RF-circuit board
 

Hi
what is the difference between RF-circuit board ( high frequency ) and
non-RF-circuit board ?
What happen when I use non-RF-circuit board for 900 MHz frequency ?

Thanks

Fero

"Fero" wrote in message
oups.com...
Hi
what is the difference between RF-circuit board ( high frequency ) and
non-RF-circuit board ?
What happen when I use non-RF-circuit board for 900 MHz frequency ?

Thanks

Fero

The differance is the material the copper is on. It can cause the tuned
circuits to be differant and it may be so lossey the material will burn if
the power is high enough.

Fero wrote:
"what is the difference between RF-circuit board ( high frequency ) and
non-RF-circuit board ?
What happen when I use non-RF-circuit board for 900 MHz frequency ? "

It could be the dielectric substrate material of the board as Ralph
wrote, or it could also be just how the board is laid out. At least,
it's not quite clear to me from your question that it's strictly the
board material.

As for material, for low-power things at least, we generally don't
bother with expensive Duroid or Teflon or similar substrates out to
1GHz. We find that good FR-4 fiberglass-epoxy material will usually
work OK. One of the concerns that you should be aware of, though, is
that the dielectric constant of FR-4 is NOT as well controlled as the
dielectric constant of the better (and much more expensive) RF
substrates. Also, the dielectric constant for FR-4 is quite a bit
higher, leading to narrower traces and therefore higher loss, to
achieve the same transmission line impedances (or smaller pads to get
the same capacitance). So if you have a layout designed for some
particular dielectric constant and it uses transmission lines and/or
physical structures to do filtering or impedance matching, expect to
have to modify it to work properly if you use a different substrate
material. Obviously, it's also important to pay attention to the
dielectric thickness if you're trying to get particular microstrip
impedances.

The freeware "RFSim99" program has a tool for doing some simple
microstrip calcs, and you should be able to find web applets that cover
much more complicated cases like buried microstrip, stripline, balanced
microstrip, etc. You can also find free/student/trial programs that
analyze more complex structures, though all that may be going well
beyond what you're interested in.

Cheers,
Tom

Hi Tom,
thanks for answer. I will make device for data-transfer on 900 MHz with
nRF905 from Nordic. I have no experience in so high frequency. This
device is low power transmitter. I am not sure what happen wenn I use
standard (non-RF) circuit board. Probably output power will be low or
cann I waiting another problems ?

Cheers,

Fero

Hi Fero,

Since I'm not familiar with the nRF905, I can't really anticipate what
problems you might run into. I do expect that at 900MHz, if you can
come up with a proper layout and execute it correctly, standard FR-4
(modern fiberglass-epoxy) dielectric shouldn't be a significant
problem. I'm assuming that the whole board is small and you don't have
more than a couple cm trace length. Obviously, if you ran a few meters
of microstrip, you'd have noticable loss. Perhaps someone with some
nRF905 experience can give you more help. I did bring up the Nordic
website, but the ap note files for the demo boards were in some format
my 'puter doesn't understand. (Why doesn't eveyone include a PDF
version??) Since Nordic seems to try to provide lots of info on their
web site, perhaps they would answer an email about your concerns.

Cheers,
Tom

The application note for the NRF905 does specify FR4 board with 1.54mm
substrate thickness. FR4 is the board material used for almost all printed
circuit boards, so you can use a regular board and just make sure the
thickness is 1.544mm.

http://www.nordicsemi.no/files/Produ...out_rev2_0.pdf


here is the link for most od the documents related to the NRF905.


http://www.nvlsi.no/index.cfm?obj=se...t=searchResult



Jim
N6BIU

--

14:04 Pacific Time Zone
Sep 5 2005

International Time
21:04 UTC
05.09.2005

Hi Tom,

I have got one more question : could this RF-4 material be used for
frequency up to 2,4 GHz too ? ( blue toot )
Namely, Nordic offers chips for this frequency, too.

Thanks a lot.

Fero

Fero wrote:
Hi Tom,

I have got one more question : could this RF-4 material be used for
frequency up to 2,4 GHz too ? ( blue toot )
Namely, Nordic offers chips for this frequency, too.

Thanks a lot.

Fero

I used ordinary FR-4 for a 6 GHz pulsed oscillator in a commercial
product, and the last I heard it was working fine in mass production.
But it's used only in a dry environment, and doesn't have any high Q
networks or filters. If your design can tolerate relatively high loss
and a moderate dielectric constant (about 5) that varies with
temperature and humidity, FR-4 is fine. If it can't, you should consider
Rogers PTFE board products or something similar.

Roy Lewallen, W7EL

1.5mm just happens to be 0.062" (1 / 16 ") which is the industry standard
board thickness.

Jim


"Jim" wrote in message
...
The application note for the NRF905 does specify FR4 board with 1.54mm
substrate thickness. FR4 is the board material used for almost all
printed
circuit boards, so you can use a regular board and just make sure the
thickness is 1.544mm.

I used it at 2.3 Gig in a 5 watt transmitter and it worked just fine.

Jim



"Fero" wrote in message
oups.com...
Hi Tom,

I have got one more question : could this RF-4 material be used for
frequency up to 2,4 GHz too ? ( blue toot )
Namely, Nordic offers chips for this frequency, too.

Thanks a lot.

Fero