EE123: Digital Signal Processing


Spring, 2018

RTL-SDR: Inexpensive Software Defined Radio

What is software-defined radio?

A software defined radio system is a system in which the components are implemented in software instead of the traditional way of hardware implementation. It consists of an RF front-end followed by and analog- to-digital converter which provides samples to a host computer. The rest of the processing is done solely in software.

Each student in the class will/or already gotten a TVB-T USB dongle based on the Realtek RTL2832U chip. This dongle was originally made to receive and decode the European standard digital television. The chip allows transferring raw I/Q samples to the host, which is officially used for DAB/DAB+/FM demodulation. The possibility of using this feature for generic “software defined radios” has been discovered by Eric Fry.

This is a photo of the dongle:

The E4000 Elonics chip is a digitally controlled tuner. The tuner selects a frequency band around a target center frequency and demodulates it to baseband. In our case, the RTL2832U chip serves as an analog to digital converter that samples the baseband signal and outputs the samples to a host computer through a USB2 port.

Some of you will get an rtl-sdr with the E4000 chip, these can tune to frequencies between 52-2200Mhz. Others will get dongels base on the Rafael Micro R820T which can tune to frequencies between 24-1766Mhz. These tuners have different architectures, but you will not see the difference while using them.

The E4000 device uses IQ baseband demodulation and sampling. Here are some Notes and Slides. The R820T used an IF (intermediate frequency) for demodulation.



SDR Software:

  • Gqrx - Linux and OSX Link

  • SDR# - Windows Link

  • HDSDR - Link

  • Linrad - SDR software for experts (windows, linux and OSX Link

  • Gnuradio Link

This is a video by Balint Seeber from Ettus research on what you can do with SDR. Balint is using a much higher end device, but many of the things he shows can be done with the rtl-sdr dongle.

I hope you enjoy this device!

please let me know if there are any problems.

-- Miki