Piezoelectric-transducer-controlled tunable microwave circuits

This paper introduces a new method to tune microwave circuits of phase shifters, filters, resonators, and oscillators, controlled by a piezoelectric transducer (PET) with computational and experimental results. An optimized PET-controlled phase shifter is demonstrated to operate up to 40 GHz with a maximum total loss of 4 dB and phase shift of 480°. PET-controlled tunable bandpass filter, ring resonator, and one-dimensional photonic-bandgap resonator show a very wide tuning bandwidth of 17.5%-28.5% near 10 GHz with little performance degradation. A new PET-controlled or voltage-controlled dielectric-resonator oscillator (DRO) is demonstrated with a tuning bandwidth of 3.7% at the center frequency of 11.78 GHz. The tuning bandwidth is slightly less than that of a mechanical tuning using a micrometer-head-controlled tunable DRO with a tuning bandwidth of 4.7%. The new tuning method should have many applications in monolithic and hybrid microwave integrated circuits     

GaAs integrated microwave circuits

GaAs has many desirable features that make it most useful for microwave and millimeter-wave integrated circuits. The process of selective epitaxial depositions of high purity single-crystal GaAs with various doping concentrations into semi-insulating GaAs substrates has been developed. These high-resistivity substrates (>10⁶ohm.cm) provide the electrical isolation between devices, eliminating the difficulties and deficiencies normally encountered in trying to obtain isolation with dielectrics, back-etching, p-n junctions, etc. This monolithic approach to integrated-circuits thus allows for improved microwave pedormance from the devices since parasitics are reduced to a minimum. Planar Gunn oscillators and Schottky barrier diodes have been fabricated for use in a completely monolithic integrated millimeter wave (94 GHz) receiving front end. The Gunn oscillators are made in a sandwich-type structure of three selective deposits whose carrier concentrations are approximately 10¹⁸-10¹⁵-10¹⁸cm^-3. The Schottky diodes consist of two deposits with concentrations of 10¹⁸and 10¹⁷cm^-3. The Schottky contact is formed by evaporating Mo-Au onto the 10¹⁷cm^-3deposits; all ohmic contacts are on the surface and are alloyed to the N⁺regions.     

High peak-power LSA operation from epitaxial GaAs

Gallium solution epitaxy, using a steady-state, temperature-gradient technique has been successfully used to grow high-quality, 150-µM thick gallium arsenide layers with less than 5 percent variation in electron density. A laser-probe, photoconductivity method has been used to precisely measure the relative variations of electron density. Using these epitaxial layers with 1.5-2 ×10¹⁵cm^-3electron concentration, LSA oscillations at X- and Ku-bands have been measured with up to 400-watt peak power and with more than 10 percent efficiency. A small iris circuit with a stepped ridge waveguide impedance transformer has delivered fundamental LSA oscillations in the X- and Ku-bands. Operating bias levels of up to 20 times threshold were observed on some diodes. The importance of the substrate (and contact) layer conductivity at the interface with the active layer, as well as the skin depth of the active layer, for efficiency and in preventing avalanche breakdown is explained. Frequency tuning with bias voltage and temperature is shown and discussed.     

LSA operation of large volume bulk GaAs samples

Peak pulse powers of 350 watts, with 3 percent efficiency at X-band frequencies, were obtained from large volume GaAs devices operating in the LSA mode. Experimental dependence of the LSA mode on circuit loading, applied voltage, and the ratio of carrier concentration to frequency are reported. The results are shown to be in excellent agreement with Copeland's theoretical calculations. The high-current state frequently observed in GaAs samples is shown to result from impact ionization in the high-field portion of dipole domains. A simple expression is derived relating the sample length and carrier concentration to the voltage at which switching to the high-current state occurs. The prevention of high-field domains to permit LSA operation of long samples at high voltages is briefly discussed.     

