Homepage - RF Cafe
Webmaster: Kirt Blattenberger | KB3UON | Sitemap | ©1996-2014
Menu below is just a small sample of what is here!
 
Custom Search
More than 10,000 searchable pages indexed.
•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

rejection of WLNA signal at input of colocated Wimax receive - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


 Post subject: rejection of WLNA signal at input of colocated Wimax receive
Posted: Thu Nov 19, 2009 11:01 pm 
 
Colonel
User avatar

Joined: Wed Aug 16, 2006 8:20 am
Posts: 31
Location: India
I am designing a transceiver where WLAN and WIMAX radios are colocated (on the same PCB).
consider an usage scenariuo when the WLAN (2.45 GHz) systems is transmitting and the WiMAX (2.51 GHz) is receiving. due to finite isolation between the antennas (<15 dB) of WLAN and Wimax, the WLAN signal will either saturate the WIMAX LNA or may produce some intermodulation product by mixing with other signals.
In the standard the minimum rejection requirements of WLAN signal at WIMAX receiver input is not specified.

I calculated that -40 dBm of any interferer signal would be desired to keep all IMD products at LNA input(IIP3=3) below the Noise Floor.

From this I found out the rejection required for WLAN signal. For example it the receiver antenan see a maximum of 5 dBm WLAN signal then the filter before LNA should attenuate the signal to -40 dBm so that any IMD generated by this signal is less than Noise floor.

However it seems that such filters are extremly difficult to realize.

I was wondering if this is the correct approach of finding the filter rejection requirements.

I would be grateful if anyone can share their views on this.

reagrds,
Ashish

_________________
Ashish Bondia,
Design Engineer- RF


 
   
 
 Post subject: Re: rejection of WLNA signal at input of colocated Wimax receive
Posted: Fri Nov 20, 2009 9:36 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 304
Location: London UK
Hi ashish
There are two separate issues here:
1) mutual interference that might be filtered
2) unacceptable high saturation of the non-linear devices
Regarding (1) I am not familiar with the relative relationship between mutual interferers in these particular systems, but in general with digital modulation, it is possible to operate even co-channel with interferers that are only -10dBc. Thus typically one obtains a Bit Error rate of say 1 in 10^-8 for a carrier to noise ratio of 10dB. This arises mainly because the modulation is quasi-synchronous, and the interferer signal clock will be out of phase coherence and thus appear as just noise.
Regarding (2) the resulting non-linearity products might be capable of being out-filtered using an elliptic function filter with the rapid roll-off side of the BPF placed between the two carriers.

_________________
At bottom, life is all about
Sucking in and blowing out.




Posted  11/12/2012
A Disruptive Web Presence

Custom Search
Over 10,000 pages indexed! (none duped or pirated)

Read About RF Cafe
Webmaster: Kirt Blattenberger
    KB3UON

RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

RF & EE Symbols Word
RF Stencils for Visio

Product & Service Directory
Personally Selected Manufacturers
RF Cafe T-Shirts & Mugs

RF Cafe Software

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel
Your RF Cafe Progenitor & Webmaster
Click here to read about RF CafeKirt Blattenberger... single-handedly redefining what an
                                 engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem! (Seize the Day!)

5CCG (5th MOB): My USAF radar shop

Airplanes and Rockets: My personal hobby website

Equine Kingdom: My daughter Sally's horse riding website