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Modern SDR Architecture with Programmable Hardware

modern sdr architecture

Put down your soldering iron. Build your next receiver using your keyboard. Modern SDR architecture makes this (almost) possible. 

If I look inside my Flex 6300 receiver I will find the modern SDR architecture shown above. Although it has analog components for antenna connection, filtering and signal amplification, all the rest is done in programmable hardware. SmartSDR software provides control and GUI using a network connection.

While today’s ADC have the speed and precision to sample the entire HF spectrum at once, it’s really the FPGA that makes it possible to handle all the data efficiently. Similarly, using Ethernet instead of USB enables much faster data transfer and remote operation. When designing using the modern SDR architecture, you also have the choice of how much DSP, visualization and demodulation you want to do in the hardware or GUI device.

Another benefit of the new approach is your ability to embed an operating system inside your radio. Most people use Embedded Linux. By programming hardware (FPGA, DSP, CPU) you can reconfigure and add features to your radio almost at will.

Steve Hicks of FlexRadio does a great job of explaining the modern SDR architecture in this video from five years ago. Take a look now or later.

Modern SDR Architecture – Connecting Modules Together

Hams, hobbyists and hackers now have the ability to implement modern SDR architecture by connecting modules together. Previously, implementation required designing a mixed signal, multi-layer printed circuit board. Not for the faint of heart.

The move towards collaborative design of a modular approach began in the ham community in 2005. Called OpenHPSDR, the community designed and built a series of modules which could be joined up to make high performance receivers and transceivers. Today, these modules form the basis of Anan radios from Apache Labs.

More recently, the modern approach moves computing power into the radio. Engineers are combining everything needed onto one or two modules or development boards. For example, Zedboard combines FPGA and powerful ARM computing; you just need to add an ADC module. Even better, Red Pitaya provides a single board which includes dual channel ADC in addition to FPGA/CPU. At the high end, the Ettus USRP B200 covers 70 MHz to 6 GHz on a single board, analog filtering included.

Shortly, we will describe how these can be assembled into configurable SDR using a variety of open-source or free tools.

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