NL8006425A - Directional microwave reception aerial - has focussing dish and element which can receive left and right-hand circularly polarised waves - Google Patents

Abstract

The directional aerial is used for receiving electro-magnetic radiation, such as micro-waves from a geostationary communication satellite. It comprises a receiving unit and a member which focusses the incoming radiation on to this unit. The unit comprises at least one receiving element having an insulating substrate plate e.g. in PTFE, aluminium oxide, quartz, with a conducting plate on one side and a conducting pattern on the other (this assembly forms a resonator). This pattern is pref. shaped such, and has two output terminals arranged such, that reception of anti-clockwise rotating circularly polarised waves produces an output signal at only one terminal whereas clockwise polarisation produces an output at the other terminal only.

Description

-1- 'X Sch / gn / 32Leuven

Short designation: Directional antenna

The invention relates to a direction-sensitive antenna for electromagnetic radiation, for example microwaves originating from a geostationary broadcasting satellite, which antenna comprises a receiving member and a focusing member focusing on the incident radiation.

;; Such an antenna is known in the form of a parabolic reflector with a horn antenna in the focus. For a correct understanding of the limitations of this known antenna, a brief overview of the requirements to which, inter alia, with the. in view of expected future developments, an antenna of the intended type must comply. This exploratory introduction concerns the reception of television broadcasting satellites.

15 The specifications for the broadcasting of television broadcasting programs11 from satellites in a geostationary orbit are defined by international agreement.

The reception of the electromagnetic radiation emitted by these satellites can be done individually or jointly. From a commercial point of view it can be noted that the antenna plus any necessary accessories for individual reception should not cost more than a known rotatable television antenna for ÜHP and VHF. It will be clear that in the case of joint reception the price aspect is less important.

The most important characteristics of the satellite signal for the zone, consisting of Western Europe and Africa, are the following: - frequency band 11.7 - 12.5 GHz 30 - polarization: circular, left or right rotation - the frequency band of 800 MHz is divided over forty channels, each country has five channels 8006425.

-2- known with either left turning or right turning polarization.

- the orbital positions of the satellites are divided with a spacing of 6 ?; 5 Example: Belgium, Luxembourg, France, the Netherlands at 19 ° West longitude with polarization 1, i.e. one type of polarization, i.e. left-turning or right-turning; West Germany, Switzerland, Austria, • Italy also at 19 ° W longitude with polarization 102, i.e. the other polarization phrase; England and

Ireland at 31 ° West longitude with polarization 2.

Some of these may be related to the aforementioned properties of the signals from the satellites. requirements are formulated for the antenna intended for individual reception: -; radiation pattern: -3 dB beam width φ = 2 ° co-polar and dross-polar reference pattern as defined in the WARC specifications.

- polarization: circular, counterclockwise or counterclockwise 20 - bandwidth 11.7 - 12.5 'GHz for Western Europe and

Africa: - antenna gain: ^ 38 dB.

- the direction of the main lobe to one or more satellite positions.

With regard to the above requirements, the following can be noted: requirements 1 and 4 are always valid irrespective of the number of channels to be received. For certain applications, the second requirement can be limited to one fixed sense of rotation. The third requirement could be formulated less strictly depending on the number of channels to be received.

The fifth requirement could, if desired, be limited to one orbital position.

The antenna already mentioned, which comprises a parabolic reflector and a horn antenna placed in its focal point, basically fulfills all the requirements with the exception of 8 00 6 42 5 · 3- the specifications with regard to polarization. Namely, the known antenna is only able to receive linearly polarized waves optimally. It is technically possible to transform the linear polarization of the horn antenna by means of a polarizing element into a circular polarization. However, the cost price can hereby hinder. In order to be able to receive both rotary sentences, an angular rotation of the polarizer is required; this could take place, for example, by means of. 10 of a small electric motor. The latter solution is of a mechanical nature and is therefore not preferable in view of the possibly less good accuracy and the possibility of aging and weathering. Moreover, it always takes some time before switching between the two orientation phrases. The use of an electric motor, which must preferably be placed close to the receiving element for optimum stability, furthermore has the disadvantage that this electric motor could partly intercept the incident radiation. het-20 does not adversely affect the antenna gain.

The object of the invention is to eliminate the limitations of the known antenna.

The object of the invention is in particular to provide an antenna which is simple and inexpensive to manufacture.

Another object of the invention is to provide a direction-sensitive antenna capable of receiving waves with both polarization inserts, without the need for relatively complicated mechanisms.

A further object of the invention is to provide a direction-sensitive antenna, in which the incident radiation is intercepted minimally.

Finally, the object of the invention is to provide an antenna which is eminently suitable for mass production.

In order to achieve the stated objectives, the invention provides a direction-sensitive antenna of the type stated in the preamble, which is characterized in that the receiver comprises at least one receiving element comprising an insulating substrate plate, a. Conductive plate arranged on one plane thereof and a plane on the other plane thereof: Conductive pattern shows »5 The described structure forms a resonator. All dimensions and interrelationships are chosen in accordance with the respective properties, the radiation to be received, namely the frequency or the frequency band to be received, as well as the polarization properties. This electromagnetic resonator must also exhibit a direction diagram that corresponds as accurately as possible to the known directional diagrams per se known for certain bundling members, for example parabolic or other reflectors or microwave lenses.

The or each conductive pattern may have such a shape and two output terminals arranged relative thereto that when receiving counterclockwise circularly polarized waves only one output terminal and upon receiving counterclockwise circularly polarized waves only the other output terminal receive output signal. This solution, which is technically the easiest to realize, has a relatively limited bandwidth and is therefore not generally usable.

More generally usable is that antenna according to the invention, which is characterized in that the or each conductive pattern has a shape and two output terminals arranged relative to it, such that when two circularly polarized waves are received the two output signals depend on the polarization. -30 sense have a positive or negative phase difference of 90 ° and that a separation network is present, the two inputs of which are connected to the said output terminals and of which one output terminal only outputs an output when receiving counterclockwise circularly polarized waves and the other output terminal. 8006425 -5- Closure only outputs an output when receiving clockwise circularly polarized waves.

In both the aforementioned cases, a selector switch may be provided for choosing one or the other output terminal, namely corresponding respectively to reception of clockwise and counterclockwise circularly polarized waves.

In order to ensure a minimal intercept effect, in particular due to the presence of the said separation network, this network can be placed behind the receiver with respect to the focusing member;

In order to be able to receive several broadcasting satellites with one fixed antenna and, for example, to be able to switch between them, the receiver can consist of at least two receiver elements placed in preselected positions and at preselected angular positions relative to the focusing member. It will be clear that the said positions must be chosen angular positions in accordance with the orbital positions of the associated satellites.

Preferably, a selector switch is provided for choosing a desired receiving element corresponding to a specific satellite. ".

When using a reflector as a focusing member, the intercept effect can be completely avoided with an antenna according to the invention, the receiver of which is placed at a distance from the axis of the reflector substantially in the focal plane thereof that the incident radiation is received. can fall freely on the entire reflector. The invention further lends itself to the construction of a relatively simple antenna, whose directional characteristic, namely both the main direction and the opening angle, is adjustable. This antenna can be characterized by a matrix arrangement of receiving elements, an adjustable phase shifter added to each receiving element, and a combination circuit connected to its outputs.

The fact is that the receiving element can be galvanically connected to a separating network which may be used. According to the invention, however, both active parts can also be electromagnetically coupled to each other.

The substrate plate may consist of material from the group which includes: polytetrafluoroethylene, aluminum 10 oxide, quartz.

The invention will now be elucidated on the basis of a drawing of a number of arbitrary embodiments, to which the invention is not, however, limited.

