Material for coupled line coupler

[maktoomi]

Hi,

Just for practice, I want to design and Fabricate a microstrip coupled line coupler at a center frequency of 4GHz (like that shown in Pozar, Fig 7.36, 3rd edition) . I have no idea of fabrication, at all. Line calculator of ADS asks me material properties. How do I select a proper material and its thickness (cost should be minimum)?

Thanks.

 

[biff44]

rogers material is fairly common. Call up your board fab house, and use what type and thickness they have in stock.

At 4 ghz, FR4 would not work too well...lossy, anisotropic, etc

 

[vfone]

For material you can use Rogers 4000 series which is a good compromise between quality and price:

https://www.rogerscorp.com/acm/producttypes/9/RO4000-Laminates.aspx

For thickness, you can start your simulation with a standard 0.8mm (available at Rogers), and if you think is necessary you can go to 1.5mm thickness.

 

[maktoomi]

Thanks a lot biff44 and vfone.
one more question. why thickness of material is important. What features of my design will be affected by material thickness (I see equations in pozar which relates to capacitance)? what thickness is good, lower or higher? How thickness is related to cost?
(I have started Microwave just few months back. Sorry for my basic questions.)

 

[vfone]

In printed microstrip most things that are affected by the substrate thickness are:
-characteristic impedance of the transmission lines (thicker substrate results in wider lines),
-radiation losses (thinner substrate leads to higher radiation losses),
-peak power handling (thinner substrate limits the breakdown due to peak power),
-bandwidth of microstrip resonators is increased with increased thickness of the substrate.

 

[maktoomi]

Thanks vfone. To start with I will simulate with 0.8mm thickness.