Diamonds and other:
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Diamonds are used elsewhere, not Rhombic, but a VERIFICATION of DIAMOND TECH: IMHO:
Diamond Hikes Power Levels Of Resistors And Terminations
The availability of high-quality diamond substrates has led to the development of high-power resistors and terminations.
Thomas Dowling and Elliot Lewis
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DIAMOND heat sinks have long been known as tremendous heat conduits. Unfortunately, the high cost of the material has limited its application in high-frequency designs until now. With recent advances in both diamond-substrate material processing and thin-film technology, the engineers at RF Power Components, Inc. (Bohemia, NY) have been successful in developing lines of cost-effective, high-power drop-in resistors and terminations with as much as 200-W power-handling capability at 4 GHz.
These resistors and terminations are built with CVD diamond heat spreaders for high power-handling capability at high frequencies.
The new resistors and terminations (see figure) are housed in drop-in and flange-mount packages. A total of four resistors and four terminations comprise the initial product lines (Table 1). Model RFP-100-100DR, for example, is a high-power resistor with only 0.4-pF capacitance that can be used past 8 GHz. It is rated for 100-W power-handling capability. A 50-W 100-W termination, model RFP-100-50-DT, exhibits VSWRs of 1.11:1 from DC to 1.5 GHz, 1.20:1 to 4.0 GHz, and 1.30:1 to 8.0 GHz. The drop-in package measures 0.16 × 0.08 × 0.05 in. (4.06 × 2.03 × 1.27 mm).
HIGH-POWER RESISTOR
Model RFP-200-100DRVV is a flange-mount 200-W resistor with only 0.54-pF capacitance and can be used in applications past 4 GHz. As a termination with the same power-handling capability, model RFP-200-50DTVV exhibits VSWRs of 1.11:1 from DC to 2 GHz, 1.20:1 to 3 GHz, and 1.30:1 to 4 GHz. The flange-mount package measures 0.50 × 0.16 × 0.13 in. 12.7 × 4.06 × 3.30 mm).
The availability of high-power components based on diamond substrates is critical for several reasons. As more communications systems, such as personal-communications-services (PCS) networks, rely on high-power but unobtrusive cell sites and base stations, engineers are pressured to design smaller, more robust power combiners and terminations. Diamond provides better thermal resistance than beryllium oxide (BeO) substrates. Diamond substrates are nontoxic, which make them attractive in light of increasing Environmental Protection Agency (EPA) restrictions and in environmentally-sensitive areas, such as Europe, which restrict the use of BeO substrates.
Diamond is superior in its thermal characteristics to such materials as BeO and AlN, and has a lower dielectric constant than most commonly-used heat spreaders (Table 2). The use of diamond heat spreaders permits conventionally-accepted performance limits for power density, component size, and frequency to be dramatically extended, such as in the new lines of high-power resistors and terminations.
It is now practical to develop diamond-based high-power passive components in part due to advances in chemical-vapor-deposition (CVD) diamond processing, which allows the production of high-quality, large-area diamond wafers. The change can also be credited to improvements in thin-film processing, allowing strong bonds to be made between metallized films and diamond substrates in spite of the diamond's lack of an oxided ceramic phase (which normally aids adhesion).
On the material-processing side, Crystalline Materials Corp. (San Ramon, CA) has been able to develop uniform CVD diamond substrates called the CrystalCool heat spreaders. The firm offers various thicknesses in sizes that are precisely laser cut to a customer's specifications. The company has successfully reduced numerous cost drivers from optimizing deposition rates, including minimizing the cost of energy (the firm's diamond fabrication plant is located in Calgary, Alberta, Canada, in a region known for its low cost of electricity).
MAKING DIAMOND
Crystalline Materials Corp. has been able to deposit larger areas of diamond, resulting in dramatic increases in yield and capacity.
The company's efforts have resulted in a cost reduction of diamond substrates by a factor of 10 during the last three years. The CVD process yields free-standing diamond material from 0.01 to 0.04 in. (0.25 to 1.02 mm) thick in industry-standard substrate sizes. Polycrystalline CVD diamond is produced by condensing carbon atoms derived from a carbon and hydrogen gas mixture onto a substrate. The carbon source is usually methane, carbon monoxide, or acetylene. This gas mixture is activated by heating between 2000 to 5000 K by means of microwave energy, combustion, or DC plasma heating. Such high temperatures dissociate the hydrogen molecules to produce atomic hydrogen; atomic hydrogen stabilizes the diamond material during growth and suppresses the formation of graphite. The activated gas impinges on a substrate maintained in a vacuum between +700 and +1100°C.
The substrate must be prepared so that the surface promotes the nucleation of the tight tetrahedral bonds characteristic of diamond. Deposition rates can range from 1 to 100 mm/hour depending on the carbon transport mechanism. Crystalline Materials Corp. employs a proprietary DC arc-jet technique which offers the highest deposition rate available. After the diamond has grown to a specified thickness, the free-standing diamond substrate is separated easily from its growth substrate, polished, and then cut to size.
