Comments for Colin Karpfinger

Comment on The Dropout’s Guide to PCB Trace Antenna Design by jay

jay — Sat, 21 Aug 2010 22:36:11 +0000

Its nice article. this the best . I am sure they are more design. keep a good works..

Comment on Ordering PCBs Designed With EAGLE by Ed

Ed — Tue, 10 Aug 2010 09:42:14 +0000

Thanks! My first board is all done, but I’ve spent all day trying to figure out how to package it up to send it to none other than Advanced Circuits. Thanks for the great, straightforward info to get me over the finish line!

Comment on The Dropout’s Guide to PCB Trace Antenna Design by Dale

Dale — Sun, 08 Aug 2010 23:16:30 +0000

Nice article. I had to do an antenna for a 413MHz design a year or 2 back and at the time had no experience with the tools you described above. All I could do in that case was to design the antenna longer as you suggested and watched an RSSI reading at the other end as I tuned the antenna by moving my finger along the length of the antenna until I got a good strong reading. From that point i could fine tune by cutting the antenna at around that point. Def not recommended for FCC approval though!

Comment on The Dropout’s Guide to PCB Trace Antenna Design by Jack

Jack — Thu, 05 Aug 2010 16:46:11 +0000

I have read a little about fractal antenna’s. I am sure they are more difficult to design. But are there some DIY pointers about them somewhere? I’ve been looking, but probably in the wrong places.

Comment on The Dropout’s Guide to PCB Trace Antenna Design by Sebastien

Sebastien — Thu, 05 Aug 2010 15:09:04 +0000

Thanks for those advice.
Usually, CE lab guy say “CE+CE doesn’t equal CE” so, buying an already CE
certified (R&TTE + ETSI 300440 …) RF module may not get rid of the lab certification process for your product including it.

Comment on The Dropout’s Guide to PCB Trace Antenna Design by Tom Granger

Tom Granger — Thu, 05 Aug 2010 13:58:52 +0000

An interesting read, do you think you could do an article on getting the fcc/ce testing? I can’t think of any good guides to getting it or the costs involved and it would be nice to hear from someone with firsthand experience.

Comment on The Dropout’s Guide to PCB Trace Antenna Design by R.Ravindra Kumar

R.Ravindra Kumar — Thu, 05 Aug 2010 12:56:58 +0000

Excellent article for the practical streetsmart designer!!

Comment on The Dropout’s Guide to PCB Trace Antenna Design by Neil

Neil — Wed, 04 Aug 2010 23:21:16 +0000

Great post! As a cell phone design engineer, I enjoyed reading it. Nice to see mightyohm here too, I read his blog. AppCad is a great and free tool from Agilent. I used to work with the author actually.

Regarding pp6′s question, that connector is used for testing and calibrating the phone in the factory, as well as in the certification labs (FCC and other industry certifications that are needed).

Comment on The Dropout’s Guide to PCB Trace Antenna Design by Colin

Colin — Tue, 03 Aug 2010 18:17:03 +0000

Thanks for all the info! I’ll check out your method for feed line calculations.

Regarding FCC testing- this design has already been FCC and CE certified. That was an interesting process as well and probably deserves its own blog post. We were able to pass with only minor corrections and dropping the tx power a couple notches.

Comment on The Dropout’s Guide to PCB Trace Antenna Design by mightyohm

mightyohm — Tue, 03 Aug 2010 16:40:50 +0000

A few suggestions (from an RF guy):

1. If you use a reference antenna design provided by an IC manufacturer, make sure that you know what PCB material and thickness they used in their design. Duplicate it precisely in your design. Even the position of vias around the antenna and the thickness of the copper layers (1 oz vs 2 oz) can make a difference, but if you match the material and overall thickness you should be ok. Watch out for multilayer boards where they use L2 instead of L4 as a groundplane, I have seen lots of this kind of stuff. Also keep in mind that the guy who made the app ckt for the IC may not be a very good antenna designer, so YMMV.

2. I use AppCAD to calculate microstrip trace widths.
http://www.hp.woodshot.com/

3. Tuning an antenna (or changing the matching network that feeds it) can affect the performance of the antenna in terms of gain and directivity. Just because it is a good match doesn’t mean that you haven’t thrown away some other performance parameter of the antenna. Some great antennas can have crappy impedance matches.

4. Testing an antenna on a network analyzer is tricky business, especially if you are in an enclosed room with other objects in it. Try to at least keep the antenna a few feet away from any large metal objects, and note how much the impedance changes as a function of orientation. However, I have done exactly what you did with good results for amateur radio antennas, so it can work!

5. The FCC has all sorts of rules regarding power output (ERP) and spurious emissions for most frequency bands, including 2.4GHz. By designing a custom antenna and PCB layout for an RF chip, I think you are now supposed to have your device tested and certified by the FCC before you can actually sell it. This is why usually hobbyists and small companies will just buy pre-certified RF modules (like the Xbee). Since the module is already certified, you don’t need to worry about the FCC unless you change something about the module design (ie. adding an external antenna). I don’t know the specifics but it would be best to check the rules before going to market (or perhaps you already have plans to get your design certified).