IEEE 802.15.4 subsystem
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IEEE 802.15.4 subsystem Git Source Tree
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| 1 | Objective: |
| 2 | |
| 3 | Reproduce sidebands observed in 200110303 and look for ways to reduce them. |
| 4 | In particular, examine the effect of the antenna tuning capacitor C16. |
| 5 | |
| 6 | |
| 7 | Test setup / changes: |
| 8 | |
| 9 | 4 original board, like in 20110303 (noise from WLAN I forgot to turn off) |
| 10 | 4a reflowed some RF vias; cleaning |
| 11 | 4b removed large solder deposits on RF; not cleaned |
| 12 | 4c cleaning after 4b |
| 13 | 4d 0.5 pF at C16; cleaning |
| 14 | 4e 1.0 pF at C16; cleaning |
| 15 | 4f C16 NC; cleaning |
| 16 | 4g resolder pin B1.1; cleaning |
| 17 | 4h replace cracked B1; switched to leaded solder; cleaning |
| 18 | 4i reflowed B1 at higher temperature; cleaning |
| 19 | 4j reflowed C8's balun side; cleaning |
| 20 | |
| 21 | 3 original board, like in 20110303 |
| 22 | 3a wait 2 h (warm-up; USRP2 freshly booted) |
| 23 | 3b cycle (unplug/plug) atusb |
| 24 | 3c retract shutters (metal) |
| 25 | |
| 26 | ------------------------------------------------------------------------------- |
| 27 | |
| 28 | Observations: |
| 29 | |
| 30 | 4 behaves as it did in 20110303 |
| 31 | 4a no change |
| 32 | 4b no change |
| 33 | 4c no change |
| 34 | 4d no change |
| 35 | 4e no change |
| 36 | 4f major regression |
| 37 | 4g regression persists |
| 38 | 4h regression persists (slight recovery seen in 4h-0 may be due to |
| 39 | temporary effects) |
| 40 | 4i regression persists |
| 41 | 4j regression persists; giving up |
| 42 | |
| 43 | 3 behaves as it did in 20110303; significantly cleaner |
| 44 | 3a sidebands are reduced |
| 45 | 3b sideband reduction persists |
| 46 | 3c ~10 dB drop at lower end of spectrum |
| 47 | |
| 48 | ------------------------------------------------------------------------------- |
| 49 | |
| 50 | Conclusions: |
| 51 | |
| 52 | - build quality seems to be principal factor in RF performance variations |
| 53 | - a warmed up board performs slightly better than a cold board |
| 54 | - C16 has no noticeable effect |
| 55 | - reflection characteristics even of distant items in the environment have |
| 56 | a strong influence on relative signal strength |
| 57 |
