Communications: directive radio wave systems and devices (e.g. – Directive – Beacon or receiver
Patent
1986-09-29
1988-06-28
Blum, Theodore M.
Communications: directive radio wave systems and devices (e.g.,
Directive
Beacon or receiver
342432, 342443, 342444, G01S 502, G01S 504
Patent
active
047542810
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a direction finder operating according to the Watson-Watt principle, wherein the antenna signals of two crossed directional antenna systems, which are both additively and subtractively superimposed upon one another, are conducted to at least one additional single channel receiver and the thus-superimposed signals, after amplitude demodulation, are employed as internally produced vector signals for phase adjustment.
From West German Pat. No. 2,757,791 there is known a phase regulation with phase shifting present at the antenna side between the X and Y direction antenna signals with the help of a signal derived from the superimposed directional antenna signals. With this, however, there is not produced in the receiver itself any further phase shifting, since only a single receiver is employed to which the antenna signals of the two crossed directional antenna systems are conducted cyclically.
In taking the bearing of an electromagnetic wave with a Watson-Watt direction finder there are obtained for evaluation two bearing signals having amplitudes that are respectively proportional to the sine and to the cosine of the angle of incidence of the wave. On the screen of the cathode ray tube of such a direction finder there appears, as a direction display, a line inclined to the vertical at the angle of incidence, provided the sender from which direction is to be determined is ideally received.
However, when several waves with different angles of incidence and phase positions arrive simultaneously at the direction finding location, not just one line is formed but instead there is produced an elliptical display figure, the elliptical dispersion of which is determined by the phase differences arising at the antenna side from reflections arriving from different directions of the incident waves of the corresponding transmitters.
Also, phase differences between the two amplification channels of a double-channel direction finder operating according to the Watson-Watt principle are manifested as an elliptical dispersion of the direction lines, and they thus bring about directional errors.
There is known from West German published patent application No. 2,432,905 a direction finder operating according to the Watson-Watt principle with the employment of only one receiver to which the antenna voltages of two crossed directional antenna systems are cyclically conducted in time multiplex and the output signals from which are divided between individual processing channels according to their antenna correlations. By means of such a single channel direction finder receiver the direction display can be obtained with the information quality of a double or triple channel direction finder receiver.
The quality of single channel direction finder receivers of the present state of the art can be considered to be so high that differences in degree of amplification for any given value and phase, as between different receivers of the same type, are held within limits of interchangeability. From this there arises the possibility of employing, instead of a high quality double channel receiver, two like, simple single receivers to which the output signals of the directional antenna system are conducted.
For all that, however, it happens that the alternating antenna voltages to be measured undergo different phase displacements in passage through the individual receivers, so that the output voltages of the receivers produce an elliptical dispersion on the screen of the cathode ray tube.
For determination of the amplitude relationships of two alternating voltages conducted from the antenna system, while measuring their phase differences, it is known from West German published patent application No. 1,616,540 to sum the two voltages whereof the amplitude relationship is to be formed, or to subtract them from one another, and to conduct them, together with the sum or difference voltage, to a phase measurement device wherein two phase differences between the three conducted voltages are measured. From this reference it is
REFERENCES:
patent: 4198633 (1980-04-01), Krajewski
Blum Theodore M.
Issing Gregory C.
Kirby Thomas F.
Nilles James E.
Wachtler GmbH
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