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rf bandpass filters 2.4GHz

Hi all,

I am transmitting in channel 3 of 802.11b, centered at 2.422Ghz.
Details aside, let me just say that it is very important for my
application that I sharpen up the spectral mask beyond that of the
802.11b standard. To be specific I need to purchase a bandpass filter
such that I get attenation of greater than 60dB at +- 15Mhz from the
center, i..e outside of [2.407Ghz, 2.437Ghz]. I am looking for
suggestions on where to purchase such filter(s) with the usual
parameters in mind, cost, lead time, etc.

I did see the filters that hyperlink sells, but it would take many of
their 8 pole filters in series to get what I need and they additionally
don't sell filters for one of the channels i would need. Maybe I need
to go custom on this? Any suggestions are greatly appreciated.
Thanks,

Kevin
 
R

RST Engineering \(jw\)

Jan 1, 1970
0
You don't need to go custom. You need to understand the impossibility of
what you are asking for.
Jim






Maybe I need
 
R

Rene Tschaggelar

Jan 1, 1970
0
Hi all,

I am transmitting in channel 3 of 802.11b, centered at 2.422Ghz.
Details aside, let me just say that it is very important for my
application that I sharpen up the spectral mask beyond that of the
802.11b standard. To be specific I need to purchase a bandpass filter
such that I get attenation of greater than 60dB at +- 15Mhz from the
center, i..e outside of [2.407Ghz, 2.437Ghz]. I am looking for
suggestions on where to purchase such filter(s) with the usual
parameters in mind, cost, lead time, etc.

The centerfrequency divided by the bandwidth gives
the Q value. The "bandwidth" means -3db. 30MHz at
2.4GHz would result in a Q of 80. Now you want -60dB
instead of -3dB. That should be doable with a Q of
roughly 1600. Right ?
A dielectric resonator could do it. Temperature
stabilized. The usual parameters : Unless from stock
because it is manufactured in high quantities,
leadtime 3month up, hand crafted microwave gear costs
in the range of military and space items.

Rene
 
Sorry I mispoke earlier. Let me restate this. Hyperlink has an 8pole
filter for several of the 802.11b channels that has the mask -3db at +-
10Mhz, -5db at +-15Mhz, -20dB +- 20Mhz.

Essentially I want to keep 2.417 to 2.437 Ghz, so one of their filters
centered at 802.11b, channel 4 would be ideal, except that they only
sell centered at the standard channels (channel 3 and 6 are the
closest), so in short I was wondering if anyone knows of a vendor that
sells such a filter centered at 2.427Ghz. Thanks for any suggestions.
 
J

Joerg

Jan 1, 1970
0
Hello Rene,
I am transmitting in channel 3 of 802.11b, centered at 2.422Ghz.
Details aside, let me just say that it is very important for my
application that I sharpen up the spectral mask beyond that of the
802.11b standard. To be specific I need to purchase a bandpass filter
such that I get attenation of greater than 60dB at +- 15Mhz from the
center, i..e outside of [2.407Ghz, 2.437Ghz]. I am looking for
suggestions on where to purchase such filter(s) with the usual
parameters in mind, cost, lead time, etc.


The centerfrequency divided by the bandwidth gives
the Q value. The "bandwidth" means -3db. 30MHz at
2.4GHz would result in a Q of 80. Now you want -60dB
instead of -3dB. That should be doable with a Q of
roughly 1600. Right ?
A dielectric resonator could do it. Temperature
stabilized. The usual parameters : Unless from stock
because it is manufactured in high quantities,
leadtime 3month up, hand crafted microwave gear costs
in the range of military and space items.

Well, one could start with cavity resonators. But they would have to be
regularly tuned and you'd needs lots of polishing paste and elbow
grease. Plus a good medical insurance plan to deal with "tennis elbow".
 
J

Joerg

Jan 1, 1970
0
Hello Kevin,

Sorry I mispoke earlier. Let me restate this. Hyperlink has an 8pole
filter for several of the 802.11b channels that has the mask -3db at +-
10Mhz, -5db at +-15Mhz, -20dB +- 20Mhz.

Essentially I want to keep 2.417 to 2.437 Ghz, so one of their filters
centered at 802.11b, channel 4 would be ideal, except that they only
sell centered at the standard channels (channel 3 and 6 are the
closest), so in short I was wondering if anyone knows of a vendor that
sells such a filter centered at 2.427Ghz. Thanks for any suggestions.

That looks like you'd have to call them for a custom version which will
probably be lots of $$. Or roll your own which requires a lot of
RF/microwave knowledge. Or hire a consultant :)

Problem is, if you are most likely the only one needing this there won't
be an existing market and chances that any other company has the right
product could be close to zilch.
 
R

Rene Tschaggelar

Jan 1, 1970
0
Joerg said:
Hello Rene,

Well, one could start with cavity resonators. But they would have to be
regularly tuned and you'd needs lots of polishing paste and elbow
grease. Plus a good medical insurance plan to deal with "tennis elbow".

