FI91028C - Satellite Antenna device - Google Patents

Description

i 91028

SATELLIITTIANTENNIJÅRJESTELY

The invention relates to a satellite antenna arrangement 5 as defined in the preamble of claim 1, in particular for a mobile earth station for voice communication.

New satellite systems are being developed, especially for mobile terrestrial communication systems. Communication and positioning systems such as Inmarsat 10 C, PRODAT, Euteltracks and Lockstar have already been introduced and are gradually being introduced. Marketing research also shows that there is a need for voice communication systems. Two systems, EMS (European Mobile System) and Inmarsat M, are being developed for mobile ground station communication systems for L-band voice-15 communications. The systems complement the services provided, in particular, for terrestrial mobile stations by providing flexible closed networks covering the whole of Europe. One of the most promising 20 applications can be considered to be truck communication networks.

Ambient antennas can be used at low data rates. The gain of these antennas is of the order of 3 ... 5 dBi, which is usually sufficient. However, audio communication requires a better signal-to-noise ratio than can be provided by omnidirectional antennas. This requirement means that the antenna gain must be at least in the order of 10 ... 12 dBi. Many antenna systems are previously known in which the antenna element is directional. Such antennas include e.g. certain slot and horn antennas and dipole antennas. The problem with these antenna units is the complexity and unsuitability of the feeder circuit adaptations for different monitoring systems.

35 In addition, the mechanical properties of these antenna elements are often unsuitable specifically for a mobile ground station.

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The object of the invention is to provide a new antenna arrangement / by means of which the above-mentioned problems can be eliminated. It is a further object of the invention to provide an antenna arrangement which is inexpensive to manufacture and suitable for mass production.

The antenna arrangement according to the invention is characterized by what is stated in claim 1.

According to the invention, the satellite antenna arrangement for a mobile earth station, in particular for voice communication, comprises an antenna unit which can be directed to the satellite in the azimuth plane, and which antenna unit is formed by a plurality of antenna elements, control units and switching units. air-insulating antenna elements arranged in parallel on the circumference of a circle at a distance from each other. According to the invention, each antenna element is formed of a circular planar conductive strip 20 arranged at a constant distance from the ground plate and terminated in a load, and that the ground plate of each antenna element is formed as a basin-like part in which the strip is mounted; and of the antenna elements, the same active antenna unit 25 simultaneously comprises two adjacent antenna elements selected by the control unit and the switching unit to receive from the desired direction and to transmit electromagnetic radiation polarized in substantially the same direction.

The antenna elements are preferably air-wave antenna elements of the traveling wave type, which are identical in structure. The antenna elements are arranged on the circumference of the circle so that they cover the entire circumferential area of 360 °. From the satellite antenna arrangement 35, the two antenna elements whose radiation beams are directed in the desired direction can then be selected by means of the control unit and the switching unit.

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91028 3

The ground plate according to the invention has a rigid mechanical structure. In addition, with such a ground plate, better insulation between adjacent antenna elements is achieved directly compared to the ground plate. In addition, such a ground plate has a stabilizing effect on the input impedance.

In one embodiment of the satellite antenna arrangement, the switching unit comprises two groups of switches by means of which two parallel antenna elements can be selected from 10 desired locations on the circumference of the circle. The switch groups are preferably formed of PIN diodes.

In one embodiment of the satellite antenna arrangement, it includes a power distribution and phasing unit with a 180 ° hybrid and two phasing.

15 In one application of the satellite antenna system, the phasing is a load line type phasing. It comprises two parallel transmission lines connected at the other end to the input and output ports and their transmission lines between the input and output ports, and switch elements mounted at the ends of the matching lines connected to the input and output ports to realize the phase difference. With the aid of the switching unit and said phase reflectors, three beam beams in different directions can be implemented for the two antenna elements selected, depending on the states of the phase switch switches. The radiation beam of the active antenna unit formed from the two antenna elements can advantageously be adjusted, e.g. ± 7 °, to the inventive normal direction of the antenna elements, and thus 30 satellites can be monitored expeditiously and reliably. In addition, with a relatively small number of antenna elements in the circumference of the circle, at least twice the number of radiation beams can be realized, which fill the azimuth plane substantially without gaps.

35 In one application of the satellite antenna arrangement, the antenna elements are provided with support members by means of which the antenna elements are arranged in the body part 4 at a suitable elevation angle with respect to the azimuth plane. The elevation angle depends on the orbital position of the monitored communication satellite and the geographical position of the ground station where the antenna arrangement is used.

