AU659019B2

AU659019B2 - XPD-optimised multi-mode angle diversity exciter

Info

Publication number: AU659019B2
Application number: AU41516/93A
Authority: AU
Inventors: Eberhard Tauscheck
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1992-06-26
Filing date: 1993-06-25
Publication date: 1995-05-04
Anticipated expiration: 2013-06-25
Also published as: DE59305840D1; BR9302665A; AU4151693A; EP0575788B1; EP0575788A1

Description

659019

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

S F Ref: 236340 Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Siemens Aktiengesellschaft Wittelsbacherplatz 2 8000 Muenchen

GERMANY

Eberhard Tauscheck Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia XPD-Optimised Multi-Mode Angle Diversity Exciter The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845/3 1 XPD-optimised multi-mode angle diversity exciter The invention relates to an XPD-optimised dualpolarisation wide-band angle diversity exciter in accordance with the multi-mode principle, comprising a square horn with transition to rectangular waveguide and a multi-ype- waveguide branch with a rectangular waveguide and two square waveguides separated from one another by a separating web.

The multi-mode principle of the arrangement is known for measuring the sum and difference patterns in radar engineering (compare also the Radar Manual by Skolnik, 1970 Mc Graw-Hill, Inc.). In the report "Doublereflector shell-type antenna for angle diversity operation in two orthogonal polarisations" by G. M6rz, K.-H.

Mierzwiak, U. Mahr, published in the ITG Technical Report on Antennas 1990 Wiesbaden, VDE-Verlag Berlin, pages 205 to 209, for example, an application for angle diversity antennas is specified. In this report, a shell-type antenna with feed system is described which is suitable for angle-diversity operation of radio relay links and which, apart from the dual linearly polarised sum lobes, also has two also dual linearly polarised diversity lobes o which are generated with the aid of higher waveguide modes in the feed system. The principle is based on a corrective effect of a central pin in the area of the zone of excitation of a rectangular multi-mode exciter.

In this arrangement, the cut-off frequencies are changed which allows an adjustment to improve the H 11

E

1 mixing with respect to the linearly polarised hybrid mode.

The reliability of transmission of radio relay links with interfering multi-path propagation can be effectively improved by using angle-diversity antennas in accordance with the sum/difference pattern principle. In this arrangement, the usual dual-polarisation exciter of a reflector antenna is replaced by an angle diversity e- exciter which simultaneously outputs two received signals -2picked up with different pattern characteristics for each polarisation.

Figure 1 shows the basic circuit of angle diversity with combiner.

The exciter 1 of an antenna arrangement exhibiting a main reflector 2 and a sub-reflector 3 has vertical polarisation terminals (sum output V s and difference output V

D

and horizontal polarisation terminals (sum output HS and difference output HD). The outputs V S and HS correspond to the terminals of a usual dual-polarisation radio relay antenna. The outputs VD and H

D

the diversity outputs, are in each case associated with a difference pattern of the elevation plane. If

V

S and V D and H S and H D are in each case conducted together via a maximum-power combiner K v and KH, which are in each case preceded in 15 the individual branches by channel branching filters 5 and converters 6 connected to a carrier supply 7, the resultant output signals UH and

U

V of the combiners 4 exhibit a htter signal/noise level ratio than comparable radio relay antenna signals without angle diversity circuit in the case of large phase errors in the multi-path field in the range of 20 the receiving antenna aperture. Since sum and difference signals are •continuously combined via the combiners to form a received signal, thnoise levels of the associated cross polarisation of both outputs are also continuously online. In the case of links with dual orthogonal polarisation it is therefore necessary to maintain very good cross polarisation discrimination values of the V s HS outputs and also of the diversity outputs VD, H D of the angle diversity antennas.

With suitable cross-sectional design of the square and rectangular waveguides with the required quality factor, it would be possible to excite the required linearly polarised useful modes (H 01

H

10

H

11

E

11

H

20 in a common rectangular waveguide by means of two square waveguides separated by a narrow separating web (Figures 2a to 2d show the four field states in the square waveguides and adjacently in the adjoining wls/4686W 3 rectangular waveguide), if it were possible to neglect secondary interference.

However, a severe interference with highly frequency-dependent characteristic, which leads to high cross polarisation peaks in the three-dimensional pattern (AZ/EL levels) of the difference outputs within required bandwidths of B 10%, is superimposed on the polarisation-conforming excitation. The cross polarisation pattern of the vertical difference output VD, with which the H 11 Ell hybrid wave is associated, is particularly critical.

The cause of this interference is attributable as follows: to adjust the linearly polarised H 1

E,

1 wave in the rectangular waveguide R, accurate relations of the 15 amplitude and phase values of the individual primary excitation modes El and H n are required in the excitation zone. If this balance is disturbed, the resultant aperture field of the exciter contains cross polarisation components with the typical distribution of Ell or H 1 waves. In the three-dimensional far-fie4l pattern of the angle diversity antenna, this results in the azimuth Swidth of the solid angle with adequate cross polarisation attenuation for the VD output being much too narrow.

Since power is transmitted from components of one 25 polarisation to those of the orthogonal polarisation when the linearly polarised excitation of the H 1

E,

1 wave is disturbed, the areas in the geometry of the transition zone which couple together the flows of both square waveguides Q 1

Q

2 and change the polarisation of the coupled fields by changes in direction of the conducting surfaces are involved as location of the interfering coupling flows. In the present arrangement, these are primarily the corners which connect the end of the separating wall between the square feed waveguides Qi, Q 2 to the broad side of the rectangular multi-mode waveguide R. Flows in the corners have a direct influence on the phase and amplitude of the HuE, 1 excitation and thus on the quality factor of the balance.

