Software Defined Radio (SDR) is a radio where proprietary hardware has been replaced by a general processor and software. SDR hardware can handle any "waveform", i.e. the software that makes a certain type of radio unique. SDR technology results in a flexible radio that can handle different radio standards simply by updating the software. As an example, an SDR device can be changed from a military radio to a GSM telephone.
The SDR waveform is defined in software. The transmitter sends a digital representation of the waveform which is converted to an analog signal in a D/A converter. The analog signals are then up-converted from the intermediate frequency to the carrier frequency before being transmitted. The receiver contains an A/D converter that is placed as closely as possible to the antenna and the channel is extracted using a digital band pass filter. The resulting signal is then demodulated by the SDR waveform software.
SDR technology is attracting more and more notice from the military. The main reason for this is that SDR results in somewhat of a "logistics revolution" as the same radio hardware can be used for all radio applications. It can even coexist with existing equipment - all that is needed is a software waveform for the existing radio application. An SDR-based radio system can even be used as a bridge between two different communications standards, which simplifies the transition to future radio technologies.
Technical Performance
The JTRS standards (Joint Tactical Radio System) specify that an SDR system (within given limits) should be able to handle all frequencies between 2 MHz and 2 GHz. Limitations are concerned mainly with channel bandwidths and are affected by the choice of technology for processing of the received signal. Performance requirements in more advanced SDR waveforms result in systems that use DSP- and FPGA-technology. In practice the bandwidth is limited more by frequency allocations and regulations than by the technology itself.
BitSim and SDR
BitSim has a profile that is well adapted to SDR technology. We have long experience of working with embedded systems, radio technology and advanced signal processing - especially systems based on FPGA-technology.
