Antenna Guru

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

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

Machine Wireless Interface

logo01

Machine

Wireless

Interface

LLC

I have been hard, hard at work these last weeks… working on the link between a really cool gizmo and the rest of the world.

After drilling down deep into the physics of microwave devices for a quarter century, it appears that I will be spreading out what I have learned.

Tonight my beloved Nurse Debi gave a name to this thing new born – Machine Wireless Interface©

Thank you, beloved…

Getting Un-hacked

It turns out that AVG Free is happy to coexist on my hard drive with trojans and exploits. How did I find out? Well, there was the malicious blog post … and then I downloaded Microsoft Security Essentials and ran it. So, way to go, MSFT, I feel like you finally are starting to care about the job instead of the bank account.

Then there was the problem of how this happened in the first place. I decided it had to do with my silly-simple password ‘system’. I Googled +password +management and did some reading. I decided on LastPass. Sure ‘nough, it’s a hassle, but so’s the lock on my front door.

Stay safe out there, cyber fam…

 

Red/blue, Black/red

[Some …uh… human being hacked into my pitiful little blog and posted a gratuitous advertisement this morning. Feeling violated I deleted it and changed my password. “Feeling violated” got me thinking about what we do with our tax money.]

Net revenue flow to (from) federal government

I read about how some people (but only 100,00 in Texas, wow!) in some of the ‘red’ states signed petitions for secession from the union. Then I got to wondering, “Where does all the federal money go? Do some states make money off the federal government, and if so, which ones?”

On average, the “Blue States” are supporting the “Red States.”

I found an answer for the interval, 1990 – 2009 here.

So, if you live in New York, Illinois, New Jersey, Minnesota, Texas, California, and so on, I can see why you might want to secede. But if you live in Virginia, Maryland, Florida, Alabama, Mississippi, Kentucky, Arizona, Louisiana  and so on, I would be very quiet if I were you — House Budget Committee Chairman Paul Ryan might come down there and garnishee your whole state and local budgets.

Just sayin’…

Related articles

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?

Picking up, putting away

We spent much of the week at a family member’s old homestead cleaning out a couple of buildings. It was like an archaeological dig; layer on layer let you roughly date what happened when. The experience saddened me— The accumulated unfinished projects in the shop and the ravaged keepsakes someone had tried to save. I kept telling myself, “But life goes on, don’t you know? Not all projects are unfinished and not all keepsakes are ravaged…”

Debi kept me distracted on the way home by playing sing-along-oldies on the stereo. Meanwhile, I was deciding that I had to clean up, pick up and put away around my house if I didn’t  want somebody else to go through what we had been through for three days.

Yesterday I started reorganizing the shop, trying to keep it that way … this time … I had to come in to prepare dinner for my beloved, remembering that mistake, and decided to listen to the Gipsy Kings while I made fajitas de pollo. I don’t understand much of their lyrics, but their music seems right when I feel sadness, but with hope…

We have to change our lives … because we are family … I have a good woman from heaven, bless me! I have a good woman, so I bless the sky…

GIPSY KINGS – AVEN, AVEN LYRICS

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’.

Brain Damage

I was doing my best to read Atlas Shrugged, because the book is in the news and mentioned by friends of mine. I tried, I really did, but I just couldn’t seem to connect with the story – I just felt I didn’t know any people who thought and acted like these characters and I could not suspend my disbelief.

Instead, I indulged in one of my favorite pastimes, reading about near-death experience (NDE).

There was another book being talked about, a new one, entitled, Proof of HeavenI pre-ordered the Kindle version and read it through in about a day-and-a-half. [Disclaimer: I have tried to link to op-ed pieces that distinctly disagree with my PoV hoping to enrich the dialog for you.] As I was reading Dr. Alexander’s description of his experience, it struck me how similar his word choices were to my attempts to describe the World of Ideas… 

I am aware of other PoV’s. That there is a religion gene. That spirituality is a mind virus. Scientists, by definition, do not have these kinds of thoughts; therefore people such as Drs. Alexander and Taylor have disqualified themselves as scientists. Clearly, there are people who think religious faith and spirituality are forms of brain damage.

Some of us think the opposite: To not perceive the spiritual portion of reality is akin to being color blind or tone deaf. Thankfully, it doesn’t last forever.

Back to the Blogosphere

October, a 31 day month, passed in a blur, especially the last three weeks.

We enjoyed some great family time with my wife’s three adult children, including two weekends when  I might normally blog. The course of my profession, which ebbs and flows, definitely has been flowing lately. So it has been a busy time, a joyful time, a thankful time, a profitable time. Now it is time to record some thoughts.

Really interesting documentary that humanized and made me admire both of these great Americans. You can watch it online…

Antenna Guru

I  urge you to watch this special Frontline episode. They do it every four years in October, and it is excellent.

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