When open-circuited stubs are preferred over short-circuited stubs?

[Terminator3]

In filters / matching schematic.
For example, if we do not want to add DC block capacitor on drain of transistor, we can use open-circuited matching stub. Also sometimes single-stub matching can be more compact with open-circuited stub and additional phasing line for rotating on Smith Chart.

There is my old question here:
https://www.edaboard.com/threads/294441/

But open-circuited subs are widely used. Is it because of VIA impedance difficulties at higher frequencies?

IMHO, most high frequency (>=10GHz) transistor matching is done using open-circuited stubs.
Also, microstrip band-pass filters are mostly built using half-wave resonators, and not interdigital quarterwave short-circuited "fingers" resonators. So i think that open-circuited stubs are somehow preferred nowdays.

 

[rizoeda]

I think when you don't have noise problem, it's easier to use open circuit.

 

[jiripolivka]

Open-circuit stubs are problematic in that they tend to radiate. Short-circuit stubs are better, and you can use a short-circuit stub connected by a quarter-wave line to have the open-circuit stub which will not radiate.
For wider bandwidth, impedance steps are used.

 

[pancho_hideboo]

Open Stub Tuner is suitable for tuning.
Here you can adjust length easily by cutting stub.

 

[vfone]

Yes, the open stubs tend to radiate, but by this reason (radiation losses) they get better "short circuit" to the ground, and they are more often used in microwave circuits than grounded stubs.

 

[jiripolivka]

Yes, the open stubs tend to radiate, but by this reason (radiation losses) they get better "short circuit" to the ground, and they are more often used in microwave circuits than grounded stubs.

I do not agree. Please look in any choke flange of a waveguide, to see a shorted stub.
If you leave a structure to radiate, it does not make a better short to ground.

 

[vfone]

Radiation losses in microstrip design (that use a dielectric substrate) have different meaning than losses in waveguides.
In microstrip design, for low dielectric constant will be less concentration of energy in the substrate region, resulting greater radiation losses. And will be in the other way for high dielectric constants.
Any simple EM simulator can show that microstrip open stubs get better "short" than microstrip grounded stubs.