# Insertion loss? - RF Cafe Forums

 RF Cafe Forums closed its virtual doors in 2010 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2010, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts. NOTICE: The original RF Cafe Forum is available again for reading, and the new RF Cafe Blog is an active board. -- Antennas -- Systems

Qacer
 Post subject: Insertion loss? Posted: Tue Feb 06, 2007 10:18 pm
 Captain

Joined: Sat Apr 23, 2005 2:09 pm

Posts: 19

Location: Tampa, FL

Hi

Is cable loss the same as insertion loss?

If I were to test a cable under a calibrated network analyzer setup, would I be able to figure out the cable loss using the S-params?

I'm thinking that insertion loss is just S12 - S11, but I don't know much anyway.

Thanks!

Jeanalmira
 Post subject: Posted: Wed Feb 07, 2007 3:47 am
 General

Joined: Tue Mar 15, 2005 11:43 pm

Posts: 67

Location: Singapore

Hi :

The insertion loss is basically the loss as the ratio of Pout and Pin. Or, well known as transmission coefficient.

So insertion loss = |S21| and since the cable is passive device, so |S12|=|S21| . If the cable is low-loss, the |S21|=|S12| must be somehow equal or close to zero dB.

In addition, S11 refers to reflection coefficient, which means how much the input power that is reflected. Again as cable is passive device, so |S11| = |S22|. at low-loss cable, the |S11| = |S22| must show low values, preferable <-20dB.

I hope it helps.

Regards,

Jean

Qacer
 Post subject: Posted: Sat Feb 10, 2007 4:54 am
 Captain

Joined: Sat Apr 23, 2005 2:09 pm

Posts: 19

Location: Tampa, FL

Thanks, Jean!

Posted  11/12/2012