Antenna Guru

RF is not 'black magic' – It's Synthesis, Optimization, Analysis and Realization.

Category Archives: Ultra-rapid Design & Prototype

A Yen for Yin and Yang

C++This has been an interesting week and it’s only Tuesday…

Yesterday I found myself involved in computer code of all things. I was actually able to dig out some C++ code I wrote for a *.dll way back in the year of ’99. My direct involvement in computer programming was short-lived — there were other people who were pretty good at it already and the integrated development environment simply wasn’t ‘real’ enough for me. Still, and all, it was neat to find (and find useful) an archived project from days gone by.

After that walk down memory lane I worked on the finishing touches of an algorithm that uses Inverse Fast Fourier Transform analysis to automatically tune split ring resonator filters as they are being manufactured.IFFT

But then I had to put that project on hold because the fellow who is commissioning the tuning algorithm wanted new (22 GHz) test fixtures built to test the prototypes he has built so far.

But the test fixture project required me to grind some special holding fixtures so that I could machine the teensy weensy test fixtures in the first place. I don’t have a precision grinder, so I used my mill.

Parallel_grinding_01

I wouldn’t want to do this all the time, but this was for a prototype and it worked out. So now, I’m back to getting those fixtures done, so we can validate the algorithm.

I like going from math books to machine shop and back. It’s interesting and fun to keep up that balance. It’s invigorating, it’s yin and yang.

Parallel_grinding_02
I wonder how that C++ code is going to turn out?

 

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What We Do (SOAR)

I am trying out some copy writing for our upcoming website. Here’s just a smidgen…

Synthesize

The most general meaning of the word is “combination of parts to form a whole”. In electrical engineering, the term strongly implies mapping from mathematical functions, e.g. Chebyshev polynomials, to some sort of network, e.g. a lumped element filter or an antenna array. We prefer the general meaning which includes the math-to-circuit idea but further conveys the thought that we bring our individual talents to bear on every problem (as necessary)– and our collective expertise spans a number of subject areas.

Optimize

Again, the general meaning of the word, “make something as functional and effective as possible,”  is what we intend to convey. We have a passion for making things and we are passionate about making them as functional and effective as possible.

Analyze

In synthesize the activity goes somewhat like this: If you give us a set of performance requirements we will try to come up with a combination of elements that performs as required. Analysis inverts that activity, like this: If you give us a combination of elements we will try to predict their performance. If synthesis involves “putting it all together”, analysis involves “breaking it down.” We often employ computational techniques to break a problem down, but we also apply philosophy and common sense.

Realize

“…bring into concrete existence …convert into actual money …be fully aware of …cause to happen …”  We have a machine shop so that we can build prototypes. We have a test lab so that we can measure them. We have project management experience because time is money. From beginning to end we like to “keep it real”.

The Internet of Things

Thingernet

The “internet of things” is already here — in the media, at least.

It is not hard to find these types of articles nowadays. Whether or not you think connecting your cow to the www is a great idea, it certainly is a popular topic of conversation. I’m all for it. Here is why, as Linus Pauling famously said

If you want to have good ideas you must have many ideas. Most of them will be wrong, and what you have to learn is which ones to throw away.

But there is a problem with the populist application of internet-to-things that goes unmentioned by the tech writers. The cacophony of “information” that results from Farmer Brown giving Bessie her own cell phone potentially threatens our shared bandwidth. This is the reason we have the FCC and the PTCRB. We need to comply with their rules so we all can remain in polite conversation.

Spurious Emissions

The physics is no longer bewildering to me, as it was thirty years ago when I was thrust into the microwave business, but the rules and regulations can still be−

PTCRB

Let’s start with this five-letter acronym for “PCS-type Certification Review Board.” Nested within this acronym is another acronym for “Personal Communications Service.” Surfing over to their home page, “Welcome to PTCRB,” one is confronted by more acronymia. (By the way, ‘ptcrb’ is not found in acronymia.com’s dictionary at this writing.) I tried unsuccessfully to find out the rules for “obtaining PTCRB Certification on a mobile device” because I couldn’t provide the required company website on the Registration Page.

RSE

This TLA stands for “Radiated Spurious Emissions.” RSE are(is?) at the crux of the PTCRB certification. Finding their source(s) and mitigating them is exactly like the other stuff I love to do. Except finding out the rules, which is exactly like the stuff I hate.

