I'm facing a doubt while designing a transceiver application using ADF7021-N in 868MHz band. I've still realized some time ago a trx application with this chip on a 4 layer pcb stackup with 1.2mm thickness and its working well; on the RF section (transmit and receive matching components) I've set the first inner layer under components to ground to have a stable behaviour of the network. Now going to 0.8mm thickness pcb, still 4 layer implementation, I'm facing a doubt about the effect of parasitics due to lowering the distance between matching components and ground plane. My question is: have you ever evaluated if there's any effect on RF performance reducing the distance from top layer components and ground plane? Is there any risk to deteriorate radio performances reducing too much this distance?
Thanks in advance.