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Principles of Modern Radar - Volume 2 1891121537

Principles of Modern Radar - Volume 2 1891121537

Principles of Modern Radar - Volume 2 1891121537

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9.2 Digital Beamforming Fundamentals 409System Availability10.950.9N:N-2 DBF0.850.80.75N:N-1 DBF0.7Monopulse0.650.6N:N DBF0.550.50.9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99Single Channel Availability1FIGURE 9-5System availabilityfor 16-channel DBF.reliability or more rapid replacement with spares than conventional systems. Also, whilethe impact <strong>of</strong> the loss <strong>of</strong> a DBF receiver on the antenna gain may be relatively small,the impact on sidelobe levels can be more dramatic and should be taken into account forapplications where maintaining low sidelobes is a high priority.I/O and Computational AspectsOnce the array data have been converted into digital samples in the receivers, they needto be communicated to the beamforming computer. Figure 9-6 shows the I/O throughputrequired for 10-, 100-, and 1000-receiver channels as a function <strong>of</strong> the ADC rate assumingthe number bits is 16 and that the I/Q samples are formed in the receiver. For large numbers<strong>of</strong> receivers and large sample rates, a beamforming processor implemented in commercial<strong>of</strong>f-the-shelf (COTS) components, such as field programmable gate arrays (FPGAs) orgraphical processing units (GPUs) is likely to be limited I/O capacity into the board andmay require a large number <strong>of</strong> boards to support the necessary data rates.10000010000FIGURE 9-6I/O throughput inGbits/sec from thereceivers to thebeamformingcomputer.Gbps100010010 Channels100 Channels1000 Channels1010020030040050060070080090010001100120013001400150016001700180019002000A/D Sample Rate (MHz)

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