[time-nuts] GNSS Antennas

[jimlux]

On 1/31/19 9:45 AM, Attila Kinali wrote:
> On Thu, 31 Jan 2019 08:51:46 -0500
> Bob kb8tq <kb8tq at 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
>