A word on Software Defined Radios (SDR)
Software Defined Radio (SDR), resembles the techniques for
creating software blocks of functional radio for reception/transmission. The
concept extends from plain AM/ FM to Wi-Max/LTE radio transceivers and beyond. In
other words, software defined radio (SDR) is defined as a radio in which the
digitization is performed at some stage downstream from the antenna. Then the
radio can use flexible and reconfigurable functional blocks for the implementation
of digital signal processing algorithms. As technology advances, the digitization
might be at, or very close to the antenna, such that almost all the radio functionalities
are realized using software using high speed and reprogrammable digital signal
processing engine
The old age
radios had everything, from RF tuner to A/V detection in complete anlog domain
with limited controls based on some varying resistance or impedance. The
current radios consist of a mixture of analog and digital building blocks. The
radio frequency (RF) functionalities are most likely being implemented using analog
circuits, while the baseband functionalities are more suitable for DSP
implementations. Now SDRs handles the capability to digitally tune to an RF
signal, sometimes a few Mhz band at once, further processing DSP will include extremely configurable FIR /IIR filters , AGC controls, DFT blocks,
Squelch, Vox controls, flexible IF creators, various modulator/demodulator
blocks, encrypt/decrypt capabilities, test/measurement visualisations etc.
SDR
implementations
Being a huge part of processing
done in software, SDR implementations are resource hungry. Most SDR
implementations are based on PC, with some analog Front End device connecting
to antenna. FPGA based SDRs are another potential since they are capable to
realise anything digitally and provide massive parallel operation. This
offloads most real-time DSP operations needed during a continuous operation of
Radio. An FPGA implementation of any functional block is highly reconfigurable
on the fly. This adds endless research possibilities in SDR.
Advantages
of SDR
·
Highly flexible and Extendable Radio
·
Research possibilities on any communication techniques
·
Prototyping and
validation of communication Transceivers.
·
Measurement/Monitoring of bands with minimal hardware
setup.
GNU RADIO-
The SDR Development Tool Kit
GNU Radio is a
free & open source software development toolkit that provides
signal processing blocks to implement software-defined radio systems.
It can be used with readily-available low-cost external RF hardware
to create software-defined radios, or without hardware in a simulation-like
environment. It is widely used in hobbyist, academic and commercial
environments to support both wireless communications research and real-world
radio systems.
GNU Radio applications are
primarily written using the Python programming language, while the
supplied performance-critical signal processing path is implemented in C++using
processor floating-point extensions, where available. Thus, the developer is
able to implement real-time, high-throughput radio systems in a simple-to-use,
application-development environment. The tool is completely open source.
Examples of
SDR implementations
The the most supported product in
GNU Radio.
- BladeRF: http://nuand.com/
Based on Altera Cyclone FPGA
platform.
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