mirror of
git://projects.qi-hardware.com/ben-wpan.git
synced 2024-11-30 09:19:40 +02:00
57 lines
1.6 KiB
Plaintext
57 lines
1.6 KiB
Plaintext
|
Objective:
|
||
|
|
|
||
|
|
Reproduce sidebands observed in 200110303 and look for ways to reduce them.
|
||
|
|
In particular, examine the effect of the antenna tuning capacitor C16.
|
||
|
|
|
||
|
|
|
||
|
|
Test setup / changes:
|
||
|
|
|
||
|
|
4 original board, like in 20110303 (noise from WLAN I forgot to turn off)
|
||
|
|
4a reflowed some RF vias; cleaning
|
||
|
|
4b removed large solder deposits on RF; not cleaned
|
||
|
|
4c cleaning after 4b
|
||
|
|
4d 0.5 pF at C16; cleaning
|
||
|
|
4e 1.0 pF at C16; cleaning
|
||
|
|
4f C16 NC; cleaning
|
||
|
|
4g resolder pin B1.1; cleaning
|
||
|
|
4h replace cracked B1; switched to leaded solder; cleaning
|
||
|
|
4i reflowed B1 at higher temperature; cleaning
|
||
|
|
4j reflowed C8's balun side; cleaning
|
||
|
|
|
||
|
|
3 original board, like in 20110303
|
||
|
|
3a wait 2 h (warm-up; USRP2 freshly booted)
|
||
|
|
3b cycle (unplug/plug) atusb
|
||
|
|
3c retract shutters (metal)
|
||
|
|
|
||
|
|
-------------------------------------------------------------------------------
|
||
|
|
|
||
|
|
Observations:
|
||
|
|
|
||
|
|
4 behaves as it did in 20110303
|
||
|
|
4a no change
|
||
|
|
4b no change
|
||
|
|
4c no change
|
||
|
|
4d no change
|
||
|
|
4e no change
|
||
|
|
4f major regression
|
||
|
|
4g regression persists
|
||
|
|
4h regression persists (slight recovery seen in 4h-0 may be due to
|
||
|
|
temporary effects)
|
||
|
|
4i regression persists
|
||
|
|
4j regression persists; giving up
|
||
|
|
|
||
|
|
3 behaves as it did in 20110303; significantly cleaner
|
||
|
|
3a sidebands are reduced
|
||
|
|
3b sideband reduction persists
|
||
|
|
3c ~10 dB drop at lower end of spectrum
|
||
|
|
|
||
|
|
-------------------------------------------------------------------------------
|
||
|
|
|
||
|
|
Conclusions:
|
||
|
|
|
||
|
|
- build quality seems to be principal factor in RF performance variations
|
||
|
|
- a warmed up board performs slightly better than a cold board
|
||
|
|
- C16 has no noticeable effect
|
||
|
|
- reflection characteristics even of distant items in the environment have
|
||
|
|
a strong influence on relative signal strength
|