darcyrandall2004
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Hello,
Recently I designed a VCO(428.6-436.6MHz) that simulated perfectly but when placed on a PCB it did oscillate but at a frequency far from the frequency I designed for.
My first step at fixing the problem and determining why this VCO oscillates at the incorrect frequency is to import the Protel layout into ADS Momentum and then create an ADS schematic component that I can use to simulate with.
Attached is a picture of the layout of my VCO. Notice the VCO is closely surrounded by a copper ground plane.
My VCO is a two layer board. The first side consists of mixed signals and a ground plane. The bottom of the VCO board is an imperfect ground plane, in parts there are other signals/tracks that couldnt fit on the top layer.
Attached is the picture of the substrate setup for momentum.
The ADS Momentum software is not very flexible. I would have thought the best representation of my board would be
Free Space
STRIP Top_LAYer
Alumina VIA Multilayer
Strip Bottom_Layer
Free Space
and then I just add internal ports for ground, lumped components, etc for use within the schematic.
Unfortunately ADS forces me to use the //////GND////// which doesnt realy represent the bottom layer of my board.
1.Can anyone recommend the an appropriate substrate configuration that represents my board?
2.I imagine placing the ground plane on the top layer within close proximity of lumped components worsens parasitic capacitance to ground plane. Does anyone have any recommendations on spacing between lumped components and the ground plane when designing for a particular frequency?
Thankyou
Recently I designed a VCO(428.6-436.6MHz) that simulated perfectly but when placed on a PCB it did oscillate but at a frequency far from the frequency I designed for.
My first step at fixing the problem and determining why this VCO oscillates at the incorrect frequency is to import the Protel layout into ADS Momentum and then create an ADS schematic component that I can use to simulate with.
Attached is a picture of the layout of my VCO. Notice the VCO is closely surrounded by a copper ground plane.
My VCO is a two layer board. The first side consists of mixed signals and a ground plane. The bottom of the VCO board is an imperfect ground plane, in parts there are other signals/tracks that couldnt fit on the top layer.
Attached is the picture of the substrate setup for momentum.
The ADS Momentum software is not very flexible. I would have thought the best representation of my board would be
Free Space
STRIP Top_LAYer
Alumina VIA Multilayer
Strip Bottom_Layer
Free Space
and then I just add internal ports for ground, lumped components, etc for use within the schematic.
Unfortunately ADS forces me to use the //////GND////// which doesnt realy represent the bottom layer of my board.
1.Can anyone recommend the an appropriate substrate configuration that represents my board?
2.I imagine placing the ground plane on the top layer within close proximity of lumped components worsens parasitic capacitance to ground plane. Does anyone have any recommendations on spacing between lumped components and the ground plane when designing for a particular frequency?
Thankyou
