transmission line length question

[liletian]

Hi Guys
I had a simple question need to confirm. I want to make a half wavelength transmission for example at 2 GHz at PCB board. Suppose the PCB have a dielectrical constant of 4. What will be length of the half wavelength transmission line?
15/2=7.5 cm
or I need to consider the dieelectrica constant of the PCB (FH4).
Can anyone help on this?
Thanks a lot

 

[FvM]

or I need to consider the dieelectrica constant of the PCB (FH4).

Yes. If the electrical field would be completely in the dielectric, the wave length is shortened by a factor of sqrt(Er). For microstrip line with part of the field in air, the reduction factor will be around 1.6..1.8. A PCB transmission line calculation program can give accurate estimations for ZL and propagation constant. If you know the characteristic C and L per length unit, you can calculate it yourself from elementary transmission line equations.

 

[liletian]

where can find the PCB transmission line calculation program? ADS??
I do not know the characteristic C and L per length unit

Yes. If the electrical field would be completely in the dielectric, the wave length is shortened by a factor of sqrt(Er). For microstrip line with part of the field in air, the reduction factor will be around 1.6..1.8. A PCB transmission line calculation program can give accurate estimations for ZL and propagation constant. If you know the characteristic C and L per length unit, you can calculate it yourself from elementary transmission line equations.

---------- Post added at 21:31 ---------- Previous post was at 21:12 ----------

how about a microstrip line?
Is it straight forward?
thanks

where can find the PCB transmission line calculation program? ADS??
I do not know the characteristic C and L per length unit

 

[FvM]

There are many calculation tools, e.g. this free tool from AWR

 

[liletian]

Hi FVM
Thank you very much.

 

[enjunear]

where can find the PCB transmission line calculation program? ADS??
I do not know the characteristic C and L per length unit

ADS has a built-in tool called LineCalc that will do this for you. You need to be in a schematic design, then go to Tools, LineCalc, Start LineCalc. The drop-down at the top-left lets you access a variety of stripline/microstrip structures. The PCB and metal material parameters are entered at the left (height, metal thickness, resistivity, dielectric constant, prop constant, etc). Plug in your design/center freq at the bottom left, and characteristics on the right. Once that's all in, use the two buttons in the middle to Synthesize or Analyze the structure.

 

[techzee]

descent amount of explanation is given on half wave and quarter wave transmission lines with single example, See if the link is useful
**broken link removed**