DE1222130B - Antenna system intended for use in a microwave Doppler back beam measuring device for determining speed and drift on board aircraft - Google Patents

Description

For use with a microwave Doppler retroreflective meter for Determination of speed and drift on board aircraft certain Antenna system The invention relates to an antenna system for use in a microwave Doppler retroreflective device is intended and for the determination of Speed. And drift on board aircraft is used. Such an antenna system known design consists of parallel slotted waveguides. which serve to alternately generate first and second pairs of beams, the one ray in each pair of rays forward and down to the ground and the other Ray is directed backwards and downwards towards the ground and the rays of the two Pairs are twisted aecimuthally in opposite directions.

Such antenna arrangements, which are preferably horizontal in the Longitudinal mounted in an aircraft are used for both sending as well used for reception.

In order to simplify the terminology is used in the description below only referred to the emission of rays. Which is the subject of the invention Forming antennas can, however, be used for both reception and transmission will.

One purpose of the present invention is directed to providing an embodiment to create a composite antenna arrangement through which the required two pairs of beams without any mechanical switching of reflectors and without any limitation of the azimuthal rotation angle can be generated.

According to the invention, the slotted waveguides of the antenna system arranged in two sets, each set a number of parallel, in one Level of adjacent rows includes, in addition to a feed line for each set, which feeds all rows of the set. Here are the rows of the one sentence arranged in the mentioned plane alternating with the rows of the other set, and at the same time switching means are provided that the relative phases of the different slots supplied or received from these vibrations for the purpose Switching from one to the other pair of beams by changing the two Feed lines alternate with one or the other end parallel to the Transceiver can be connected.

The length of the rows and the number of rows in each set will be determined by the required angular widths of the beams. The second pair of rays is used when using the same antenna arrangement by switching the feed device generated so that the transverse feed line alternates for each set of rows fed from opposite ends.

Two different forms of antenna design are already known.

One design has four separate linear antenna systems provided in the form of four waveguides horizontally in the longitudinal direction of the aircraft, wherein the four antenna systems are arranged such that their beams in the necessary directions. In the other embodiment, two are linear Antenna systems are used, one of which is forward-facing and the other others produce a backward beam. Each of the antenna systems is provided with a mechanically adjustable reflector, which serves to guide the beam deflect to either the port or the starboard side, the two being Reflectors are coupled and designed such that when the forward-facing Beam is deflected to port, the aft beam is deflected to starboard distracted, and vice versa.

It is still known that instead of a single dipole series, several Arrange parallel dipole rows as well as the beam angle by controlling the to change relative meal phases. Electric rod dipoles are known to be waveguide slots equivalent to.

The switching of the radiation direction is also known Switchover of the feed a row of slots from one end the other end.

A. Advantage of the inventive design of an antenna system Compared to one of the earlier arrangements, it results from the omission of all mechanically moving parts except switches. This is essential for aircraft antennas, as this enables the antenna to be built into the aircraft surface. If there are mechanically moving parts, the system must be inside the aircraft be installed and in this way not only takes up more space, but also makes it more difficult also the achievement of intensive and exact measurement signals.

Because in some known arrangements there are separate receiving and transmitting antennas are used, the surface area of the system is significantly larger than that of the invention Layout. The use of baffles also means that the depth of the antenna system compared to the arrangement according to the invention is significantly larger.

The antenna system must expediently be on the underside of the aircraft be attached in an opening provided in the outer skin of the same. As a result the much smaller dimensions of this opening required for the attachment of the invention Plant is required, becomes a significant advance in terms of space utilization and mechanical stability when installed in aircraft achieved due to the known antenna arrangement was not to be expected without further ado.

The smaller area and reduced depth of the invention according to the invention Antenna installation is mainly achieved by using a number of parallel, nested ones Rows of radiation slits that are used to generate each pair of beams are obtained. When using the arrangement according to the invention, in which the emitting waveguide actually extend over the entire required radiation aperture is it is no longer necessary to provide baffles. Furthermore, it will be because the different Waveguides must be spaced apart, allows the separated To interleave waveguide of two radiator arrangements so that two antenna arrangements into the same opening as is otherwise required for a single antenna arrangement can be inserted. It is thus possible in the area that is used for Generation of the necessary narrow beam widths required is two independent To incorporate antenna arrays that produce two beams, which are independent of each other can be controlled with respect to their respective directions. It is then by attaching switching means to change the relative phases of the signals possible to cause each of the nested antenna assemblies to it produces rays in two alternating directions; thus it is possible to use the required two pairs of alternating beams. with a very small one To obtain antenna arrangement.

Each row of slots can pass through a rectangular waveguide. educated be, .wherein the slots on one side of the waveguide, and expediently at a narrow side of the waveguide are formed.

The azimuthal twist angle β for each set is given by the following expression - provided that the rows of each set are not fed in phase, which is necessary for the smallest azimuthal twist angle: whereby . the wavelength of the signals means, I, g represents the conductor wavelength in the feed line, s denotes the effective distance between the couplings and the feed line.

The feeds to the various rows are preferably in phase brought to generate azimuthal twist angles of the same size. To the two azimuthal Twist angle is the same. can train the guide wavelengths and the effective ones Distances for those located along the transverse feed line, the two Sets feeding points are chosen according to the above equation so that values of the angle, 8 are of the same size, but with opposite signs result. This can be done by a suitable choice of the conductor wavelengths or the distance or both factors can be effected. It can e.g. B. the two azimuthal The angle of rotation for the two sets of rows is thus made the same size, that one uses feed lines with different cross-sections, whereby different conductor wavelengths for the two transverse feed lines result; the spacing of the rows for the two sets made the same will. According to another embodiment, the azimuthal angles of rotation for the two sets of rows are made the same size by using different Distances are used for the feed points assigned to the two series sets, the along the transverse feed line and the rows in each set Food.

In a practical embodiment of an antenna system according to the invention can alternating rows of each set of the slotted waveguides are fed in antiphase will. It can also each radiating waveguide at one end with the associated be coupled transversely running feed line.

The switching means can in a simplified manner from a single Switch for switching the feeds to the two separate, transverse ones Feed lines exist.

The antenna system can be arranged in an aircraft in such a way that that the rows of slots form lines extending in the longitudinal direction of the aircraft extend, with all radiation slots extending in a substantially horizontal Plane when the aircraft is in a normal attitude. It can be a stabilizing device be provided, which serves to increase the antenna system in the horizontal plane stabilize or partially, e.g. B. in the slope plane to stabilize.

In the following description, reference is made to the drawings will.

F i g. 1 is an explanatory diagram; F i g. 2 is a scheme, which a form of an antenna system for a. Doppler rear view measuring device illustrates; F i g. 3 is a diagram showing a circuit arrangement for use in the antenna system according to FIG. 2 illustrates; F i g. 4 is a perspective view from the bottom of an embodiment of the antenna system according to FIG. 2, with individual parts omitted; F i g. 5 is a plan view from the upper part of part of the antenna system according to FIG. 4th

According to FIG. 1, an explanatory diagram shows the shape of the radiation pattern that is required in a Doppler rear view measuring device to determine the airspeed in relation to the ground and the drift of an aircraft. An aircraft is shown diagrammatically at 10 ; and the point O represents a point on the ground vertically below the aircraft. This point is on the course of the aircraft, which is indicated by the line XX. 0Y is a perpendicular to the line X-X through point 0 on the earth's surface. The antenna system must generate four directional beams, the intersection points of which with the earth's surface are shown at 11, 12, 13 and 14. For the sake of simplicity, these four rays will hereinafter be referred to as rays 11, 12, 13 and 14, respectively. It can be seen that beam 11 is directed forward on the port side, beam 12 is directed rearward on the starboard side, beam 13 is directed forward on the starboard side and beam 14 is directed rearward on the port side. The beams 11 and 12 are to be used at the same time, as are beams 13 and 14. The beams 11 and 12, however, are not required at the same time as the beams 13 and 14. A switching system is therefore used so that the beams at alternating time intervals 11 and 12 and then beams 13 and 14 are broadcast simultaneously.

It is to be understood, as already mentioned, that the antenna system both could be used to receive as well as transmit, although for the sake of simplicity in the following description in particular with reference to the emission of rays should be taken.

According to FIG. 2 two composite antenna arrangements are shown which consist of a number of waveguides with radiation slots. The waveguides which form one of the antenna arrangements provided with radiation slots are interleaved with the waveguides which form the other antenna arrangement, ie the waveguides which form the two antenna arrangements are arranged alternately in the same plane. One of the antenna arrangements is formed from waveguides 61 to 66 and the other from waveguides 71 to 76. These waveguides are shown in FIG. 2 is shown diagrammatically by lines, while the radiation slots are shown in the form of short lines extending obliquely over the waveguide. Each of the conductors 61 to 66 has slots which all radiate in phase, as indicated by the similar inclination of the slashes representing the slots, while the conductors 71 to 76 have radiation slots; every other slot of which broadcasts in antiphase; as indicated schematically by the opposite inclination of the alternating slots. Assuming that a single conductor of the waveguides 71 to 76 lies in the longitudinal direction of the aircraft, with the radiation slots pointing downwards, and that this waveguide is fed from one end, it emits a beam which goes in one direction in the longitudinal plane, which is dependent on the slot spacing and the guide wavelength, the angular deflection starting from the vertical is given by the following equation: Where O is the angle of depression of the axis of the beam from the horizontal, A is the wavelength of the signals, Agt is the guide wavelength in the slotted waveguide, s' is the distance between the slots along the guide, n = 0, ± 1, ± 2, etc.

If the spacing of the slots is such that only n = 0 gives a solution, then there is only one principal ray and For the waveguides 61 to 66 with the radiation slots brought into phase, the depression angle 0 is given by the following formula: and if there should only be one ray, is It can thus be seen that when the slot spacing in the two sets of waveguides is equal to a quarter of a waveguide wavelength, the two beams appear at equal and opposite dip angles; in other words, one beam is directed forward and the other is directed backward. According to the embodiment of the present invention, each of the antenna assemblies consists of a series of waveguides arranged in parallel rows which extend in the longitudinal direction of the aircraft. By feeding these conductors into an appropriate phase relationship, the beams are directed to one side or the other of the longitudinal plane passing through the aircraft. The angular deflection to the side of the vertical plane is referred to as the azimuthal twist angle. When the forward beam is deflected to port, that is, to form beam 11, reversing the phase relationship of the feeds to the conductors producing that beam will deflect the beam to starboard, thus creating beam 13. These transverse deflections are called azimuthal Angle of twist β in FIG. 1 shown. The azimuthal twist angles are dependent on the relative phases of the "feeds" going to the different rows and thus also on the distance between the feeders going to the different rows along the transverse feed lines and the conductor wavelength along this line. In order to obtain the smallest azimuthal twist angle , the different rows must not be fed in phase, that is, alternating rows are fed in antiphase; and the azimuthal twist angle ß is given by the following formula: where .1g is the conductor wavelength in the feed line and s is the effective spacing of the couplings to the various rows along the feed line.

.. It can be seen that this azimuthal angle of rotation is dependent on the conductor wavelength and the distance between the couplings leading to the rows. In order to generate azimuthal angles of rotation of the same size on both sides of the vertical plane for the two beams emanating from the two sets of rows, the rows must be fed in a suitable phase relationship. All rows of the two sets could optionally be fed by a single transverse feed line; and the distances of the rows 61 to 66 could be kept smaller than the distances of the rows 71 to 76, so that the azimuthal angle of rotation β is positive for one set and negative for the other set. In order to achieve the required switching of the beams for the purpose of generating the four beams - as explained above ^, this can run transversely. . Feed line from both ends by means of a switch. are fed, which alternately connects each of the two ends of the line to the transmitter and receiver of the Doppler retroreflective device. However, in order to ensure an even distribution of the energy emanating from the transmitter between the two sets of rows 61 to 66 and 71 to 76, these two sets of rows are preferably provided with separate, transverse feed lines 80, 81 -, as shown in FIG. 2 illustrates .- powered. The transmitter and receiver of the Doppler retroreflective measuring device, which is indicated schematically at 82, can be alternately connected to one or the other of two energy distributors 83, 84 by means of a switch 85, which connect the output power of the transmitter between the two transverse feed lines 80, 81 to distribute. These energy distributors also serve to combine the received signals in order to feed them through the switch 85 to the receiver. In this arrangement, the lines 80, 81 can have different cross-sections, so that the required azimuthal angles of rotation are obtained, if desired, with similar spacings for the rows 61 to 66 and the rows 71 to 76. Switch 85 enables the phase relationship of the various rows to be reversed; and thus - provided that in each set the conductance values of the couplings from the transverse feed line to the various rows are symmetrical - by switching the feed from one end of the feed line to the other, the azimuthal twist angle is obtained without changing the angular width of the beam or the depression angle vice versa. The different rows end with bogus charges. The slots are formed on the narrow sides i of the waveguide and are directed downwards when the aircraft in which the antenna arrangement is installed is in a normal flight position. All radiation slots are thus in a horizontal plane. The waveguides can be mounted on a suitable support plate 88 (FIG. 4), e.g. B. an aluminum plate of cellular structure attached.

F i g. Figure 4 is an isometric view from the bottom of one embodiment the antenna system according to FIG. 2. From FIG. 4 emerges; that the emanating Waveguides forming the slot arrangement include rectangular waveguides in which the slots are attached to the narrow sides. According to the drawing, each contains of the conductor sets forming an antenna array radiating slots eight waveguides. As in Fig. 4, the waveguides of one set 71 to 76, illustrated in the drawing by conductors 71, 72, slots that do not radiate in phase while the waveguides of the other set, e.g. B. the Conductors 61, 62 are provided with slots radiating in phase. The waveguide 71 to 76 are separated from the transverse feed line by right-angled coupling conductors 81 and waveguides 61-66 similarly from the transverse feed line 80 fed. The leads to the conductors 71 to 76 are not brought into phase, as well as the leads to the conductors 61 to 66. The coupling conductance for each Set are designed symmetrically so that the azimuthal twisting angle through Switching of the connections to the ends of the feed lines 80, 81 can be reversed can be used without changing the beam widths or depression angles. The energy distributors 83, 84 and the switch 85 (FIG. 2) are in one on the upper part of the antenna system located unit 86, as in F i g. 5 shown with an input conductor 87 for connection to the transmitter and receiver of the navigation system is.

In order to feed the various waveguides 61 to 66, the input conductor 80 feeds a rectangular conductor 55 in the unit 86 by means of right-angled bends. Another rectangular conductor 56, which feeds the input conductor 81 , is arranged adjacent to the conductor 55 and extends parallel to it. These two conductors 55, 56 have coupling slots that go from one to the other to form 3-dB directional couplers, as in FIG. 3 is illustrated in detail. In Fig. 3, each of the four rectangles 48, 49, 50 and 51 represents a 3 db directional coupler. The numerals 1, 2, 3 and 4 are used to identify the various arms of the coupler, the designations being taken to mean each signal introduced into the first arm is shared equally between the second and third arms. The first and fourth arms are decoupled from one another, as are the second and third arms. The input conductor 45 is connected to the first arm of the 3-db directional coupler 49 so that the input signal is evenly distributed between the second and third arms of the coupler 49. In the output lines of the second and third arms of the coupler 49, a switch is arranged, which is indicated schematically by a transverse dashed line 52 and which can be operated to put either a short circuit or an open circuit across the two conductors. Assuming the switch is in the open circuit, all of the power from the transmitter is shared between the second and third arms of coupler 49, these arms being connected to the first and fourth arms of coupler 50 so that all of the Energy is dissipated through the third arm of the coupler 50 . This arm is connected to the fourth arm of the coupler 51, so that the input signal applied thereto is divided equally between the second and third arms. These two arms are coupled to the conductors 55, 56 by bends 53 and 54 in the E-plane. When switch 52 shorts out the third and second arms of coupler 49, all input energy from the transmitter is reflected back into the fourth arm, which is connected to the third arm of coupler 48. The signals introduced into the third arm of the coupler 48 are shared equally between the first and fourth arms which are connected to the second ends of the aforementioned conductors 55, 56 by bends (in the E-plane) 57 and 58, respectively. It can thus be seen that by changing the setting of the switch 52, the transverse conductors 55, 56 and thus the feed conductors 80, 81 can be fed from both ends.

The switch 52 can be used as a mechanical switch, e.g. B. as a piston or wing switch, be formed in the waveguide; or it can be an electric Switch, e.g. B. a ferrite device can be provided by an electrical Signal can be controlled in such a way that, depending on the requirements, open circuits or short-circuit circuits be generated.

The conductors 61 through 66 and the conductors 71 through 76 do not become in phase fed, d. i.e. every other conductor is fed in phase opposition to enable that a small azimuthal twist angle is obtained. Doing so will be the distance the conductors 61 to 66 and the conductors 71 to 76 and the cross sections of the feed lines 80, 81 - as explained above - selected in such a way that the azimuthal angles of rotation same size but opposite signs. The guiding values of the zu the conductors 61 to 66 leading couplings of the feed line 80 and to the Couplings of the feed line 81 going through conductors 71 to 76 become symmetrical in this way formed that by changing the setting of the switch 52, the phase relationship of the leads to the different conductors in each set for the purpose of switching the Beams is reversed, neither changing the beam widths nor the depression angles will.

If the feed lines 80, 81 are fed from the coupler 51, goes all available idle energy that is passed through the feeder lines and flows out from the distal end, into the first and fourth arms of the coupler 48, whereupon between the second and third Arne of this coupler is distributed. A load 59 is connected to the second arm of this coupler, to absorb the energy supplied to that arm while all in the third Arm conducted energy is absorbed in a load 60 associated with the second Arm of the coupler 50 is connected. In the same way, if the feed lines 55, 56 are fed from the coupler 48, any idle energy that may be present, those from the far end of the feed lines into the coupler 51 flows, half absorbed in a load 61, which is with the first arm of the Coupler 51 is connected. Due to the fact that the switch 52 is on short circuit is set, the other half is absorbed in the load 60.

When looking at the system in the receiving position, it becomes clear that, when switch 52 is set to open circuit, all received and signals fed to the fourth arm of the coupler 51 without loss in the input conductor 45 go and that - if the switch 52 is set to short circuit the signals received and applied to the third arm of the coupler 48 without loss pass into the entrance ladder 45.

The antenna system according to FIG. 2 through 5 will be like this in an airplane built in that the rows of radiation slots are in the longitudinal direction of the aircraft and extend in a horizontal plane when the aircraft is in a normal attitude occupies. The antenna system can be stabilized if necessary, namely either only in the slope plane, or it can also be completely stabilized. It can be seen that, through the arrangements explained above, particularly compact, Space-saving and material-saving antenna systems are created, in which none are mechanically movable reflectors are present and whereby sharply directed beams are generated will. It is also pointed out in particular that the azimuthal angles of rotation can be kept as small as it seems desirable.

Claims (5)

Claims: 1. For use in a microwave Doppler retroreflective meter for determining the speed and drift on board aircraft Antenna system, consisting of parallel slotted waveguides, which serve to alternately generate first and second pairs of beams, the one ray in each pair of rays forward and down to the ground and the other Ray is directed backwards and downwards towards the ground and the rays of the two Pairs are azimuthally twisted in opposite directions, d a - characterized by, that the slotted waveguides are arranged in two sets, each of which Set comprises a number of parallel rows lying next to one another in a plane in addition to a feed line for each set, which feeds all rows of the set, and the rows of the one set in the mentioned plane alternate with the rows of the other set are arranged, and that switching means are provided at the same time which indicate the relative phases of the or of these received vibrations for the purpose of switching from one to the other Change the pair of beams in that the two feed lines alternate with each other one or the other end can be connected in parallel to the transceiver. 2. Antenna system according to claim 1, characterized in that alternating rows of each sentence are fed in phase opposition. 3. Antenna system according to claim 1 or 2, characterized in that each radiating waveguide at one end with the associated transverse feed line is coupled. 4th Antenna system according to one of Claims 1 to 3, characterized in that the Feeds to the various rows are phased so that they are the same Generate large azimuthal angles of rotation, for which purpose the feed lines differ Have cross-section so that there are different guide wavelengths for the two transverse feed lines result, the spacing of the rows in each of the two sentences is the same. 5. Antenna system according to one of claims 1 to 4, characterized in that the switching means consists of a single switch for Switching the supplies to the two separate transverse feed lines exist. Documents considered: German Patent No. 809 568; German patent application B 8688 VIII a / 21 a4, 48/63 (published May 26, 1954); British Patent Nos. 589136, 669,463; U.S. Patent No. 2,426,228; H.-7., Fischer, Radartechnik, Leipzig 1956, pp.174 to 205; Flight and Aircraft Engineer, 72 (1957), 2529 (July 12), pp. 41/42.