software defined radio

A radio consisting of a receiver and/or a transmitter, where each has the following properties, respectively: (a) the received signal is digitized and then processed using software-programmable digital signal processing techniques (digitization may occur at the rf, IF, or baseband); (b) the modulated signal to be transmitted is generated as a digital signal using software-programmable digital signal processing techniques; the digital signal is then converted to an analog signal for transmission (the conversion to analog may occur at baseband, IF, or rf); and (c) a key element of these radios is that software programmability allows easy changes of the radio’s fundamental characteristics such as modulation types, operating frequencies, bandwidths, multiple access schemes, source and channel coding/decoding methods, frequency spreading/despreading techniques and encryption/decryption algorithms.