You can easily combine configurable SDR devices with open source software to build and operate virtually any wireless protocol and modulation scheme. Let’s take a look.
If you want to homebrew a modern software defined radio, two types of platforms make it easy. First, you can use configurable SDR devices. These include HackRF One, LimeSDR Mini, FreeSRP and Ettus USRP shown above clockwise from top left. All employ modern SDR architecture and are pre-programmed for you to configure into a variety of radios. Second, you can select a general purpose development platform and program the hardware yourself from scratch. We will talk about these platforms, for example Red Pitaya and Diligent Zeboard in future articles.
A few companies are providing configurable SDR devices – transceivers, covering HF to microwaves. Typically, creators employ open source hardware and use many software tools, some open source like GNURadio. Transmit power varies by frequency, but usually ranges from 0 – 10 dBm, or up to 10 milliwatts. Control and data flow over USB. All contain the equivalent of ADC/DAC, FGPA and microcontroller.
Who uses these devices? Businesses, universities and hobbyists who want to quickly configure and experiment with different types of wireless communications and modulation techniques. In particular, hobbyists benefit from very active open source communities that provide advice, software and sometimes firmware to re-program the hardware.
Michael Ossman and friends created HackRF One an 8 bit half-duplex transceiver covering 1 MHz to 6 GHz, running a Maxim integrated transceiver providing wideband wireless direct conversion to baseband with programmable filters and gains. Clones are also available on e-bay.
LimeSDR has a variety of devices running Lime Microsystems LMS7002 field programmable RF transceiver. Many users pick the new “mini” at US$139 providing 12 bit performance from 100 kHz to 4 MHz. Tons of software is available on GitHub.
A recent arrival is FreeSRP. Believe it or not, a 17 year old student created this $400 configurable SDR device, by combining an FGPA with the Analog Devices AD9364 transceiver on a chip. You can run this as a transceiver from 70 MHz to 6 GHz.
A good place to check out these options is Myriad RF. All in all, if you want to start experimenting creating your own SDR solutions, these relatively low cost devices get you going in no time.
Configurable SDR Devices – It All Started with USRP
Back in 2001, some folks associated with the GNURadio project decided to create a Universal Software Radio Peripheral and formed Ettus Research. They made the first USRP in 2005. Early designs focused on a baseband motherboard (ADC/DAC, FGPA) with different daughter boards for frequency conversion and filtering. More recently Ettus was purchased by National Instruments and have moved their designs to the embedded model running Linux.
You can pick up the new B200/210 devices which use open source FPGA programming and the popular AD9364 transceiver. Take a look at this video of the B200 exploring the wireless world. While the Ettus gear is low cost of academic and business use, it’s still pretty expensive for a hobbyist.
The takeaway is that you can combine these configurable SDR devices with GNURadio (or other software) and have pretty well any kind of wireless system up and running under your complete control. In some cases the designs and FPGA code are available, too.