Wireless RF IC's

Are pretty much all modern transceiver IC's the same as far as the circuit? All the ones I have looked at recently use a crystal and some passives for the antenna which I assume are for impedance/resonance matching?

Obviously the IC capabilities are different and the impedance matching techniques are too but basically it seems pretty simple circuit wise? Hardest part being the antenna(After all, thats really all there is).

So, for the most part I can be pretty ignorant about all the special transmission techniques and concepts(QAM, SSB, ISM, etc...) and still do wireless very easy using these IC's? As long as I get the antenna approximately right and hook up a uC/P then I should be able to do some wireless(may be degraded but...)? Seems like it from what I've read in the datasheets.

Guess I'm just supprised that it would be that easy but I suppose the IC pretty much takes care of everything? (as far as just bit banging is concerned)

Also, how does one deal with interference. In the 2.4Ghz range I'd imagine it would be a huge problem? I'm looking at the

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Which has Zigbee and operates from 2.4Ghz to 2.483Ghz with 5Mhz between channels. Hence I guess there is a maximum of about 16 channels. I know that there are special techniques to deal with it but generally how does it keep thousands of different signals on the same band? (Since so many users use this channel(cell phones, mobile stuff such as laptops, zigbee devices, etc...). Is it all really in the DSSS technique and the channels are quite noisy or what?

Reply to
Jon Slaughter
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IMHO I'd avoid the ones that need an external SAW filter. These filters attenuate about 10dB in the pass band which cuts sensitivity.

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Reply to
Nico Coesel

It doesn't really matter now. I didn't know you had to get FCC approved to do such things ;/

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Is a real cheap modual(10$) that, I think, has zigbee support. While I'd rather do my own using TI's cc2480, which seems to have a ton of features, I didn't realize it would cost me 10-20k to actually commercially use it ;/

Reply to
Jon Slaughter

??? Over here there are unlicensed frequencies which may be used without any form of paying fees. Ofcourse accountability for causing too much interference still stands. You probably need FCC / UL approval to sell a product in the US, but that is another case.

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Reply to
Nico Coesel

Yes but my product will be "commercial". i.e., it will be sold(not in large quantities though... maybe 100/yr). How can I justify making spending

10-20k$ just to add wireless capabilities and only make potentially a few thousand? Makes no sense. I can't understand why it would cost so much(actually I'm not sure the cost but this is what I found someone else saying) when the IC itself has already been FCC approved and the antenna is really the only additional RF component. It should be allowed that if one follows spec given in the datasheet to be ok.

Under a certain power limit and over a certain frequency it should be free for commercial use since the range is extremely limited.

Reply to
Jon Slaughter

As I understand it: FCC certification (a.k.a. type acceptance) is required at some point for devices which operate under Part 15

It's possible to buy RF communication modules (e.g. chip, antenna, crystal, etc. all pre-assembled on a daughterboard) which have been certificated by their manufacturer. I believe that it's legal to use a module of this sort in your device, without having to have your device go through another round of certification testing, as long as you don't modify the module.

It's the FCC's position that the radio *system* is what is being certificated - that is, the IC itself, any power amplifier stage after the IC, and the antenna (and its support components).

An IC whose output was legal when used with one type of antenna, might violate Part 15 limits (on power or ERP or spurious emissions) when used with a different sort of antenna.

If you buy a module (system) and modify it in any way (e.g. with a new antenna) you're responsible for certification of the final product. If you don't modify the module, but use it in ways compatible with the ways in which it was certificated, then [I believe] you're "good to go" with no further testing.

AAUI, it isn't just the power level at the design frequency that's at issue. It's whether the device/system can interfere... i.e. whether it's violating the spurious-frequency emission limits. This isn't something that can necessarily be determined just from the IC's specs.

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Dave Platt                                    AE6EO
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Reply to
Dave Platt

yes, as I mentioned the one I was looking at.

