DE2007049C3 - Bearing system - Google Patents

Description

The invention relates to a direction finding system for frequency-selective direction finding of electromagnetic high-frequency oscillations in terms of azimuth and elevation with a large number of antennas with downstream receivers, their output signals be evaluated.

A serious disadvantage of conventional shortwave DF systems is their failure in interference fields. If an interference field builds up from azimuthally strongly diverging beams - this case is due to the steep incidence of rays with bearings at close range (50 - 300 km) is usually given - this is rarely the case possible to obtain a reliable short-term bearing.

From US-PS 30 38 122 it is already known to determine the direction and / or frequency of incident radar pulses by means of a number of parallel-sounded brcitbandiger radar pulsemp ^r anger with directional antennas, the lobes of which are offset from one another so that they have a predetermined larger angular range Cover completely, carry out a coarse bearing by determining the receiver with the largest pulse amplitude and also using a number of narrow-band receivers connected to an antenna with all-round characteristics, whose frequency channels are so smoothed that they completely cover a given wide frequency range, to carry out a rough frequency measurement. With this known device, it is not possible, at least with affordable expense, to carry out an accurate, frequency-selective bearing with regard to the azimuth and elevation in the event of multiple wave incidence - that is, when there is an interference field.

The object of the invention is to provide a Peilsysiem that is also under the The aforementioned unfavorable conditions provide the physically possible information, i.e. each individual incident wave determined by field strength, azimuth and elevation.

This object is achieved according to the invention in that a network of automatic field strength sensors (field probes), by means of which the complex field strength is scanned, is designed regularly or statistically over a floor area with the extension A> λ (A = largest wavelength to be received) and that the high-frequency signals picked up by the field probes are evaluated in a central computing device taking into account the respective position of the individual field probes according to amount and phase.

This is used to scan the complex field strength of the interference field on the ground. You get at With a finite number of probes, there is no locally continuous registration of the field strength, but it is not necessary, because it is sufficient for the complete recording of the information obtained in the field strength distribution

take samples at intervals of d <-. Are

the probes are statistically distributed over the ground surface, see above the mean distances can be as large as desired. The uniqueness of the bearing practically suffers as a result not if the total number of probes is sufficiently high (approx. 100).

The information about the direction of incidence is obtained from the local field strength distribution recorded in this way of the individual rays is calculated by two-dimensional Fourier transformation. In the special case of statistical distributed samples is an interpolation of the irregular measuring point grid before the actual Fourier transformation (Probe distribution) on an equidistant computation grid is expedient. It should also be noted that the Fourier transform is not the only possible way to calculate the incident rays.

Since the aperture of the field probe system and the measuring accuracy of the probes are finite, the incident rays cannot be reconstructed as sharply as desired by computational evaluation of the field strength distribution. Rather, the result is that resembles an antenna diagram, with one sharp lobe for each incident beam. The Kculenbreite Atx is with the aperture A in the known manner

l \

,1

connected. Two discrete neighboring rays at a distance of Atx can just be resolved separately. However, if the distance from Atx is large, each individual ray can of course be much more precise than

on ±, be localized by the milel of the lobe is evaluated.

The Fourier transformation between complex local field strength distribution (x, y) and complex beam distribution (»angular spectrum«) F (ö, £) is described by

ff

= ff

/(-V,3'lcxp[-2.7./sin//(.vL-osi

where y - ft is the elevation and ζ is the azimuth.

F (ö, ξ) is a bearing in a broader sense, because it also contains the elevation, from which one can, for example, infer the distance of the transmitter.

A practical embodiment of the field probe direction finding system according to the invention is described below.

The field probes are compact, miniaturized HF receivers for the 1.5–7.5 MHz range. They also contain a simple VHF telemetry transmitter and command receiver for connection to the mobile DF center (truck) in the middle of the probe field. The probes are set up in an area of approximately 1 km or dropped from the air. The shortwave receiving oscillators of all probes are phase-synchronized by the control center in order to enable the field strength phase to be measured. The running time of the commands and the synchronizing signals to the probes and back are taken into account in the evaluation by the computer (Fourier integrator) in the control center. For this purpose before the Peilbetriebes is a Eichpeilung (calibration) - perhaps with the help of an aircraft - necessary, from which the computer ordinates the initially unknown Sondenkoo ^r by reversing the problem and determine appropriate maturities from the known here bearing values.

The bearing evaluation takes place immediately after receipt of the probe data. Provided that there is enough fast special computer is the computing time for a

υ full # -f diagram on the order of magnitude from 1 see. One possibility of executing the Fourier transformation for all # -J points simultaneously in analog is offered a projection device using coherent light, the Fourier transform as optical Process executes.

With the direction finding system according to the invention can be due to its large spatial due to the large aperture Resolution and sensitivity of the bump can also be taken if it is significant

r, is weaker than the sky wave.

Claims (5)

Patent claims: 1. DF system for frequency-selective direction finding of electromagnetic high-frequency oscillations i with regard to the azimuth and elevation with a large number of antennas with downstream receivers, the output signals of which are evaluated, characterized in that a network of automatic field strength sensors (field probes), by means of which the complex field strength is scanned, is designed regularly or statistically over a floor area with the extension A> λ (A = largest wavelength to be received) and that the β high-frequency signals recorded by the field probes are evaluated in a central computing device taking into account the respective position of the individual field probes according to amount and phase. 2. DF system according to claim 1, characterized in that with statistical distribution of the probes the distance between neighboring ones above the ground Probes larger than ^. 3. A direction finding system according to claim 1, characterized marked> ί characterized in that the field probe receiver according to the overlay are ungsprinzip ^r and that the superimposer oscillators tuned away together from a central location and are phase-synchronized. jo 4. DF system according to one or more of claims 1 and 3, characterized in that the Field probes contain command receivers and teleinetry transmitters, with the help of which the field probes matched and the field strength signals picked up by the field probes to the central computing device be dropped off; be discontinued; be deducted; be dismissed. 5. Peilsystem according to claim 1, characterized in that the searched Peiiinformation from the Local field strength distribution recorded by the field probes via a two-dimensional Fourier transformation is determined in the automatic computer.