Douglas J. Carlson

Low cost Multifunction Phased Array Radar concept

MIT Lincoln Laboratory and M/A-COM are jointly conducting a technology demonstration of affordable Multifunction Phased Array Radar (MPAR) technology for Next Generation air traffic control and national weather surveillance services. Aggressive cost and performance goals have been established for the system. The array architecture and its realization using custom Transmit and Receive Integrated Circuits and a panel-based Line Replaceable Unit (LRU) will be presented. A program plan for risk reduction and system demonstration will be outlined.

Active control of the electrical properties of semi-insulating GaAs

The resistivity of semi-insulating gallium arsenide has been controlled over the range 2 x 10 7 to 5 x 10 8 Ω.cm by the carbon monoxide concentration in the puller atmosphere. To achieve this range of resistivity the CO levels were varied from 0.01% to 32%. The relationship between CO concentration, carbon in the crystal and resistivity was found to hold over the whole of this range, until the carbon content exceeded 3 x 10 16 at cm -3 and the material became P-type. Very low CO concentrations were achieved by gettering with hot titanium, and higher CO concentrations by the use of argon and CO 2 mixtures. A flow-through gas system was used to maintain the concentration ratios of the various species at the desired level. The concentrations of Ar, CO, CO 2 , H 2 O and H 2 were monitored throughout the growth runs with a residual gas analyzer.

Czochralski growth of single crystals of Ni3−xMnxSn

Abstract Single crystal growth in the Heusler alloy system Ni 3- x Mn x Sn was explored using the Czochralski technique. For x close to 1.0, single crystals (as indicated by X-ray Laue pictures and metallography) were grown under an Ar atmosphere, in vitreous C crucibles, at growth rages of ∼ 0.5 inch/h, using a stirring speed of 30 rpm. When x in the melt was not close to 1.0, constitutional supercooling problems and dendritic “globs” made it extremely difficult to increase boule diameter and control growth on seeds. Lattice parameters, pyrometer temperature readings and differential thermal analysis suggest that Ni 2 MnSb is close to a congruently melting composition, so that solids frozen very far from x =1.0 differ in composition from the liquid and as a consequence their growth would be expected to be difficult. However, with care boules with substantial sized single crystal grains with x as large as 1.5 and as small as 0.9 could be grown.

Commercial manufacturing practices applied to phased array radars

Transmit/Receive Modules for Phased Array Radar are often identified as a key cost driver for the system. The cost structure of the module is driven by both the performance specifications and the choices made in design and manufacturing of the module. Seeking a path to dramtically lower the cost of T/R modules for phased array systems, commercial processes and practices have been adopted for the MMIC design, MMIC packaging and module construction. These new manufacturing approaches offer a path to cost reduction while maintaining a high level of performance.

Aperture PCB assemblies: Transition to production ready designs

MACOM designed the initial radar panels for the next generation surveillance radar with limited funds, with the philosophy that the initial design would be kept as simple as possible and that incremental improvements would be made as the program progressed, with the intent of having a tile assembly that is easy to manufacture by the first build of a larger radar (approximately 80 panels). The design is now being updated for an 80 panel order with the goal of optimizing the design electrically, for assembly and for test. This paper will discuss both the design, assembly, packaging, and test updates that are being made to have a board and board assembly that is easy to manufacture and test, with the goal of keeping cost as low as possible. These techniques will not only be used for the MPAR tiles, but also for tiles that are currently being developed for other programs.

Advances in GaN technology and design for active arrays

Gallium Nitride HEMT technology has reached the maturity where it is reliably being deployed for both military and commercial applications. But, because of its extreme ruggedness, reliable high temperature operation, and high operational RF power density, GaN based amplifiers can offer both new capability and challenges for Phased Array Systems. This work will present the basics of GaN technology, amplifier design methodologies and tradeoffs, and comparisons to traditional GaAs technology for use in phased array T/R modules.

Improved phosphorus injection synthesis for bulk InP

High purity, stoichiometric InP is being produced in crucible-shaped, 3-kg charges by the phosphorus injection method in a high-pressure magnetic liquid encapsulated Czochralski (MLEC) crystal growth system. Dedicated heaters in the phosphorus injector assembly are used to heat and controllably inject the phosphorus vapor into the liquid encapsulated indium melt. Glow discharge mass spectroscopy and van der Pauw measurements of the polycrystalline charges and the Czochralski wafers confirmed the low background levels of impurities.