DE2937007A1 - Radio direction finder with two channels - compares phase of summed offset voltages with phase of reference voltage - Google Patents

Abstract

The direction finder uses two voltages dependant on the reception direction of the electromagnetic waves and as auxiliary voltage independent of the latter. The initial two voltages are phase-shifted by 90 degrees relative to one another and summed, to obtain a compound voltage, compared in phase with the auxiliary voltage to determine the reception direction. The two initial voltages are supplied via respective channels (X,Y), one incorporating a phase-shifter (1) and both coupled to a summing circuit (2), connected to one input of a phase detector (3). This receives the auxiliary voltage at its other input and provides a phase difference signal from which the azimuth angle (4) of the received waves can be directly obtd. This phase difference is also used to adjust a phase-shifter (6) receiving the auxiliary voltage its output used to compensate channel noise.

Description

DF method

The invention relates to a direction finding method for determining the direction of incidence electromagnetic waves from two bearing voltages depending on the direction of incidence and an auxiliary system independent of the direction of incidence.

It is known to use antenna systems for DF methods which in two channels, the so-called bearing channels, information about the direction of incidence contained in the form of two bearing voltages. Often the DF voltages correspond to the sine resp. Cosine directly proportional to the direction of incidence. However, this can be used to determine the direction of incidence can only be set in a range of 1800. The remaining ambiguity is eliminated with the so-called page identifier. Either a third one will do this Auxiliary channel is used or the input signal of a bearing channel is switched to an auxiliary signal switched. The auxiliary signal is not direction-dependent and is often triggered by Summation of all individual antenna signals obtained.

When switching a bearing channel to the auxiliary signal, the During this time, the direction finder will be able to find its bearings.

It would also be possible that a signal occurs only briefly, and the page identification is no longer successful within the signal duration. On the other hand, the effort involved in operating a third channel as an auxiliary channel is considerable and carry out the page identification continuously.

The bearing value is displayed, which is typical for two-channel bearing methods with a cathode ray tube (Watson-Watt display). The bearing value is called the angle of inclination taken from the main axis of an often elliptical figure.

The determination of the bearing value can be done automatically, whereby the ambiguity in 3600 is retained as long as there are no measures for page identification be performed. Signals that come from other directions, but in terms of frequency cannot be sufficiently separated from the signal of interest (co-channel interference), lead to the fact that the automatically determined bearing value between the actual Directions of arrival is shifted. Sometimes, by paying attention to the spread of the Bearing values, an indication of the presence of a co-channel interference can be obtained, so that the incorrect value can be sorted out automatically. However, this is an observation time that exceeds the signal duration may be required.

The problem of co-channel interference can often be avoided by the bandwidth is chosen to be much smaller than the signal bandwidth. Through this the direction information is not changed, but the information content of the The shipment is lost. It is therefore necessary to have a channel with to provide sufficient bandwidth.

For this it is advisable to use the auxiliary channel as a third channel, because the total antenna voltage available here in terms of its amplitude generally exceeds the bearing voltages of the other two channels, thus a greater sensitivity is achieved. However, for reasons of effort usually a third channel can be dispensed with.

The invention is based on the object of a direction finding method of the initially specified type, that with only two channels a side-clear bearing without having to accept the disadvantages associated with switching. In addition, the direction finding method is intended to allow monitoring of the direction-finding signals without loss of sensitivity and be possible without an additional listening channel. The procedure should further be suitable, in a simple and advantageous manner, co-channel interference quickly to recognize and thereby avoid incorrect bearings with an automatic device.

This object is achieved according to the invention in that the two DF output voltages with conventional bearings are phase-shifted by 90 ° with respect to one another and are summed, so that only one cumulative DF channel remains, and by measuring the phase difference between this channel and the auxiliary channel (all-round voltage of the antenna system) the Direction of incidence of an incident wave is determined. In general it is There is not a strict relationship between the difference between the semesters and the direction of incidence linear, so that you can conveniently use a table to determine the bearing values served. What is decisive, however, is that the phase differences in the arrangement according to the invention from Co to 3600 unambiguous bearing values from 0 ° to 3600 can be assigned To the The auxiliary channel superimposed on the cumulative DF channel with adjustable phase and fixed attenuation be that the signal components largely compensate, the compensation practically only succeeds if there is no co-channel interference. The phase is here set to the value that results from the phase difference measurement between the cumulative DF channel and auxiliary room results. A disturbance of the compensation is an indication of co-channel disturbance interpreted.

