Apparatus for the observation and indentification of helicopters
AssigneeHollandse Signaalapparaten B.V.
InventorsRichard E. M. G. La Grange, Willem A. Hol
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Abstract
Apparatus for the observation and identification of helicopters by means of an FM-CW radar apparatus provided with transmitter means (1), antenna means (2) and receiver means (3). Blade flashes caused by the rotor blades are digitized by A/D converter (4) and processed by Fourier analysis means (5) and processor (6) in order to determine the range from a helicopter to the radar apparatus and the rotor symmetry characteristics. These symmetry characteristics, together with the blade flash repetition frequency yield a substantially unambiguous indication of the helicopter type.
Claims12
An FMCW radar apparatus for the detection and identification of at least one helicopter having rotor blades, comprising:
- transmitter means coupled to directional antenna means, for the transmission of periodical linear frequency-modulated signals, with a time duration of one period taken at least substantially equal to an expected duration of one blade flash from the helicopter rotor blades;
- receiver means coupled to the antenna means and provided with mixing means for the generation of heterodyne signals from a signal representing the transmitted signal and received radar echoes;
- Fourier analysis means for the transformation per period of the heterodyne signals for obtaining a spectrum of the blade flash;
- and
- processor means for deriving from the spectrum and its symmetry structure the helicopter distance and the symmetry structure of its rotor.
Dependencies are inferred from the claim text.