To me it sounds mainly like a way for them to get money(assuming those costs are correct). If some company fabs and ic and creates a certain for testing it and that circuit passes the FCC's tests then that circuit to almost exact specs(anything within reason) should be valid. The main issues are mainly with the antenna design and the IC and just common sense with proper layout.

If it is so critical to keep noise down then they should designate a band for commercial use but free to use without restriction. This way you use at your own risk. The only requirement is that proper IC's and lay are used. You can't enfore the layout but if the IC is correct then it should do most of the job. Cause, after, all, what is preventing from someone not getting certified and designing a good circuit?

The point being, is that some reason should prevail(but never does when money is involved). Simply making a "one size fit's all" rule isn't very practical. I understand their "goal" is to provide clean wireless comm but a little bit of reason can go a long way. How bout the makers of the circuits supply the model pcb layout that they used along with all the necessary specs(pcb dielectric, passive values, etc.) and only modifications unrelated to the rf section can be chained? Is that unreasonable? The devices could be restricted to only be used on private property and not for roaming and also for non-critical devices. This way it can be used on by businesses for their own use. Because of the short distances it would be highly unlikely to cause any drastic problems even if someone did screw something up big time.

If a device is limited to around 50m and even 90% within spec I doubt much harm can come from it?

Of course I'm just learning about rf and maybe any slight change, such as being 0.1% off on some passive's value, might cause some interference with some plane 30k ft in the sky? Of course, then again there will always be some genius to FTUBAR.

If it really is an antenna problem then one should be able to by self contained FCC compliant antenna modules and then combine them onto the pcb with their own design based around an FCC complaint IC's with no big issues(here then it's only a connection matter and one of ground plains and coupling cap's).

Somewhere there has to be some compromise. It seems to me, ignorant as I am, that it's mainly just a "tax" on companies that develop any RF device. After all, its a company so they can afford it and/or just pass on the cost to the consumer.

Reply to
Jon Slaughter

My recollection is that most of the money goes to the (privately operated) test lab, not to the FCC?

"Should" is a rather subjective judgement. Yes, it would be nice... but they haven't done so to the extent that you desire (although the various ISM [Industrial, Scientific, and Measurement] bands come fairly close in many ways.)

As I said... the testing isn't only done to ensure that the device does not interfere *within* its intended frequency band of operation. It's also done to ensure that the device does not emit interference

*outside* of its intended freequency band.

...

... and you might be surprised how messily an RF device can behave, if it's hooked up to a load (e.g. antenna) it wasn't designed to handle, or as a result of parasitic reactances or unexpected cross-coupling on the circuit board.

Something as simple as the length of the transmission line (coax or PC-board traces) between an amplifier stage, and a filter which follows it, can cause a transmitter to go from clean-and-stable to oscillating-like-a-banshee.

I'm rather a tyro at this stuff myself (Amateur radio license, and several years of experience in maintaining a multi-band repeater system) but I've learned that making RF work right can be a lot more subtle than one might expect.

My advice is: if you want to use RF, make sure that your design is being done by an RF-competent engineer and tested in accordance with good engineering practice. You can let that be done by the module company (and accept the pass-through licensing) or you can do it yourself and hire it done (and pay the R&D and certification costs).

How about "A PC board trace which is an inch too long, causes some interference which jams a medical sensor in the next room."

... or "causes a wandering 'birdie' signal which interferes with police and fire-department radio systems." I recall reading about a case a couple of years ago, in which a temporary traffic-signal system (which used RF between the lights at the end of a road segment with poor visibility) seriously interfered with a small town's police radio system, and cut off communication with the police cars for several days. Turned out that the road-repair company had bought a non-certificated (in the U.S.) model - good RF hardware, but it was designed for the EU and was transmitting on the wrong band.

... and that's why there's a testing requirement.

The FCC's *primary* job, as defined by Congress, is to manage the airwaves and spectrum-space so as to prevent harmful interference. That's why they were originally set up, back in The Day.

Their primary job is *not* to make life convenient for you and me.

... and that basic capability is *already* available to a significant extent, in at least some Part 15 applications.

