Date:2011-03-07 08:45:15 (8 years 4 months ago)
Author:Werner Almesberger
Commit:a60fb1e26d6f1e73a87ee08158c2b62b0c28bcc7
Message:usrp/sps/20110306: examine sidebands ("spikes") and try to reduce them

Files: usrp/sps/20110306/Makefile (1 diff)
usrp/sps/20110306/README (1 diff)

Change Details

usrp/sps/20110306/Makefile
1# we need bash for {1,2,3}
2SHELL=/bin/bash
3
4TRIES_1=a b c d e f g
5TRIES_2=i j
6TRIES_3=a b c
7RUNS=atusb-20110214-4-0 atusb-20110214-4-1 atusb-20110214-4-2 \
8  $(TRIES_1:%=atusb-20110214-4%-{0,1,2}) \
9  atusb-20110214-4h-0 atusb-20110214-4h-1 \
10  $(TRIES_2:%=atusb-20110214-4%-{0,1,2}) \
11  atusb-20110214-3-0 atusb-20110214-3-1 atusb-20110214-3-2 \
12  $(TRIES_3:%=atusb-20110214-3%-{0,1,2}) \
13
14all:
15    echo $(RUNS)
16upload:
17    rsync -e ssh --progress index.html *.png \
18      www-data@downloads.qi-hardware.com:werner/wpan/20110306/
19
20index:
21    PATH=..:../..:$$PATH time ../row $(RUNS) >index.html
usrp/sps/20110306/README
1Objective:
2
3Reproduce sidebands observed in 200110303 and look for ways to reduce them.
4In particular, examine the effect of the antenna tuning capacitor C16.
5
6
7Test setup / changes:
8
94 original board, like in 20110303 (noise from WLAN I forgot to turn off)
104a reflowed some RF vias; cleaning
114b removed large solder deposits on RF; not cleaned
124c cleaning after 4b
134d 0.5 pF at C16; cleaning
144e 1.0 pF at C16; cleaning
154f C16 NC; cleaning
164g resolder pin B1.1; cleaning
174h replace cracked B1; switched to leaded solder; cleaning
184i reflowed B1 at higher temperature; cleaning
194j reflowed C8's balun side; cleaning
20
213 original board, like in 20110303
223a wait 2 h (warm-up; USRP2 freshly booted)
233b cycle (unplug/plug) atusb
243c retract shutters (metal)
25
26-------------------------------------------------------------------------------
27
28Observations:
29
304 behaves as it did in 20110303
314a no change
324b no change
334c no change
344d no change
354e no change
364f major regression
374g regression persists
384h regression persists (slight recovery seen in 4h-0 may be due to
39    temporary effects)
404i regression persists
414j regression persists; giving up
42
433 behaves as it did in 20110303; significantly cleaner
443a sidebands are reduced
453b sideband reduction persists
463c ~10 dB drop at lower end of spectrum
47
48-------------------------------------------------------------------------------
49
50Conclusions:
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

Archive Download the corresponding diff file



interactive