SE531442C2 - Electromagnetic transmission line arrangement with a phase changer - Google Patents

Description

radiating from other antenna elements will cause a change in the composite electromagnetic beam. So by moving the dielectric body longitudinally, it is possible to change the direction of the beam, for example in height, so-called electrical down tilt ("electrical down tilt").

Usually a supply line extends to a connection point and from there two branch lines extend in opposite directions. The dielectric body covers part of the supply line and the opposite branch lines and is movable longitudinally, parallel to the two branch lines. When the dielectric body, which is relatively long (much longer than its width), is displaced longitudinally, the signal will be further delayed in one branch line and less delayed in the other branch line, thus causing the associated antenna elements to transmit signals with different delays so that it transmitted wave changes its main direction. A plurality of such supply line parts can be arranged parallel to each other, possibly in a winding pattern, for supplying a desired number of antenna elements.

An example of such a transmission line arrangement is shown in document WOZOO6 / 130083Al.

Another transmission line arrangement, according to the prior art, is shown in JP63296402 where a tapered dielectric body is movable perpendicular to a transmission line.

The dielectric body has the shape of a triangle with a vertex in the direction of travel. The base of the triangle is relatively short so that the tapered body has an effective width (in the longitudinal direction of the transmission line) approximately corresponding to the width of the transmission line.

With such a very short dielectric body, the resulting signal delay will be very small and it will be difficult to avoid a reflection due to the lack of input impedance matching measures.

There is a desire to provide a change of the radiating microwave path in azimuth, i.e. laterally relative to a central horizontal direction from the antenna.

Of course, such a change can be obtained by turning the whole antenna mechanically or by changing the direction of all or some of the antenna elements. However, this is complicated and very costly.

There is therefore a need for a cost effective way to change the phase, and possibly also the amplitude, of the electromagnetic signals propagating in the transmission line arrangement of the antenna. In particular, there is a need for a transmission line arrangement with branch lines extending from a connection point to different vertical columns of antenna elements so that it is possible to change the delay of the signal transmitted to one column in relation to the signals transmitted to another column.

Theoretically, it may be possible to arrange a number of similar or identical transmission arrangements, according to the prior art, interconnected in series, one of them being used for vertical phase control and another being used for azimuth control. However, such an arrangement would be unreasonably complicated and expensive.

BRIEF DESCRIPTION OF THE INVENTION I 202 A main object of the present invention is to provide a cost-effective transmission line arrangement where the adjustment of the phase change can take place in a more favorable manner, and where the structure as a whole is relatively simple. This is achieved in such a way that the longitudinally extending dielectric body, which is longer than Å / 4 (Å is the wavelength of the electromagnetic wave propagating along the branch line in the absence of any dielectric material), is displaceable laterally relative to the branch line into a delay position and at least partially covers the branch line along its full length, and that the dielectric body has a longitudinal distribution of its dielectric material which is arranged to cause, when moved laterally into the delay position, a controlled phase change but also to ensure, together with the at least one the branch line, an input impedance matching of the transmission line arrangement.

The invention provides a myriad of possibilities for an antenna constructor to arrange one or more conductive branch lines extending from a connection point, for example in a fork-like pattern parallel to each other or in some other configuration, and control the signal phase and the delay of the signal at each branch line so that a The desired radiation pattern is obtained from the antenna elements which are connected to the various branch lines.

As will be seen below, there are many different embodiments of the dielectric body or bodies which can be used in accordance with the invention, and some of these embodiments are very advantageous from a design and manufacturing perspective. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further described with reference to the accompanying figures, which show some preferred embodiments of the invention in which: Fig. 1 schematically shows an antenna, according to the prior art, provided with a transmission line arrangement which enables adjustment of the elevation angle of a beam emitted from the antenna by displacing a dielectric body in the longitudinal direction; Fig. 2 schematically shows the transmission line arrangement, according to prior art, belonging to the antenna according to Fig. 1; Fig. 3 schematically shows an antenna provided with a transmission line arrangement according to the invention, the latter arrangement being shown schematically as a box-like unit, which enables adjustment of the azimuth direction and / or the azimuth beam width; Figs. 4a and 4b schematically show two embodiments of a transmission line arrangement, according to the invention, with a single transmission line extending between two ports; Figs. 5a and 5b show an equal power divider with two parallel transmission lines and three separate body parts, which form a dielectric body and are displaceable laterally between the two transmission lines and to a neutral position therebetween; Figs. 6a, 6b and 6c show a differential power divider with two parallel transmission lines and three separate body parts of a dielectric body, which are movable laterally between the two transmission lines and a neutral position therebetween; and Figs. 7a, 7b and 7c schematically show three embodiments of a transmission line arrangement according to the invention for three branch lines, which extend parallel to each other from a connection point.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS The microwave antenna 1, according to the prior art, schematically shown in Fig. 1, has a vertical column with five individual antenna elements 2 mounted on a linear row on a substantially planar reflector 3. When the antenna is fed from a microwave power shown in the figures) via a supply structure in a control unit 4 (left in Fig. 1) it can transmit and receive electromagnetic signals in a well-defined beam, for example between a base station and mobile telephones in a cellular mobile communication system.

