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switch matrix - RF Cafe Forums

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 Post subject: switch matrix
Posted: Mon Jun 06, 2005 6:36 am 

Joined: Mon Jun 06, 2005 12:38 am
Posts: 2
i am working on switch matrix in the frequency range of 18GHz.
when i interconnect the switches(electromechanical switch) in series by using semi rigid cable, return loss is becoming bad in ku band frequencies.
please give ur suggestion for improving the performance.

Research engineer

 Post subject:
Posted: Mon Jun 06, 2005 7:46 am 
User avatar

Joined: Mon Sep 01, 2003 6:59 pm
Posts: 38
Location: Boston
Can you replace most or all of your coaxial cable with waveguide? Waveguide loves 18 GHz and you eliminate the lousy connectors that coax has to use. In fact, a lot of your cable problems could be due to the connector interfaces. One way to check is to do a TDR on the path and see if your reflections are concentrated at connectors. Sometimes a judicious trimming of cable lengths can significantly reduce VSWR induced ripple and slope.

- Maxwell

 Post subject:
Posted: Tue Jun 07, 2005 12:09 am 
hi max,
thank you for your reply.I may not be able to use wave guide in system.i have to use coax only. please post your suggestion regarding connectors and cables works at 18GHz


 Post subject:
Posted: Fri Jun 10, 2005 6:43 am 
You need to minimize the cable length to under a quarter wave length in order to minimize the standing wave, you may want to scrap the cable and use sma "bullets" to connect the switches. Another trick is to adjust the phase in between the switches by either changing the length of the cable or using a phase shifter. I had a similar situation once where I was not meeting my output power requirement due to mismatch in between various modules. Like you, I was using cable. I resolved the issue by pains takingly adjusting the cable length in between each module until I obtained optimized perfromance.

Posted  11/12/2012