if we can design some special resonators in the path of each wave guide with special characteristics then we can reach the filtering behavior of the mentioned structure. for example by changing the amount of refractive index of the substrate mechanically with MEMS devices we can obtain it.
I agree with Hamed. as you know, every waveguide acts as filter, so when you design the structure, you will have to check refractive index of that because some materials have negative of this value which does matter. so, you will have check all the important parameters which you are using for designing your structure.
Yes Dear Mr Anand, Ms Smrity and Mr Hamed,
It has been well described by Liao, Lee, Gupta and Rao and a proven science being practiced for about 50 years.
Please read these authors.
Best wishes Anand.
Dear Anand,
A substrate integrated waveguide (SIW) is a printed (PCB) version of the conventional rectangular waveguide. The two wide walls are composed by the copper metallization between each row of vias, and the vias substitute the vertical narrow walls of the conventional rectangular waveguide. These rows of metallized vias are close to a perfect electric conductor boundary condition since those vias are very close to each other (in terms of wavelengths). To be more accurate, the vias are inductive boundary conditions. The first propagating mode is very close to the one that could be found in a rectangular waveguide with the same cross section filled with the substrate dielectric. As any waveguide of this type, the system behaves as a high-pass filter, due to the existence of cutoff frequency. But I understand that you are interested on how design "professional" filters with this technology. Well, basically you can implement with this technology most of the H-plane filters that can be implemented with rectangular waveguide technology. You must, of course, take into account the differences due to the substitution of the vertical electric walls of the rectangular waveguide by the inductive boundary condition imposed by the vertical metal vias. But this is, in my opinion, a minor difference in theoretical terms. A lot of literature has been published in recent years on the topic. You might look for some reviews or semina papers by Prof. Ke Wu (Polygrammes, Montreal,Canada) and his group.
Dear Anand,
A useful paper "Low Loss Tunable Filters in Substrate Integrated Waveguide" by S. Sirci, J. D. Martínez, M. Taroncher and Vicente E. Boria available at https://www.researchgate.net/publication/256536142_Compact_and_Low_Cost_Substrate_Integrated_Waveguide_Cavity_and_Bandpass_Filter_Using_Surface_Mount_Shorting_Stubs
It considers vias in the design of filters.
AR Reddy
Conference Paper Compact and Low Cost Substrate Integrated Waveguide Cavity a...
Thank you for your answers.
Can anyone tell me the physics behind the vias?
Dear Anand,
The vias are metallic and play the role of the vertical narrow solid walls in the conventional rectangular waveguide. These vertical walls are almost perfect short-circuits and confine the electromagnetic field inside the waveguide. In the case of the SIW there are gaps between the vias thus allowing the field to extend a little outside the region limited by the rows of vias. However, since the separation between vias is very small in comparison with the operation wavelength, the field is also highly confined between the rows of vertical vias. From the electrical point of view the vias are better seem as inductive loads than as a short-circuit if a transverse resonance scheme is going to be used to determine the dispersion curves of the SIW modes.
Regards,
Francisco
Thank you sir for this explanation.
Can you please suggest some material where I can learn about these basics of the SIW, mainly about its physics.
I am not an expert but you might start with this link and the references in it:
http://www.microwaves101.com/encyclopedias/substrate-integrated-waveguide
Understanding of SIW physics depends on your previous background. If you are familiar with rectangular waveguides you can follow the topic without too much effort.
Regards,
Francisco
vias also help in better isolation from other ckts... see papers on via fencing in planar PCB ckt..seek input from experts am i correct??
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