RF Cafe Software
About RF Cafe
1996 - 2016
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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These images have been chosen for their uniqueness. Subject matter ranges from historic events, to really cool phenomena in science and engineering, to relevant place, to ingenious contraptions, to interesting products (which now has its own dedicated Featured Product category).
Cool Pic Archive Pages
Here we have the Telstar 14R/ Estrela do Sul 2 satellite staged in an anechoic antenna test facility for performing RF testing at Space Systems/Loral. It is a Ku-band satellite that will service markets in Brazil, the Continental U.S., the North Atlantic Ocean Region, as well as the Andean and Southern Cone region of S. America. Telstar 14R has 46 Ku-band transponders (27 fixed, 19 switchable) and five antenna beams with on-orbit switching capability to allow its capacity to be reconfigured depending on market demand. The chamber is absolutely huge. If you have ever worked in a tiny, cramped anechoic chamber while tripping over cables and struggling to set up measurement antennas, you will appreciate the voluminous-ness of this facility.
In the mid 1990s, seemingly overnight cell phone towers began appearing across the face of the Earth. Now, even on country roads and in the middle of deserts, you can find them almost everywhere. Boy, are they ugly. Overhead power lines are not exactly beautiful, but at least they invoke a sense of nostalgia as part of Americana. Of course, for anyone born from the 1990s on, so are cell towers. One way that communities have been dealing with the unsightliness is by shrouding the towers in faux trees. I have seen some of them in my travels along the East Coast. The ones I spotted do a pretty good job of masking the presence of the tower and its antennas. The cost must be pretty high. This website has a great collection of different styles and installations of camouflaged cell towers. Just ignore the comment where the author claims, "Cell phone signals are in the same frequency range as microwave ovens at about 100 gigahertz."
Researchers Lutz Bornmann and Loet Leydesdorff recently published a paper whose results are maps displaying the relative numbers of science papers each city of origin has cited by other science papers. Chemistry, physics, and psychology categories are given. A detailed explanation of how the maps are generated is provided, including how circle sizes are calculated and how colors are assigned, based on statistical analysis. If the observed value is greater than the expected value, green is assigned. If the observed value is less than the expected value, red is assigned. Where is that huge red circle? Moscow. Its size means the number of published papers from Moscow relative to the number of papers that cite those papers is high; i.e., Muscovites do a lot of writing citing other sources, but not many writers cite papers from Muscovites. A big green circle is what <more>
This is sheet 3 of 293 pages that comprise Apple's patent #7,479,949 B2, January 20, 2009, for "Touch Screen Device, Method, and Graphical User Interface for Determining Commands by Applying Heuristics." It is the iPhone patent, in full detail. Steve Jobs and 24 other people are listed as inventors. Can you imagine the team of lawyers and engineers that had to work just to document every minute detail in order to be able to defend the patent's propriety if the need ever arises? This points out one of the primary complaints against the patent system as is it currently implemented. Some items are so mundane and ordinary that it takes no stroke of genius to include in a design, and therefore should not be declared as part of the patent. It is not inconceivable that if some company - or even a hobbyist - was to arrange the speaker, optical sensor, and proximity sensor in the same order across the top of a similar device, he could be subject to a lawsuit. There's a good reason why lawyers own the biggest houses in town.
Virginia Tech researcher Taeyoung Yang and colleagues have developed an efficient Compact Ultra-wideband Antenna (CUA) for a range of home, automotive, medical, and military applications. The antenna has achieved a near optimal performance for size and bandwidth. "To our best knowledge, our invented antenna is the world's smallest with more than a 10:1 bandwidth. It has more than 95 percent efficiency for signal transmission, and a fairly constant omnidirectional radiation pattern," said Yang. Gain is reportedly 5 dBi over the entire band. The goal was to create a shape that can be easily printed on the inside of a plastic enclosure for mass production. This design would make a good conversation piece - it looks like a spinning top inside an axial wind turbine.
Remember the late 1990s in the U.S. when the tech boom was in high gear and commercial office space and tightly packed suburban neighborhoods were going up at blazing speeds? Then, in the spring of 2000, six months before the election, all heck broke loose on the NASDAQ, and then the DOW followed. Millions of Joe-Sixpack-turned-day-trader types watched in horror as their early retirement plan activities were traded in for filling out Wal-Mart greeter applications. Insult was added to injury when the folks now responsible for your body cavity searches at the airport flew jets into buildings and farm fields. Nearly overnight, vacancy rates went from about 1% to 50% or more. Well, the same sort of scenario is playing out in China. The worldwide economic recession is causing entire new cities to remain vacant, except for a few gatekeepers. Not that long ago, China was using more concrete than all the other countries of the world combined.