Rather, I think it is a *process* intended to reduce the risk to consumers, of having unacceptable interference which requires expensive efforts to mitigate (e.g. product recalls).

If you want a regulatory change in this regard, you're free to do what any of us U.S. citizens is: file a petition to request a change in the rules. The FCC *has* accepted some petitions with regard to liberalizing Part 15 radio setup and operation over the past few years (particularly with respect to WiFi).

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Dave Platt                                    AE6EO
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Reply to
Dave Platt

I was looking into this as well. Linx says FCC testing is about $5k for Tx and Rcv.

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They have a pretty detailed pdf here about FCC testing.

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Another useful place is Micrel lots of appnotes and info if you haven't already found it.

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Reply to
Hammy

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My experience with the FCC is that there are two distinct parts. The first part is the equipment authorization part. That is a process done by the manufacturer and submitted to the FCC. If you look at your wireless entry door lock device for your car, you will see FCC ID: XXXXXXXXXXXX

if you go here:

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you can find out a lot about any device that has an FCC ID associated with it. For instance my car device is FCC ID : KOBLEAR1XT. The KOB is the grantee code. every manufacturer gets a grantee code. KOB is the "Lear" company code.

Anyhow, when a company wants to sell a product that radiates, they need to get an equipment authorization (there are some exceptions to this such as products sold as lab equipment) . It is up to the company to do the neccessary testing to demonstrate that they are compliant with FCC standards. You must decide what your device is going to be used for and then get your authorization in accordance with those rules. For instance, if you want to get an authorization to sell equipment that transmits in the aviation bands, then you need to go to part 87 rules and do all your testing in accordance with thise rules. If you want to sell a device like a garage door opener (this can be used by any unlicensed operator) then you need to look at the part 15 rules. BTW part 15 is usually requires the most work to get the authorization becuase it will be used by unlicensed people.

My point is, I do not think the chip manufacturer is involved in FCC certification , except that their chips better allow the user of the chip to pass his tests when he wants to manufacture a device using the particular chips.

The second aspect to FCC policy is the end user. After the manufacturer gets the right to sell equipment that can transmitt per the authorization certificate, the user must have the license to operate the equipment. So there are two parts to the formula.

Part 15 equipment does not require a licensed operator, but most stuff sold does require a licensed user.

Reply to
brent

10 dB loss means nothing if it is placed after appropriate pre- amplification.

er hammer!"

Reply to
brent

If the circuit is is virtually the same(no major major modifications) as the one that was used by the IC manufacturer for their FCC testing and if it passed then it should pass for all time. This is like saying that every single circuit board must be tested because slight changes could drastically change it's behavior. That simply isn't the case... or if it is they still allow it. It is the design that is important(which I'm including the physical layout) rather the exact device. They obviously understand this to a degree.

They do allow "minor" modifications as I just found out without requiring any notifications.

Ok, but then thats not following the original design spec. Unexpected cross-coupling? Parasitic reactances? If the circuit is routed by exactly what was used by the IC's fcc testing(which had to have such a circuit to test with) then it should behave almost exactly the same. Obviously there will be minute differences and some things could potentially make a big difference such as dielectric of the pcb. But basically if you copy their design on the RF side then it should pretty much be functionally equivalent. Any actual differences shouldn't cause any real problems.

Your not changing the length. Or, if it is a separate IC and antenna as I mentioned somewhere, the FCC could specify a maximum allowed distanced. (which is based on the original design)

Yes, but I'm not talking about RF from scratch. I'm basically talking about copying an already proven design.

Well, since the design was done by some TI guys then it is good enough? So I have to waste money to simply duplicate what they have already done? Hence the "scam". If I were to get their exact gerber documents and used the same components listed in their BOM(in the datasheet) then I haven't changed anything except possibly the pcb thickness/dielectric and copper thickness. Obviously I could use the wrong valued cap, for example... but that could potentially happen with a certified design when reproduced.

An inch pretty big. If you've changed something like that from spec then it's not really an unessential modification. If the band is only for commerial unlicensed use then I would imagine medical sensors should not be using it. As I said... non-critical apps such as your TV communicating with your comp.

