[time-nuts] GNSS Antennas

jimlux jimlux at earthlink.net
Thu Jan 31 19:53:08 UTC 2019


On 1/31/19 5:51 AM, Bob kb8tq wrote:
> Hi
> 
> If you take a hammer to one of these antennas, they seem to mostly play games
> with transmission lines on pc boards. The number of components involved is pretty
> small.
> 
> If hammering one apart does not sound like a great thing to do, there are pictures
> here and there. I have yet to see a picture that shows enough to actually make sense
> out of. I’d bet that is intentional.
> 
> Looking at network analyzer sweeps, it becomes pretty apparent that whatever
> combination of things are involved, they only work inside each of the target sub-bands.
> Once you get to the edge, it all falls apart. It comes back together once you get to
> the edge of the next sub-band. Some of that is intentional filtering so sorting it out
> that way … not so much.
> 
> Bob
> 


These things are designed by someone sitting down with HFSS or similar, 
starting with a cookbook layout and iterating the design manually until 
it works.  It's faster than xacto-knife, copper foil tape, etc.
You can literally click and drag and watch the S11 change in real time 
if you've got enough CPU horsepower.

Someone who is reasonably facile with the tools (and has a design to 
start with) can probably knock one out in a day or two of work.

Then a week to get the prototype back from fab and you test it, and call 
it done.

I'll bet they don't agonize too much about axial ratio off boresight or 
perfect phase center vs look angle.. It's more about "is the degradation 
tolerable for the desired application".






More information about the Time-nuts_lists.febo.com mailing list