|
From: | Matt Ettus |
Subject: | Re: [Discuss-gnuradio] Single-tone test using USRP2 with RFX2400 and XCVR2450 |
Date: | Sun, 26 Apr 2009 00:00:22 -0700 |
User-agent: | Thunderbird 2.0.0.21 (X11/20090320) |
Yongsang Kim wrote:
Hi, all. I did single-tone test using USRP2 with RFX2400 and XCVR2450. There are some undesired signals in the results. My single-tone test is as follows: - Wired connection between USRP2 and Spectrum analyzer - Single-tone is transmitted from USRP2 using the following commands ./usrp2_siggen.py -f xxxx ./usrp2_siggen.py -f xxxx -w xxxx - For daughter board, RFX2400, XCVR2450 and Basic TX are tested - Newest GNU radio and firmware - PC specification (I'm pretty sure that the spec is good enough to transmit single-tone stably) -- CPU: Intel core2quad processor Q9550 -- Ethernet card: Intel 82567LM Gigabit LAN (PCI express slot) -- Memory: 4GB DDR2 800 MHz SDRAM memory Except the case of Basic TX, there are some undesired signals in the results. So, I guess the undesired signals are generated by RFX2400 and XCVR2450, not by mother board. I'm afraid that the undesired signals cause some kind of distortion of desired signal. (In fact, when I transmit OFDM signal using XCVR2450, I fail to demodulate the received OFDM signal) The resulting spectrum figures are shown in the following link and I marked the undesired signals in the figures.
What you are seeing are normal transmitter non-idealities, including DC offset (aka carrier feedthrough), and IQ imbalance (aka sideband suppression. These can be improved through tuning, but they are not bad as is. Also, on the XCVR you are seeing the phase noise skirts as well.
Matt
http://141.223.23.5/Spectrum.zip Short descriptions for each figures are as follows: 1. File name: RFX2400_2p375GHz_01 Used daughter board: RFX2400 GNU radio command: ./usrp2_siggen.py -f 2.375e9 2. File name: RFX2400_2p375GHz_02 Used daughter board: RFX2400 GNU radio command: ./usrp2_siggen.py -f 2.375e9 -w 2M 3. File name: XCVR2450_2p52GHz_01 Used daughter board: XCVR2450 GNU radio command: ./usrp2_siggen.py -f 2.52e9 4. File name: XCVR2450_2p52GHz_02 Used daughter board: XCVR2450 GNU radio command: ./usrp2_siggen.py -f 2.52e9 -w 2M 5. File name: BasicTX_30MHz_01 Used daughter board: Basic TX GNU radio command: ./usrp2_siggen.py -f 30e6 6. File name: BasicTX_30MHz_02 Used daughter board: Basic TX GNU radio command: ./usrp2_siggen.py -f 30e6 -w 2M I would appreciate that if somebody let me know what is problem of my daughter boards or my test. Thanks.
[Prev in Thread] | Current Thread | [Next in Thread] |