Joerg,
a Q of 1600 in the S Band is not that
extreme, or is it ?

Rene
 
T

Tam/WB2TT

Jan 1, 1970
0
Sorry I mispoke earlier. Let me restate this. Hyperlink has an 8pole
filter for several of the 802.11b channels that has the mask -3db at +-
10Mhz, -5db at +-15Mhz, -20dB +- 20Mhz.

Essentially I want to keep 2.417 to 2.437 Ghz, so one of their filters
centered at 802.11b, channel 4 would be ideal, except that they only
sell centered at the standard channels (channel 3 and 6 are the
closest), so in short I was wondering if anyone knows of a vendor that
sells such a filter centered at 2.427Ghz. Thanks for any suggestions.
Can't you do this at IF?

Tam
 
J

Joerg

Jan 1, 1970
0
Hello Rene,
Joerg,
a Q of 1600 in the S Band is not that
extreme, or is it ?


It is amazing what can be done with cavity resonators but for this job
it needs to be high precision and multi-stage. An example of how they
look in the professional world is shown on page 7-4:

http://www.emsp.tu-berlin.de/lehre/mixed-signal-baugruppen/bericht_high_speed_teil8.

Sorry, the text is only available in German which you'll understand but
the others here may not. My other sources for hi-Q resonators are also
all German, such as the most excellent hands-on book series "UHF
Unterlage". That'll show you step by step how to build them. But don't
even think about it if you don't have access to a precision lathe ;-)
 
J

Jimmie D

Jan 1, 1970
0
Hi all,

I am transmitting in channel 3 of 802.11b, centered at 2.422Ghz.
Details aside, let me just say that it is very important for my
application that I sharpen up the spectral mask beyond that of the
802.11b standard. To be specific I need to purchase a bandpass filter
such that I get attenation of greater than 60dB at +- 15Mhz from the
center, i..e outside of [2.407Ghz, 2.437Ghz]. I am looking for
suggestions on where to purchase such filter(s) with the usual
parameters in mind, cost, lead time, etc.

I did see the filters that hyperlink sells, but it would take many of
their 8 pole filters in series to get what I need and they additionally
don't sell filters for one of the channels i would need. Maybe I need
to go custom on this? Any suggestions are greatly appreciated.
Thanks,

Kevin
Perhaps you could get one of the hyperlink models and modify it.
 
C

Chris Jones

Jan 1, 1970
0
Hi all,

I am transmitting in channel 3 of 802.11b, centered at 2.422Ghz.
Details aside, let me just say that it is very important for my
application that I sharpen up the spectral mask beyond that of the
802.11b standard. To be specific I need to purchase a bandpass filter
such that I get attenation of greater than 60dB at +- 15Mhz from the
center, i..e outside of [2.407Ghz, 2.437Ghz]. I am looking for
suggestions on where to purchase such filter(s) with the usual
parameters in mind, cost, lead time, etc.

I did see the filters that hyperlink sells, but it would take many of
their 8 pole filters in series to get what I need and they additionally
don't sell filters for one of the channels i would need. Maybe I need
to go custom on this? Any suggestions are greatly appreciated.
Thanks,

Kevin

Send your spec to these guys, they should be able to help you or at least
tell you whether it can be done. I hope you can afford their products.
Their tunable notch filters are very nice and might be one way of avoiding
a custom design, though I don't know if they cover your frequency.
http://www.klmicrowave.com/index.shtml
 
J

Joerg

Jan 1, 1970
0
Hello Chris,
I am transmitting in channel 3 of 802.11b, centered at 2.422Ghz.
Details aside, let me just say that it is very important for my
application that I sharpen up the spectral mask beyond that of the
802.11b standard. To be specific I need to purchase a bandpass filter
such that I get attenation of greater than 60dB at +- 15Mhz from the
center, i..e outside of [2.407Ghz, 2.437Ghz]. I am looking for
suggestions on where to purchase such filter(s) with the usual
parameters in mind, cost, lead time, etc.

I did see the filters that hyperlink sells, but it would take many of
their 8 pole filters in series to get what I need and they additionally
don't sell filters for one of the channels i would need. Maybe I need
to go custom on this? Any suggestions are greatly appreciated.
Thanks,


Send your spec to these guys, they should be able to help you or at least
tell you whether it can be done. I hope you can afford their products.
Their tunable notch filters are very nice and might be one way of avoiding
a custom design, though I don't know if they cover your frequency.
http://www.klmicrowave.com/index.shtml


And if Kevin decides to build it himself he'll need really good
polishing paste. My trusty "Wenol" paste ran out a while ago and a few
days ago I found it: At an upscale kitchen store!

(Such pastes are not healthy, make sure it doesn't get on the skin)
 
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