5 In one application of the satellite dish arrangement, the support members are adjustable members for adjusting the elevation angle. By means of the support members, the elevation angle of all the antenna elements is set the same in the azimuth plane, so that the elevation angles of the radiation beams of the antenna elements are correct considering the position of the satellite. The elevation angle varies between 10 ° and 50 ° and is preferably adjustable, e.g. at intervals of 10 °. The width of the radial beam still covers the said range of 10 ° without a very strong attenuation in the reinforcement of the edge region of the beam.

In one application of the satellite antenna arrangement, the antenna arrangement is provided with a shield.

In one application of the satellite antenna system, it comprises a directional device for carrying out satellite tracking and tracing. A detector and measuring unit are connected to this directing device for measuring the signal level in the radio frequency range used. The directing device is connected to the control unit and the switching unit to select the two co-operating antenna elements from among the antenna elements which provide the best signal-level communication connection to the satellite. The orientation device is most preferably implemented with a microprocessor-based data processing device comprising 30 sets of peripheral and connection units. The various functions are suitably programmed in the aiming device.

The advantage of the invention is that the satellite antenna arrangement is relatively simple and suitable for a small space. Such an antenna arrangement is inexpensive in terms of manufacturing cost and is thus suitable for mass production.

A further advantage of the invention is that it is active

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91028 5 antenna units, which simultaneously include two antenna elements, provide high gain.

A further advantage of the invention is that the input circuit of the antenna arrangement is relatively simple and provides an efficient and simple way to connect and phase out the desired radiation beams from selected antenna elements.

A further advantage of the invention is that, depending on the number of antenna elements, twice the number of radiation beams is obtained. Of the circumferential antenna elements, there are always two active elements and they produce two radiation beams with a predetermined phasing.

A further advantage of the invention is that the adjustment of the elevation angle is simple and can be implemented either mechanically or with a suitable actuator.

A further advantage of the invention is that the antenna unit provides a suitable radiation pattern with a wide coverage area. The satellite antenna system-20 is suitable for small elevation angles up to approx. 10 °, which are particularly important for the use of the antenna system at northern latitudes.

Further advantages of the invention are as follows: the satellite search routines operate quickly when the arrangement is started. Furthermore, the system takes into account a reasonably large alignment error of the antenna unit, taking into account the bandwidth and gain loss of the antenna unit. A further advantage of the arrangement is that it operates with a low signal-to-noise ratio. Furthermore, the antenna arrangement operates reliably despite short- and long-term changes in the signal level. A further advantage of the antenna arrangement is that it recovers quickly from interference situations. In addition, the antenna arrangement causes minimal distortion to the communication channels.

The invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a plan view of a satellite antenna arrangement according to the invention; Figure 2 shows a cross-section A-A of the satellite antenna arrangement of Figure 1; Fig. 3a is a top view of the antenna element and Fig. 3b is a side view; Figure 4 is a block diagram of the main parts of a satellite antenna arrangement according to the invention; Figure 5 schematically shows a hybrid; Fig. 6 schematically shows a phaser; Fig. 7 shows a layout diagram of a power distribution and phasing unit; Figure 8 shows radiation beams; Fig. 8a shows radiation beams of an active pair of antenna elements and Fig. 8b shows radiation beams of 15 antenna units with 12 antenna elements; and Figure 9 shows a directing device in block diagram form with associated units and devices.

Figures 1 and 2 show an embodiment 20 of the invention. satellite antenna arrangement as an illustrative diagram. The antenna arrangement comprises an antenna unit 1 with a plurality of antenna elements 1; l1 to l12, which are arranged on the disc-shaped body part 2. They are arranged parallel to the circumference of the circle in the reu-25 na region of the body part 2. They are arranged at a distance from each other so that they fill the entire circumferential area one sector at a time. In this application example, the antenna unit 1 is formed of twelve antenna elements l1 to 12.

The antenna arrangement also comprises support members 3 by means of which the elements 11 to 112 of the antenna unit 1 are arranged at a suitable angle of inclination a with respect to the body part 2. The support members 3 are e.g. support rods which are periodically or continuously adjusted manually or by a suitable actuator. to set the angle a.

The antenna arrangement further comprises a control unit 91028 7 sik 4 and a switching unit 5. Of the antenna elements l1-112 the same active antenna unit e.g. 6 simultaneously comprises two antenna elements l7, 18 selected såteilyå.

The satellite antenna arrangement is provided with a protective dome 7 for protecting the antenna elements 11 to 12 and other devices 10 belonging to the antenna arrangement.

