In this section you will use the Universal Software Radio Peripherial (USRP) for both receiving and transmitting signals. The USRP is a I/Q receiver with wide bandwidth (100 MHz sampling rate), programmable center frequency, programmable gain and choice of sample rates.

For detailed information on the usage of the USRP, you can find the data sheet and user manual as well as the range of compatible daughterboards at the website below


Refer to the block diagram in Figure 41 to understand the receive path of the USRP as it is set up in the lab. The USRPs in the lab have the WBX daughtercard installed which feature a programmable attenuator, programmable local oscillator and analog I/Q mixer. The WBX daughterboard is an analog front end for the GNU Radio software. It consists of a local oscillator implemented as a wideband frequency synthesizer, thus allowing the USRP to receive signals in the range from 50 MHz to 2.2 GHz. The WBX Daughterboard performs complex downconversion of a 100 MHz slice of spectrum in the 50-2200 MHz range down to -50 to +50 MHz range for processing by the USRP motherboard.

The main function of the USRP motherboard board is to act as a Digital Downconverter (DDC). The motherboard implements a digital I/Q mixer, sample rate converter and lowpass filter. The samples are then sent to the host PC over a gigabit ethernet link.

We will first learn about FM waveform generation and reception in software simulation-only without the URSP, then FM receiver implemented with the USRP, general IQ receiver implemented with the USRP, and finally the USRP transmit function.