Can anyone tell me, where I can find a schematic of power amplifier: frequency 2.4-2.5 GHz, power about 1W. I'd prefer a simple schematic with one transistor, I tried google, but I cud find only very complicated systems. Does anybody know, where I can find something like this?
greets Wojtek N.
I would look for ap notes and data sheets on transistor manufacturers web sites.
Tam
wnas hath wroth:
Sure. Let's trash the Wi-Fi/ISM band with more powerful signals. The stuff barely works now, so lot more interference shouldn't hurt. Be the first in your neighborhood to rule Wi-Fi.
Most of the manufacturers have application notes. For example, Maxim:
Most of the chips will belch about +20dBm (100mw). If you want more, you'll probably need to either combine outputs, or build a discrete power amplifier. Note that you can purchase wireless access points that already belch +23dBm (Buffalo Hi Power) up to +26dBm (2wire
2701HG series).Building the amplifier is only part of the problem. You need to have some way to switch between xmit and recv. You can butcher your access point to provide the necessary signals, but most amplifiers use an RF detector at the input. Getting this to respond quickly is not a trivial exercise.
The amplifier will also require an AGC (automagic gain control) that insures that your Wi-Fi signal does not get clipped or distorted by overdriving the amplifier. It's mainly to compensate for wide variations in drive levels and coax cable losses. It's sometime used in conjunction with an ALC (automagic level control) that monitors the output power and also insures that the amplifier remains linear.
Most power amplifiers also include a receive amplifier. These don't improve the sensitivity much, but do compensate for coax cable losses in receive. Be careful here as too much gain will cause the front end to overload early and trash what little dynamic range you have.
Of course, you need some way to power this device. You could run an extra two wires between the wall wart and the power amplifier, but that looks tacky on the roof. More common is a power over coax adapter, that supplies the necessary DC power via the input coax, and provides isolators to separate the 2.4GHz drive signal from the DC.
You're not done yet. After you get the power amplifier working, there's the little matter of harmonic filtering. You'll need an output filter (band pass or low pass) to reduce the harmonics of
2.4GHz generated in the power amplifier to acceptable limits.There should also be some form of VSWR protection. This isn't necessary for fairly low power systems. However, higher power amplifiers will tend to self destruct if transmitting into a dead short, open connector, or typical cantenna.
There's still more. Once you've designed and bench tested all the aforementioned, you'll probably discover that it's not very stable over temperature. You'll need to temperature compensate the amplifier so that it works over the typical outdoor temperature range. Of course, the amplifier will be only about 10% efficient at 2.4GHz, so you'll have a non-trivial amount of heat to dissipate somewhere. A heat sink will possibly be required. If enclose in a metal box, some means of moving the heat to the outside will be required to prevent self-incineration.
Deploying such devices are both a violation of FCC rules-n-regs, and good taste. See FCC Part 15 under "intentional radiators". A wi-fi power amplifier is like an alligator, which has a big mouth, and tiny ears. From my perspective, they are little better than jammers. To work properly, the operating range of both the client and the access point should be equal. That can be done if both ends of a wireless link have power amplifiers, but not when only one end is belching excessive power. Its small ears can't hear any of the laptops or clients that are running perhaps -15dBm.
I forgot to mumble something about test equipment. You'll need a rather expensive collection. I'm rebuilding my 1960's museum pieces with something more 1980-ish. I expect to burn about $10K this year and that's cheap.
You might want to check around to see if some of the local hams and engineers have labs you can borrow. Without test equipment, you're working blind.
Good luck.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
You overestimate me. It's just for academic project:)
greets Wojtek
wnas hath wroth:
?????
Hmmm... Reverse DNS points to:
Ok, you're in Poland. I didn't see a university so I assumed you were actually going to design and build something. I guess not.
Besides doing your projects for you, we can also do your homework and write your papers for you. For a nominal charge, I'm sure we can also arrange to have someone take your exams for you. When and if you do graduate, we can perhaps do your job for you.
I think you might find it more educational if you did your own research and design work.
Powodzenia (good luck).
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Acctually getting schematic is just a tiny part of designing work. I don't want you to make my job, I would be grateful if you just gave me for example a tiitle of book where I could find examples of systems like I need. I don't want to get ready design, I just wanted to see how it could look like, and build my own design.
For a nominal charge, I'm sure we can also
I have beeen succeded without such methods for a few years, and I'm sure 'll take care in the future.
Dzieki (thanks)
Wojtek N
wnas hath wroth:
That's fair enough. However, I don't think you'll find much in the books. The application notes and design articles should be sufficient for the amplifier portion. The other parts of the design I mentioned are a bit more difficult to find. Also, I don't have a very good collection of up to date books. Sorry.
You didn't specify the power level, gain, and power supply specifications. I can't supply an example of all of these. A random sample:
For the lower power end, the Maxim sample board is a good start:
Also RFMD:
If you want to avoid the RF matching problems and use a ready to run module, see:
Some home made amps:
For far more power (than is legal), there are many commerical units:
(50 watts)
However, none of these offer schematics or design info. However, if you plan to build something useful, you might compare your design and performance with what these offer.
Also, you can get considerable insight into the design by snooping around the FCC ID web site.
To get a list of everything from a manufacturer, just type in their grantee code. For example: MFM Teletronics K7M or MYF HyperLink Technologies They usually have a photograph of the inside of the device. For example, inside photos of a Teletronics access point, with the 500mw power amplifier and DC injector shown near the bottom of the page:
2.4GHz amps are also popular for ham radio satellite and ATV work. Search for AO40 amplifiers, L-Band amps, or satellite power amplifiers. There are probably some in the ARRL publications but I'm too lazy to look.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Jeff Liebermann hath wroth:
Ooops. It's C-band or 23cm, not L-Band.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
The bottom line is asshole like this f*ck up the band for everyone else. Pardon my french, but there's no other way to say it.
I be damned if I'm going to help him one bit!
You want more power??? Bid for a license like everyone else. Not Bill Gates. Too bad. How's it feel to want?
-mpm
IRAQ was adacemic. What's your point.
Just STOP. What you intend to do is ILLEGAL and harms others. What is the point??? I guess I just don't get it.
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