nrd_au
Newbie level 5
Hi all,
I designed my 1st RF PCB for a high pass filter with a bias tee circuit to work in the 1.7GHz - 1.9GHz band inject about 48V-5A DC. It didn't work. It is showing about 20db of insertion loss and the impedance is all over the place (see figures below).
![1627271816260.png 1627271816260.png](https://www.edaboard.com/data/attachments/100/100986-69426c2b7d5dccd094457676ec1e8f6c.jpg)
I made the PCB stackup and calculated the race widths according to instructions I read online (many sources) but obviously, I am missing something.
I used PCB-way to manufacture the PCBs so the 4 layer stack is from their website (given below). RF traces were on the bottom layer. L1, L2 and L3 were ground.
Below is the stackup from Altium
![1627265674118.png 1627265674118.png](https://www.edaboard.com/data/attachments/100/100974-64c19dc76f4501c31c727ccac642e4dd.jpg)
I used the impedance calculator in Altium with the trace type selected as "single" which I believe is Microstrip. It gave me a trace width of 6.906mil. Below is the calculation.
![Altium trace width calculation Altium trace width calculation](https://www.edaboard.com/data/attachments/100/100975-6db068fdde266a8a1898f05b542cd46a.jpg)
Below is the schematic
![1627271295560.png 1627271295560.png](https://www.edaboard.com/data/attachments/100/100983-f699d3580333545fa5043c87d6c79f2d.jpg)
Below is my layout.
![Bottom view Bottom view](https://www.edaboard.com/data/attachments/100/100976-b2af105638732149d1c335012555b5db.jpg)
![Bottom view 3D Bottom view 3D](https://www.edaboard.com/data/attachments/100/100977-1f81b4dfbd7b937136105f43b4fb71b8.jpg)
![Top view Top view](https://www.edaboard.com/data/attachments/100/100979-85f07dc5a537708f3ce6adab014c7329.jpg)
![Bottom view 3D Bottom view 3D](https://www.edaboard.com/data/attachments/100/100982-b37393faf831988fc5d352c060d0c104.jpg)
Looking at the design I should have done the following but do not think them alone would explain the results.
1. Via stitching on the ground plane
2. Add teardrop connections for connecting the pads and rf traces
What other things can I do to improve the design?
THANKS!!!
I designed my 1st RF PCB for a high pass filter with a bias tee circuit to work in the 1.7GHz - 1.9GHz band inject about 48V-5A DC. It didn't work. It is showing about 20db of insertion loss and the impedance is all over the place (see figures below).
![1627271816260.png 1627271816260.png](https://www.edaboard.com/data/attachments/100/100986-69426c2b7d5dccd094457676ec1e8f6c.jpg)
I made the PCB stackup and calculated the race widths according to instructions I read online (many sources) but obviously, I am missing something.
I used PCB-way to manufacture the PCBs so the 4 layer stack is from their website (given below). RF traces were on the bottom layer. L1, L2 and L3 were ground.
Below is the stackup from Altium
![1627265674118.png 1627265674118.png](https://www.edaboard.com/data/attachments/100/100974-64c19dc76f4501c31c727ccac642e4dd.jpg)
I used the impedance calculator in Altium with the trace type selected as "single" which I believe is Microstrip. It gave me a trace width of 6.906mil. Below is the calculation.
![Altium trace width calculation Altium trace width calculation](https://www.edaboard.com/data/attachments/100/100975-6db068fdde266a8a1898f05b542cd46a.jpg)
Below is the schematic
![1627271295560.png 1627271295560.png](https://www.edaboard.com/data/attachments/100/100983-f699d3580333545fa5043c87d6c79f2d.jpg)
Below is my layout.
![Bottom view Bottom view](https://www.edaboard.com/data/attachments/100/100976-b2af105638732149d1c335012555b5db.jpg)
![Bottom view 3D Bottom view 3D](https://www.edaboard.com/data/attachments/100/100977-1f81b4dfbd7b937136105f43b4fb71b8.jpg)
![Top view Top view](https://www.edaboard.com/data/attachments/100/100979-85f07dc5a537708f3ce6adab014c7329.jpg)
![Bottom view 3D Bottom view 3D](https://www.edaboard.com/data/attachments/100/100982-b37393faf831988fc5d352c060d0c104.jpg)
Looking at the design I should have done the following but do not think them alone would explain the results.
1. Via stitching on the ground plane
2. Add teardrop connections for connecting the pads and rf traces
What other things can I do to improve the design?
THANKS!!!
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