The entire antenna can be mechanically rotated if desired, as indicated by the rotation arrow P1, but this aspect has no significance in relation to the present invention.

The electromagnetic beam from the antenna 1 can be controlled in height, namely in a vertical plane through the column with antenna elements 2, through an adjustable electric power divider which feeds the various antenna elements. The control unit 4 has two input supply lines 5, 6, one for each polarization (each antenna element is cross-polarized as is known in the art). Inside the control unit 4, the power is divided into five signals, which are identical with respect to the frequency content, but are changed in phase in relation to each other. As a result, some signals will be more delayed than others and it is possible to obtain a beam which is more or less inclined in the vertical plane, so-called electrical down tilt ("electrical down tilt"). 2 shows a previously known method of obtaining such a controlled phase change and signal delay by a branch line arrangement according to the prior art with an input transmission line 7 oriented perpendicular to two output transmission lines 8, 9, which consist essentially of a material of metal strips and arranged in parallel with a ground plane (not shown in the figure) so that the electromagnetic signals can propagate from the input transmission line 7 and, after equal division at the connection point 10, further along each of the output transmission lines 8, 9. One, two or more such power dividers can be connected in series so that a desired division of power and delay can be obtained by the propagating signal.

The delay is achieved by arranging a dielectric body 11 along the two output transmission lines 8, 9, and a dielectric body part 12 along a part of the input transmission line 7. The propagation speed of the electromagnetic signal depends on the dielectric constant of the material in the volume where the electromagnetic wave propagates. In order to adjust the speed and thereby the delay at the output terminals of the output transmission lines 8, 9, the dielectric body 11 is displaced back and forth in a controlled manner longitudinally along the lines 8, 9 in the direction of the arrow P. Thus the relative speed will change and thus also the respective speed delays. In practice, the shape and configuration of the dielectric body is adapted to the particular antenna construction where the need for impedance matching is also taken into account in order to avoid reflection of the signal. In this way, the vertical inclination or inclination of the beam can be controlled to a certain extent. 10 15 20 25 30 531 442 As discussed above, there is a need for further adjustment of the beam, especially in azimuth. To this end, a new transmission line arrangement has been developed in accordance with the present invention.

Fig. 3 shows an antenna with three vertical columns with antenna elements 21, 22, 23. Each such column is adjustable by means of associated control units 24, 25, 26 as described above. Thus, the height of the composite electromagnetic beam from the antenna can be controlled by these control units. As in Fig. 1, the entire antenna 20 can be mechanically rotated (arrow P1), but this aspect is not part of the present invention.

In series with these control units, preferably at the input side to reduce necessary hardware, there is a new type of control unit 27 which serves to control the antenna beams in azimuth.

The control can take place with regard to the main direction and / or the width of the beam.

The basic idea of the present invention is the arrangement of a transmission line (or lines) together with a dielectric body (or body segments, separate body parts or bodies) which is movable laterally in a transverse direction relative to the transmission line. A number of embodiments of such an arrangement will be described with reference to Figures 4a, 4b. Sa, 5b, 5c, 6a, 6b, 7a and 7b.

Fig. 4a shows a single transmission line 30, an underlying ground plane 35 (shown schematically) and a longitudinal dielectric body 31 with three different segments, namely a central segment 32 and two end segments 33, 34.

The dielectric body is movable in its entirety in the transverse direction shown by the arrow P2 and can be displaced between a neutral or inactive position (bottom in Fig. 4a), where it does not affect the speed of the propagating path , and an active position or a "delay position", where it causes a corresponding delay of the signal propagating along the associated branch line 30. With such an arrangement with a transversely displaceable dielectric body, many possibilities are provided to configure a transmission line arrangement having a , two or more transmission lines extending from a connection point.

In order to avoid power losses being transmitted, the input impedance, for example at the left end of the transmission line in Fig. 4a, must be matched when the dielectric body is placed in its active position. One way to do this is to use a quarter-wave matching where each of the end segments 33, 34 has a dielectric constant 21 and the central section has a dielectric constant 22, the matching being obtained by: el = 'V82 Li = Mun / el) = A / (Anhm), where L1 is the physical length of each end segment 33, 34 and Å is the wavelength in air. Certainly, instead of adjusting the dielectric constant, it is also possible to change the geometric configuration of the respective segments, for example by varying the width (thickness) or by drilling heels through the dielectric material. Those skilled in the art can ensure that the impedance of the dielectric body seen from both ends (in the longitudinal direction) matches the characteristic impedance of the transmission line. This matching is obtained only for a specific frequency. Within a relatively narrow frequency band, however, it is not necessary to take this into account.

The main purpose of the transversely displaceable dielectric body 31 is to obtain a predetermined delay of the signal and this can be achieved by correctly selecting the length L2 of the central body 32, which can be done by the person skilled in the art.

Instead of an integrated dielectric body with uniform end segments, it is also possible to use separate body parts as shown in Fig. 4b. Here, a central portion 42 corresponds to the central section of Fig. 4a while the left and right body portions 43, 44 correspond to the end segments of Fig. 4a.

It has been found that the arrangement according to Fig. 4b works very similar to the arrangement in Fig. 4a. All three body parts must be movable laterally, preferably synchronously in the transverse direction (arrow P2).

In principle, a transmission line with a dielectric body, or with a number of separate body parts, all of which are laterally movable in the transverse direction, can provide a desired delay to cause, for example, a change of the beam in azimuth. If two of the vertical columns are fed with power through the supply lines which have only one phase delay which causes a slope and the third vertical column, for example the middle one, is further slightly delayed, the width of the beam will be narrower. Such a transmission line arrangement can be integrated in a prior art arrangement, where a transversely displaceable dielectric body is integrated in each part of the control unit 4 in Fig. 1 (which also comprises longitudinally displaceable dielectric bodies).

However, typically in an antenna with two or more vertical columns of antenna elements, it is more practical to have a separate control unit 27 in series, as shown in Fig. 3. In such a control unit there is a connection point for each polarization (two connection points). with parallel transmission lines extending parallel therefrom, usually two or three such lines from each connection point. These transmission lines are then connected in pairs to the respective elevation phase control units 24, 25, 26 (Fig. 3).

In a transmission line arrangement with two parallel transmission lines, the input power can be divided equally or differently at the connection point.

An equal power divider in strip line is shown in Figs. 5a and 5b. A conductive input supply line 50 is divided into two equally conductive branch lines 51a, S1b, which extend in a fork-like manner from a connection point 51c.

The power divider is located in a box-like, relatively flat housing 55, with upper and lower metal walls (or covers), which serve as ground planes.

In Fig. 5a, there are three separate dielectric body parts 52, 53, 54 placed in a neutral position on a straight (imaginary) line C centrally between the branch lines. These body parts may correspond to the parts 32, 33, 34 shown in Fig. 4b. In this mode, the power is divided equally on the branch lines Sla, 51b. Each branch line has narrower and wider sections adapted to provide impedance matching at the input so that there will be only a minor reflection of the input wave.

As shown in Figs. 5a and 5b, each dielectric body is divided into two parts, an upper part and a lower part.

In the example shown, for a frequency band of 1710 MHz - 2170 MHz, the specifications are as follows: Length / distance dielectric (mm) constant (S) Body part 52: 9 3 Body part 53: 5 3 Body part 54; 4 3 Distance dl 32 Distance d2 31.5 In Fig. 5b, the three separate dielectric body parts 2, 53, 54 have been displaced laterally or transversely (in relation to the imaginary central line C) to cover one (šlb) of the branch lines. In this way, the signal on the branch line 51b will be delayed as described above with reference to Figs. 4a and 4b. There is some input reflection, but the size of this is almost negligible, provided that the dielectric constants and the length of the body parts are correctly selected, as in the example above.