4 The invention is based on the object of specifying a solution, by means of which these disturbances are eliminated in a simple manner, for an arrangement of the type initially described.

According to the invention, this object is achieved in such a manner that when the H 01

H

10

H

20 and

H

1

,E,

1 modes are excited by the two square waveguides into a rectangular multi-mode waveguide, the volume areas in the transition area of the square waveguides to the rectangularwaveguide are filled up with strictly locally limited high-attenuation ferromagnetic attenuating material in the corners on both sides of the separating web.

This results in a high attenuation of the inter- 15 ference currents which does not act too far beyond the corners on both sides of the separating web, the field impedance of the attenuating material producing only •little reflection in the waveguide. This effectively and selectively suppresses interference without the unavoidable co-attenuation of the useful mode fields in the rectangular waveguide R becoming too great. Due to the measures according to the invention, the currents are eliminated by attenuating their coupled electrical and magnetic fields. A material having the desired charactoo. 25 teristics can be produced, for example, by mixing carbonyl iron and various synthetic resins.

Advantageous embodiments and further developments of the subject-matter of the invention are specified in the subclaims.

In the text which follows, the invention is explained in greater detail with reference to illustrative embodiments shown in the drawing, in which: Figure 3 shows a diagrammatic representation of the waveguide transition with interference currents in the area of the corners of the separating web and, Figure 4 shows the attenuating material in the area of Sthe interference currents.

5 In Figure 3, the transition area of the two square waveguides Q 1

Q

2 to the rectangular multi-mode waveguide R is shown in a part-representation, the waveguides being drawn dashed. A separating web S is located between the two square waveguides Q 1

Q

2 The volume areas in the corners of the separating web S in the transition area of the two square waveguides Q 1

Q

2 to the rectangular waveguide R are designated by V 1

V

2 and identified by circles. In these corners V 1

V

2 interference currents is,, isn occur which extend in the longitudinal direction and transverse direction of the waveguides and in the direction of the transverse web (compare the arrows drawn in Figure 3).

In a part-representation with the same perspec- 15 tive as Figure 3, Figure 4 shows the transition area between the square waveguides Q 1

Q

2 and the rectangular waveguide R, in which an attenuating element D enclosing the transverse web S in the corner areas is arranged. The attenuating element D is constructed as a U-shaped flat plate and rests with one flat side against the broad side Sof the rectangular waveguide R and against the adjoining sides of the two square waveguides Qi, Q 2 The centre opening is constructed in such a manner that the two legs of the U shape formed by this opening enclose the transverse web S in its end area. The attenuating element in each case fills up a small volume of the excitation zone in the area of the corners Vi and V z in such a manner that it extends into the two square waveguides Q, Q 2 encloses a part of the break-away edge of the separating web S and slightly protrudes into the rectangular waveguide R. The resultant moulded U-shaped part consists of high-attenuation ferromagnetic material. The figure only shows one attenuating element located in the area of the corner V 1 A correspondingly constructed attenuating element is arranged oppositely located in the area of the corner V.

The rectangular multi-mode waveguide R can exhibit a cross-section which is constant, stepped or expands continuously to form a horn. It can have very short 6 dimensions or possibly also be omitted in its entirety.

The ferromagnetic attenuating material then protrudes into the space in front of the aperture.

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Claims

1. XPD-optimised dual-polarisation wide-band angle diversity exciter in accordance with the multi-mode principle, said wide-band angle diversity exciter comprising a multi-mode waveguide branch with a rectangular multi-mode waveguide and two square waveguides separated from one another by a separating web, wherein in response to excitation of the Hol, Hlo, H20 and H 1 1 uE modes by the two square waveguides into a rectangular multi-mode waveguide, the volume areas in the area of transition of the square waveguides to the rectangular multi-mode waveguide are filled up with strictly locally limited high-attenuation ferromagnetic attenuating material in the o1 corners on both sides of the separating web.

2. Wide-band angle diversity exciter according to claim 1, wherein the two volume areas in the corners are arranged symmetrically on both sides of the separating web in such a manner that the attenuating material encloses in a U shape the corner areas of both square waveguides, a small part of the rectangular multi-mode waveguide and the edge areas of the separating web between the square waveguides.

3. Wide-band angle diversity exciter according to claim 1 or 2, wherein the rectangular multi-mode waveguide exhibits a constant cross-section.

4. Wide-band angle diversity exciter according to claim 1 or 2, wherein the rectangular multi-mode waveguide exhibits a cross-section which expands in the form of steps to form a horn.

Wide-band angle diversity exciter according to claim 1 or 2, wherein the rectangular multi-mode waveguide exhibits a cross-section which expands continuously to form a horn.

6. Wide-band angle diversity exciter according to claim 1 or 2, wherein the rectangular multi-mode waveguide exhibits a very short length tending towards zero and the ferromagnetic attenuating material correspondingly protrudes into the space in front of the aperture.

7. Wide-band angle diversity exciter substantially as described herein with reference to Figs. 3 and 4 of the accompanying drawings. 30 DATED this Sixth Day of February 1995 Siemens Aktiengesellschaft Patent Attorneys for the Applicant SPRUSON FERGUSON IN:\lbcclOO282HRW XPD-Optimised Multi-Mode Angle Diversity Exciter ABSTRACT When the H 01 H 10 H 20 and H 11 E 11 modes are excited by two square waveguides Q 2 separated from one another by means of a separating web into a rectangular multi-mode waveguide, followed by a horn, the volume areas in the transition area of the waveguides are filled up with high-attenuation ferromagnetic attenuating material in the corners on both sides of the separating web Figure 4. 9 o0 9 9 meff o ,t wls/4680W