Software Defined Radio

Topics: Signal processing, Phase, Modulation Pages: 8 (2667 words) Published: December 13, 2011
EL 5023/EE4183 Wireless Information Systems Laboratory
Lab #11 Software Defined Radio (SDR) I. Experimental Procedure Equipment List Universal Software Radio Peripheral (USRP) with Flex900 Radio Spectrum analyzer (Agilent E4411 or equivalent) PC with Matlab/Simulink R2011B CAT 6 Ethernet cable SMA(male)-to-BNC Adapter (for spectrum analyzer) 915 MHz Antenna (qty 2) A. INSTRUMENT CONNECTIONS: Connect the antenna to the SMA connector labeled RF1 port on the front of the USRP. Connect another antenna to the spectrum analyzer. Power the USRP with a 6v/3A power adapter. B. CONFIGURE PC: a. Connect the CAT6 cable between the PC and the GB Ethernet port of the USRP. b. Manually set the PC’s Ethernet port IP address under the same subnet mask as the USRP. The USRP2 uses a default IP of (class C). Simply follow these steps on your PC: i. Under Start Manu, go to Settings -> Network Connections ii. Select Local Area Connection, right click the icon and choose Properties iii. Select Internet Protocol (TCP/IP) and click Properties below the mini window iv. Record the default settings. You will need to reset the values after finishing the lab. v. Manually set up the IP to with Subnet Mask Leave the Default Gateway and DNS settings at their original configuration. vi. Click OK and close all the sessions vii. To check your IP address setting. Go to Run and enter cmd. When the terminal windows opens, enter ipconfig. What is the IP address you are using? Does it list the settings above. Close the command window.

C. START MATLAB/SIMULINK a. Open MATLAB2011b and change the current directory to: C: \usrp2_block\commusrp b. Type in the command setupsdru, which includes the USRP libraries to the software. After entering this command, the prompt “>>” will return with no additional information provided. c. In the command window, type in Simulink and you will open the Simulink library browser. d. Do you see Communications with USRP2 library? Click on the library, what blocks are available in this library? e. Create a new Simulink model and drag SDRu Transmitter onto the model page. Double click on the block to open the parameters menu. For the USRP IP Address, use the pull down to select the device, the IP address should be selected. Set the Center Frequency (Hz) to a Desired Value using Table 1 below. Verify that the Gain(dB) is set to 0dB. Specify the Interpolation for the SDRu transmitter using one of the values listed in Table 2 below. The default value is 512. As the Digital-to-Analog Converter (DAC) in the USRP is clocked at a fixed 100MSPS, the USRP sample rate is approximately 195 kHz (100M/512). For now, enter a value of 200 into the Interpolation Desired Value. What is the sample rate of the USRP when the interpolation factor is 200? Click OK to Lab #11 Software Defined Radio (SDR) © Polytechnic Institute of NYU 1 Rev A 12/05/11

EL 5023/EE4183 Wireless Information Systems Laboratory
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Table 1 Center Frequency (Hz) values for SDRu Transmitter

Bench Number 1 2 4 5 6

Center Frequency (Hz) 904e6 908e6 912e6 916e6 920e6

Table 2 Interpolation Factors

Factor Range 1 to 128 128 to 256 256 to 512

Notes Must be even Must be divisible by 4


To optimize real-time operation, perform the following adjustments to the Simulink environment parameters. i. In the Simulation->Configuration Parameters -> Data Import/Export dialog, turn off all Save to Workspace variables, Signal Logging and Data Memory by unchecking all associated boxes. Click OK to close. ii. As a suggestion, do not use Simulink scopes (sinks) unless absolutely necessary. Scopes load down the CPU and prevent the steady flow of data over the Ethernet connection. To visualize your data, send it to a workspace variable and post-process it.

D. CW CARRIER GENERATION The RF carrier frequency of the Local Oscillator in the RF hardware is configured in the SDRu Transmitter block. This frequency...
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