Krenzo
Newbie level 4
I went and made a PCB for a UWB pulse generator I posted about before (https://www.edaboard.com/threads/206991/), and it appears that I should have thought more carefully about ground isolation in my design.
I have a SMA connector that receives input of a 3.3V pulse (100 MHz) into a comparator (P pin is directly connected and N pin goes through a delay line first to generate a short pulse output). The comparator has 50 ohm internal terminations to ground for the P and N pins. My problem is that the 3.3V pulse goes through the terminations and to ground, and then it gets into the output of the circuit that feeds into my pulse detector connected via a shielded line.
So, I'm about to start on a revision of the PCB, and I want to have separate ground planes for the input and the output of my pulse generator. How should those planes be connected together to prevent the input pulse from interfering with the output? I've seen designs that use inductors while others suggest using a narrow trace to connect the planes. Is there a good source of information on what to do use in my situation?
Also, why do I see in some designs RF connectors having a large block of copper on the top layer of a PCB that connects to the ground of the connector and then that section of copper has a few vias to an internal ground plane? Is this the same principle of helping with ground isolation?
I have a SMA connector that receives input of a 3.3V pulse (100 MHz) into a comparator (P pin is directly connected and N pin goes through a delay line first to generate a short pulse output). The comparator has 50 ohm internal terminations to ground for the P and N pins. My problem is that the 3.3V pulse goes through the terminations and to ground, and then it gets into the output of the circuit that feeds into my pulse detector connected via a shielded line.
So, I'm about to start on a revision of the PCB, and I want to have separate ground planes for the input and the output of my pulse generator. How should those planes be connected together to prevent the input pulse from interfering with the output? I've seen designs that use inductors while others suggest using a narrow trace to connect the planes. Is there a good source of information on what to do use in my situation?
Also, why do I see in some designs RF connectors having a large block of copper on the top layer of a PCB that connects to the ground of the connector and then that section of copper has a few vias to an internal ground plane? Is this the same principle of helping with ground isolation?