The antenna elements 11 to 12 are identical air wave antenna elements of the wave type, as shown in Figs. 3a and 3b. Each antenna element consists of a thin planar strip 8 of a curved thin conductive material, such as copper. The strip is mounted on an insulating board, e.g. utilizing known circuit board technology. The strip is a standard plate with a substantially circular arc shape that fills a sector of 270 °. The nominal wavelength of the antenna element is close to the wavelength used. The strip 8 is arranged at a constant distance h from the ground plate 9. At each end of the strip 8 there are triangular connecting parts 10 and poles 11, 12. One pole acts as an input terminal and the other as a load terminal.

The radiating power of the antenna element l1 to l12 can be obtained by obtaining the width b and the distance h of the microstrip 8 from the ground plane 9. Optimal antenna gain is achieved when about 90% of the power supplied to the antenna element is converted to rain and 10% is absorbed into the matching 30 load.

The active antenna unit e.g. 6 is formed electrically by selecting two parallel antenna elements, such as l7, 18 from among the antenna elements l1 to l12. It achieves significant advantages over a single antenna element. It has been found that the optimal gain values and beamwidths of the antenna element depend on the shape and size of the ground plate. The maximum direction of the main beam depends somewhat on the frequency used and deviates from the normal ground plate by about 5 - 15 °. The deflection angle TSma also depends on the shape of the ground plate. By means of two parallel antenna elements 11 to 12 in the cooperating 5, which elements are arranged at a distance from each other and which are fed in parallel with a suitable phase difference, the angular dependence of the main beam on the frequency can be approximately eliminated.

10 The ground plate 9 is a trapezoidal plane, the edges 9a, 9b, 9c and 9d of which are angled so that the ground plate forms a shallow basin (note that the edges are horizontally turned for the sake of clarity in Figure 3a). The average width 1 of the ground plate 9 is of the order of the total width of the strip 8 and the distance of the antenna elements, and the length k of the ground plate is in turn of the order of 1.5 to 2.0 x a. The depth s of the basin ground plate is of the order of 0.1a. In a preferred embodiment, the dimensions of the ground plate are: height k = 150 mm, width 20 base width 11 = 150 mm, narrow base width 12 = 90 mm and ground plate depth h = 20 mm. The ground plate 9 is of any suitable conductive material, such as aluminum.

Figure 4 shows a block diagram of a satellite antenna arrangement according to the invention. The input terminals 11 of the antenna elements l1 to 12 of the antenna unit 1 25; li1 to li12 are connected to two switch groups 13, 14 and the second terminals 12 of the switching unit 5, respectively; 121 to 122 are connected to the adapter loads 15; 151 to 1512. The antenna elements l1 to I12 are grouped so that the adjacent elements 30 l1, 12; l2, l3; 13, 14, ... are connected to different switch groups 13, 14. Thus, the antenna elements 11 to 12 are alternately connected to the first switch group 13 and the second switch group 14. Each switch group 13, 14 in this case comprises six bays 13; 131-136 35 and 14; 141 to 146. By means of the control unit 4, the switch groups 13, 14 are controlled so that two parallel elements l1, l2 can always be selected; l2, l3; ... to work

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91028 9 simultaneously as an active antenna unit.

The inputs 16, 17 of the switch groups 13, 14 are connected to a power distribution and phasing unit 18. The power distribution and phasing unit 18 comprises two phasers, i.

5 the first stage 19 and the second stage 20, as well as the 180 ° hybrid 21. The first input 21a of the hybrid 21 is the input of the power distribution and phasing unit 18 and is connected to the detector and measuring unit 29 as well as to the receiver-transmitter unit (not shown in the drawing).

10 One of the inputs of the hybrid 21 is connected to the ground via the load 22. The outputs 21c, 2 Id of the hybrid 21 are connected to the input of the first phaser 19 and the input of the second phaser 20, respectively.

The hybrid 21 is shown schematically in Fig. 15. The input and output ports are denoted by the same reference numerals as in Fig. 4. The input port 21a is a differential or D port and the input port 21b is a sum or S port. When the signal is input from the D-port, the output gates 21c, 21d provide output signals which are 180 ° out of phase with each other. While a signal is applied to the hybrid from the S-port, the signals in the same phase are output from the output ports.

The phasers 19, 20 are implemented by means of transmission lines and switching elements, as shown in Fig. 6. The stage 19, 20 comprises two parallel transmission lines 23a, 23b and 24a, 24b connected at one end of both the input and output ports PI, P2 and transmission lines 25a, 25b connected between the ports.