CTIA

Originally dubbed the “Cellular Telephone Industries Association,” but now calling themselves, “CTIA – The Wireless Association,” lets you browse their website. I found a Test Plan for Wireless Device Over-the-Air Performance there, but no mention of allowed RSE levels.

Time to change tactics… I decided to look at websites of companies who operate the equipment.

The Horn reflector antenna at Bell Telephone Laboratories in Holmdel, New Jersey (Wikipedia)

AT&T

Sometimes I forget all the great engineering that came out of the old Bell Telephone Laboratories. So it was great to find this App Note: Antenna Fundamentals. (Maybe I liked it so much because it was like an advertisement for what I am good at doing!) I especially liked this quote:

A failure to meet FCC regulations or PTCRB radiated-spurious-emissions-conformance requirements due to a level of harmonic energy generated by the device is often blamed on the antenna. In truth, the antenna can often influence the level of the harmonics but does not generate these signals. An antenna almost never has gain at the harmonics of the intended band of operation. Provided the radio has acceptable harmonic performance, excessive harmonic generation is typically an interaction between the impedance of the antenna and the impedance of the final stage of the transmitter.

−ATT Antenna Fundamentals – Technical Brief, p.  34

Heck, yeah!

This is a great Tech Brief, especially because it doesn’t push one type or brand of antenna over another, and it isn’t written to scare anybody into becoming a customer …but I still didn’t have my RSE answer.

ECN

(I don’t remember what the letters stand for, but it’s been a trade magazine for a long time. I emailed the editor, so maybe he’ll get back to me on this.) Bleary-eyed, I clicked on a link to their article, Cellular Carrier Certification Requirements and scanned down the page… Bingo!

Note that PTCRB limits follow ETSI limits, not FCC limits.

ETSI

(European Telecommunications Standards Institute) After all that, I really appreciated their website: The first link on their homepage was Standards. It still took a while to get to the right document, but at last I believed I had found it:

ETSI standard ETSI EN 301 502 V10.1.1 (2012-01)

Table 4.2.5-1: Spurious Emissions Measurements outside the transmit band

Band

Frequency offset outside

relevant transmit band

Maximum power limit

Multicarrier BTS

9 kHz to 1 GHz

≥ 2 MHz

≥ 5 MHz

≥ 10 MHz

-25 dBm

-20-4,2*(Δf-5) dBm

-36 dBm

1 GHz to 12,75 GHz

≥ 2 MHz

≥ 5 MHz

≥ 10 MHz

-25 dBm

-20-3*(Δf-5) dBm

-30 dBm

Making … Progress

It has been about three months since this progress report (of sorts)… so maybe it is time for an update.

Machining Precision Fixtures

You may recall the story about Rudy’s Big Idea (and parts two, three & four) and how I got started making my own prototypes. This effort has continued and expanded quite a lot. It might seem ridiculous for a highly educated professional to be turning cranks on a sixty-five year old milling machine, but there are certain subtle benefits—

  • If the ‘machinist’ has an idea what the prototype is supposed to do (s)he can often do the job just a little better and just a little faster. Making the first one of something is sort of like playing from sheet music in this regard.
  • It is nice to have a second pair of eyes take a look at the design. If that pair of eyes belongs to someone who is both an experienced designer and the prototype builder, so much the better.
  • Medium to large companies tend to have their own prototype shops but not the little guy, the entrepreneur.
  • Medium to large companies, in this economy, do not have excess capacity for onesy-twosy’s. At the same time, they need to innovate in order to survive.
  • Once you’ve made one, and it works, you often need to develop a process for making more. Who better to develop the process than an experienced engineer/maker?

So, this passionate little act of desperation is turning into a pretty purposeful enterprise.

Reality Checks

I did not expect it when I started on this path, but the world is full of “lone rangers” in little companies who get inspiration to try a new (to them) idea. Take, for example the patch array shown here. A fellow who had no microwave/RF design experience and no way to measure the interim results of his prototype wanted to get a “reality check” on his design. This was an extremely low-budget “moon shot” of an idea for this little company. You might even call it a “passionate little act of desperation…”

I am not exactly sure how he found me, so I’ll just chalk it up as one of those things. And it turned out that I had been through much of his unknown journey before. We had a couple of skype calls and I sent him a little memo outlining some of the gotchas and some of the things not to sweat at all. And this lone ranger rode a little more confidently off into the sunset. I hope we’ll meet again.