GaAs HBT's for microwave integrated circuits

The status of the microwave GaAs heterojunction bipolar transistor (HBT) technology is reviewed. Microwave circuits for advanced military and commercial systems continue to increase their dependence on the performance, functionality, and cost of active components fabricated using solid-state technology. The performance advantages provided by GaAs HBT's, for several critical circuit applications, have stimulated a worldwide development activity. Progress in HBT device technology and microwave circuit applications has been extremely rapid because of the broad availability of III-V compound semiconductor epitaxial materials and prior experience with GaAs field-effect transistors (FET's) and monolithic microwave integrated circuits (MMIC's). The great flexibility of HBT's in microwave circuits makes them prime candidates for applications in complex multifunctional microwave/digital IC's in next-generation systems     

砷化镓双栅场效应管及其在微波电路中的应用

本文简述砷化镓双栅场效应管的基本特性及其在放大器、倍频器.混频器、振荡器、移相器和开关等微波电路中的应用.     

High-purity semi-insulating GaAs material for monolithic microwave integrated circuits

Liquid-Encapsulated Czochralski (LEC) growth of large-diameter bulk GaAs crystals from pyrolytic boron nitride (PBN) crucibles has been shown to yield high crystal purity, stable high resistivities, and predictable direct ion-implantation characteristics. Undoped (≲low 10¹⁴cm^-3chromium) and lightly Cr-doped (low 10¹⁵cm^-3range) -GaAs crystals, synthesized and pulled from PBN crucibles contain residual shallow donor impurities typically in the mid 10¹⁴cm^-3, exhibit bulk resistivities above 10⁷Ω . cm, and maintain the high sheet resistances required for IC fabrication (>10⁶Ω/□) after implantation anneal. Direct²⁹Si channel implants exhibit uniform (± 5 percent) and predictable LSS profiles, high donor activation (75 percent), and 4800- to 5000-cm²/V . s mobility at the (1 to 1.5) × 10¹⁷cm^-3peak doping utilized for power FET's. It has also been established that LEC crystals can provide the large-area, round     

GaAs microwave devices and circuits with submicron electron-beam defined features

This paper describes the fabrication and application of GaAs FET's, both as discrete microwave devices and as the key active components in monolithic microwave integrated circuits. The performance of these devices and circuits is discussed for frequencies ranging from 3 to 25 GHz. The crucial fabrication step is the formation of the submicron gate by electron-beam lithography.     

Periodic slow-wave low-loss structures for monolithic GaAs microwave integrated circuits

Slow-wave structures on GaAs semi-insulating substrate, obtained by periodically loading a coplanar line with high-Q overlap capacitors, are described. They operate up to X-band, reducing significantly the signal phase velocity by a factor nearly independent of the frequency. Owing to their low transmission losses, they are particularly suitable for monolithic GaAs f.e.t. circuits.     

High-temperature microwave characteristics of GaAs MESFET deviceswith AlAs buffer layers

AlAs buffers used to reduce the leakage current of high-temperature GaAs MESFET devices are shown to have no detrimental effect on the microwave performance measured to 200°C. The f_t values decrease with increasing temperature, but do not appear to be influenced by the AlAs buffer. The f_max values also decrease with increasing temperature; however, they are improved with increasing AlAs buffer thickness due to a concomitant decrease in the device output conductance, At 200°C ambient temperature, f_t and f_max values of 14.5 GHz and 36.7 GHz, respectively, were measured     

Computer simulation of multifrequency LSA oscillations in GaAs

The use of transmission lines in an equivalent circuit as suggested by Copeland [1] (instead of the usual lumped circuit elements) has resulted in computer simulation of the multiple-frequency operation associated with LSA oscillation in GaAs [2]. This technique is useful in determining design parameters for eliminating the low-frequency subharmonic and/or maximizing efficiency. For mobilities of 6000 cm²/Vċs, efficiencies are generally less than 1 percent if a lower frequency is present, and as high as 8.4 percent when it is absent.     

Vertical microstrip transition for multilayer microwave circuits with decoupled passive and active layers

A novel broadband (including dc) microstrip-to-microstrip vertical transition for multilayer microwave circuits is proposed. This transition solves the problem of the discontinuity typically appearing in via hole transitions between two microstrip transmission lines in different layers. An analogy existing between this transition and a rectangular coaxial line is discussed. A parametric study alongside with the experimental results of the transition are presented. Reduction of local oscillator to radio frequency leakage in a mixer with this transition is demonstrated.     

