This Reissue application is a reissue of application Ser. No. 06/572,286, filed Jan. 20, 1984, which is incorporated by reference herein.
This invention is concerned with radar type altimeters. Specifically, the radar altimeter of the present invention is one which maintains a signal to noise level below a value which affords detection by an intercept receiver.
Radar altimeters are well known. In order to provide covert operation, i.e. not detectable by an intercept receiver, the radar signal should be a minimum to reduce the chances of radar detection by the intercept receiver.
The novel radar system of the present invention provides a radar altimeter which operates near the oxygen absorption line. The frequency of the transmitter is adjusted in accordance with a measurement of the signal to noise ratio of a preselected range bin (return signal) thereby minimizing detection by an intercept receiver.
As shown in
Shown in
By way of example, the radar system shown in
The output of detector 340 is presented to a hold circuit 342 for holding the value of the signal-to-noise ratio upon a predetermined bin selection provided by the output of bin selector 345. The output of hold circuit 342 is then presented as one input to comparator 350. Comparator 350 compares the output of hold circuit 342 to a preselected reference level input. The comparator provides an output signal to integrator 360 which integrates the output signal of comparator 350. The output of integrator 360 is then presented to the control input 301 of oscillator 300 for adjusting the oscillation frequency, i.e. the carrier frequency in proportion to the output of integrator 360.
The operation of the radar system of
The output of the holding circuit 342 is then presented to comparator 350 which is compared with the reference signal indicative of the preselected acceptable signal to noise ratio. The output of the comparator is then integrated via integrator 360 and presented to the adjustable oscillator 300 for adjusting the oscillation so as to increase or decrease as the case may be to maintain the preselected signal to noise ratio. The combination of comparator 350 and integrator 360 provides a negative feedback control means so as to maintain the signal-to-noise ratio as aforesaid.
It will be appreciated by those skilled in the art that the embodiment shown in
Number | Name | Date | Kind |
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3098225 | Anderson | Jul 1963 | A |
3381292 | Hansen | Apr 1968 | A |
3522605 | Mader et al. | Aug 1970 | A |
Entry |
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U.S. Patent and Trademark Office, “Office Action”, U.S. Appl. No. 06/572,286, dated Aug. 5, 1986, pp. 1-4, Published: US. |
Schlesinger et al., “Principles of Electronic Warfare”, Prentice-Hall, Inc., 1961, 4 Pages, Englewood Cliffs, New Jersey. |
U.S. Patent and Trademark Office, “Notice of Allowance”, U.S. Appl. No. 06/572,286, dated May 28, 2019, pp. 1-6, Published: US. |
Schlesinger et al, Principles of Electronic Wafare, 1961 by Prentice-Hall, p. 144. |
Number | Date | Country | |
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Parent | 06572286 | Jan 1984 | US |
Child | 17006350 | US |