Sector scan ADF system
First Claim
1. An automatic direction finding system for instantaneously determining the direction of the location of a radio frequency source with respect to the receiving location comprising:
- a regular polyangular directional antenna array consisting of four or more antennas whose spacing is not limited by frequency, each antenna having a directional pattern of identical directional shape and of equal value, the antennas being switched in sequence to effectively produce a rotating pattern;
a switcher means which combines the separate antenna signals onto a common signal port on which is superimposed an AM modulation related to the direction of the signal source;
a receiver means which processes the common RF signal and feeds the resultant signal to a detector means;
the entire system being synchronized by a controlling means which coordinates the actions of a driver means, a filter means, an accumulation means, and a display means;
said driver means creating switching voltages which control said switcher means, the output of said detector means being followed by said filter means which can then integrate and store the bearing information, said accumulation means averaging bearing information from said filter means which output is then fed to said bearing display means, error detecting to minimize erroneous bearings being built into said bearing display means as well as a bearing status indicating means to display the current status of the indicated bearing.
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Abstract
An automatic radio direction finding system having inputs for a circular array with a plurality of directional antennas, each being switched in sequence producing a directional pattern in azimuth. The combined RF signal is carried through the receiver as a normal AM modulated signal and the intermediate frequency output of the receiver is detected and the added modulation is recovered, filtered, and accumulated in such a manner that random signals will cancel and any repetitive signals will increase in amplitude and be stored. The vector information of this stored 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 on a numerical readout in degrees azimuth. The averaging techniques are employed to eliminate jitter in the last digit. A second display, a circular bar-graph, also uses averaging to remove jitter, and gives the operator a more instinctive feel for the tendencies of a changing bearing.
9 Citations
7 Claims
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1. An automatic direction finding system for instantaneously determining the direction of the location of a radio frequency source with respect to the receiving location comprising:
a regular polyangular directional antenna array consisting of four or more antennas whose spacing is not limited by frequency, each antenna having a directional pattern of identical directional shape and of equal value, the antennas being switched in sequence to effectively produce a rotating pattern;
a switcher means which combines the separate antenna signals onto a common signal port on which is superimposed an AM modulation related to the direction of the signal source;
a receiver means which processes the common RF signal and feeds the resultant signal to a detector means;
the entire system being synchronized by a controlling means which coordinates the actions of a driver means, a filter means, an accumulation means, and a display means;
said driver means creating switching voltages which control said switcher means, the output of said detector means being followed by said filter means which can then integrate and store the bearing information, said accumulation means averaging bearing information from said filter means which output is then fed to said bearing display means, error detecting to minimize erroneous bearings being built into said bearing display means as well as a bearing status indicating means to display the current status of the indicated bearing.- View Dependent Claims (2, 3, 4, 5, 6, 7)
Specification