I may try that. I can delete traces one by one but that's tedious, and leaves a trace-shaped slot in the planes which may itself have been the bad guy. As Russel points out, I suspect it's some trace or finger of ground plane that's causing the problem but that's kinda like narrowing down a purse snatching subject to "middle aged male". On Thu, Jul 31, 2014 at 10:43 AM, wrote: > > I am doing a lot of PCB trace antenna design lately, and I am seeing > another > > occurence of something that I had seen before, where a given antenna > > design that should be workable, simply won't tune in a given design. > > > > Previously all I had to address this was renting some time on a VNA and > > hacking a physical prototype. > > > > Today I am working with XFdtd simulating the entire PCB, plus all the > > surrounding materials. That makes the tuning process one of time on a G= PU > > instead of rental lab time and X-acto knives. > > > > It seems that there is some other structure on the PCB that is resonati= ng > > in some way that interferes with the antenna. I've done some > > investigation with stitching vias and definitely things are a lot more > stable > > with those in place, but it's not affecting the main problem that I am > seeing. > > > > I am wondering if others have hit this, and if so what they did to > isolate and > > get rid of the problem? > > What happens if you 'mask' other bits of the PCB with the equivalent of a > metal can - rather like gets fitted to actual modules. > > By having a small 'grounded can' that gets a simulated decent ground > connection to mask an area can you effectively mask that area from the > simulation? > > > -- > Scanned by iCritical. > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .