DE3131494C2 - Monitoring device for the landing course transmitter of an instrument landing system - Google Patents

Abstract

To monitor the signals (CSB, SBO1, SBO2) emitted by the landing course transmitter (LKS), a course monitor (10) with a dipole (8) and a course width monitor (16) with a dipole (9) are provided in the near field. To compensate for the phase fields present in the near field, a further signal (ΔCSB) is added to the signal (CSB, SB01, SB02) received by the dipole (9) of the course width monitor. This is done in such a way that the resulting signal (CSB *, SBO1 * and SBO2 *) corresponds to a signal that would be received in the far field. The resulting signal is fed to the course width monitor (16).

Description

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The invention is based on a monitoring device as specified in the preamble of claim I. Such a monitoring device is known from the article "Modern Radio Landing Systems" by H. Rausch, Elektronik-Anzeiger, 6th year, 1974, No. 11, pages 223-227.

The instrument landing system ILS is from the International Civil Aviation Organization (ICAO) standardized and introduced worldwide. It is particularly important that the signals emitted - namely the I. Landing course signals and the glide slope signals - adhere to the prescribed values. Only then is it safe Landing possible by evaluating the emitted signals. The signals deviate from the prescribed ones Values, then the alarm is given by the monitoring equipment or the system is switched off.

The signals emitted by the landing course transmitter are monitored, among other things, to determine whether they are the show correct landing course and whether the course width has the prescribed value. A course supervisor is required for this with a Dipc arranged in the landing course level! and a course width monitor with one to the side provided by the landing course level arranged dipole. The angle between the landing course plane and the The straight line between the landing course transmitter and the dipole of the course latitude monitor is about 2.5 °.

In practice, there is an area of approx. 50 m to 150 m in front of the dipoles for setting up the dipoles Landing course transmitter. An installation at a greater distance is because of the required freedom from obstacles not possible. In this area, the near field, the emitted signals do not yet have the relation each other that exists in the far field. This is due to the size of the spatial expansion of the Antenna line of the landing course transmitter and the resulting propagation conditions of the emitted electromagnetic waves.

It is therefore not possible with the two monitoring devices to check whether the emitted signals in the far field abi form correct landing course signals. In the known systems, therefore, additional monitoring, the so-called integral monitoring, is necessary.

It is the object of the invention to design the monitoring device so that it is possible in the To carry out a full monitoring of the landing course signals in the near field.

This object is achieved with the means specified in claim 1. Advantageous further training can be found in the subclaims.

It can already be monitored in the near field whether the emitted landing course signals in the field are their prescribed Will have values without integral monitoring being necessary.

The invention is explained in more detail with reference to the drawings, for example. It shows

F i g. 1 a picture to explain the origin of the phase errors present in the near field.

2 shows a qualitative representation of the phases and amplitudes of the emitted by the landing course transmitter Signals,

3 to 5 phasor diagrams to explain the Phase relationships between the signal, which consists of carrier and sideband signals, and the Signals that consist only of sideband signals, and

6 is a block diagram of the new monitoring device.

For horizontal guidance of the landing aircraft, signals are emitted from antennas 2 of the antenna line of a landing course transmitter LKS via two mirror-image modulation degree direction diagrams whose intersection line (same degree of modulation) defines the landing course plane LK. The course of the difference in the degrees of modulation (DDM) is for the range ± 2.5 ° on both sides of the landing course level. LK prescribed linearly and precisely. There is a direct relationship between the DDM and the angular deviation from the landing course level. It must be monitored whether the DDM has the value assigned to this direction in a certain direction (course width monitoring

chung),

Landing course transmitters and how they work are generally known (?, B, from the mentioned reference Ie) and are therefore not explained in more detail here. It is only used to better understand the following Description pointed out that from a landing course transmitter several signals via different Directional diagrams are emitted. The signals are

10

- Signals (SBOi, SBO2) that only consist of sideband signals, hereinafter referred to as SSO signals,

- Signals (CSB), which consists of carrier and sideband signals, hereinafter referred to as CSS signal.

In FIG. 1, the antenna line of the landing course transmitter LKS consists of twelve antennas 2 (I to XII). The field strengths and the relative phases of the signals emitted by the antennas 2 are shown qualitatively in FIG. It can be seen that the field is stronger! the signals emitted by the external antennas are less than the field strengths of the ve; signals emitted by the central antennas. This applies to both the SBO and the CSS signal. The SSO signals are radiated out of phase by the two halves of the antenna. The phases of the CSS signals are phase shifted by ± 90 ° with respect to the phases of the SSO signals.

In the landing course level, the components of the SBO ! Signal and the SSO2 signal, which are emitted by the left and right halves of the antenna row, cancel each other out, while the components of the CSS signal can be received on this level. To the side of the landing course level LK , the paths SI to S X11 from the antennas 2 to an observer (dipole 1) are different. For an observer in the far field, the path difference to the outer antennas I, XII is 2AS. The differences in the path lead to phase shifts in the components emitted by the individual antennas.

In the far field is the wave front 4 of the electromagnetic waves emitted by the antenna array completely flat, while the wavefront 5 in the near field, z. B. in the area of the dipole 1, is still distorted. This is due to the asymmetrical distribution of the route differences. For landing i; ur signals are sent in The far field is exploited and therefore the distortion in the near field is irrelevant for the purposes of landing. However, it causes difficulties in terms of monitoring, which, as already mentioned, is in the near field should be carried out.

How the components for the signals CSB and SBO are put together in the far field is shown in FIGS. 3a and 3b shown. The rotation of the phases of the individual components compared to the illustration in FIG. 2 is due to the path differences. There is a symmetrical phase rotation with respect to the landing course plane. The phase rotations assumed in the illustration in FIG. 3 apply to a direction (“course width”) in which the DDM is 15.5%.

If the signal is transmitted correctly, the SSO signals must be in phase or in phase opposition to the CSS signal his (Fig. 3c).

If the dipole 1, which receives the signals emitted by the antennas 2 of the landing course transmitter LKS , is at a distance in front of the antennas 2 of, for example, 50 m, then the connecting lines between the dipole 1 and the antennas 2, in contrast to the conditions in the far field, are not more parallel (Fig. I). There is therefore no continuous change in the path lengths (S \, SII, .. “SXII) from dipole 1 to antennas 2.

If the components received from dipole 1 are reassembled as in FIG. 3 in such a way that the CSB and SSO signals are obtained, then one arrives at the vectors shown in FIG. The vector CSB is shown in FIG. 4a and the vector SBO is shown in FIG. 4b.

Because of the distortion of the wavefront (5, FIG. I) in the near field, the signals SBO1 and SSO 2 are no longer in antiphase or in phase with the signal CSB (FIG. 4c). (M at a distance of 150 and a transmitting antenna width of "25 m of 17.5 °) by the phase error is now not actually present in the far field DDM = 15.5%, but a dDMA measured in this direction 14.5% . The course width monitor would display a false »-se an error. It is also possible that if the emitted signals do not comply with the prescribed values, a DDM of 15.5%, which does not actually exist in the far field, is displayed, ie the interference is not recognized.

The signal received by dipole 1 is therefore not suitable for course width monitoring in the known device.

This disadvantage is no longer present with the new monitoring device. Add another signal to the signal received from the dipole of the course width monitor (CSB, SBO 1, SBO 2)! 4CSS so that in the resulting signal the signals SBOV or SBO 2 * are again in phase opposition to or in phase with the CSB * signal. Course width monitoring is then possible in the near field as in the far field. If far-field monitoring is not possible, no further monitoring devices are required for the course width, such as integral monitoring.

The ACSB signal to be added can be obtained by exploring part of the signal received by the course supervisor's dipole.

Setting the correct amplitude and phase can also be done in different ways. A The exemplary embodiment is described below with reference to FIG. 6 described. After knowing this exemplary embodiment and the principle on which it is based, the skilled person can also implement other solutions.

In FIG. 6, the landing course transmitter LKS, the antennas 2 of the antenna line of the landing course transmitter and the landing course LK are shown. For monitoring the radiated from the dipole to be L.indekurssignale 8 of the Ku ^ri 5überwachers 10 in the plane and receiving the localizer course width observer 16 from the dipole. 9

The dipole 9 is arranged, for example, in a direction offset by 2 5 ° from the landing course plane. at the known monitoring device, the signals received by the dipoles 8 and 9 are direct the course supervisor 1O or the course width supervisor 16 supplied. Course Supervisor and Course Width Supervisor are known from the literature cited in the introduction to the description and are therefore not explained in detail.

From the signal received by the dipole 8 of the course supervisor, which is the CSS signal, a part ACSB is decoupled in a directional coupler 11 and fed to an input of a 3 dB coupler 15. That

The signal received by the dipole 9 of the course width monitor is fed to the further input of the 3 dB coupler 15 via an adjustable attenuator 12 and an adjustable phase shifter 13. One output of the 3 dB coupler is terminated with a resistor 14. The desired sum signal CSB *, SBOi *, SBO V, in which the phase error present in the near field is compensated, is passed from the other output to the heading width monitor 16.

