Tuesday, June 30, 2015

Combining High Power and High Frequency in rf and Microwave.

Combining high power and high frequency in rf and microwave.

The following paragraphs are excerpts of an interview with Alen Fejzuli, president of Res-Net Microwave, Inc. His plain-speak comments are intentionally "teched down" for the listener and writer, a non-engineer. 

On the design approach:

Designing for rf and microwave requires solid understanding of transmission line theory, and application of  "high frequency rules," if you will, to the design of our components. The Smith Chart, wavelength, VSWR -- these items are all foreign to the world of digital design. 

On the products and basic challenge:

Res-Net Microwave has been known for more than 25 years as a manufacturer of high power components -- resistors, attenuators, and terminations. Typically, when you're designing high power components there are physical limitations. The world of physics is against you. You're trying to make high frequency components that also need to dissipate a lot of power. In order for a resistor or terminator to dissipate a lot of power, it tends to require considerable size. However, as frequency increases, wavelength decreases, and once wavelength becomes smaller than the component, a number of effects take place that change the properties and performance of the component. For example, at low-frequency resistor looks like a resistor.  On the other hand, at high frequency a resistor will have parasitic capacitance and inductance, which limits the high frequency performance. 

On size and power:

How well a component dissipates power is driven by the type of material that is used, for example, we use Alumina, Aluminum Nitride (AlN), Beryllium Oxide (BeO), and, now, synthetic diamond (CVD diamond). Each of these materials dissipate power at a specific rate, AlN, BeO, and CVD in increasing order (lowest to highest, Figure 1).  With the introduction of CVD diamond material into our manufacturing processes, the differences have become dramatic. For example, we have little (CVD) resistors that are 40 by 20 mils that can dissipate 20 watts, even in that small size. A BeO component of the same size might dissipate 5 or 6 Watts, an ALN maybe 3 Watts.  

On size and LOTS of power:

If you look at a 1000-watt resistor on BeO material, it is 1 square inch in size, pretty big!  We can reduce the size of that component down to roughly __0.2 square inch___ by using a CVD diamond substrate to create a component of the same power rating. Furthermore, due to its size, the larger high power resistor also acts like a big parallel plate capacitor.  The combined effects of the resistor and capacitor create a low pass filter which limits the high frequency performance of these high power components.

More generally, capacitance is always present in our world, and that's why there's always a tradeoff between power and frequency.

On size and frequency:

This benefit of reducing component size without sacrificing power dissipation brings us back around to the wavelength factor -- once the wavelength becomes smaller than the component, reflected power and VSWR increase with power (presuming frequency remains the same), parasitic capacitance increases with frequency (presuming power remains the same), and general performance diminishes quickly with increases in both power and frequency.
And that's how Res-Net has made the world of physics work for us, instead of against us. By minimizing the size required to dissipate the power called for, we're not only maximizing power -- we're also maximizing the high frequency range of the component and circuit.


That 40 by 20 mil CVD diamond resistor I mentioned previously operates well up to 35 GHz at 20 watts. We have miniature terminations spec'd at 26.5 GHz, 50 watts. 

Wrap-up: Small is good. Very very good.

In the digital world, the push to smaller and smaller components is driven mostly by space and weight limitations and the general push for miniaturization. In the rf and microwave world, there's a 4-way relationship between size, power, frequency/wavelength, and performance. We like to think we're pushing the limits on all fronts.

Figure 1.   

Monday, June 8, 2015

Hats off to a winner, and remembering heroes.

This past Saturday, June 6, 2015, horse racing fans around the world (plus many million curious onlookers) watched American Pharoah win the Belmont Stakes and become the first Triple Crown winner in 37 years.

Some were saying that it couldn't be done, that breeding for sprinters and distance horses had become so specialized that there may not be another Triple Crown, ever. But the jockey, Victor Espinoza, explained that he knew he could win early on, coming out of the first turn, just by the way the horse was running. It really appeared that the horse was reaching out farther than all other contenders in the field. Hats off.

It also marked the 71st anniversary of American and other Allied soldiers struggling to achieve a foothold at the beaches of Normandy. For the fortunate ones, D-Day would become a very long day. Hats off and thank you -- all of you -- on that June 6, in 1944.

Monday, June 1, 2015

Space. What now?

Remember the race to put a man into space and, then, to put a man on the moon? OK, we lost the first heat, but ran away in the final.

Those were the incredible days early days of NASA, when U.S. citizens looked on with chest-pounding pride at rocket liftoffs and eventually, a televised moonwalk. So much seemed to be happening as U.S. scientists pieced together progressive missions and experiments that made sense to the public, who shared in success celebrations and major lessons learned. Later, SkyLab, Space Shuttle, Space Station, Explorer, Mariner, Hubble........all inspirational.

Meanwhile, the public also learned about "spinoff" commercial products and technologies that developed with the help of NASA's needs for new solutions -- and dollars spent to meet these needs. Spinoffs helped justify to some extent the huge spending that was taking place.

Beginning in 1976, NASA created a publication entitled "Spinoff" to document such products and technologies, and to maintain a database. As of 2015, there are over 1,800 spinoff products in the database dating back to 1976. Spinoff examples include:

Infrared ear thermometers; heart pump for patients awaiting heart transplants; development of artificial muscle systems with robotic sensing and actuation capabilities; temper foam technology (memory foam); scratch-resistant eyeglass lenses; lightweight super effective space blankets often used in first aid kits; small aircraft anti-icing systems; highway safety surface grooving; much improved radial tires; moisture and chemical detection sensors; video enhancing and analysis systems and image stabilization; intumescent epoxy material, which expands in volume when exposed to heat or flames, acting as an insulating barrier and dissipating heat through burn-off; baby food, commonly enriched with microalgae food supplement; freeze drying; water purification systems; solar cells; microencapsulating technology enabling the creation of a "Petroleum Remediation Product" for oil spills on water; structural analysis software; powdered lubricants; "OpenStack" cloud computing technology, and about 1,770 more....

At its peak in 1965, NASA employed 411,000 in-house and contractor-dedicated people. In 1966, NASA spending made up 4.41% of the federal budget! In 2012 NASA employed 79,000 in-house and contractor-dedicated people and made up roughly 
0.5% of the federal budget.

Relatively speaking, the aeronautical frontiers back then were much closer to home and easier to understand than the vast gallactic and astronomical frontiers we're exploring now. The spinoffs were more tangible in many instances -- memory foam mattresses vs. cloud software. And, frankly, it's tough to attach a direct personal benefit to a discovery such as this:

"MACS0647-JD is a candidate, based on a photometric redshift estimate,[1][2] for the farthest known galaxy from Earth at a redshift of about z = 10.7,[3] equivalent to a light travel distance of 13.3 billion light-years (4 billion parsecs). If the distance estimate is correct, it formed 420 million years after the Big Bang.[4] It is less than 600 light-years wide."

But there's no disputing the decline in NASA spending, and a disconnect with the American public that wonders "What now? What next?"

Lastly, for those of us involved in design and manufacturing who have benefitted from the many discoveries from NASA efforts over the years, the question arises -- how much of those millions and billions was spending, and how much was actually investment in the nation's future?

Note: Many thanks to Wikipedia and it's contributors and editors for much of the above-noted information.