hannel Filter B Channel Band Filter 1 Filter A Digital Antenna Output Filter Phase Splitter Tuning Control Loop Tuning Control Loop Figure 2.3-2 Super-heterodyne with baseband IQ sampling. between the different responding groups has often been also be utilized for advanced interception functions such hindered by the fact that different communications as voice recognition and code decryption. Additionally, if systems rarely work with one another because the fre- a network of SDRs is used, then triangulation can be used quency and air interfaces are different. As shown in to aid in the location of the rogue transmission. Figure 2.3-4, SDR provides an ideal solution to these dilemmas. A centrally deployed base station could be Manufacturing platform used to receive the transmissions of one agency and reformat and rebroadcast them on the frequencies of the Although there are many applications where the dynamic other responding agencies. Since the system would be configuration of an SDR is required, perhaps one of reconfigurable as new agencies arrive or depart, the SDR the most practical applications is that of a standardized could be rapidly changed to support the required ser- communications platform. For example, most manufac- vices. When the disaster is over, the system can easily be turers of cellular infrastructure equipment sell platforms stowed and redeployed at a later time as required. for a variety of air standards such as GSM, CMDA, IS-136, and AMPS, to name but a few. Typically, each of Interception these is a different piece of hardware that must be manufactured and inventoried. If a single design could be As already outlined, early applications of SDR were for fabricated that could have identical hardware, the cost of military interoperability. Another military application for manufacturing would be significantly reduced because SDR is the interception of communications. Since the only one system would need to be inventoried. The frequency and modulation format of these transmissions hardware could the