Figs. 6a, 6b, 6c show an embodiment with a different power divider similar to the divider shown in Figs. 5a and 5b. but with two branch lines 61a and 61b, which extend from a supply line 60 which has a connection point 61c and is arranged to provide a power ratio of 3dB between the branch lines. For this purpose, the conductive branch line 61b has a section with a narrower width in the vicinity of the connection point. There are three dielectric body portions 62, 63, 64 (each having upper and lower portions) similar to those shown in Figs. 5a and 5b, which are movable transversely or laterally into a position as shown in Fig. 6b, or into a position as shown in Fig. 6c for covering the branch line 61b and 61a, respectively.

In the position shown in Fig. 6b, the signal in the branch line 61b will be delayed, while in the position shown in Fig. 6c, the signal in the second branch line 61a will be delayed. Due to the thinner (less wide) branch line 6lb, there will be some imbalance in the phase of the two ports in the neutral position (Fig. 6a), but the power ratio will be essentially the same anyway, about 3dB.

Embodiments with three branch lines are shown in Figs. 7a, 7b and 7c.

In Fig. 7a, the three conductive branch lines 71a, 71b, 710 are referred to and extend from a supply line 70 with a connection point 70c. The upper and lower (or first and second) branch lines 71a and 71b have sections with a stepwise reduced width, the impedance Z being higher and the power supplied along these two lines being less than in the central line 71c, in the absence of some dielectric bodies located on the wires.

However, a specially designed dielectric body 72 is provided to enable a change in the relative delay of the signal transmitted through the lines 71a, 71b. The dielectric body is manufactured as an integral body 72 and has an upper or first rectangular body portion 72a having a longitudinal extent substantially corresponding to the straight portion of the upper or first branch line 7la, and a lower or other rectangular body portion 72b having a longitudinal extent corresponding to the straight portion of the lower or second branch line 71b, and two relatively thin transverse portions 73 and 74 connected to the body portions 72a and 72b at their ends. The length of these transverse sections is greater (or less) than the distance between the branch lines 72a, 72b so that only one (72a or 72b) of the body parts will cover an associated branch line 7la, 7lb at any one time.

As shown in Fig. 7a, the dielectric constant sr of the body portion 72a is selected so that the impedance of the branch line 71a with the body portion 72a covering the body portion 71a is the same as the impedance Z0 of the central branch line 71a without any covering dielectric material. Likewise, the stepwise reduction of the width of lines 71a and 7lb is such that all three branches will have the same input impedance at all times regardless of the location of the integrated dielectric body, either with body portion 72a covering branch line 7la or with body portion 72b covering branch line 7lb (at a transverse movement in the direction of arrow P2).

Of course, this transmission line arrangement can be used, for example, in a control unit 27 in order to delay the signal in one of the columns 21, 23 on the edges in Fig. 3.

Since the input impedance of the three branch lines is the same, the power will always be distributed equally between the lines.

If it is desired to control the power distribution between the three lines, an embodiment shown in Fig. 7b can be used.

In this example, the structures are the same as in Fig. 7a except that the branch lines and the dielectric body extend longitudinally with extensions of branch lines 7laa, 7lbb and 71cc, and extensions of dielectric body parts 72aa, 72bb as well as a extra body part 72cc which partly covers the extension of the branch line 71cc. The structure is such that the input impedance (at the input or left end of the three branch lines) will depend on the transverse position of the integrated dielectric body 72 '. The extensions 72aa, 72bb, 72cc have a selected length and dielectric constant.

In the position shown by the dielectric body 72 *, the input impedance of the lower or second branch line 71bb is higher than for the other two branch lines so that the power transmitted along the lower or second branch line will be lower. It will be appreciated that the relative power at the columns on the edges (in the antenna 20 in Fig. 3) can be adjusted so that the beam is adjusted to a certain extent in azimuth.

In the embodiment shown in Fig. 7c, the structure is the same as shown in Fig. 7b, but there is a further dielectric body 75 arranged parallel to the central branch line and is movable in the transverse direction (arrow P3).

Thus, the signal to the middle column of the antenna 20 in Fig. 3 can be delayed to reduce the width of the beam emitted from the antenna 20.

Those skilled in the art can use the teachings of this specification, within the scope of the claims, for example, to modify the direction of the "transverse" motion of the dielectric body. Thus, this movement can also be performed at an angle (less than 90 ° and preferably less than 45 °) to the perpendicular transverse direction. In the delay position, the dielectric body (or deSS separate parts) must be oriented longitudinally along the associated transmission line. However, the movement towards or away from this position can be performed in different ways, even with a pivoting movement about a fixed (or movable) axis.

The transmission line arrangement may also be slightly curved instead of being completely flat. Furthermore, it is possible to use the new transmission line arrangement for other purposes, for example to control a beam in height instead of in azimuth.

