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Multiple input ports in RF problems

Posted Sep 23, 2009, 4:36 a.m. EDT RF & Microwave Engineering Version 4.2a 5 Replies

Roberto Olmi
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Hello to everyone.

The RF module Users Guide, at page 72, says (Note at the top of the page) that it is possible to have more than an excited inport, with the drawback that S-parameters are not correctly computed.

On the contrary, COMSOL seems to not allow this: I need to excite a microwave cavity with two waveguides at the same time, but the program does not allow me to put a waveguide excitation on both ports.

Any suggestion?

Thnaks,
Roberto
5 Replies Last Post Dec 14, 2012, 6:59 a.m. EST
Robert Koslover Certified Consultant
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Posted: 1 decade ago Oct 3, 2009, 1:26 p.m. EDT
Well, it works for me. I just designed a custom waveguide structure with 3 excited input ports and 4 output ports.

Any chance you are failing to specify unique port numbers for each port? The default port number for each port is 1. If this is your problem, then number your ports 1, 2, 3, etc, and it should work.
Well, it works for me. I just designed a custom waveguide structure with 3 excited input ports and 4 output ports. Any chance you are failing to specify unique port numbers for each port? The default port number for each port is 1. If this is your problem, then number your ports 1, 2, 3, etc, and it should work.
Lukas Alberts
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Posted: 1 decade ago May 6, 2010, 10:17 a.m. EDT
Hello,

for me it says definitely
Error: 5025
More than one port used as input.
- Port number: 5,2
- Boundaries: 29,1
- Application mode: In-Plane TE Waves (rfwe)

2 input ports with differen portnumbers.. 2 and 5..

is the way to add a rfwe physics module?
but then one has to repeat the subdomain definitions..

thanks

lukas
Hello, for me it says definitely Error: 5025 More than one port used as input. - Port number: 5,2 - Boundaries: 29,1 - Application mode: In-Plane TE Waves (rfwe) 2 input ports with differen portnumbers.. 2 and 5.. is the way to add a rfwe physics module? but then one has to repeat the subdomain definitions.. thanks lukas
Felix Vega
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Posted: 1 decade ago Jun 8, 2010, 12:13 p.m. EDT
You should try to do superposition
You should try to do superposition
Shang xiaobiao
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Posted: 1 decade ago Jun 7, 2012, 11:11 a.m. EDT

Well, it works for me. I just designed a custom waveguide structure with 3 excited input ports and 4 output ports.

Any chance you are failing to specify unique port numbers for each port? The default port number for each port is 1. If this is your problem, then number your ports 1, 2, 3, etc, and it should work.


Hello,
I have number my ports 1, 2, 3, etc, but it shouldnt work

thanks

[QUOTE] Well, it works for me. I just designed a custom waveguide structure with 3 excited input ports and 4 output ports. Any chance you are failing to specify unique port numbers for each port? The default port number for each port is 1. If this is your problem, then number your ports 1, 2, 3, etc, and it should work. [/QUOTE] Hello, I have number my ports 1, 2, 3, etc, but it shouldnt work thanks
Oleg Zero
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Posted: 1 decade ago Dec 14, 2012, 6:59 a.m. EST
Hello Everyone,

I have the follwoing problem.

I have a junction (dicontinuity) of two optical waveguides*. One is simgle mode, the other supports more than one solution, a multimode. My goal is to characterise the coupling of light from the multi-mode one to the single mode one. I suppose this problem can be solved with help of the S-paramters, when having N + 1 ports associated with N + 1 boundary mode analysis nodes in the solver**.

However, in order to make the simulation most general, I need to have N ports set to ''on'' all with specific power P_n and phase offset Phi_n. Unfortunately, as there is more than one port set to ''on'', COMSOL starts to have problems with ''reconstricting'' a wave (superposition of all modes), which yield unphysical results at the output.
Should it be the otherwise, exciting many modes from the single-mode input, only one port would be activated and results would be consistent.

Could anybody explain me exactly how the S-paramters are computed, please? Also, I don't understand how the ports' input power P_in and phase offset Phi_in come in to the equations.
I suppose, making a complete Port-Sweep could help, as I read it activates only one port at a time. However, when doing this, I only obtain one row in the matrix...

I would be very thankful for the answer.
Oleg

*) optical waveguides - a core-and-cladding stack of dielectric material guiding light through the refractive index contrast. So in COMSOL it could either represent an integrated photonic wire or a splice of two fibres.
**) normally, I have N ports, all are set to 'numerical' and there is N boundary mode analysis nodes associated with each port, each computing one effective refractive index specific to that port.
Hello Everyone, I have the follwoing problem. I have a junction (dicontinuity) of two optical waveguides*. One is simgle mode, the other supports more than one solution, a multimode. My goal is to characterise the coupling of light from the multi-mode one to the single mode one. I suppose this problem can be solved with help of the S-paramters, when having N + 1 ports associated with N + 1 boundary mode analysis nodes in the solver**. However, in order to make the simulation most general, I need to have N ports set to ''on'' all with specific power P_n and phase offset Phi_n. Unfortunately, as there is more than one port set to ''on'', COMSOL starts to have problems with ''reconstricting'' a wave (superposition of all modes), which yield unphysical results at the output. Should it be the otherwise, exciting many modes from the single-mode input, only one port would be activated and results would be consistent. Could anybody explain me exactly how the S-paramters are computed, please? Also, I don't understand how the ports' input power P_in and phase offset Phi_in come in to the equations. I suppose, making a complete Port-Sweep could help, as I read it activates only one port at a time. However, when doing this, I only obtain one row in the matrix... I would be very thankful for the answer. Oleg *) optical waveguides - a core-and-cladding stack of dielectric material guiding light through the refractive index contrast. So in COMSOL it could either represent an integrated photonic wire or a splice of two fibres. **) normally, I have N ports, all are set to 'numerical' and there is N boundary mode analysis nodes associated with each port, each computing one effective refractive index specific to that port.

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