Impedance Matching

[doneirik]

Hi,

I have a 13.56 (inductively coupled) MHz RFID reader with an antenna connected over a 50 ohm cable. In order to test some new antennas my boss cut the antenna cable in two and connected new antennas at the open ends.

My question is: Cutting a 50 ohm cable in two, will the two parts still be 50 ohm cables?


regards
eirik

 

[VisiGoth]

Yes. The impedance (Z) is independent of length.

However, some (older) systems are designed for cost by not using a 50 Ohm system, but rather they will translate the complex narrow band Z across a known fixed length of cable and then complex math to that Z. It is doubtful that was done in your particular application. But if it was, the cable length is part of the design. This trick would only be used in extremely cost sensitive high volume designs or by frugal Ham hobbyists.

 

[dw7672]

I need to know how to do impedance matching between the coaxial cable and the microstrip antenna using the HFSS program