A SIW component consists on a

synthetic waveguide formed by the top and the bottom

metal plates of a dielectric slab and is bounded transver-

sely by two sidewalls of cylindrical metallic via-holes. The

rows of vias connect top and bottom metal layers for-

ming the cavity walls. Input and output coupling is achie-

ved using tapered microstrip transmission lines or

coplanar current probes. Adjusting the geometrical di-

mensions of the taper or probes, the input/output cou-

pling can be controlled.The SIW components can be fabricated on printed circuit

boards (PCBs) or low-temperature co-fired ceramics

(LTCCs) technologies. They enable a significant reduction

of size, weight and cost compared with metallic wave-

guide designs. As the SIWs are based in the

TEn0modes,the characteristic of conventional waveguides are preser-

ved and the propagation of energy of these modes is substantially limited in the substrate. Thus, they have a higher Q-factor and lower loss than other planar guided-wave structures, for instance microstrip lines and coplanar waveguides (CPW). In fact, conventional planar resonators provide a moderate unloaded Q-factor, typically less than Qu

Dear Ananya Parameswaran, Your answer (Q=3200) is correct. Q = stored energy / loss. As your filter does not have any radiation loss (as found in antenna), your SIW filter will show always higher Q than conventional microstrip filter.

Thank you Devi palanisamy and Sudipta Maity for your answers.

Getting Qu of 3200 is quite high. Achieving such high unloaded q-factor in SIW is not possible. If you use the lowest loss substrate RTD5880, you will get it around 750. You check the value. There is one paper on unloaded Q-factor calculation by R.S. Kowk which you can follow to determine Qu very accurately.

@ Arani Ali khan, thank you so much.

I just forgot to mention one thing: In case of higher order modes of rectangular Dielectric Resonator Antenna (RDRA), I got Qt = 22,000. I check several papers. I found 10000, 15000, 36000 etc value for filters. Therefore, your predicted value is correct.

Far difference between SIW resonator and dielectric resonator. The loss of a resonator is dominated by copper loss which is not present in DR. Replace all metals of SIW by PEC then Qu will exceed even 5000.

It is correct that SIW has conductor loss. Thats why, SIW may show lower Qt than DR.  It is always better to mention 'MODE'. In fundamental mode, Qt is small most of the time.Equilateral Trinagular DRA (ETDRA) shows Qt = 8 at fundamental TMz_101 mode whereas Equilateral Trinagular Microstrip Antenna (ETRMA) shows Qt = 100 at fundamental TMz_10 mode. Patch has conductor loss due to patch and ground plane whereas ETDRA has conductor loss due to ground plane only. But, ETDRA shows lower Qt than ETMA. Measured data can be verified by Kishk's paper (2001) for ETDRA and K F Lee's (1988) pape for ETMAr

Similarly, RDRA shows lower qt than RMA at fundamental mode. But, at higher order mode (m,n,p>1), depending on size and permittivity, we got high Qt. There are several papers at IEEE transaction, published in early 1960-1990. In RDRA, we got Qt = 20000 for TEy_519 mode. The value of Qt is highly dependent on dimensions and permittivity.

You have to ensure that you are measuring unloaded Q-factor to study individual cavity loss property. SIW resonators show unloaded Q-factor less than 1000 (When copper losses are included). Check that the measurement process is correct or not.