SE442074B - ELECTRICALLY CONTROLLED GROUP ANTENNA WITH REDUCED SIDOLOBS - Google Patents

Description

8402140- 10 15 20 25 1.

The invention is then characterized as appears from claim 1 characteristic part.

DESCRIPTION OF THE FIGURES The invention will be described in more detail with reference to the accompanying drawings therein Figure 1 shows a group antenna of a per se known structure but with further features of the invention; i i figure 2 shows parts of two antenna elements included in the group antenna according to figure 1; figure 3 shows a cross section of an antenna element according to figure 2; Figures 4 and 5 show radiation diagrams.

EMBODIMENTS The group antenna according to figure 1 consists of a number (in figure 4) of antenna elements in in the form of rectangular waveguides V1, V2, V3 and V4 lying parallel along their respective short pages. Supply waveguides M1 and '(obscured in the figure) MZ-Mli are connected to each of the waveguides Vl-V4. Each waveguide is equipped with radiation apertures in the form of longitudinal slits 511, 512, ... on the conductor V1, S21, S22 ... on the waveguide V2, S31, 532, ... on the waveguide V3 and S41, 842, ... on the waveguide V4. All slots shown are so-called wide-side slots, ie evenly wide slits placed on the wider part of the respective waveguide. The end portion of the supply waveguides M1-M11 which are attached to the waveguides V1-Vli has a feed port (not shown in Figure 1) through which electromagnetic field energy (for example within the X ~ band) is supplied to each waveguide V1-V4.

The other end of the supply waveguides is connected by suitable input elements to phase shifter F1-F11 (P3, F is obscured in Figure 1) to control the phase of the entered the field relative to a reference phase (for example, the phase of the field to waveguide Vl).

Use of wide-side slits with constant element spacing d (d = dl = d2 = ...) _ according to figure 2, in the radiation diagram of the group antenna gives rise to side lobe peaks, whose height depends on the equipment angle. Figure 4 shows a radiation diagram in one plane parallel to the waveguides and through the lobe maximum when the antenna is equipped to 200 from the normal direction. The side lobe tops consist of so-called grid lobes 10 15 20 25 30 84021404 corresponding to the element distance 2d. If the slots S11, 512, ... Sly S22, ... etc on the waveguides Vl-Vli instead had mutually different element spacing dl: d2 = ... would the lattice lobes from the individual waveguides Vl-Vli end up in different places in the radiation diagram and are not added together to the strong peaks (SPSZ) according to figure 4. According to the invention different element distances are provided by changing the waveguide wavelength in the individual waveguides.

Figure 2 shows a section of the group antenna according to Figure 1 with two waveguides. Episode. The slots S11, S12 and S13, S14 on the waveguide V1 are spaced apart. the dz and the slots S21, S22, S23, S24, etc. on the waveguide V2 have mutual the distance d2 = dl. To achieve the intended reduction of the side lobe stops according to Figure 4, the waveguide wavelength γg in each of the waveguides V1-V11 is changed so that I get different. This is described below in connection with Figure 3. As a result, different are obtained distance dydz between the slots of the different waveguides Vl-Vli.

Figure 3 shows a cross section of a waveguide VI with the slots S11, S12 and a part of adjacent waveguides V2. The waveguide Vl is on its inner surface, the one that is directed towards the slots S11, S12, provided with a raised part or backR symmetrically located around the waveguide's symmetry line C. This consists of two side walls RV1 and RV2, respectively, which extend perpendicular to the inner surface Y and in its longitudinal direction along the entire length of the waveguide. Lateral- the walls RV1, RVZ are bridged by a wall RVB perpendicular to the side the walls. The height of the two walls RV1, RV2 from the surface Y is denoted h.

The waveguide V1 constitutes a so-called back waveguide and. in this, waveguide wave length Äg for a given waveguide width and heightb are made to vary within some limits by varying the height of the back h. The height h is thus constant for one certain waveguide in the group antenna, ie for the waveguide V1 the height of the ridge is R equal to hl, for the waveguide V2 the height R2 of the ridge is = h2 (hlshz) etc. Since the slot distance dzÃg / Z, the grid lobes can thus be spread over the antenna lobe angle intervals and thereby reduce their effect on the side lobe level.

Figure 5 shows the radiation diagram of a group antenna with a back-wave conductor there this principle has been used. The diagram according to Figure 5 is directly compared with that according to Figure 4, since the antennas otherwise (apart from the ridge R1 and RZ) are completely equivalent. 8402140- "1 1D Wide-side slots have great advantages in group antennas of the type referred to here: a) very low losses' b) simple and cheap au manufacture c) established and well-functioning calculation methods.

The proposed array antenna retains the above advantages due to the abrasion resistance. the slits but with reduced sldolobes.

The invention is not limited to guide guides V1-V4 where the guide wavelength / lgr Ågzr .. for the different waveguides have been varied by those in in connection with Figure 3 the measures taken. The essence of the inventive idea is 'that the wavelengths Ågl, Ãgzp .. have been made different, which means that it is mutual the distance dl, d2, ... must be dimensioned so that dlçdz etc. This gives one variation of the positions of the grating lobes for the whole group antenna, which results in one reduction of lateral lobe level.

Claims (1)

84021404 CLAIMS Electrically controlled group antenna with reduced side lobes, consisting of at least two adjacent antenna elements which each consist of preferably rectangular waveguides (V1, V2 ...), one side surface of which is provided with radiating openings along (S11, S12 S21, S22 ...), characterized in that in order to spread the grating lobes coming during electrical control of the antenna from the individual antenna elements to different positions in the group antenna's radiation diagram, the guides in the antenna are designed so that the guide wavelength ( g) for at least a part of the path guides (V1, V2) assume different values between them, and thereby the mutual distance of the wide-side slits (dl, dz) is different for selected guide guides. * roar QUALrr-wl fl