SIM900 or Quectel M72 : Designing the antenna feed circuit

[Tomas Freeman]

Hello Forum, This is my first post here.

I looking for help with Designing the antenna feed circuit for my GSM Unit. I want make GSM 2G+ mobile phone. I use Calvus, P/N A10340, Penta-band SMD Antenna. It is my first project with GSM device and do not know how to calculate 50 Ohm impedance feed. Can some one can help me? Send working prototype board in Eagle od PDF?

I started my blog to share this project to open hardware community on diygsm blogspot com webpage "D.I.Y Open Hardware GSM mobile phone". I have working prototype, able to send txt message and call. Now need help with antenna circuit.

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I have read technical specification, Designing the antenna feed circuit, Chapter 6


**broken link removed**

In general it is best to place the antenna matching circuit close to the antenna (position A), as this minimises loss in the transmission line by ensuring it is operating into a matched impedance. If this is done, then particular care must be taken to ensure that the transmission line x-y is designed to have a uniform 50-ohm characteristic impedance.

The dimensions of both kinds of transmission lines can be calculated using a simple Windows computer program TXLINE, available free of charge from: http://www.taconic-add.com/en--downloads.php

But software mentioned is not working in Windows 7 or 8.

 

[Tomas Freeman]

I have found similar post here:
https://www.edaboard.com/threads/205981/

The AppCAD looks promising.

I have designed my microstrip at 50Ohm. But i have problem with choice with Epsion r, how to find correct material type?

 

[Tomas Freeman]

Hello Again,

I am attaching schematic diagram of example antenna feed circuit.


As i assume microstrip is from X to point y.

I have found that material is FR4.

Finaly i have correct input parameters :H, T, FR4, 800MHz, 50
Output is : W and Z0.

Final picture: