869.4MHz Bandpass

[nighthunter]

Hi everybody. I am viewing EEVBlog for a longer time and learned a big from here, but now i have some problem. I am working on a TRX based on RFM12BP, but on the output i am getting a lot garbage on the whole range from 100MHz to 1Gig. I am using 869.400MHz (869.4MHz, while it is a long range device and i need to go to the limit of output power (500mW). The question is coult someone help me to design a bandpass filter for the antenna? In and out impedance is 50Ohms. The spectral graph that was measured is attached.

[Lord of nothing]

Gratings from Austria. 
Do you look on Ebay? Some Ebay seller sold "cheap" Filter for common Freq Bands.
Maybe you also would ask here: forums.radioreference.com/

[nighthunter]

Hi, yes ive searched on ebay, but did not found anything that is suitable for me. I will ask on the radioreference forum.

[LaserSteve]

How much space do you have?
Most SMD filters cannot handle the power level you suggest.

How many units do you need?

This is where I would start....

http://www.hparchive.com/Bench_Briefs/HP-Bench-Briefs-1989-01-03.pdf

If I only needed one or two:

http://www.changpuak.ch/electronics/interdigital_bandpass_filter_designer.php

or get some US 850 Mhz cellular band filters on Ebay

Lets narrow down some production  parameters, shall we? One , Two, or Many?



Steve

[nighthunter]

Hi LaserSteve. The problem is that now there are only 4 units (total there will be about 25 of this units), but i need to certify it. I have about 8-9 square centimeters in a place about 2cmx4cm in size. Would you be able to help me with this?

[daqq]

Take a look at what minicircuits is offering - they have a nice range of bandpass filters. Such as:
http://194.75.38.69/pdfs/CBP-840C+.pdf

Also, wow, that's a whole lot of extra signal. How and where are you measuring this? On the antenna output, or just by air?

Also, nice to see another Slovakian fellow here 

[LaserSteve]

Do you have access to CNC machining?  If Not,  CBP-840C+ is not a bad option for 25 units.
Ideally filtering is done before and after final amplifier, may we have more details about your RF chain please?
A two Dollar ceramic SMD filter from Digikey some place before your final amplifier may reduce your problem significantly.

Steve

[nighthunter]

The spectrum was measured right on antenna connector - so direct coupled with spectrum analyzer. I ordered som of the ceramic filter, but will it handle the output power of +24dBm? CNC machining is right by me now a problem, but i have a workshop nearby.

[daqq]

Try contacting the manufacturer - minicircuits has a very good support line.

[LaserSteve]

Do you have a schematic or block diagram? It helps to know where to put the filters.

Steve