Hello everyone,
I am trying to design planar antenna 868 MHz, I am limited by shape/dimensions of existing PCB, so I was thinking about modifying existing antennas from TI (DN023, DN024, DN031), see below.
I tried, I failed.... it was impossible to achieve similar results as it was state in design note. So I decided to simulate basic monopole antenna, which should be easy and than to modify it. I need antenna for 868 MHz so by basic math quarter-wave in free space is approx. 86 mm long, in PCB it should be around 65 mm.
I create model to simulate (see below) with ground big enough 85 mm what is quarter-wave in free space and monopole from 50 to 85 mm, width 2 mm, ground bottom and monoople top are perfect E, lumped port 50 ohm, at FR4 1.6 mm, airbox is 345 mm big (full wave in free space) X,Y,Z and antenna is in the center of it. It should work (not perfect) without matching circuit, I want to add it in next step.
After simulation I get s11 parameters like these.
What am I missing or doing wrong? Could any of you guys help me with that? Thank you very much in advance for your answers.
