Ironically, SDR programmable hardware has really brought software defined radio to the next level. In this series, we’ll explore how this is done. And how you can do it yourself.
Commercial, government and scientific folks have been using SDR programmable hardware to evolve software defined radio for more than a decade. In this series, we will describe how their tools, techniques and devices have grown and are now within reach of hobbyists and hackers.
It is fairly straightforward to embed most of a software defined radio into hardware. Especially when you use direct sampling to digitize radio signal right at the antenna. Notice that I said straightforward, not simple or easy. You need to do lots of heavy lifting to make it all work. The key is accessibility and learning.
The good news is that an Arduino-like paradigm shift is underway in SDR. Arduino provides an ecosystem to enable millions of people, even youngsters, to use micro-controllers. This ecosystem includes hardware, development boards, integrated development environments and software libraries. Equally important, the Arduino ecosystem is low cost, often open source, and supported by a huge community of interest numbering in the millions.
While most people use SDR “off the shelf”, your ability to build or configure your own software defined radio is also increasing exponentially. The new DIY SDR ecosystem includes development boards, tools to program or configure these, and development tools like GNURadio.
SDR Programmable Hardware – Inside the ICOM 7300
Before we get into the details, let’s look at the basic SDR programmable hardware paradigm. It’s easily demonstrated inside the new and extremely popular ICOM 7300. The following information is taken from the ICOM 7300 Service Manual.
The core of the 7300 is comprised of four chips which cost less than $200 in single unit quantities. We will focus on the receiving chain.
- An analog-to-digital converter (ADC) from Linear Technology. Sampling at 130 MHz with 14 bits, the ADC is basically connected to the antenna.
- An Intel Cyclone IV Field Programmable Gate Array (FPGA). This contains FIR Filtering, Numerically Controlled Oscillator and FFT to convert received signals to a 36 kHz IF.
- A Texas Instruments DSP chip is programmed for a complete DSP subsystem.
- And finally comes the ARM Cortex A-9 microcontroller which controls everything and provides video output, too.
The ADC costs around $100, while the other three chips are $20-$30 each. You will find that the FGPA, DSP and ARM devices are supported with many programming tools and code libraries available for use.
In future articles, we will describe how this basic model of SDR programmable hardware is becomming widely available for use by hams, hobbyists and hackers to build and configure their own radios.