Modeling a distributed LPF in Microwave Office

I'm trying to implement the low-pass filter from Pozar's Microwave Engineering (2nd ed, p. 466-468) in Microwave Office using the Taconic TLY-5 substrate

(Model TLY_5_200 from the AWR Web site libraries).

Doing that I have encountered a number of questions, which I cannot figure out from the Getting Started and User Guides. (Are there NO books on MWO? I'm

located outside of any areas where MWO courses are offered)

1) Er=2.2 is a reasonably low value for microstrip (correct?). (higher impedance or higher Er equals lower line width to implement) The T/W and W/H ratio's

of the 217.5Ω lines using my chosen substrate is still outside of recommended values, as well as outside of the required values to use MSTEPS.

Is my computed values incorrect, or can the filter not be realized on my chosen substrate?

2) Is schematic 1 an acceptable first approximation of the stub filter? (apart from the ripple, the simulated graph closely matches Pozar's response in

figure 8.37, p. 468)

3) Is schematic 2 (using MTEES and MSTEPS) the correct way to model the filter more accurately? (assuming the T/W and W/H issues have been addressed)

PS: The line length was computed as λ/8=(2.9979*0.675)/(40*8) where 2.9979*0.675 accounts for the wave speed in the substrate, 40 for the frequency and 8 for

one eighth wavelength.

Hello,

I want to mention couple of things...
1. Schematic 1 is wrong & it is not the way Microstripline elements are connected
2. In schematic 2, it is not correct way of using MSTEPS

You need to connect Microstripline elements at Node 1 or infront of S elements..,
You see the layout then you will understand may be better...

upload your MWO file (*.em), I will try to modify & send you some instructions on
How to impliment Microstripline Filters using MWO...

Thank you.

Hello,

Attached is the modified MWO schematic which provides better results in Simulation & Layout...
If you see I used MTEEXS which is a em based model & it is accurate compared to MTEE, MTEES...

Also since your width ratio is very rastic from high value to low value...I recommend you to simulate using electromagnetics simulations of the strcture...

I have attached modified MWO project files for your reference...

Thank you very much for the corrections.
Can you explain how MTEEXS correctly models the physical change in width?
I understand that higher order modes are present at the discontinuities. I assume that directly connecting MLINs with different widths ignores these modal changes. (To get to a layout, I used View->View Layout, and then Edit->Snap Together.)
What I do not understand is that the layout generated has nonzero length for the MTEEXS model. It is stated (http://edocs.soco.agilent.com/displa...+T-Junction%29 , note 1) that "A reference plan [sic] shift is added to each of the ports to make the reference planes consistent with the layout".
Is the generated layout of any use for manufacturing?
I would have thought that the MTEEXS model would not be included in the physical realization - am I correct?

(Also, MWO won't let me add ports to the generated layout, but does allow it if I create a new EM structure and draw the schematic by hand, which is really confusing me.)

Hello,

Go through the following AWR Help menu & details on em based models at following KB links...
Which will address all your queries...

MWO/AO/VSS User Guide > Schematics > Element Catalog Supplementary Information > EM-Based Discontinuity Models

https://awrcorp.com/download/faq/eng...s/xmodels.aspx

---manju--

I am new to Microwave office ,, and also i was trying to implement that filter from pozar and i have managed to get it done but it is the layout and extracting the gerber file that i need help in ?
So could anyone please help me with that :
How can I make the layout from my schematic then extrac the gerber file?

Thanks in advance.

khalifas,

upload ur pozar book filter simulation MWO file, I will try to help you to build layout...

did u used the TXLine calculator to build microstripline schematic?