[time-nuts] pin-wheel antenna

[Jim Lux]

On 4/21/13 5:18 AM, Attila Kinali wrote:
> On Sat, 20 Apr 2013 12:52:03 -0700
> "Tom Van Baak" <tvb at LeapSecond.com> wrote:
>
>
>> For the rest of you:
>>
>> http://www.leapsecond.com/images/gps-pinwheel-1.jpg
>> http://www.leapsecond.com/images/gps-pinwheel-2.jpg
>>
>
> Thanks a lot...
>
> So the design changed slightly from what Kunysz reported in whis two
> papers [1,2] back in 2000... I wonder what this small, detached stripe
> at the end of the "spokes" does. It's not mentioned in the papers.
> But [2] shows some bragg reflector or something similar at the outer
> perimeter (i guess to have a similar effect as a choke ring), maybe those
> stripes replaced those.
>

I would imagine that they loaded the antenna into HFSS or some other 
simulation code, and manually iterated it to improve the performance. 
Little protrusions or adjacent stripes are usually for tuning: trying to 
get the match right, or to suppress some high order lump or bump in the 
pattern or VSWR curve.

Just like "snowflakes" when tuning RF circuits in microstripline.