15 Show in the drawing:

Pig. 1 is a perspective view of an exemplary embodiment of an antenna according to the invention;

Fig. 2 is a schematic representation of a receiving element according to the invention with a switch for switching between the two polarization sentences;

Fig. 3 is a perspective view of the first exemplary embodiment shown in FIG. 2;

Fig. 4 shows a second exemplary embodiment of a receiving element according to the invention, which behaves substantially the same as the first exemplary embodiment according to FIGS. 2 and 3;

Fig. 5 a third exemplary embodiment of a receiving element according to the invention provided with a separating network and a switch for switching between the two polarization sentences;

Fig. 6 is a perspective view of the said. third embodiment and the separation network;

Fig. 7 is a perspective view of the third exemplary embodiment and the separation network in a first preferred mutual position; 8 00 6 42 5 -1-

Fig. 8 is a view corresponding with FIG. 7 in a second preferred position;

Fig. 9 is a schematic representation of a fourth exemplary embodiment of a receiving element according to the invention;

Fig. 10 is an axial section through the antenna shown in FIG. 1;

Fig. 11 is a schematic representation of one direction diagram of the antenna according to the invention; FIG. 12 an example of an antenna, wherein the focusing member consists of two reflectors in Cassegrain configuration;

Fig. 13 is an axial cross section through an antenna suitable for reception from two main directions; FIG. 14 shows a double-shaped receiving element according to FIG. 13 in front view;

Fig. 15 a first embodiment of the receiving element of FIG. 14;

Fig. 16 a second exemplary embodiment of the received element according to FIG. 14;

Fig. 17 is a circuit diagram associated with the antenna of FIGS. 13 to 16;

Fig. 18 shows the directional characteristic (and L of the antenna according to Fig. 13 to 17; 25, Fig. 19 an arrangement in which the receiving element is placed such that no interception of the incident radiation takes place;

Fig. 20 is a schematic representation of an antenna with variable directional characteristic; FIG. 21 is a schematic example of an antenna according to the invention, in which the focusing member is designed as a microwave lens;

Fig. 22 a fifth exemplary embodiment of a receiving element according to the invention; and FIG. 23 a sixth exemplary embodiment of a receiving element according to the invention.

800 6 42 5 -8-

Fig. 1 shows a perspective view of an antenna according to the invention, consisting of one through one. base 1 carried parabolic reflector 2 and a receiving member 4 positioned through a bracket 3 and positioned in the focal plane of the reflector 2.

Fig. 2 shows the basic construction of a "microstrip receiving element" 5. This first exemplary embodiment is designed in such a way that output connections 6 and 7 are provided at two adjacent corners. These each correspond to the reception of waves of a certain polarization sense. A switch 8 is provided for selecting one or the other polarization phrase as required. It will be understood that for the present frequency range generally micro-waves, a low-frequency type switch is not useful. The switch 8 is then also generally designed as a remotely controllable semiconductor element and can for instance consist of a diode network.

Fig. 3 shows a perspective view of the receiving element 5. This element 5 consists of a. substrate plate 9, a conductive plate 10 disposed on its rear face, which together with the flat pattern 11 on its front forms a microwave resonator. The receiving element following figures 2 and 3 has a relatively small bandwidth, namely around 20: MHz in the frequency range around 12 GHz.

Fig. 4 shows a second exemplary embodiment of a receiving element according to the invention. This consists of a substantially square conductive pattern 12, in which a slot 13 is arranged in a diagonal direction and in it.

center of two adjacent sides of which output terminals 14, 15 are provided. This variant also has the disadvantage of a relatively small bandwidth.

Fig. 5 shows a third exemplary embodiment of a receiving element according to the invention, which. has a very large bandwidth. This exemplary embodiment comprises a four-way conductive pattern 16 with two output terminals 17/18 connecting to the center of two adjacent sides, which are or can be connected to the input terminals 19, 20 of a separation network 21 comprising two Has 5 output terminals 22, 23. These output terminals correspond to the two polarization phrases. The switch 8 is therefore also present here for choosing between them.

The separation network is designed as a three-dB coupler. Its properties are consistent k. with that of the microwave resonator. For example, distances a indicated sufficiently by the reference numerals 24 and 25 to the relationship: 15 a ~ = (n + \\. Λ where n = 0,1, 2, etc. Furthermore, the characteristic impedance of the supply line is adapted to the output impedance of the resonator.

FIG. 6 shows a perspective view of the resonator 26. It consists of a substrate of a substrate plate 27 with a conductive back plate 28, the pattern 16 with output terminals 17, 18. The separation network 21 is in principle designed in the same manner. It consists of a substrate plate 29 with a conductive back plate 30 and a conductive pattern 31, provided with two input terminals 32, 33 and two output terminals 34, 35.

Fig. 7 shows a first mutual preferred position 30 of the resonator 26 and the separation network 21.

Fig. 8 is a perspective corresponding to FIG. 7. view of a second mutual preferred position.

Obviously, in Figures 7 and 8, the same reference numerals are used as in Figure 6.

Figures 7 and 8 each show a solution, wherein in the case of a reflector as a focusing member the effective surface area intercepting the incident radiation is as small as possible.

Fig. 9 shows a fourth exemplary embodiment of a receiving element according to the invention. The resonator 36 comprises a square conductive pattern 37 with four output terminals. closures 38, 39, 40 41. Furthermore, power dividers with two inputs and one output each are provided. The outputs 38, 39, 40, 41 are connected via conductors 44, 45, 46, 47 to the respective inputs of the power dividers 42, 43. The length of the conductor 44 is a predetermined amount greater than that of the conductor 45. The same applies to the conductors 47 and 46, respectively. The length difference is (n + \). Λf where n = 0, 1, 2, .... The results of the present receiving element are in principle equal to those of the third exemplary embodiment according to Fig. 5. The outputs 48, 49 of the power divider 42, 43 respectively correspond to the outputs 22, 23 according to fig. 5.

Fig. 10 shows an axial cross-section through the antenna 20 according to FIG. 1. The receiving element 4 is located in the focus of the parabolic reflector 2.

Fig. 11 shows the directional characteristic of the antenna according to the invention. The maximum of the main lobe 50 Corresponds to the aforementioned antenna gain 25 of, for example, a minimum of 38 dB. This antenna gain is designated by the reference numeral 51. The -3 dB line 52 corresponds to an opening angle φ, which is indicated by reference number 53 in Figure 11 and has a value of, for example, 2 °. In the context of this discussion 30, no further attention will be paid to the desired lateral debris, i.e. the steepness of the lob flanks 54, 55.

Fig. 12 shows an antenna 56 according to the invention, which consists of a receiving member 58 arranged in a first reflector 57 and one associated with the first reflector 57. working reflector 59. Suffice it to refer to the known Cassegrain configuration, also referred to as mirror telescope, and to refer to the beam path as shown in Figure 12.

FIG. 13 shows an axial section through an antenna according to the invention, of which the receiving member 60 consists of two receiving elements 61, 62, as shown more clearly in FIG. 14. The elements 61 and 62 have a preselected mutual angular position for which reference is made to the figures. 15 and 16, illustrating two possible embodiments thereof: It will be apparent from the foregoing that two specific main directions are obtained by the specific choices of the position and angular position of the elements 61, 62. These 15 can for instance differ 6 ° from each other. In the example shown, the microwave resonators of the elements 61, 62 are designed as shown in FIG. 5; a reference to this and a discussion thereof has therefore been omitted.

FIG. 15 shows a first embodiment of the member 60. For distinction, the exemplary embodiment according to FIG. 15 is provided with addition a and the exemplary embodiment according to FIG. 16 with addition b. The element 60a includes a substrate plate 63 with a flat back electrode 64 and conductive patterns. The receiving member 60b comprises a rear electrode 67 on a substrate 68 and a conductive pattern 69 and 70 arranged on the front surface thereof. The angles indicated by 71 and 72, respectively, have a value corresponding to the desired difference in direction between the respective main lobes. Mentioned as an example is a separation of 6 °. In this case, the angles 71, 72 can each be 3 °. As for the results, the embodiments of Figures 15 and 16 are entirely identical. .

8006425 -12-

Fig. 17 shows very schematically a possible switching structure with the receiving member 60. The element a1 is connected via a separation network 73 to a switch 75 for selecting the desired orientation. Likewise, the element 62 is connected via a separation network 74 to a switch 76 for selecting the desired orientation sense. The output contacts of the switches 75 and 76 are connected to a switch 77, with which a selection of reception takes place via the element 61 or 62.

As discussed previously, switches 65, 66 and 67 will generally be constructed as, for example, remote-controlled semiconductor devices, for example, diodes.

It is noted that more than two elements may also be present.

