Return to Question

The small antenna itself has an S11 of -3 dB around MICS band (verified with simulation and network analyzer). In application, the antenna is mounted on a transceiver PCB of 30150.8 mm which has 2 metal layers. From simulation, including the PCB into the antenna model (by modeling it as a thin cubic with 2 metal faces) made the S11 reach to -15 dB, with an increase of 50 MHz in resonant frequency and the S11 curve gets a lot sharper. The small antenna is quite poor as a radiator because there is a dimension restrict for the device. I guess adding the PCB just improves impedance matching with no contribution to radiation. My question is how should I conclude the influence from the PCB. Is it a grounding effect, or coupling, or extra impedance?

The small antenna itself has an $S_{11}$ of -3 dB around MICS band (verified with simulation and network analyzer). In application, the antenna is mounted on a transceiver PCB of 30150.8 mm which has 2 metal layers. From simulation, including the PCB into the antenna model (by modeling it as a thin cubic with 2 metal faces) made the $S_{11}$ reach to -15 dB, with an increase of 50 MHz in resonant frequency and the $S_{11}$ curve gets a lot sharper. The small antenna is quite poor as a radiator because there is a dimension restrict for the device. I guess adding the PCB just improves impedance matching with no contribution to radiation. My question is how should I conclude the influence from the PCB. Is it a grounding effect, or coupling, or extra impedance?