IEEE 802.15.4 subsystem
Sign in or create your account | Project List | Help
IEEE 802.15.4 subsystem Git Source Tree
Root/
Source at commit a60fb1e26d6f1e73a87ee08158c2b62b0c28bcc7 created 13 years 22 days ago. By Werner Almesberger, usrp/sps/20110306: examine sidebands ("spikes") and try to reduce them | |
---|---|
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 |