RF coil - RF Cafe Forums

RF Cafe Forums closed its virtual doors in late 2012 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 2012, 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. Here is the full original RF Cafe Forums on Archive.org

Lechko

Post subject: RF coil

Posted: Wed Jul 13, 2005 8:06 am

Lieutenant

Joined: Wed Jul 13, 2005 8:01 am

Posts: 1

Hi everyone, im new to this group so i hope you can help me...

I've been working with HFSS for a while now, designing RF coils for MRI. The structure is pretty simple - a single turn coil with a coax feed. the feed is blocked by a copper block on its port end, and the inner coax connects to the coil... (coil radius=7cm) the problem is that i keep getting negative real part for my impedance in low freq. (around 100MHz).

Happend to any of you? what's that supposed to mean in HFSS?

thanks in advance

Alex

Kirt Blattenberger

Post subject:

Posted: Tue Jul 19, 2005 7:26 pm

Site Admin

Joined: Sun Aug 03, 2003 2:02 pm

Posts: 308

Location: Erie, PA

Greetings Lechko:

I am not a HFSS user, but negative impedances in other simulators often indicate you are sampling at physical point that is located at or near a peak in a standing wave on the line. Constructive interference there can create a voltage greater than that which is applied. This is an indication of an impedance mismatch at the sampled frequency.

Or, it could be something else :lol:

- Kirt Blattenberger :smt024

Posted 11/12/2012