On Mon, Sep 10, 2012 at 10:56 PM, Michael Hill
<address@hidden> wrote:
Can anyone provide any insight into why i'm getting the results I am?
The aim of this test was to measure the OIP3 during transmit, then determine the IIP3.
*Conditions*
I conducted two-tone tests using f1 = 4 MHz and f3 = 5 MHz.
The LO was set to 2400, 2450, 2500, 4900, 5400 and 6000 MHz (I'm using the XCVR2450 with the USRP N210)
The Amplitude variable has been set to 0.25, and the gain has been stepped from 0 to 35dB.
The two tone test was essentially setup as the same in this link but with the the output measured by an oscilloscope, thus i'm sure i've done it right..
http://lists.gnu.org/archive/html/discuss-gnuradio/2011-10/msg00433.html
*Measurements*
I've measured the power amplitudes, also the gain has been calculated at each step (since the gain request may not actually get the specific gain).
Measurements have been taken with an agilent spec amp at 300Hz.
I've then calculated the OIP3 and subtracted the actual gain to get the IIP3.
*Results*
However, my data is a bit odd... An example has been provided in the table below. It seems that my intermodulation products are not increasing at 3dB for each 1dB..
What does this imply?
Examples of my transmit IIP3 results are attached, these seem somewhat in the jagged ball park of the receiver results below for the WBX.
http://code.ettus.com/redmine/ettus/documents/16
Not an apple to apple comparison I know.. but I don't have much to go on..
am I missing something basic (I am still.. in my opinion.. new)
(Note: units below are MHz for frequencies, and dB for gain, dBm for the output power.)
| Carrier |
|
m1 |
m2 |
m3 |
m4 |
| 2400 |
|
3 |
4 |
5 |
6 |
| |
|
|
|
|
|
| 2400 MHz |
|
2403 |
2404 |
2405 |
2406 |
| |
|
|
|
|
|
| Gain |
|
|
|
|
|
| 0 |
|
-50.27 |
-11.88 |
-11.58 |
-49.31 |
| 1 |
|
-49.79 |
-11.05 |
-10.79 |
-48.74 |
| 2 |
|
-49.37 |
-10.37 |
-10.09 |
-49.06 |
| 3 |
|
-48.77 |
-9.62 |
-9.36 |
-47.62 |
| 4 |
|
-48.89 |
-8.93 |
-8.67 |
-47.66 |
| 5 |
|
-48.16 |
-8.08 |
-7.79 |
-47.26 |
| 6 |
|
-48.5 |
-7.43 |
-7.16 |
-46.71 |
| 7 |
|
-47.9 |
-6.63 |
-6.36 |
-48.1 |
| 8 |
|
-47.52 |
-5.98 |
-5.7 |
-46.06 |
| 9 |
|
-46.65 |
-5.24 |
-4.98 |
-46 |
| 10 |
|
-48.13 |
-4.58 |
-4.36 |
-46.07 |
| 11 |
|
-46.95 |
-3.84 |
-3.63 |
-47.07 |
| 12 |
|
-47.6 |
-3.23 |
-3.02 |
-45.6 |
| 13 |
|
-47.14 |
-2.51 |
-2.32 |
-46.78 |
| 14 |
|
-47.74 |
-1.81 |
-1.62 |
-48.15 |
| 15 |
|
-47.98 |
-0.98 |
-0.78 |
-45.74 |
| 16 |
|
-47.06 |
-0.31 |
-0.14 |
-46.42 |
| 17 |
|
-47.58 |
0.48 |
0.67 |
-47.57 |
| 18 |
|
-46.64 |
1.24 |
1.39 |
-47.44 |
| 19 |
|
-46.15 |
2 |
2.2 |
-46.19 |
| 20 |
|
-43.16 |
2.87 |
3.04 |
-44.33 |
| 21 |
|
-40.62 |
3.71 |
3.86 |
-42.54 |
| 22 |
|
-39.47 |
4.48 |
4.61 |
-39.99 |
| 23 |
|
-36.41 |
5.24 |
5.36 |
-37.01 |
| 24 |
|
-35.01 |
6.03 |
6.16 |
-35.63 |
| 25 |
|
-32.85 |
6.81 |
6.94 |
-33.63 |
| 26 |
|
-31.27 |
7.72 |
7.87 |
-31.36 |
| 27 |
|
-29.14 |
8.62 |
8.7 |
-30.24 |
| 28 |
|
-27.78 |
9.59 |
9.7 |
-27.9 |
| 29 |
|
-26.18 |
10.68 |
10.82 |
-26.36 |
| 30 |
|
-24.77 |
12.03 |
12.14 |
-25.26 |
| 31 |
|
-25.29 |
12.04 |
12.15 |
-25.62 |
| 32 |
|
-18.65 |
13.93 |
14.03 |
-19.96 |
| 33 |
|
-10.29 |
15.26 |
15.33 |
-10.31 |
| 34 |
|
-9.91 |
15.25 |
15.33 |
-10.09 |
| 35 |
|
-4.42 |
16.22 |
16.3 |
-4.33 |