Polyphase-discrete Fourier transform spectrum analysis for the Search for Extraterrestrial Intelligence sky survey

G. A. ZimmermanCommunicationsSystemsResearchSectionS. GulkisSpacePhysicsand AstrophysicsSectionThe sensitivity of a matched filter-detection system to a finite-duration contin-uous wave (CW) tone is compared with the sensitivities of a windowed discreteFourier transform (DFT) system and an ideal ba31dpass filter-bank system. Thesecomparisons are made in the context of the NASA Search for Extraterrestrial In-telligence (SETI) microwave observing project (MOP) sky survey. A review ofthe theory of polyphase-DFT filter banks and its relationship to the well-knownwindowed-DFT process is presented. The polyphase-DFT system approximatesthe ideal bandpass filter bank by using as few as eight filter taps per polyphasebranch. An improvement in sensitivity of "-'3 dB over a windowed-DFT systemcan be obtained by using the polyphase-DFT approach. Sidelobe rejection of thepolyphase-DFT system is vastly superior to the windowed-DFT system, therebyimproving its performance in the presence of radio frequency interference (RFI).