One of the perks of attending the International Microwave Symposium (IMS), hosted by the Institute of Electrical and Electronics Engineers (IEEE), is that you are given the opportunity to see a part of the history of microwave engineering. At the two IMS shows that Melanie and I have been to (2009 and 2011), a portion of the contents of the National Electronics Museum, headquartered in Linthicum, Maryland, (only a few miles from the Baltimore Convention Center) was on display. Safely locked behind protective glass and guarded by a paid sentinel are relics of our profession's past. Prototypes of magnetrons, circulators, filters, phased array antennas, traveling wave tubes, waveguide, oscillators, and a host of other devices dreamed up by those whose names are on the "Honor Roll" plaques, as on display. Some items are simply labeled with part numbers, like with many of the vacuum tubes, while others have information sheets with lots of detail. Unlike at the IMS2009 show when I only photographed a few of the exhibit items, this time I got every one. <more>
Space-based telescopes do not suffer atmospheric perturbations that terrestrial telescopes suffer. Since the optical quality of telescopes has progressed far beyond the distortions introduced as a star's image passes through layers of air and particulate matter, methods needed to be developed to counter the problem. An array of pistons are methodically distributed across the back of the primary objective (aka mirror) and a computer makes adjustments for the clearest image. Since atmospheric changes occur rapidly, the system must make many adjustments every second in order to prevent images from smearing (light points turn to streaks or smudges). Sometimes, no acceptable guide stars are available for the telescope's star tracking system. The Gemini South telescope 589 nm laser system solves that problem by using a 50 W laser to excite sodium atoms in the upper atmosphere to create a cluster of 5 guide stars. Having 5 exactly known points allows the adaptive optics to precisely tune the mirror shape, thereby achieving diffraction limited images.
IC wirebonding and stacking technology has been as much a vital part of high density electronics packaging as has been shrinking gate sizes and semiconductor fabrication techniques. This photo from Elpida of a stack of 20 die (1.4 mm molded package height) is from way back in 2007. ½-mil or thinner gold wire is needed to cram that many wires into such a small space. The precision, accuracy, and speed requirements of the electromechanical bonding machines boggle the mind. Sometimes combining die in a common package is not possible because of semi compound variations (Si, GaAs, GaN, etc.) or a need to test individual models prior to high level assembly. That is where Package-on-Package (PoP) techniques are needed. Amkor, a leading packaging CM, published a comprehensive presentation on state-of-the-art PoP capabilities for the SMTA.
General Electric recently opened its vault of Edison-era devices that include early solar cells, fuel cells, a 100-year-old electric car charger. EVs (electrical vehicles) were the vehicle of choice for women in the early 1900s, and outsold internal combustion engine vehicles for a while. An x-ray control panel, and even a selenium purifier that looks like a naval mine are also on display. General Electric now has a Tumblr site that hosts many photos of past innovations that provide insight into its technical roots. How about a 10,000W light bulb, or an 1880s vintage electrical generator? This stuff may look crude and even obvious, causing you to question why it was considered break-through, but a hundred years from now, future generations will look at 2011 products and remark about the crudeness of our era.
Todd McLellan is a master of the exploded view. Shown here is an electromechanical clock radio (the kind where the number cards flip down at the passing of each minute). Todd completely disassembles his vintage technology subjects and then neatly arranges all of the components for the shoot. He even removes all of the electronics components from the PCB. Among the items thusly treated are a mechanical typewriter, a rotary dial phone, and a spring-driven mantle clock. A nifty time-lapse video is included that shows the disassembly process of the clock radio. Because of the way the website is set up, there is no way to link directly to the page with the images, so just go to toddmclellan.com and click on the "New Work" menu option. If you are a classics motorcycle buff, you will appreciate the photo collection.
A cosmic amoeba? Nope, it is a 1.2 terapixel image (each one imaged in five colors) covering about 1/3 of the sky, as mapped by the Sloan Digital Sky Survey. Each orange dot in this map is an entire galaxy. The sequence of zooms shown in the upper panels zeroes in on the nebula NGC 604 in nearby galaxy Messier 33 (the Triangulum Galaxy - about 2.5 MLY away). The image is almost like a fractal in terms of nearly infinite resolution, except there is no repetitive structure involved here. SDSS astronomers began assembling the image in 1998 with what was then then the world's largest digital camera (138 MPx). Included are 260 M stars and 210 M galaxies. The map is expected to be complete by 2014. According to SDSS-III scientists, this image is so big and detailed that you'd need 500,000 HDTVs to view it at its full resolution. Don't bother trying to download the complete image... unless you happen to have a 30 TByte hard drive.