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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