Can't your simulation software show you a field strength map or a current flow map? That should give you a good idea of what is interacting with the antenna. On Thu, Jul 31, 2014 at 1:40 PM, David VanHorn wrote: > 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 b= ad > 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 a= nd > > > 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 > GPU > > > instead of rental lab time and X-acto knives. > > > > > > It seems that there is some other structure on the PCB that is > resonating > > > in some way that interferes with the antenna. I've done some > > > investigation with stitching vias and definitely things are a lot mor= e > > stable > > > with those in place, but it's not affecting the main problem that I a= m > > 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 > > > -- > 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 .