Vladimir Sokolov

Laser link performance improvements with wideband microwave impedance matching

The wideband microwave performance of a laser link was improved using a lossless microwave impedance-matching network. Matching has been achieved from 3 to 9.5 GHz, which is more than one octave with a 5 dB associated improvement in both throughput loss and noise figure for the optical link. The improved noise figure makes it possible to use the laser link with lower-gain amplifiers in front of the laser, and the improved throughput loss reduces the gain needed after the link. It is concluded that impedance matching not only improves the performance but also reduces power consumption in the whole system.

Comparison of MESFET and HEMT MMIC technologies using a compact Kaband voltage-controlled oscillator

To compare the capability of MESFET and HEMT technologies for monolithic microwave integrated circuit (MMIC) implementation we have fabricated and tested discrete field-effect transistors (FETs) and a novel Ka-band monolithic voltage controlled oscillator (VCO). We implemented the circuit with three different active devices: moderate- and high-doped ion-implanted MESFETs (metal-semiconductor FETs) and AlGaAs/GaAs HEMTs (high electron mobility transistors). A comparison of the measured oscillator phase-noise and an independent comparison of the temperature dependence of MESFET and HEMT RF equivalent circuits yields two general guidelines: MESFETs are preferred over HEMTs for applications requiring low phase-noise and temperature insensitive operation.

Lattice-engineered MBE growth of high-indium-mole-fraction InGaAs for low-cost MMICs and 1.3- to 1.55-um OEICs

Using molecular beam epitaxy (MBE) and lattice engineering techniques, the feasibility of combining photonic devices applicable to the 1.3 to 1.55 micrometers wavelength range and monolithic microwave integrated circuits (MMICs) on GaAs is demonstrated. A key factor in the MBE growth is incorporation of an InGaAs active layer having an indium arsenide mole fraction of 0.35 or greater and its lattice compatibility with the underlying semi-insulating GaAs substrate. The InGaAs layer used for the photonic devices, can also serve as the active channel for the high electron mobility transistors for application in MMICs. Several examples of active and passive photonic devices grown by MBE are presented including an optical ridge waveguide, and a photodetector for detection of light in the 1.3

Low-noise MMIC performance in Kaband using ion implantation technology

mUm range. The material structure includes a 3-layer AlGaAs/GaAs/AlGaAs optical waveguide and a thin InGaAs absorbing layer situated directly above the optical waveguide. Metal-semiconductor- metal (MSM) photodetectors are formed on the top surface of the InGaAs layer for collection of the photo-induced carriers. The optical ridge waveguide is designed for lateral incidence of the light to enhance the MSM photodetector responsivity. Initial measurements on the optical waveguide and photodetector are presented.

Phase shifter technology assessment - Prospects and applications

The progress made in producing low noise MMICs in Ka-band using an ion-implantation technology is reviewed. The technology is characterized by 3.8 dB noise figure with 14-16 dB gain and is suitable for high volume applications where the cost is to be kept low.

Three dimensional package for monolithic microwave/millimeterwave integrated circuits

Capabilities and limitations of MMIC phase shifter technology at microwave and millimeter wave frequencies are reviewed. MMIC-based phase arrays make it possible to integrate active elements at the array face, i.e., to incorporate transmit power amplifiers and/or low noise amplifiers at each antenna element. Active elements make it possible to increase power efficiency and reliability and provide graceful degradation. Monolithic integration of the various transmit/receive functions including phase shifting is considered to be feasible through at least the lower millimeter-wave frequency range (about 30-100 GHz). MMIC integration also allows more flexibility in array design including those that are intended for airborne conformal applications.