Communications: directive radio wave systems and devices (e.g. – Plural radar
Patent
1985-07-30
1987-09-22
Tubbesing, T. H.
Communications: directive radio wave systems and devices (e.g.,
Plural radar
342175, 342188, 342129, G01S 1387
Patent
active
046958428
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a radar arrangement including a transmit/receive antenna which can be alternately connected, by way of a transmit/receive switch to transmitting and receiving devices.
Aircraft radar arrangements are generally subject to restrictions regarding weight and space requirement. While in conventional radars, the fixed target echoes are suppressed by MTI [moving target indication] or similar measures, for low-flying aircraft it is necessary to be able to detect, in addition to moving targets, obstacles, such as trees, poles or high tension wires, so as to avoid collisions with such obstacles.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a radar arrangement of the type described above which meets the above-mentioned requirements.
The above and other objects are accomplished in the context of an aircraft arrangement of the type first described above which includes the provision of a transmitting means comprising first and second transmitting devices for generating transmitting signals at a first frequency (f.sub.1) and at a second frequency (f.sub.2), respectively, with the first frequency (f.sub.1) lying in a region of maximum atmospheric attenuation and being used for obstacle warning and the second frequency (f.sub.2) lying in the vicinity of the first frequency (f.sub.1) and in a region of low atmospheric attenuation and being used for moving target detection, the first and second transmitting devices being jointly connected with the antenna by the transmit/receive switch, and the provision of a receiving means including first and second frequency selective devices jointly connected to the antenna by the transmit/receive switch and first and second receiving channels connected to the first and second frequency selective devices, respectively, the first frequency selective device passing first received signals corresponding to echoes of the first transmitted signal of frequency (f.sub.1) to the first receiving channel to be processed for obstacle warning and the second frequency selective device passing second receive signals corresponding to echoes of the second transmitted signal of frequency (f.sub.2) to the second receiving channel to be processed, independently and separately of the first receive signals, for moving target detection.
The invention makes it possible, when operated at the first frequency, to give a warning about obstacles and, when operated at the second frequency, to use one and the same device for the detection of moving targets and navigation. This arrangement results in a considerable reduction of expenses, as well as weight and space requirements. Due to the fact that both frequencies lie closely adjacent one another, the same waveguides, antenna and other components can be used for both frequencies. The detection of moving targets and navigation requires the use of radiation which can be transmitted over a long range so that the frequency provided for this purpose is placed into a region which has low atmospheric attenuation. For a warning about obstacles, however, the maneuvering volume must be covered within a certain reaction time, i.e. as a function of velocity, which does not require such long ranges. To avoid unnecessary interference in other HF systems, there should be as little radiation as possible beyond the monitoring volume of the obstacle warning radar so that high atmospheric attenuation is an advantage for this operating mode.
The invention meets both requirements in an advantageous manner in that obstacle warning is performed by means of a first frequency which has been placed at a maximum of atmospheric attenuation and detection of moving targets and navigation are effected by means of a second frequency placed to one side of this maximum. The second frequency is most favorably placed below the first frequency at the steeper and more deeply descending low-frequency side of the attenuation maximum.
In the receiving branch of the arrangement, the echo signals belonging to different tr
REFERENCES:
patent: 3772689 (1973-11-01), Root, Jr.
patent: 4041489 (1977-08-01), Lewis
patent: 4110754 (1978-08-01), Endo
patent: 4118703 (1978-10-01), Williams
patent: 4538148 (1985-08-01), Petitjean
Jehle Franz
Meinel Holger
Hellner Mark
Licentia Patent-Verwaltungs-GmbH
Tubbesing T. H.
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