Feed line matching with antenna

[Sherry1]

Hi I made a 2 layer FR4 PCB for the chip antenna. One end of the 50 Ohm feed line starts from antenna pads, the other end of the feed line goes to SMA connector. The width is calculated using coplanar waveguide with ground calculator.

when i use VNA and find out the impedance and add matching network, the S11 only gets worse.
Sometimes impedance comes like (say) 65+j45 and so I have to manually break the trace and put capacitor in series to introduce -45j reactance. But breaking the trace itself changes everything.

Any suggestions how do i match the 50 ohms feed line to the antenna ?
Shall I use balun? or Shall i print broken feed trace?

 

[E Kafeman]

It seems to be a problem with VNA measurement setup.
1. VNA impedance calibration and correct delay/port extension must be set for the location where you intend to place the matching component to get desired impedance at this point.
2. Correct matching component should be selected based on real S21 parameters for actual component family, for best result.
Check this link, which can help you with both these points.