Again, I don't know a lot about RF and I realize the potential for major problems. My point is that if you are basically copying the original design, which is FCC approved and the band is for non-critical use then it shouldn't be an issue. Given that the range would be only, max, a few hundred feet LOS in 2.4ghz at 0.1dBm at most, if someone screws up or intentionally makes major changes, then it will only effect things in that range. If it becomes a serious problem, say they overpowered the device, then the FCC will come in as normal and be able to see what they did and that they made changes from original spec and fine them.

I just can't imagine, for example, if I took TI's gerber(they give the copper layout in their datasheets) and BOM and follow the rules given in the datasheet(after all, they want you to pass the tests) that I'd be so far off to cause any problems at all. It might not be as efficient but I doubt it would fail any tests.

Of course, again, there are people that can't even tie their shoelaces but somehow got a degree in engineering... so...

But again, I'm basically ignorant on the subject. I just feel that it can't be too critical to design such a thing... one because relatively speaking, it is a very simple circuit just from the number of components and layout. Second, the manufacturers pretty much tells you exactly what to do.

Am I wrong to assume that if you follow there method to the T and don't make any blunders that you could bring down the space shuttle?

Hehe, well, thats a pretty significant error. Huge relative to what I'm saying.

Then there should be a "Free" band. That people can use at their own risk and not critical. Say I make a design and follow spec's exactly but old joe engineer wants to cut costs so he uses some cheaper caps but at the wrong value. Joe sold some products that were used in the same location as mine and it caused mine to screw up... since it's non-critical it's no big deal. Obviously something is wrong. At some point the FCC comes out and then gets one of Joe's devices and find out what he did and fines him.

A lot of things have changed though. Back in the day you didn't have integrated RF modules that did 90% of the work. In those cases it was much easier to screw stuff up.

True... I guess that is the job of any government. But they shouldn't stifle entrepreneurship or small business growth nor techological advancement... that is, if it's not going to cause problems.

The product recalls is the companies responsibility. If I only have 100 devices sold a year then there is not much recall.

Hehe... well, as I said... I really don't know enough about it. I'm just venting my frustration. I really wanted to implement my own RF device for my new nifty little widget to give it some very competative features. Luckily I have found some RF modules that can do the trick but they are a bit limited.

The main point is that I see a logical gap in the regulation. Basically it is overregulated to some degree. Regulation is good in moderation but there is such a thing as too much. But as I have said many times... I know very little about it. But the ideas I have stated are either wrong or right(for hte most part). If I were to produce an exact copy of the fcc tested design then it should behave exact. (I know, nothings exact) What the FCC could do then is allow for a quick test of the device for a much lower cost and or create a band for such non-tested or "quick-tested" devices.

The IC's and design used would have to be fully tested and would be the responsibility of the manufacturer. But any "exact" implementation of that would then fall under that testing and only a simple "compliance" test could be required(or none at all if a proper spec for the band exists). The IC's could have a "compliance" test mode which would create a test situation so that the testers would have to do very little work. Would probably take < 5 mins to do such a test.

The results could be compared not only against the FCC's requirements but against original chips spec. If they are not with reason do to component variations then it could be rejected.

Again, my point is simply that the situation could probably be improved unless I'm missing something that invalidates my logic. (in theory it makes sense)

Reply to
Jon Slaughter

You might be right. I thought I saw in several datasheets the mention of FCC "compliance". But even though it might not be necessary it is "necessary". I can't imagine a manufacturer creating a RF IC and not getting it tested since it has to be tested by the end user anyways.

Hence it might be better to push all the work on the manufacturer since they have to go through it anyways. They could then just give the schematic/gerber files for the design and as long as you don't deviate then it should fall within compilance.

I mentioned to dave that maybe the FCC could create a "utility" band that was unlicenced by only used by FCC licensed IC's. The IC's would be tested and you could only use the design by the manufacturer(the one the FCC tested of course). The band would not be for critical communications and the IC and design should elimintate any issues with interfering with other bands.

Optionally they could enfore a cheaper method of compliance where the IC's would be required to run a compliance mode(say simply by toggling a pin). It would run an FCC approved test that could be completely automated. The results could be compared to the original design's results and the FCC's requirements. This should be enough solve any real issues involved.

Reply to
Jon Slaughter

Thanks, that clears up some. I guess cheaper(about 5k instead of 15k) than I thought. Still quite expensive IMO. It's not like I'm desigining an tranceiver from discrete components ;/

Reply to
Jon Slaughter

Do you have all the equipment required to make sure your design meets all FCC requirements, and the time to test and certify every transmitter or receiver? If not, its cheaper to buy the modules already built & tested even without paying the testing fees to get FCC certification. Even with a sample PC layout & parts list you can build an entire run of boards that fail the FCC requirements. Ironically, RF gear built for the government doesn't always need FCC approval. OTOH, the FCC can't get into secure government or military facilities.

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Reply to
Michael A. Terrell

Of course not but I imagine I could get it tested relatively easy(local college or some EE type of shops).

I guess you could be right that if the manufacturers suggestions/design is on the edge then it is possible to produce something that is out of FCC spec. Again, it would be nice if the FCC created a band that was for non-critical use and for used only by licensed RF IC's. The manufactuer would simply deal with all the design and compliance testing and as long as you implemented "exact" what they did then it shouldn't be a problem. The FCC would come up with the minimum requirements and require the IC to have some "test" feature that would automate testing.

The IC's could be pretty stringently controlled so that even your average doofus couldn't screw it up too much and still be within compliance.

What I feel is that the rules are still based on the old discrete methods where design was critical and involved many variables. With the IC's there are basically only 2 components. The IC and the Antenna. The IC is pretty much self contained. The Antenna could be critical but as long as the user followed the spec decently it should be relatively safe.

To me it is just almost completely redundant. If the manufacturer creates a design that passes spec well(I'm sorta assuming this though) and I implement that design, then because it is so simple(being just a few components) that it would be hard for me to screw up. (basically if the manufacturer gave the schematic/gerber files and you just copy and pasted... I think you would still be within spec even if degraded).

As I said, if the IC's are designed with such a test feature then the FCC could require a compliance test but it would be much cheaper since it would all be automated and the results could be compared to the manufactured results. Any anomalous results would result in a failure.

If that is still a problem(non-critical, manufactured to compliance, forced tested) they could further specify such things as low power, short distance, low devices, low data rate or comm rate, etc. The idea is to open up the market for very cheap wireless devices for simple non-critical communications.

Of course, Is suppose if it is free then it will be abused and you would have people overpowering devices just to get into that band. Hence I guess the forced testing would be the way to go... but it probably could be done really cheap and require just minutes. A test point which initiates the test mode(as specified by the FCC) but also sends some manufacturer and IC code so they can pull up the original results to compare to. Then it goes through whatever output characteristics that are needed(I guess whatever was originally used) and compared to the original results along with the FCC band requirements. I'm sure it could be for around 100$ instead of 5k$.

I'm not sure if the manufacturers would go through the trouble but I think it's a good idea ;)

Reply to
Jon Slaughter

The current procedures are in place because too many companies have produsced substandard equipment. You referred to 'two components' but the variation in blank PC boards can be large enough to cause problems. I saw enough of it in manufacturing RF equipment at Microdyne. At that frequency a slight variation in board thickness can change the capacitance between layers and cause out of band operation.

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Reply to
Michael A. Terrell

Amplifier = extra noise (less sensitivity) + power consumption.

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Reply to
Nico Coesel

large=20

few=20

Type acceptance and type approval are both long gone (over 20 years gone). Currently it is handled with a "Document of Conformance" from a lab they regulate.

so=20

else=20

antenna is=20

one=20

What part of the FCC has had to become an income source instead of a money hole is so hard to understand?

free=20

Reply to
JosephKK

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