Monolithic GaAs interdigitated couplers

This paper described the design, fabrication, and performance of two monolithic GaAs C-band 90° interdigitated couplers with 50- and 25-ω impedances, respectively. A comparison of the performance of these two couplers show that the 25-ω coupler has the advantages of lower loss and higer fabrication yield. the balanced amplifier configuration using 25-ω couplers will require a fewer member of elements in the input-output matching circuit of the FET amplifier. The fewer number of matching elements results in great savings in the GaAs real estate for microwave monolithic integrated circuits (MIMIC's). Both the couplers have been fabricated on a 0.1-mm-thick GaAs SI substrate. The measured results agree quite well with calculated results. The losses of the 50- and 25-ω couplers are 0.5 and 0.3 dB, respectively, over the 4-8-GHz frequency band.     

Three-guide optical couplers in GaAs

Three-guide optical couplers consisting of three 4.75-μm-wide slab-coupled rib guides separated by 4.25μm have been fabricated in GaAs. The performance of these couplers at 1.28 μm is in close agreement with that predicted using a modified effective-index method to obtain an approximate analytical solution for this type of coupler. The coupling length needed to symmetrically transfer power from the center guide to the two outside guides was 3.2 mm. At this length, less than 1 percent of the power remained in the center guide. The length needed to transfer power from one outside guide to the other outside guide was ≈ 6.4 mm, which isapprox sqrt{2}- times that of a similar two-guide coupler and twice that required to couple power from the center guide to the two outside guides. The power transfer efficiency in this case is not as good as when power was inputted into the center guide. Three-guide couplers of this type should prove useful as power dividers and combiners, especially in cases where waveguide bend losses preclude the use of"Y"- junctions. They may also prove useful as replacements for two-guide couplers where either sharper transfer characteristics are desired or where losses due to waveguide bends are again unacceptable.     

Ultrabroadband GaAs monolithic amplifier

A 500 kHz?2.8 GHz, 13.5 dB GaAs monolithic amplifier has been developed for gigabit baseband pulse amplification. Input VSWR was reduced using inter-gate-drain negative feedback. The interstage circuit is a DC coupled circuit consisting of a high impedance transmission line.     

Ultra-broad-band GaAs monolithic amplifier

GaAs monolithic IC design and fabrication techniques suitable for baseband pulse amplification have been developed. The developed GaAs monolithic amplifier has a two-stage construction using two source-grounded FET's. To reduce input VSWR without serious noise-figure degradation, an inter-gate-drain negative feedback circuit was adopted. An interstage circuit is a dc-coupled circuit consisting of an appropriate impedance transmission line. Gate voltage for the second-stage FET is self-biased. The amplifier has 13.5-dB gain over the 3-dB bandwidth from below 500 kHz to 2.8 GHz. Less than 6-dB (7-dB) noise figure was obtained from 700 MHz to 2.2 GHz (150 MHz to 3 GHz). Input VSWR is less than 1.5     

Monolithic GaAs Lange coupler at X-band

Monolithic 3-dB Lange couplers have been fabricated on semi-insulating GaAs. Loss at the center frequency of 9.5 GHz is 0.7 dB.     

Stable monolithic GaAs FET oscillator

A monolithic X-band GaAs FET oscillator has been developed. Passive circuit components are lumped capacitors and inductors on semi-insulating GaAs; the chip size is 1.2 × 1.4 mm2. Stabilised with a Ba2Ti9O20 dielectric resonator, the oscillator delivers more than 30 mW output power at 10.8 GHz with a maximum chip efficiency of 20%. The frequency drift is better than 1 × 10?6/K from ?20°C to 80°C.     

High-efficiency monolithic GaAs IMPATT diodes

Impedance-matching circuits were integrated on the same chip as the IMPATT diodes to produce monolithic impatt diodes for millimetre-wave applications. A drastic reduction of device-to-circuit parasitic elements was achieved by placing the external circuitry very close to the device. Oscillators fabricated in this fashion gave the highest efficiencies reported so far in the 30?35 GHz range with 28% conversion efficiency using hybrid-Read structures.     