In addition, the phaser 19, 20 includes in each of the 30 ports PI, P2 an arrangement of wires 26a, 26b; 27a, 27b are coupled coupling members 28a and 28b. The switching elements 28a, 28b are implemented by means of suitable diodes and can be switched to a conductive state or a closed state.

Both switching members 28a, 28b are simultaneously 35 in the same state, whereby the phaser 19, 20 is symmetrical in structure. The transmission characteristics of the phaser 19, 20 from the port PI to the port P2 or vice versa are the same. The losses of such a load line type phaser 19, 20 are small and the frequency range is wide. In addition, the matching properties of the phaser are good.

A preferred embodiment of the power distribution and phasing unit 18 is shown as a layout diagram in Figure 7. The hybrid 21 and the phasers 19, 20 are made on the same substrate by the microstrip method.

The phasers 19, 20 are optimized in this application to provide a phase shift of 33 °. This means a separation angle of about 14 ° (i 7 ° from the straight center) for the radiation beams available from the active antenna unit. By changing the states of the phasors 19, 20 and in particular their switching members 31, 32, the direction of the radiation beam of the active antenna unit can be changed between the normal, i.e. mid-direction and outer positions of the ground plane 9, as shown below.

Staging devices 19, 20 are used to direct the radiation beam when implementing satellite tracking. By appropriately controlling the switches 28a, 28b of the stage 19, 20, it is possible to switch from the right beam "Right" to the left beam "Left" or the center beam "Mid", which beam is illustrated in Fig. 8a. The connection from the right beam "25" to the left beam "Left" or vice versa is carried out in such a way that the state of the coupling members 28a, 28b of both phasors 19, 20 is changed. In Tål-lo, the phase shifters change into mirror images of each other. Correspondingly, if only the state of the second switching-30 member 28a or 28b is changed, the radiation beam shifts from the center beam "Mid" to either the right "Right" or the left "Left" radiation beam. The width of the radiation beams is somewhat affected by the elevation angle α and also the reception and transmission band used. The power distribution and phasing unit 18 described above is mainly intended for the frequency range 1.5 to 1.7 GHz.

The active antenna unit is formed by two adjacent antenna elements 1 ', 1% 12, 13, .... Two radiation beams can be arranged on the active antenna unit, as described above, which beams differ from each other by up to 15 °. By means of the antenna 1 of the antenna-5, a double number of radiation beams is obtained on the circumference of the circle compared to the number of antenna elements l1 to 12. Thus, twenty-four beam beams can be realized on the twelve antenna elements, which are distributed substantially evenly at the azimuth-10 level on the circumference of the circle. This is illustrated in Figure 8b.

Figure 9 shows a block diagram in the form of a blocking device 30 with its connection and peripheral units. The orientation device 30 comprises a data processing unit 31a 15 and a memory unit 31b connected thereto. A number of peripheral units are further connected to the data processing unit 31a via a suitable bus 32 via the connection units, such as the elevation angle detector 33 via the connection unit 34, the control unit of the detector and measuring unit 29 and the phase control 4 is also connected to the directional device bus 32. The directional device 30 further includes an interface unit 38 for input of information such as programming and other information to the directional device 25 and an interface unit 39 for connecting the directional device to external systems.

In addition, the orientation device 30 preferably includes a compass connection unit 40 for connecting the compass 41 to the arrangement.

The connection unit 34 of the elevation angle detector is connected to an elevation angle detector 33 measuring the elevation angle α of the antenna elements 1, which is arranged between the body part 3 and the antenna elements 11; 11-112 (cf. Fig. 2). The detector and measuring unit 29 includes 35 for measuring the rf level of the intermediate frequency part and the rf detector as well as the measuring part. This measurement signal is fed to the directing device via the A / D converter 34. The switching unit 36 is connected to the switching members 28a, 28b of the phase dividers 19 and 20 of the power distribution and phasing unit 18. The support members 3 are in this case provided with an actuator 42 (cf. Fig. 2), such as an electric motor 5, for lengthening and shortening the support members 3. The support member 37 is connected to the support actuator 42.

By means of the orientation device 30, the search and tracking of the satellite connector is carried out as follows. When starting the satellite-10 tennis arrangement, the elevation angle α of the elements 11 to 112 of the antenna unit 1 is checked. If the elevation angle α does not correspond to the position of the earth station relative to the latitude and the satellite, it is corrected e.g. at 10 ° intervals between 10 ° -50 °. The shape and width 15 of the radiation beam is such that the 10 ° beams are good enough to apply the antenna gain and the signal / assembly. The elevation angle α is corrected by adjusting the length of the support member 3 to suit the length of the support member 3 so that the desired elevation angle 20a is achieved. The elevation angle α is obtained via the elevation angle indicator 33 to the orienting device 30.