COMBINING SKILLS
Working with this materials supplier, the engineers at RF Power Components have combined their processing capabilities to the diamond substrates in order to produce resistors and terminations that are compatible with RF/microwave industry standards. In many cases, these resistors and terminations will drop into existing conventional circuits. Construction is similar to existing ceramic resistors and terminations based on thin-film technology.
As an example, a diamond-based resistor with a chip size of 0.080 × 0.155 × 0.025 in. (2.03 × 3.94 × 0.64 mm) and a resistor film size of 0.03 × 0.10 in. (0.76 × 2.54 mm) provided power dissipation of 100 W. The thermal resistance for this unit is 0.5°C/W, with operation at 100 W resulting in a flange temperature of +87°C and a resistor film temperature of +137°C (for a temperature delta of 50°C).
Designers who require compact, high-power/high-frequency resistors or terminations with low parasitic capacitances and low VSWR performance will find the devices quite useful. The resistors permit the construction of power combiners and dividers with high power-handling capability, low insertion loss, and high isolation. While the cost of the patent-pending diamond-based resistors and terminations is somewhat higher than that of BeO devices, overall manufacturing costs may be comparable. External resistor matching is virtually eliminated with the diamond-based devices, resulting in less circuit losses, less overall associated passive components, and less occupied printed-circuit-board space. P&A: stock. RF Power Components, Inc., 125 Wilbur Pl., Bohemia, NY 11716-2482; (516) 563-5050, FAX: (516) 563-4747.
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Diamonds Are Microwave Tubes' Best Friend
MIDDLESEX, UK--Alumina, beryllia, boron nitride, and aluminum nitride have long been used in various parts of microwave tubes due to their high electrical resistance and good thermal conductivity. But these materials could fall by the wayside due to the findings of a research program conducted by Thorn Microwave Devices Ltd. (TMD) and funded by the UK Defence Research Agency. TMD discovered that chemical-vapor-deposited (CVD) diamond offers many advantages over the traditional materials and has none of the disadvantages. CVD diamond offers up to ten times the thermal conductivity and one-quarter the coefficient of expansion together with high electrical resistivity compared with the traditional materials. One of the materials that CVD diamond could replace is beryllia, which features high resistance and good thermal conductivity, but is reported to be a carcinogen. TMD has established the machining, chemical and thermal processing, metallization, and brazing capabilities of CVD diamond. The next step is to build a prototype microwave tube using the new material.
Si And Ge Form New Marriage For High-Frequency Chips
HEILBRONN, GERMANY--The founding fathers of semiconductor technology materials--silicon (Si) and germanium (Ge)--are linking up in a joint process called silicon-germanium (SiGe) to be used for fabricating high-frequency chips for mobile communications applications. The new semiconductor cocktail is the brainchild of Temic Telefunken's Microelectronic group, which claims that the technology offers advantages over conventional silicon and the newer gallium-arsenide (GaAs) processes. The company says that it has developed SiGe devices whose operating speed is significantly faster than silicon. And it says that SiGe is much simpler and less expensive to implement than GaAs. These factors make it a natural for fabricating ICs for communications applications such as mobile and cordless phones. The company hopes to use the process to produce low-power, low-noise devices that will improve voice quality, run longer on a battery charge, and be less expensive than current ICs. Production of SiGe devices is scheduled for early this year using a process that is compatible with standard semiconductor processes now in use.
Save IEEE-488, Plead Instrument Manufacturers
PALO ALTO, CA--IEEE-488, the venerable communications warhorse of data transfer in test systems, could undergo major surgery if the Institute of Electrical and Electronics Engineers (IEEE) convinces enough engineers that the standard must be brought up to the capabilities of today's higher-speed systems. In the opposing camp are noted instrument makers such as Hewlett-Packard Co. and Keithley Instruments GmbH, along with ines, Inc., a maker of GPIB interface cards, and ACEA, a test-and-measurement development company in Wierden, Netherlands who argue that any changes to the standard could lead to significant implementation problems and testing uncertainty among a large population of IEEE-488 users. The revised standard, to be known as High-Speed 488 or HS-488, is to be voted on soon although the actual date for casting ballots has not been set.
Opponents of HS-488 claim that it constitutes a radical change to the form and function of IEEE-488 and could lead to disruptive errors for the installed customer base, which is worldwide. In fact, many companies rely on the consistency and operational simplicity of IEEE-488, which measures data accurately and without extensive troubleshooting of test setups. A key complaint of the opposition is that HS-488 has not been tested adequately on-site, particularly in the areas of interoperability and noise immunity, and very little documentation of this testing has appeared in the technical media.
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Chucka
P.S.-= A Search of RF Power only yielded RFP a FORREST ( WOOD) Products company at S.I. and then S.I. came up with this as a dead end:
<<... RF POWER PRODUCTS INC
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P.S.- However the RF power Text Seached led to S-C talk about Resistance and in the origibal referred post to the link below, and in the two replies, I just see that RESISTANCE IS FUTILE! Psst- It is all involving power and superconductivilty and transmission losses and electronic coolness and electronics overheating CONTROLS, the CORE TECHs of Rhombic address these issues, I am NOT saying all links apply as anything but anther way of verifing the underlying TECH, semblance is not need be identical. Similar is enuff! Enough SAID!RE:
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