Furthermore, the auxiliary channel can be equipped with an additional output, the has a suitable bandwidth for listening in.

In order to avoid that the same phase response of the cumulative DF channel and Auxiliary channel must be made by continuously repeated calibration, can both channels modulated in a known manner and / or frequency shifted relative to one another and are superimposed so that they are amplified with only one amplifier, and a phase adjustment can be omitted.

The advantages achieved with the invention are in particular: that with only two in-phase receiving channels a bearing that is unique in 3600 can be done without additional measuring time for performing the conventional Page identifier required for direction finders.

Furthermore, you can listen in with the greatest possible sensitivity in the auxiliary channel what in a conventional DF channel because of the insufficient sensitivity is usually not possible or requires a third channel. The one with conventional The effort required for direction finding for this third channel for listening in is according to the invention avoided.

Co-channel interference and the associated misdirection can automatically can be recognized, which is not possible with conventional direction finders. Will be on detection omitted from co-channel interference, then it is sufficient if the cumulative DF channel and auxiliary channel only have the same phase response, whereas with conventional direction finders the two DF channels must have the same phase and amplitude response.

Based on the figure, the basic structure of a direction finder arrangement is shown below for carrying out the method according to the invention.

After one of the two bearing voltages X or Y has a qOO phase shifter 1 has happened, the two bearing voltages in a summing element 2 become the Summarized DF voltage combined and on one input of a phase detector 3 given. The auxiliary voltage H. Aus is at the other input of the phase detector the measured phase difference ç can be directly the azimuth angle w of the incident Wave to be determined.

The measured phase difference ç can now also be used for setting an adjustable phase shifter 6 can be used to convert the auxiliary voltage shifts the measured value of the phase difference ç. This phase shift can can also be carried out with the opposite sign in the heat sink channel. With interposition an attenuator 5 to compensate for different sensitivity factors When generating the auxiliary voltage and the cumulative DF voltage, the two voltages are superimposed in a further summing element 4. The signal components compensate each other largely in the absence of co-channel interference, so that at the output of the summing element 4 no or only a weak signal can be picked up in such a case.

If, on the other hand, a noticeable signal occurs at the output of this further summer 4 Signal on, this can be an indication of the presence of co-channel interference (Gks) can be interpreted.

The directional finding method, which is unambiguous on the side, is suitable for automatic direction finders because the phase difference measurement can be done digitally and the associated Bearing value can be obtained from a table. It is irrelevant here whether the method with narrowband receivers or so-called (frequency) multi-channel receivers is applied.

Claims (6)

Claims 1. DF method for determining the direction of incidence electromagnetic waves from two bearing voltages depending on the direction of incidence and an auxiliary voltage independent of the direction of incidence, characterized in that that the two bearing voltages shifted from each other by 90 ° in phase and then are summed, so that only a cumulative bearing voltage remains and that through Measurement of the phase difference between this total DF voltage and the auxiliary voltage the direction of incidence is determined. 2. DF method according to claim 1, characterized in that the Phase of total DF voltage or auxiliary voltage around the measured value of the phase difference is shifted so that with preselected damping of the auxiliary voltage, the superimposition of the two voltages results in extensive compensation as long as there is no co-channel interference is present, and that a disturbance of the compensation as an indication co-channel interference is interpreted. 3. DF method according to claim 1 or claim 2, characterized in that that with several selectable bandwidths the auxiliary channel has an additional output at which a suitable bandwidth for listening is always available. 4. DF method according to claim 1 or claim 2, characterized in that that the cumulative DF voltage and the auxiliary voltage against each other in a known manner frequency shifted and / or modulated so that they can be used with only one amplifier are amplified and a phase or amplitude adjustment is avoided. 5. Arrangement for performing the method according to claim 1, characterized by means of a 90 ° phase shifter (1) in the signal path of one of the two DF voltages, by a subsequent summing element (2) for summing the two bearing voltages to a cumulative DF voltage and a phase detector (3) to measure the phase difference between auxiliary voltage and total DF voltage. 6. Arrangement according to claim 5, characterized by a further summing element (4), at one input of which the auxiliary voltage and on via an attenuator (5) whose other input is the total DF voltage, and a controllable one Phase shifter (6), which is set by the phase detector, to one of the both entrances.