coax amplitude ripple issues - RF Cafe Forums

 Post subject: coax amplitude ripple issues

Posted: Mon May 29, 2006 3:11 am 

I'm having some issues testing our system- I can't shake the amplitude ripple I'm reading from the coax cables I'm using. I've tried changing cables, using different lengths, making sure connections are tight, having isolation in the path, and nothing is working.

Any thoughts? I'm testing in a high heat/humidity region, so maybe that's the issue . . .

Thanks so much.

 Post subject:

Posted: Thu Jun 01, 2006 11:05 am 

Are you sure that the cables & connectors are rated for the frequencies that you're operating at? If you're transmitting anything with a square edge, then you;d better make sure that the cable is rated at least 5x your highest fundamental or the harmonics that make up the edges will be reflected and possibly be causing your amplitude ripple.

Otherwise, maybe the impedance of your source and/or load are not close enough to the cable/connector impedance and you are seeing VSWR (that's my name!) mismatch induced ripple. If your source/load is even 10 ohms off of your transmittion path impedance the amplitude ripple can be noticealbe of long distances.

You didn't mention how long the cable run is or your signal frequency & modulation type, so all I can do is make these guesses. Hope they help.

--- VSWR ---

 Post subject:

Posted: Thu Jun 01, 2006 9:13 pm 

I'm in the 10-13 GHz region. I'm using the appropriate isolators, and my cable runs are only around 12ft. However, in talking with a senior RF tester, he says that my adapters may be causing the issues- I'm using a fair number of adapters to connect my SMA isolators to my N-type coax. Minimizing them may be the key. Any thoughts?

Thanks for your input.