Ka-band monolithic GaAs balanced mixers

Monolithic integrated circuits have been developed on semi-insulating GaAs substrates for millimeter-wave balanced mixers. The GaAs chip is used as a suspended stripline in a cross-bar mixer circuit. A double sideband noise figure of 4.5 dB has been achieved with a monolithic GaAs balanced mixer filter chip over a 30- to 32-GHz frequency range. A monolithic GaAs balanced mixer chip has also been optimized and combined with a hybrid MIC IF preamplifier in a planar package with significant improvement in RF bandwidth and reduction in chip size. A double sideband noise figure of less than 6 dB has been achieved over a 31- to 39-GHz frequency range with a GaAs chip size of only 0.5 × 0.43 in. This includes the contribution of a 1.5-dB noise figure due to IF preamplifier (5-500 MHz).     

GaAs monolithic integrated optical preamplifier

A GaAs monolithic integrated optical preamplifier has been developed based on the transimpedance principle. By associating the amplifier with an external p-i-n diode, a sensitivity of -38 dBm was measured at 140 Mbits/s and 10^-9error rate with a signal wavelength of 1.3 μm. A TiWSiN-integrated technology was used to realize larger than 100-kω feedback resistors and gate leakage could be minimized by improving Schottky contact deposition and employing selective implantation. The optimization details of the FET and resistor elements, as well as the design techniques for integrated transimpedance amplifiers are presented.     

GaAs monolithic analogue frequency halver

A new 12 GHz GaAs monolithic analogue frequency halver is presented. The circuit uses two FETs to parametrically produce the subharmonic output frequency. A bandwidth of 650 MHz was obtained for an input power level of 14 dBm. The typical conversion loss was 9 dB.     

GaAs MESFET's fabricated on monolithic GaAs/Si substrates

GaAs MESFET's have been fabricated for the first time on monolithic GaAs/Si substrates. The substrates were prepared by growing single-crystal GaAs layers on Si wafers that had been coated with a Ge layer deposited by e-beam evaporation. The MESFET's exhibit good transistor characteristics, with maximum transconductance of 105 mS/mm for a gate length of 2.1 µm.     

Photoelastic optical directional couplers in epitaxial GaAs layers

Photoelastic channel optical waveguides showing strong lateral confinement at ?=1.55 ?m have been fabricated by etching a narrow slot through a Au Schottky contact deposited on an n/n+ GaAs layer. Such structures allow electro-optic directional coupler switches of short coupling length (~2 mm) to be easily realised.     

High-efficiency W-band GaAs monolithic frequency multipliers

High efficiency monolithic frequency multipliers have been designed, fabricated, and tested in the W-band. In microwave monolithic integrated circuits (MMICs), transmission lines with various impedances are used not only to transfer the input and output signals, but also to match the impedances of active devices to those of the input and output ports, with open and/or short stubs. Thus, loss in the transmission lines is one of the major limiting factors on circuit efficiencies. This paper presents high-efficiency MMIC frequency doublers with a balanced pair of GaAs Schottky barrier planar diodes operating in the W-band. The geometries of transmission lines were optimized to reduce the loss and thus to improve the efficiency. The demonstrated efficiency of 36.1% is the highest efficiency reported for a diode-based MMIC frequency multiplier in the W-band.     

Ion-implanted GaAs slow wave monolithic structure

The use of MeV ion-implantation for realization of a GaAs monolithically compatible device is demonstrated. Ion implants up to 6 MeV in energy are used employing Si and S atoms. The fabricated device is an electromagnetic slow wave microstrip-like structure designed for performance into the millimeter wave regime. Phase shift θ and insertion loss L measurements are performed for frequencies 2–18 GHz at room temperature. Comparison of the experimental ion-implanted device results to epitaxial device results indicates comparable electrical performance, with no more than a 30% reduction in θ but with an improvement in loss behavior, namely a L reduction up to 40%. These θ and L differences between the ion-implanted and epitaxial devices are attributed to differences in doping profiles. Theoretical modelling of θ characteristics produces agreement with experimental data to within a few percent.     

44-GHz monolithic GaAs FET amplifier

Millimeter-wave monolithic GaAs FET amplifiers have been developed. These amplifiers were fabricated using FET's with MBE-grown active layers and electron-beam defined sub-half-micrometer gates. Source groundings are provided through very low inductance via holes. The single-stage amplifier has achieved over a 10-dB gain at 44 GHz. A 300-µm gate-width amplifier has achieved an output power of 60 mW with a power density of 0.2 W per millimeter of gate width.     

Gigahertz band GaAs monolithic limiting amplifier

The letter presents the design and performance of a gigahertz band limiting amplifier IC using GaAs MESFET IC technology. With a two-chip connection, an AM/PM conversion of 0.7°/dB over 43 dB input dynamic range at 1 GHz has been achieved.     

Ultra-broad-band GaAs monolithic direct-coupled feedback amplifiers

GaAs monolithic direct-coupled amplifiers with load resistor and feedback resistor have been developed. The fabricated amplifier using the self-aligned implantation for n⁺-layer technology (SAINT) FET's has a 10-dB gain, a 7.2-dB noise figure, and input VSWR less than 2.0 over the frequency range from dc to 4 GHz.     

2.5-THz GaAs monolithic membrane-diode mixer

A novel GaAs monolithic membrane-diode (MOMED) structure has been developed and implemented as a 2.5-THz Schottky diode mixer. The mixer blends conventional machined metallic waveguide with micromachined monolithic GaAs circuitry to form, for the first time, a robust, easily fabricated, and assembled room-temperature planar diode receiver at frequencies above 2 THz. Measurements of receiver performance, in air, yield at T_receiver of 16500-K double sideband (DSB) at 8.4-GHz intermediate frequency (IF) using a 150-K commercial Miteq amplifier. The receiver conversion loss (diplexer through IF amplifier input) measures 16.9 dB in air, yielding a derived “front-end” noise temperature below 9000-K DSB at 2514 GHz. Using a CO₂-pumped methanol far-infrared laser as a local oscillator at 2522 GHz, injected via a Martin-Puplett diplexer, the required power is ≈5 mW for optimum pumping and can be reduced to less than 3 mW with a 15% increase in receiver noise. Although demonstrated as a simple submillimeter-wave mixer, the all-GaAs membrane structure that has been developed is suited to a wide variety of low-loss high-frequency radio-frequency circuits     

94 GHz microstrip monolithic GaAs mixer

A microstrip monolithic GaAs mixer has been designed and fabricated for operation in the millimetre-wave band. A 6.5 dB minimum conversion loss has be achieved in narrowband operation (fLO = 93.7GHz and fIF= 130MHz); this figure includes the effect of losses and mismatch in the circuit and test fixture.     

A GaAs monolithic low-noise broad-band amplifier

Describes the design, fabrication, and performance of GaAs monolithic low-noise broad-band amplifiers intended for broadcast receiver antenna amplifier, IF amplifier, and instrumentation applications. The process technology includes the use of Czochralski-grown semiinsulating substrates, localized implantation of ohmic and FET channel regions, and silicon nitride for passivation and MIM capacitors. The amplifiers employ shunt feedback to obtain input matching and flat broad-band response. One amplifier provides a gain of 24 dB, bandwidth of 930 Mhz, and noise figure of 5.0 dB. A second amplifier provides a gain of 17 dB, bandwidth of 1400 MHz, and noise figure of 5.6 dB. Input and output VSWR's are typically less than 2:1 and the third-order intercept points are 28 and 32 dB, respectively. Improved noise figure and intercept point can be achieved by the use of external RF chokes.