LSA operation of a gallium arsenide device in microstrip

Two LSA microstrip oscillators were made. The poor performance of the first oscillator was found by a time-domain computer simulation to be caused by poor circuit design and the effects of the LSA device package. A second circuit was constructed which eliminated the device package and used a more straightforward design. Thirty watts of RF power was generated in the second circuit at a frequency of 1.96 GHz, with an efficiency of 12.5 percent.     

Modelling of microwave GaAs f.e.t. in common-gate operation

The common-source and common-gate equivalent circuits of GaAs f.e.t. at microwave frequencies are established and used to simulate the variations of gain and noise figure with frequency. The results obtained explain why the experimental minimum noise figure and source admittance in the common-gate configuration are different from the theoretical expectations based on low-frequency calculations.     

Failure mechanisms in large-scale integrated circuits

A study was made of the factors affecting the reliability of large-scale integrated (LSI) circuits. Particular attention was given to the effect on array reliability of the additional processing steps required to obtain multilevel metalization. The additional significant steps are low temperature deposition of a second dielectric layer on metalized LSI wafers, etching of vias through the second dielectric, and second level metalization. Consideration was also given to the effect of other trends in LSI, such as the use of smaller geometry and closer spacings. Possible new failure modes in multilevel arrays are: 1) shorts or increased leakage through or along deposited second layer dielectrics, 2) opens or increased series resistance in conductors, and 3) silicon surface effects. A review of literature on LSI was supplemented by results of a number of concurrent LSI programs and experimental studies. Test vehicles were designed to provide fundamental information about each of the categories of failure. Data obtained using these test vehicles to evaluate the multilevel metalized array structures are presented. A discussion concerning the merits and limitations of the specially designed test vehicles for process development, process control, and reliability tests is given. It is concluded that with the proper in-process controls, tests and screens, LSI arrays will be substantially more reliable per function accomplished than are conventional integrated circuits.     

Design of broadband microwave circuits

The relation between the scattering-matrix eigenvalue phase/frequency responses and the energy stored in a general microwave junction filled with an anisotropic material can be used to facilitate the design of broadband microwave circuits. The technique of this approach is illustrated for a waveguide Y-junction circulator.     

射频/微波电路中的薄膜无源器件

就在不久之前,大多数微波电容器还都基于多层陶瓷烧制技术。在生产过程中,多层高导电性的金属合金电极层和低损耗的陶瓷绝缘层交错排列,从而得到所需要的电容值。然后,将合成的叠层进行高温烧制,将其烧结成单片结构。这一工艺目前仍然很好地满足大容量射频电容器以及大功率电容器的需要。     

Detailed computer analysis of LSA operation in CW transferred electron devices

In the first part of the paper the importance of the microwave circuit parameters on the attainment of LSA oscillation in ideal uniform devices is investigated. It is shown to be desirable for the circuit to have high-dynamic impedance. In consequence stray capacity at the device, due to the device configuration or to the mounting arrangement, is to be avoided. The existence of a capacityCin parallel with the cold-device capacity C0effectively raises the lower limit for LSA operation ton/f > 2 times 10^{4}[(C+C_{0})/C_{0}]. In the second part of the paper devices with typical doping and mobility profiles are considered to operate in circuits with low-dynamic impedance as well as in circuits with high-dynamic impedance. The results presented show that the LSA operating efficiency can be very sensitive to certain inhomogeneities, notably doping ramps of order 12½ percent and high-resistivity regions at the cathode contact. The efficiency degradation is, however, very dependent on the circuit in which the device is operating. Finally it is shown that the efficiency of a CW device may be raised by several percent in some cases by compensating for the mobility profile with a suitable doping gradient.     

Ion implantation of GaAs integrated circuits

The conditions required for the fabrication of low pinch-off voltage MESFETs by ion implantation have been established. Calculation of the device characteristics from measured carrier concentration profiles has shown that of Vp of -1.5V is best achieved using low implant energies together with ion doses of 2 × 10¹² cm^?2. Characterisation of the implant and annealing conditions has enabled the implanted dose to be corrected for the activation after annealing. Measurement of the processed devices has shown the variation in saturation current to be as low as 3 mA over 75% of the wafer area, showing suitability for use in logic circuit fabrication.