Unauthorized Tech Support

This one was also totally unexpected. Somebody gets a big idea for a product that does some little important job and then reports the data remotely, sort of like taking a blood pressure cuff and hooking it to the guts of a cell phone. Usually the person is a competent practitioner, someone who is experienced at engineering a system out of components available commercially, e.g. from DigiKey. They order their parts, build their prototype enclosure, debug the prototype and start the certification process when… BAM! They run into unforeseen problems.

Usually at this point in the process the company is too invested in the gizmo for wholesale modifications. Also usually, the designer (who is a competent practitioner, remember) has followed the reference designs and application notes provided by the component vendors pretty closely. The natural thing to do at this point is to reach out to the vendors for some tech support, and this is usually what these fellows do. The answer they get back is something like, “Well, you’ll have to move this component to the other end of the board,” or “Well, you’ll have to make the housing a little longer/wider/taller.”

Oh for crying out loud! Why not just start over? Why not give up?

Well some do, perhaps, but fortunately some don’t. A (growing) few are showing up here for what I like to call “Unauthorized Customer Service.” We don’t change the BoM in major ways; instead we figure out little tweaks and things to get that design to work.

Sure, I’d like to be in there at the beginning and get a bigger piece of the design pie on my own plate, but it is what it is, and it’s growing. Why walk away?

Man, Waddyacall It?

Finally there’s this issue of branding, also totally unexpected. It turns out that companies tend to shy away from contractors named, “Joe Somebody.” So, at minimum, I am told, I have to form either a corporation or a limited liability company (LLC). I toyed with “Antenna Guru” but it just didn’t produce many hits when I tried it out. My initials are “mwi” which look somewhat like a meander line if you tweak them a little. So the big question is, “What do I call this thing?” Should it be something like “Micro Wave Inventions, LLC” or is it better to call it what it is, “Mark W. Ingalls, LLC?”

Man, what-do-you-call it?

Just Wail

You’ve got to learn your instrument. Then, you practice, practice, practice. And then, when you finally get up there on the bandstand, forget all that and just wail.

Charlie Parker

I was called in to help on a design project to marry a cell phone with a portable medical device. As it usually happens, almost everything about the project is pretty well set in stone and the mortar is drying fast. Trouble is, the equipment failed the approval testing that it needs to be legal. (Sort of like when you car won’t pass inspection, except the inspection costs $20,000 …)

There is no time to design a new antenna for the device. I fired off an email to a buddy of mine who works at the company who made the antenna, and his antenna expert said, “Make the housing bigger.” (Sort of like when the Wizard of Oz told Dorothy, “Go see the Wicked Witch and ask her for her broomstick.”) This is one of those cases where the left brain just ain’t gonna cut it… So I took a stroll through the imaginary door into the world of ideas. What I came back with sort of resembles the ignominious “coat hanger antenna,” but actually has some theory behind it – it’s called a “coiled coax balun.” It’s almost free, and it worked for this project.

Stay ‘tuned’.

New Workstation

Business is on the uptick this month. That’s the good news.

The bad news is that my old computer takes all night to solve big simulation problems (and I haven’t maxed out the software yet =-o) but I don’t have enough all nighters for the number of project deadlines coming at me. So, I went ahead and ordered:

