Phase difference between ports

[kellogs]

Hi,

I am trying to get the phase difference between X1 and X2.

Is it the same as phase(S[1,1]) ?

Thank you

[n4es]

If the source is port 1, X1 is port 2, and X2 is port 3, the phase difference between X1 and X2 would be the difference between phase(S[2,1]) and phase (S[3,1]).

[kellogs]

Phase difference between [X1 port 1] and [X2 port 1]

Source port: P1

Thanks

[kellogs]

Like this?

phase(S[2,1])-phase(S[3,1])

But how do I convey the port numbering to Qucs ?

[n4es]

[kellogs]

Ok, so no way to use the touchstone .s1p files I guess.

[kellogs]

Hurrah!

Have I chosen P2 & P3 Z well ? i have made it much larger than the Z range from X1 & X2

Thanks

[n4es]

OK. It appears that you are simulating a lumped-element 180-degree power splitter to feed a dipole antenna. You might want to do a time domain (transient) simulation to be sure you are seeing what you expect. I don’t know if uSimmics will accept .S1P file in a time domain simulation. If not, substitute resistors that are close to the real part. Look at the Port 2 and Port 3 waveforms on the same graph at a few frequencies. I think you want outputs of equal amplitude and 180 degrees out of phase.

[kellogs]

I might want outputs of equal amplitude and 180 degrees out of phase. it does not seem to happen though.

 

I am not so sure that I want to see 180 deg difference in a transient simulation though; the cut=off frequencies are like:

LPF branch of the balun: f_0 + delta_f

HPF branch of the balun: f_0 – delta_f

[n4es]

Attachments:

1. 

   splitter-with-dipole.png
   

[kellogs]

https://www.fars.k6ya.org/docs/Stearns_K6OIK-Antenna-Impedance-Models.pdf

Page 48, yes ?

This is a bit over my head… so in your schematic, the right side is a narrow band (?) 315 MHz dipole equivalent circuit and that low S11 implies good 180 deg phase diff for the discrete components balun. Right?

[kellogs]

So what I did was to rotate P2 180 degrees and take out the GND between P2 and P3. Don’t really know if it is legit but this way I am getting expected values for both reflection coef and phase difference at dipole arms.

[n4es]

Well P2 and P3 are always going to show 180 degrees apart without the ground connection in between. That is probably not useful information.

I just now noticed that you are using a bowtie dipole, which is broader bandwidth and higher feed impedance than the wire dipole model that I used. I’m not sure how practical it is to use 1-port s1p data for half of a dipole, which depends highly on the common-mode reference to something, such as a reflector screen or just the shield of the feed line. Bowtie used to be fed with 300-ohm twin lead. I don’t know how you would measure one half of the dipole that way.

You might want to download free EZNEC and simulate the bowtie. You can probably find a close example design to get started. Get s1p for the balanced feed impedance, then use an ideal 1:1 transformer in uSimmics to feed it with a balanced circuit.

[kellogs]

Oh, is that so ?… With the GND between P2 and P3 I have noticed that the phase differential goes towards 180 as each of the Z goes towards 0.

The half-dipole .s1p’s that are being used are just the initial .s1p file (real antenna measurement, full dipole) where the impedances have been halved.

Definitely going to use an ideal 1:1 transformer with the initial s1p file.

Thank you for the replies, much appreciated!

[kellogs]

Simulation with lattice network for my halved dipole:

Looks good to me. So halving the dipole as I have done is OK then ?

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