Submillimeter-Wave Detection with Submicron-Size Schottky-Barrier Diodes

Schottky-barrier diode detection has been extended to 7.2 THz (42 mu m) using 0.5-mu m-diam diodes. The diodes were fabricated on bulk-doped n-type GaAs using electron lithographic techniques; diameters as small as 1000 /spl Aring/ have been achieved. A new approach in Schottky-barrier design, the contact array diode, is proposed. The diode is fabricated from readily available bulk doped material, and a performance is indicated that is competitive to the conventional epitaxial Schottky-barrier mixer well into the submillimeter wavelength region. A scanning electron microscope (SEM) photograph of diode array structures is shown.     

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.     

Low noise GaAs varactor and mixer diodes prepared by molecular beam epitaxy

Schottky-barrier varactor and mixer diodes have been made from Ge-doped GaAs layers grown by molecular beam epitaxy. A microstrip parametric amplifier circuit incorporating a hyperabrupt varactor diode has given a noise temperature of 120 K and bandwidth of 180 MHz at 15 dB gain when pumped at 34 GHz, and a mixer diode mounted in a cryogenic receiver circuit had an s.s.b. noise temperature of 180 K at 90 GHz.     

Design of Submillimeter Schottky Mixers Under Flat-Band Conditions Using an Improved Drift-Diffusion Model

Minimum conversion loss in millimeter and submillimeter-wave Schottky mixers is achieved when the diodes are slightly pushed into the flat-band regime. The discrepancies found between experimental results and physics-based harmonic balance simulations for a 330 GHz antiparallel diode pair subharmonic Schottky mixer showed that traditional drift-diffusion models with conventional boundary conditions at the Schottky contact do not correctly predict the behavior of the Schottky-based mixers working under flat-band conditions. In this work, we employ Monte Carlo simulations to get physical insight of the Schottky diodes working in the flat band regime. New boundary conditions obtained from this analysis have been included in our drift-diffusion simulator which has resulted in an improvement of our circuit simulator to predict mixer operation under flat band regime.      

Interfacial Stress and Excess Noise in Schottky-Barrier Mixer Diodes

This paper presents evidence linking excess noise in submillimeter-wave Schottky-barrier mixer diodes to stress at the devices' GaAs-SiO/sub 2/ interface. At the periphery of the Schottky anodes, the SiO/sub 2/ film is discontinuous and the stress surpasses the GaAs yield stress, resulting in damage to the surrounding material. By modifying the device structure in three independent manners, the stress and damage at the diode periphery were either increased or decreased; in each case, the noise temperature increased or decreased accordingly.     

Low-noise heterodyne receivers for near-millimeter-wave radio astronomy

Increased interest in the near-millimeter wavelength region, covering the range 3 mm to 300 µm, during the past decade has stimulated the development of sensitive heterodyne receivers for a wide range of applications. This review paper considers current low-noise receiver technology with emphasis on applications in radio astronomy. A brief discussion of the astrophysical importance of radio astronomy at millimeter wavelengths is presented. The concepts of receiver design and the particular problems associated with this region of the spectrum are discussed. The optimization of material parameters and device topology for both Schottky-barrier diodes and superconducting mixer elements is considered. The extension of waveguide mixer technology into the submillimeter region and the development of quasi-optical receivers is reviewed. Consideration is given to the recent development of efficient harmonic generators for local oscillator (LO) applications at near-millimeter wavelengths.     

Unbiased InP detectors in the submillimetre wave region

High sensitivity unbiased detectors employing Ni-nInP Schottky-barrier diodes have been developed in a submillimetre-wave region. The voltage sensitivities of 120 V/W at 300 GHz and 17 V/W at 450 GHz were obtained, which are about three times higher than those of the usually used unbiased Si point contact diode detectors.     

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.     

K-Band Integrated Double-Balanced Mixer

A novel microwave integrated circuit (MIC) double-balanced mixer with good isolation between the three ports is described. The mixer is fabricated using a combination of microstrip lines, slotlines, and coupled slotlines, together with four beam-lead Schottky-barrier diodes. The K-band magic-T has been developed for the double-balanced mixer. The minimum conversion loss measured at a signal frecuency of 19.6 GHz is 4.7 dB. Isolation between RF and LO ports is greater than 20 dB from 18 to 21 GHz. The mixer can be expected to have wide applications in MIC receivers and transmitters up to the millimeter-wave band.     

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.     