WORKSTATION PC

  • COOLER MASTER, HAF 932 Advanced (RC-932-KKN5-GP) Black Tower Case w/ Window, EATX, 7 slots, No PSU, Steel
  • COOLER MASTER, Silent Pro M 850W Power Supply w/ Modular Cables, 80 PLUS® Bronze, ATX12V 2.3 EPS12V 2.92, 6x 8/6-pin PCIe, SLI® Certified, Retail
  • ASUS, P9X79 WS, LGA2011, Intel® X79, DDR3-2400 (O.C.) 64GB /8, PCIe x16 SLI CF /2+4*, SATA 6Gb/s RAID 5 /4, 3Gb/s /4, USB 3.0 /4, HDA, GbLAN /2, FW, SSI CEB, Retail
  • INTEL, Core i7-3930K Six-Core, 3.2 – 3.8GHz TB, LGA2011, 12MB L3 Cache, HT EM64T EIST VT XD, 32nm, 130W, Retail
  • COOLER MASTER, Hyper 212 Plus CPU Cooler, Socket 2011/1155/1156/1366/775/AM3/AM2, Copper/Aluminum, Retail
  • CORSAIR, 16GB (4 x 4GB) Vengeance™ LP Blue PC3-12800 DDR3 1600MHz CL9 (9-9-9-24) 1.5V SDRAM DIMM, Non-ECC
  • EVGA, GeForce® GTX 560 (KR) 810MHz, 1GB GDDR5 4008MHz, PCIe x16 SLI, 2x DVI + mini-HDMI, Retail
  • SEAGATE, 1TB Barracuda®, SATA 6 Gb/s, 7200RPM,64MB cache
  • RAID, No RAID, Independent HDD Drives
  • SONY, AD-7280S Black 24x DVD±R/RW Dual-Layer Burner, SATA, OEM
  • MICROSOFT, Windows 7 Ultimate 64-bit Edition w/ SP1, OEM

That’s a lot of stuff. My plan is to transfer all my big, power hungry design software onto this workstation and access it remotely via my laptop.

Funny thing (now that I’m free of it), I remember how it would have been impossible to upgrade my computer because of increased business at my former employer’s: We were authorized to waste money but not to spend money…

Really, it’s about balance: Now that I can fabricate prototypes quickly, I need to be able to design them more quickly. So, the next logical step will be a CNC mill, I suppose? H-m-m-m-m…

Making … Progress

Does society need individuals with equivalent skills in theory and implementation?

I believe so, yes!

Slowly, slowly, making progress. 

In the old days most little towns had a blacksmith, sort of like most little towns today have a “Gas-n-Go.” Where are they all going? Out of town to get the things they need. But personal transportation wasn’t well developed in the old days, so the things one needed had to be brought closer to hand. I am not wistful for the small-town of old, except that I have always been attracted to the old-time blacksmith as an archetype. (“Competencies: Physical strength, conceptualization,” says Wikipedia.)

Have you ever felt energized visiting a museum replica of a blacksmith’s or carpenter’s shop?  I have; I even tried cabinetwork years ago… it didn’t stimulate my mind enough, so it rebelled. Eventually I drifted into electrical engineering and graduate school. At my first (and only) job after graduate school I would grow frustrated waiting for all the “high priority” (= “supporting current production”) jobs to get built on schedule while my “R&D” (= “future of the company”) jobs languished or were piecemealed. Fortunately, the two machinists that worked in the shop, Scooter and Scott, were sympathetic and let me use equipment that would otherwise have sat idle. They treated me as their apprentice, and I tried to give them back as good as they gave, for example helping go between them and some of the less than sympathetic engineers who didn’t understand the reality of tolerance.

This experience really empowered  practical creativity, because I could make a little widget to try out a theoretical idea.  This made improving even the larger systems faster because I could give my boss concrete evidence that my ideas might work. Some did and some didn’t, but many new ideas and improvements to old ones flowed freely from my mind to my hands and on to production.

Then I got promoted.

Actually, it was more complicated than that. The dot-com bubble popped in 2001 and my employer was forced to reduced staff commensurately. The facility where I worked was closed and the property was sold off. I was offered the choice of a transfer and a big raise or to hit the bricks.

I chose the raise.

But the cost was that I had to forego turning cranks in the shop. The new place’s shop was bigger and faster-paced. The superintendent didn’t like the idea of a “guest machinist.” Gradually, I found my professional responsibilities shifting more to conference calls and giving advice, with less time spent tinkering.

That’s over now. I am starting to right myself. Today I have three customers– I am developing a special antenna of one. I am available to discuss resonant lines on a will-call basis for another. The third customer pays me a fixed retainer and asks me to help out however and wherever I am able. I really love working for the third customer, but I actually get to make things for all of them. It is up to me to decide how best to serve their individual needs.

Is it even a good idea to be equally devoted to theoretical understanding and practical know-how? Or is the cautionary phrase, “Jack of all trades, master of none” more sensible? For me, it was never really a choice so much as a compulsion to hang out in the shared space between the two. Slowly, slowly, I am finding people whose projects need equal parts theory and practice.  Designer and builder. Making headway.

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