On 1/31/19 9:45 AM, Attila Kinali wrote:
On Thu, 31 Jan 2019 08:51:46 -0500
Bob kb8tq <kb...@n1k.org> wrote:
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.
Transmission line phase shifters are pretty narrow band.
Getting them to 5% bandwidth with reasonable phase and
amplitude stability is already not straight forward. But
for a combined GPS/Galileo/Glonass L1/L2/L5 antenna,
a bandwidth of over 30% would be needed. Not an easy task
at all. Making them work for a few select bands is a lot
easier, if still a bit non-standard. At least EM simulation
tools help a lot with that.
A straight up branch line coupler or two parallel microstrips would have
that problem.
That's the beauty of the Lange coupler.. it holds the 90 degrees over a
pretty wide bandwidth (octaves are doable)
Attila Kinali
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