After setting the elevation angle α, the satellite search phase is started. The level of the satellite radio frequency signal, i.e. the rf level, is measured by the detector-25 and the measuring unit 29 by activating the antenna element pair l1, l2; l2, l3; l3, l4; etc. one at a time and kSyming through all the antenna elements l1 to l12. The rf level measurements obtained from the sequentially activated antenna units are stored in the memory 31b. During this measurement 30, the radiation beams of each pair of antenna elements, as well as the right and left radiation beams, are passed through, so that the azimuth level must be completely transmitted through the radiation beams shown in Figure 8b.

When the first series of measurements is performed, the pair of antenna elements of the antenna unit 1 in connection with which the maximum rf level signal is measured is activated. After that, we move on to the monitoring phase.

Il 91028 13

The monitoring phase is based on monitoring the rf signal level with two radiation beams, i.e. with the left and right radiation beams, as previously described in connection with the division and phasing unit. In this way, 5 the antenna unit 1 is kept in a continuously electrically directed manner to the satellite object in order to maintain the communication connection despite the movements of the earth station.

An electronic compass 41 or other indicator capable of tracking the turn of the vehicle can be added to the aiming device, and this can effectively help the aiming device 30 to keep the active antenna unit pointed at the satellite.

The invention has been described above with reference to one preferred embodiment thereof, but many modifications are possible while remaining within the scope of the invention as defined by the appended claims.

Claims (8)

14 A satellite antenna arrangement for a mobile earth station, in particular for voice communication, comprising an antenna unit (1) which can be directed to a satellite in the azimuth plane and which antenna unit (1) is formed by a plurality of antenna elements (11 to 112), a control unit ( 4) and a coupling unit (5) having antenna elements of the antenna unit identical to 10 wave-wave type air-insulating antenna elements arranged parallel to the circumference of the circle at a distance from each other, characterized in that each of the antenna elements (11 to 112) is formed from 15 is arranged at a constant distance from the ground plate (9) and terminated in the load (15), and that the ground plate (9) of each antenna element (11 to 112) is formed as a basin-like part inside which the strip (8) is mounted; and the antenna drain elements in the same active antenna unit (6) 20 simultaneously comprise two adjacent antenna elements selected by means of the control unit (4) and the switching unit (5) to receive from the desired direction and to transmit in a substantially parallel direction. Satellite antenna arrangement according to Claim 1, characterized in that the switching unit (5) comprises two groups of switches (13, 14) by means of which two parallel antenna elements (l1, l2; l2, l3; l3, l4; .. ·) can be selected. from the desired 30 locations on the circumference of the circle. Satellite antenna arrangement according to Claim 1 or 2, characterized in that the antenna arrangement comprises a power distribution and phasing unit (18) with two phase repeaters (19, 20) 35 and a 180 ° hybrid (21). Satellite antenna arrangement according to Claim 1, 2 or 3, characterized in that each phase repeater (19, 20) has two parallel transmission lines (23a, 23b; 24a) connected at the other end to the input and output ports (PI, P2). 24b), transmission lines 5 (25a, 25b) arranged between the input and output ports (PI, P2), and switching means (28a) mounted at the ends of the matching lines (26, 26b; 27a, 27b) connected to the input and output ports (PI, P2) , 28b) to implement a phase difference. Satellite antenna arrangement according to one of the preceding claims 10, characterized in that the antenna elements (11 to 112) are provided with support means (3) by means of which the antenna elements are arranged in the body part (2) at a height corresponding to the azimuth plane (BB). ). A satellite antenna arrangement according to claim 5, characterized in that the support members (3) are adjustable means for adjusting the elevation angle (α). Satellite antenna arrangement according to one of the preceding claims 20, characterized in that the antenna arrangement is provided with a protective dome (7). Satellite antenna arrangement according to one of the preceding claims, characterized in that the antenna arrangement comprises a directing device (30) for performing satellite search and tracking, to which a detecting and measuring unit (29) for measuring the rf signal level is connected and which directing device is connected. and 30 switching units (5) for selecting the two co-operating antenna elements (e.g. 6) from among the antenna elements (11 to 112), which antenna elements provide the best signal level communication connection to the satellite. ________ No. 16