Software Defined Radio (SDR) is an advanced radio technology in which flexibility is achieved in using radio functions such as modulation and demodulation of radio signals are carried out exclusively by use of different software running on a reconfigurable hardware. Just by downloading new software, SDR can reconfigure and upgrade to new standards. SDR does not change hardware components.
SDR is a radio communication transceiver system in which all the typical components of a communication system such as mixers, modulators/demodulators, detectors, amplifiers are implemented through software rather than hardware. Thus, the system is compatible with various communication standards by upgrading software on same hardware platform.
SDR system is ideally expected to tune to any frequency band and receive any modulation across a large frequency spectrum by means of a programmable hardware which is controlled by software.