Numerical Analysis of Subharmonic Mixers Using Accurate and Approximate Models

A full nonlinear numerical analysis technique is applied to subharmonically pumped mixer circuits where the two diodes are not identical. Results indicate that a slight imbalance in the diode parasitic parameters can significantly affect the mixer performance. A bilinear approximation of the Schottky-barrier diode characteristic is described, permitting accurate determination of the conversion loss peaks for millimeter-wave subharmonically pumped mixers. This approximation provides an analysis which requires significantly less computer time than a full nonlinear analysis.     

Conversion Loss in GaAs Schottky-Barrier Mixer Diodes

In this paper, the intrinsic conversion loss of GaAs Schottky-barrier mixer diodes is analyzed in light of a more accurate diode model. This analysis resolves the discrepancy between the predictions of an earlier intrinsic conversion loss model and expefimental results. In particular, it is shown that a) cryogenic cooling should not degrade the conversion loss, and b) the diode diameter can be smaller than previously predicted before conversion-loss degradation begins to occur, Evidence is also presented which indicates that mixer diodes must be pumped beyond flat-band if the minimum, possible conversion loss is to be obtained. A more complete model of the conversion loss, which includes the parasitic circuit elements, is discussed and found to be in agreement with the qualitative results of the intrinsic conversion-loss model.     

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     

Submillimeter Heterodyne Detection with Planar GaAs Schottky-Barrier Diodes

Planar surface-oriented Pt/GaAs Schottky-barrier diodes have been fabricated and used to detect signals at submillimeter wavelengths. Video detection has been observed up to frequencies as high as 890 GHz. Harmonic mixing between the ninth harmonic of a 74.21-GHz signal and the second harmonic of 333.95-GHz radiation has also been obtained.     

3mmFM/CW组件中鳍线混频器的研究

采用场分析及电路阻抗匹配进行综合设计 ,运用梁式引线二极管采用微组装压焊技术 ,研制出应用于 3mm FM/CW组件中的 3mm鳍线混频器。对于单端结构获得小于 10 d B的变频损耗 ,对于平衡结构获得小于 9d B的变频损耗 ,这两种结构的鳍线混频器都分别成功地应用于 型和 型 3mm FM/CW组件。     

A Broad-Band Second-Harmonic Mixer Covering 76-106 GHz

A broad-band second-harmonic millimeter-wave mixer has been constructed. The circuit consists of a single unencapsulated Schottky-barrier diode and embedding network which includes a wave absorber in the IF output terminal. The conversion loss of the mixer is 14.6/spl plusmn/0.9 dB over a frequency range of 76-106 GHz. The mixer is pumped by a Iocal oscillator that is tuned over the range of 37.15-52.15 GHz. The IF is kept constant at 1.7 GHz. The new mixer looks attractive for use in broad-band millimeter-wave measuring equipment, such as spectrum analyzers.     

Hybrid Integrated Triplers Frequency Doublers and to 300 and 450 GHz

High-power wide-band submillimeter-wave frequency sources have been developed. A frequency doubler to 300 GHz has delivered an output power of 5 mW with 3-dB-down bandwidth of more than 10 GHz. A frequency tripler to 450 GHz with an output power of 0.5 mW has also been tested. These multiplier output powers are highest values in the respective frequency regions up to date. The successful performances have been achieved by use of GaAs Schottky-barrier diodes and hybrid integrated circuits which are specially designed to obtain high output power.     

60 GHz monolithic GaAs front-end circuit for receiver applications

A millimetre-wave planar mixer diode compatible with GaAs MESFET based integrated circuit fabrication has been developed. Selective ion implantation was used to optimise the diode and FET doping profiles. A novel feature reported here is the use of a deep implanted buried n+ layer to minimise diode series resistance, yielding diode cutoff frequencies in excess of 500 GHz. Monolithic balanced mixer diodes integrated with an MESFET IF amplifier fabricated by this technique have given 5dB conversion loss at 60 GHz.     

Broad-Band Noise Mechanisms and Noise Measurements of Metal Semiconductor Junctions

Classic work on optimized heterodyne receivers has concentrated on the network aspects of mixers with limited emphasis on device properties. We present experimental results of GaAs Schottky-barrier diode noise measurements in the frequency range from 0.1 to 88 GHz and a detailed analysis of noise generation in these diodes which can explain the observed current and frequency dependence.     

Investigations of optically pumped submillimeter wave laser modes

A complete theory for waveguide laser modes for oversized metallic and dielectric waveguides with circular cross section has been developed for the submm wavelength region. The experimental investigations have been done by a submm heterodyne technique for the first stage using a Schottky barrier diode in an open structure mixer.