of 4 μm² and exhibit a total zero-bias capacitance of 4.0-4.5 fF (including a parasitic capacitance of approximately 1.0 fF) and a series resistance of 6-8 Ω. Diode chips have been incorporated in hybrid integrated circuit (MIC) mixers for 33-50 GHz and 75-110 GHz and an MIC frequency tripler for 90-140 GHz. Fully monolithic (MMIC) subharmonically pumped mixers for 75-110 GHz have also been fabricated and tested     

Optimization of MOVPE grownInxAl1-xAs/In0.53Ga0.47Asplanar heteroepitaxial Schottky diodes for terahertz applications

The feasibility of InP-based planar heteroepitaxial diodes for terahertz multiplier and mixer applications is explored. A variety of In _xAl_1-xAs/In_0.53Ga_0.47As (x=0.52, 0.4) diodes have been grown using LP-MOVPE and this allows systematic characterization of the effects of barrier thickness, InAs mole fraction and active layer thickness on the diode DC and RF performance. A new fabrication technology is developed for planar diodes using dielectric-free air-bridged anode fingers and trench isolation to minimize series resistance and parasitic capacitance. A qualitative model is suggested to explain the forward current conduction mechanism of the reported diodes. The control of forward current conduction and reverse leakage by epitaxial design together with the demonstrated figure-of-merit cutoff frequency of 2.6 THz make the diodes suitable for multiplier and mixer terahertz applications