# Modeling a distributed LPF in Microwave Office

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##### Newbie level 5
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

You need to connect Microstripline elements at Node 1 or infront of $elements.., You see the layout then you will understand may be better... upload your MWO file (*.em), I will try to modify & send you some instructions on How to impliment Microstripline Filters using MWO... ---manju--- #### vistadude ##### Newbie level 5 Thank you. #### Manjunatha_hv ##### Advanced Member level 3 Hello, Attached is the modified MWO schematic which provides better results in Simulation & Layout... If you see I used MTEEX$ which is a em based model & it is accurate compared to MTEE, MTEE$... Also since your width ratio is very rastic from high value to low value...I recommend you to simulate using electromagnetics simulations of the strcture... I have attached modified MWO project files for your reference... ---manju--- ### vistadude points: 2 Helpful Answer Positive Rating #### vistadude ##### Newbie level 5 Thank you very much for the corrections. Can you explain how MTEEX$ 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 MTEEX$model. It is stated (http://edocs.soco.agilent.com/display/ads2009/MTEE+(Microstrip+T-Junction) , note 1) that "A reference plan [sic] shift is added to each of the ports to make the reference planes consistent with the layout". Is the generated layout of any use for manufacturing? I would have thought that the MTEEX$ 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.)

#### Manjunatha_hv

Hello,

Go through the following AWR Help menu & details on em based models at following KB links...

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

---manju--

#### khalifas

##### Newbie level 4
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 ??
How can I make the layout from my schematic then extrac the gerber file?

#### Manjunatha_hv

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?

---manju---

khalifas

points: 2