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oresat / oresat-c3-hardware

C3 (Command, Communication, and Control) our Command and Data Handling (C&DH) card.
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UHF TX 5th order LPF dropping 6 dBm #62

Closed andrewgreenberg closed 9 months ago

andrewgreenberg commented 10 months ago

Either replace with values from 2023-10-24 testing (see #oresat-comms), or replace with some solid state device.

andrewgreenberg commented 10 months ago

OK I've updated this to: L17, L18 are 18nH, and C87 = 3pF, C86 = 8.3 pF, and C85 = 3pF.

Close this issue if you want to stick with this, otherwise let me know better values and/or a good IC.

glennl commented 9 months ago

Let's keep this as is. Rationale: The components chosen gives a break frequency of around 700 MHz, which keeps the the passband S21 around -0.15 dB, and the first harmonic (which is what we want to supress) at 900 MHz with S21 around -10.5 dB. The insertion loss of 6 dB is the voltage loss, and power loss is 3 dB, which is expected. SAW devices are not much better for overall S21. SAW's shine with steep skirts, but we are okay with this response.