| 摘要 |
An automatic radio direction finding (ADF) system having inputs for four quadrature antennas each having a cardioid pattern. Each input is amplitude modulated in quadrature and then combined in a hybrid circuit to produce a nondirectional pattern. The combined rf signal is carried through the receiver as a normal signal and the AM detected intermediate frequency of the receiver is fed to a processor. The sum quadrature modulation is recovered, filtered, and accumulated in such a manner that random signals will cancel and any repetitive signals at the modulation frequency will increase in amplitude and be stored. The vector information of this recovered modulation when decoded with respect to the phase of the original modulation, contains the actual bearing information. The signal is then averaged over several cycles and displayed in digital format in degrees of azimuth with respect to car heading. This averaging eliminates jitter in the last digit of the numerical readout. A second display a circular bar-graph, also uses averaging to remove jitter and gives the operator a much better indication of the tendencies of a changing bearing. Therefore, when used as a mobile DF, the bar-graph is the more useful of the two displays, and conversely the numerical readout is superior for a fixed site.
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