Fig. 18 shows the directional characteristics of the antenna according to FIGS. 13 to 17. After the discussion of FIG. 11, a closer look will be omitted.

Fig. 19 shows a parabolic reflector 79 obliquely disposed relative to the incident waves 78, which focuses the incident waves 78 on a receiving member 80, which, as will be apparent from FIG. 19, incident waves incident completely outside the track. located. This does not intercept the incident radiation at all.

Fig. 20 shows a receiver 81 consisting of four receiver elements 82, 83, 84, 85 'connected to adjustable phase shift networks 86, 87, 88, 89 whose outputs are connected to a combining circuit 90. By controlling the phase shifts, an adjustment of the directional characteristic can be obtained. It will be appreciated that more than four receiving elements may be present and the matrix configuration may not necessarily be square.

800642 'φ ..' * -13-

Fig. 21 shows an antenna consisting of a micro-wave antenna 91, which focuses the incident rays 92 on a receiver 93. There can be no question of an intercepting effect. The microwave lens is of known type and will not be described here. The results are essentially the same as those achieved with a non-open transmission but reflection-based focusing member.

Fig. 22 shows a fifth exemplary embodiment of 10. a receiving element according to the invention.

Fig. 23 shows a sixth exemplary embodiment thereof.

The examples of Figures 22 and 23 are only suitable for receiving linearly polarized waves.

Also embodiments other than those discussed here fall within the scope of the invention. For example, a more extensive Cassegrain configuration can be used in order to obtain a smaller installation length. Other reflector shapes, lens configurations and combinations thereof are also usable.

The conductive pattern of the micro-resonator may have shapes other than those shown above. For example round, annular, elliptical, oval and so on. A conductive pattern consisting of a flat spiral or crossed open deep poles, as well as crossed slots, see for orientation the slot 13 according to Fig. 4.

Also. reference is made to the possibility of electromagnetically coupling the receiver 30 between a receiving element and an associated separation network.

8 00 6 42 5

Claims (11)

1. Directional antenna for receiving electromagnetic radiation, for example microwaves from a geostationary broadcasting satellite, which antenna comprises a receiving member and a focusing member focusing on the incident radiation 5, characterized in that the receiving member comprises at least one receiving element which comprises an insulating substrate plate , a conductive plate arranged on one face thereof and a conductive pattern flat on the other face thereof. 2. Antenna according to claim 1, characterized in that the or each conductive pattern has a shape and two output terminals arranged relative to it, such that when receiving counterclockwise circularly polarized waves only one output terminal is received and when receiving clockwise circularly polarized waves, only the other output terminal outputs an output signal. Antenna according to claim 1, characterized in that it or each. conductive pattern has such a shape and two output terminals arranged relative to it that when receiving circularly polarized waves the two output signals exhibit a positive or negative phase difference of 90 ° depending on the polarization sense and that a separation network is present, where -25 of the two inputs are connected to the said output terminals and of which one output terminal only outputs an output when receiving counterclockwise circularly polarized waves and the other output terminal only outputs an output when receiving clockwise circularly polarized waves. Antenna according to claim 2 or 3, characterized by a selector switch for choosing one or the other output connection. 800 6 42 5 -15- V. φ '' Antenna according to claim 3, characterized in that the or each separation network is placed behind the receiver relative to the focusing member. Antenna according to any one of the preceding claims / 5, characterized in that the receiving element consists of at least two receiving elements placed in pre-selected positions and at pre-selected angular positions relative to the focusing element. Antenna according to claim 6, characterized by a selector switch for choosing a desired receiving element. Antenna according to any one of the preceding claims / wherein the focusing member is a reflector with the. characterized in that the receiving member is positioned at such a distance from the center line of the reflector / substantially in the focal plane thereof that the incident radiation can incident freely on the entire reflector. Antenna according to any one of the preceding claims / characterized by a matrix arrangement of receiving elements, an adjustable phase shifter added to each receiving element, and a combination circuit connected to its outputs. 10. Antenna according to claim 3, characterized in that the receiver is electromagnetically coupled to the separation network. 11. Antenna according to one of the. previous claims, characterized in that the substrate plate consists of material from the group, which includes: polytetrafluoroethylene, aluminum oxide, quartz. 8006425