To set the correct phase shift and damping in the attenuator 12 and the Phase shifter 13 proceeds as described below.

When the landing course transmitter LKS is put into operation, it is measured, ie it is checked whether the emitted signals have the prescribed values. For this purpose, measurements in the far field are carried out, among other things.

If the emitted signals have exactly the prescribed values, a phase shifter (eg a "90 ° line") is inserted into the lead from the transmitter to the antenna line with antenna 2 in the landing course transmitter, which creates a phase shift of 90 °. The adjustable phase shifter 13 and the adjustable attenuator 12 are then set so that a DDM equal to 0 is measured in the course width monitor 16. Once this has been achieved, it is ensured that the phase relationship between SBO and CSB is also correct for the near field. Now the phase shifter in the landing course transmitter is removed again and a check is made to see which DDM is displayed in the course width monitor 16. If this does not have the prescribed value of f \ 5%, then the attenuation in 12 and the phase shift in 13 are changed until the value 15.5% is reached. The phase shifter is now inserted again in the heading transmitter and a check is made to determine whether the DDM = O is displayed again in the heading width monitor. If this is not yet the case, readjustment then takes place again. This continues until the course broadcaster shows a DDM of 0% and 15.5%, depending on whether the 90 ° phase shift takes place in the landing course transmitter or not.

If this is fulfilled, then there is no far-field monitoring more necessary. If the landing course transmitter needs to be measured again during further operation the new monitoring device can be used for this purpose. It's not an additional one Far field measurement necessary.

The necessary phase relationship and the amplitude ratio of the signals to be added to each other (CSB, SBOi, SBO2 and ACSB) can also be set by determining the distance between the dipole 9 and the antennas 2 (phase setting) and the height of this dipole 9 above the ground (Amplitude setting) varies.

By adding another CSS signal (Δ CSB) , the phase of the CStf signal is rotated with respect to the SSO signals so that the resulting CSO signal (CSB *) is in phase or in phase opposition to the SBO2 * - or SBOi 'signal. This is shown in FIG. 5. The fact that the phases of the SSO signals are also rotated in the exemplary embodiment according to FIG. 6 is irrelevant, since only the phase relationship between the CSS signal and the SSO signals is important.

While in the known monitoring devices through the existing near field phase error rotations of the phases of the SBO I and SBO were 2 signals against the CSS signal possible, the first with phase changes a DDM showed increase for the course width monitor and another phase rotation (around the double value) led back to the old DDM value, there is now a lowering of the DDM for all phase errors as in the far field.

In addition 6 sheets of drawings

Claims (4)

Patent claims: I. Monitoring device for the landing course transmitter (LKS) of an instrument loading system, from which signals (SBO 1, SBO 2), which only consist of sideband signals, and a signal (CSB), which consists of carrier and sideband signals, are emitted with two im Dipoles (8, 9) set up in the vicinity of the landing course transmitter, one of which is arranged in the landing course level (LK) and the other to the side of the landing course level, and with receiving and evaluation devices (10, 16) for the signals received from the dipoles, characterized in that a device (15) is provided in which an additional signal (ACSB) from the received signal (CSB, SBO 1, SBO 2) to the signal (CSB, SBO 1, SBO 2) received from the side of the landing course level (LK) Carrier and sideband signals is added so that the resulting signal (CSB *, SBOV, SBO2 *) corresponds to a Signa! corresponds to that would be received by the dipole (9) if it were not set up in the near field, but in the far field of the landing course transmitter (LKS) . 2. Monitoring device according to claim 1, characterized in that the additional signal (A CSB) is part of the received signal from the dipole (8) arranged in the landing course level (LK). jo 3. Monitoring device according to claim 1 or 2, characterized in that the phase and the amplitude of the dipole (9) arranged to the side of the landing course level (LK ) received signal (CSB, SBO 1, SBO2) by the combination with J5 the additional signal ( ACSB) can be changed in such a way that in the resulting signal the phase of the signal (CSB *), which consists of carrier and sideband signals, has the correct relationship to the phases of the signals (SBOi *. W SBO 2 *), which only consist of sideband signals. 4. Monitoring device according to claim 2, characterized in that the relative spatial position of the two dipoles (8, 9) to each other and the degree of decoupling when decoupling part of the signal (CSB) received from the dipole arranged in the landing course level are selected so that in the resulting signal, the phase of the signal (CSB *), which consists of carrier and sideband signals, has the correct relationship to the phases of the signals (SBOi *, SBO2 *), which only consist of sideband signals.