Author Topic: 869.4MHz Bandpass  (Read 1473 times)

0 Members and 1 Guest are viewing this topic.

Offline nighthunter

  • Contributor
  • Posts: 6
  • Country: sk
869.4MHz Bandpass
« on: December 12, 2016, 08:46:31 pm »
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.
 

Offline Lord of nothing

  • Frequent Contributor
  • **
  • Posts: 665
  • Country: at
Re: 869.4MHz Bandpass
« Reply #1 on: December 13, 2016, 10:30:36 am »
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/
Made in Japan, destroyed in Sulz im Wienerwald.
 

Offline nighthunter

  • Contributor
  • Posts: 6
  • Country: sk
Re: 869.4MHz Bandpass
« Reply #2 on: December 13, 2016, 05:08:48 pm »
Hi, yes ive searched on ebay, but did not found anything that is suitable for me. I will ask on the radioreference forum.
 

Offline LaserSteve

  • Frequent Contributor
  • **
  • Posts: 686
  • Country: us
Re: 869.4MHz Bandpass
« Reply #3 on: December 15, 2016, 11:54:37 am »
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
« Last Edit: December 15, 2016, 11:56:38 am by LaserSteve »
"I've Never Heard of a Nuclear Meltdown Caused by a Buffer Overflow"  filssavi
 
The following users thanked this post: nighthunter

Offline nighthunter

  • Contributor
  • Posts: 6
  • Country: sk
Re: 869.4MHz Bandpass
« Reply #4 on: December 15, 2016, 05:20:42 pm »
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?
 

Online daqq

  • Super Contributor
  • ***
  • Posts: 1308
  • Country: sk
    • My site
Re: 869.4MHz Bandpass
« Reply #5 on: December 15, 2016, 10:14:33 pm »
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  :)
« Last Edit: December 16, 2016, 06:57:06 pm by daqq »
Believe it or not, pointy haired people do exist!
+++Divide By Cucumber Error. Please Reinstall Universe And Reboot +++
 

Offline LaserSteve

  • Frequent Contributor
  • **
  • Posts: 686
  • Country: us
Re: 869.4MHz Bandpass
« Reply #6 on: December 16, 2016, 04:50:26 am »
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
"I've Never Heard of a Nuclear Meltdown Caused by a Buffer Overflow"  filssavi
 

Offline nighthunter

  • Contributor
  • Posts: 6
  • Country: sk
Re: 869.4MHz Bandpass
« Reply #7 on: December 16, 2016, 08:02:50 pm »
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.
 

Online daqq

  • Super Contributor
  • ***
  • Posts: 1308
  • Country: sk
    • My site
Re: 869.4MHz Bandpass
« Reply #8 on: December 16, 2016, 10:28:41 pm »
Try contacting the manufacturer - minicircuits has a very good support line.
Believe it or not, pointy haired people do exist!
+++Divide By Cucumber Error. Please Reinstall Universe And Reboot +++
 

Offline LaserSteve

  • Frequent Contributor
  • **
  • Posts: 686
  • Country: us
Re: 869.4MHz Bandpass
« Reply #9 on: December 17, 2016, 08:29:48 am »
Do you have a schematic or block diagram? It helps to know where to put the filters.

Steve
"I've Never Heard of a Nuclear Meltdown Caused by a Buffer Overflow"  filssavi
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf