search

SFUSatClub / CubeSat-Radio

Cubesat comms module designed for the Canadian Satellite Design Challenge
8 stars 3 forks source link

Check RF path #25

Closed TobiNakamura closed 7 years ago

TobiNakamura commented 7 years ago

microstrip Check CPWG, passives, wall of ground vias.

TobiNakamura commented 7 years ago

The substrait thickness is not 0.2mm, its 1.6mm. The track width is a bit worrisome. image

TobiNakamura commented 7 years ago

image

TobiNakamura commented 7 years ago

PCBWay confirmed that Dk is 3.8. calc

Alenux55 commented 7 years ago

Do we want to update the trace width to get it closer to 50 Ω? At the current thickness, we'll get 52.5 Ω

Alenux55 commented 7 years ago

Also, do we want to add fencing vias along the RF traces? According to this document, if the vias are spaced less than about 2 inches, we won't run into ground impedance issues.

Further, from the same document: Spacing the ground vias at 1/8th of a wavelength gives good isolation here also, but for the ultimate isolation available (i.e., greater than the 120 dB that a modern network analyzer can measure) it has been found that the via spacing should be kept to 1/20th of a wavelength or less.

In our case, 1/20 of the wavelength is about 3.5 cm, which is easily doable.

Alenux55 commented 7 years ago

Never mind about the via fencing

TobiNakamura commented 7 years ago

RF traces are now 0.6mm width with 0.2mm spacing to ground.