Claims (14)

10 15 20 25 30 531 442 17 PATENT REQUIREMENTS 1. An electromagnetic transmission line arrangement with a phase changer, comprising at least one conductive branch line (30; 5la, 5lb; 7la, 71b, 71c) extending from a connection point to an associated output port for propagating electromagnetic signals in a high frequency band along the branch line, at least one ground plane (35) located parallel to but at a distance from the transmission line arrangement, the phase changer including at least one dielectric body (31; 52, 53, 54; 72; 72 ') movably mounted in a space between the ground plane and the branch line; and is movable in space so that a variable phase change and a controlled delay are obtained by the electromagnetic signals when they propagate along the branch line, the at least one dielectric body (31; 52, 53, 54; 72; 72 ') having a longitudinal extent. between its ends, which is longer than its width and also longer than Å / 4, Å being a wavelength of the electromagnetic the wave propagating along the branch line in the absence of any dielectric material, characterized in that - the at least one longitudinally extending dielectric body (31; 52,53,54; 72; 72 ') is laterally displaceable (P2; P3) in relation to the branch line (30; 5la, 5lb; 71a, 7lb, 7lc) to a delay position where it at least partially covers the branch line along its full length, and - the at least one dielectric body has a selected longitudinal distribution of its dielectric material (2), which is arranged to cause a controlled phase change when moving laterally into the delay position, but also to ensure, by the selected longitudinal distribution of its dielectric material together with the at least one branch line, an input impedance matching of the transmission line arrangement. The electromagnetic transmission line arrangement according to claim 1, wherein the at least one dielectric body comprises at least three separate dielectric body parts (42; 43; 44) distributed along the branch line (40), a central body part (42) having a length arranged to cause a desired signal delay and two end body portions (43,44), each having a length and a dielectric constant, which together with the branch line provide the impedance matching. The electromagnetic transmission line arrangement according to claim 2, wherein the separate dielectric body parts (42, 43, 44) are synchronously displaceable laterally (P2) into the delay position. Electromagnetic transmission line arrangement according to claim 2 or 3, wherein the separate dielectric body parts (62,63,64) are laterally displaceable between at least two delay positions, each of which covers an associated branch line (62b, 6la), which extend from the connection point. (61c) to an associated output port, AND also possibly to one or more neutral positions (C) therebetween. The electromagnetic transmission line arrangement of claim 1, wherein the at least one dielectric body comprises an integrated body (31) having at least one central segment (32) having a length (L2) adapted to cause a desired signal delay, and two end segments. (33,34), each of which has a length (L1) and a dielectric constant to provide the impedance matching. An electromagnetic transmission line arrangement according to any one of the preceding claims, wherein the at least one dielectric body comprises at least two parallel body parts (72a, 72b), each of which is located in the vicinity of an associated branch line (7la, 7lb) extending from the connection point ( 70c) to an associated output port and are displaceable laterally (P2) with a common movement of the whole dielectric body between a delay position of a first body part (72a) in relation to a first branch line (7la) with a second body part (72b) which is placed in a neutral position, and a neutral position of the first body part (72a), with the second body part (72b) placed in a delay position relative to a second branch line (71b). An electromagnetic transmission line arrangement according to any one of the preceding claims, comprising at least two parallel branch lines (6la, 6lb; 71a, 71b) extending from the connection point (6lc, 70c), the parallel branch lines having different input impedances so that an uneven power distribution between the branches obtained. The electromagnetic transmission line arrangement according to claim 7, wherein the dielectric body (62,63,64) is arranged so that the uneven power distribution is obtained when it is moved laterally into the respective delay position. The electromagnetic transmission line arrangement according to claim 7, wherein the dielectric body (72 ') is arranged so that the uneven power distribution is obtained when it is moved transversely (P2). The electromagnetic transmission line arrangement of claim 9, wherein two parallel body portions (72a, 72b) each include an extension (72aa, 72bb) with a selected dielectric constant. An electromagnetic transmission line arrangement according to any one of the preceding claims, wherein the at least one dielectric body is laterally movable between a neutral position, which has no effect on the signal propagation along the branch line, and the delay position. Electromagnetic transmission line arrangement according to any one of the preceding claims, wherein the lateral movement is performed in a transverse direction (P2, P3) in relation to the branch line. An antenna (20) having at least one column (21,22,23) of antenna elements, comprising an electromagnetic transmission line arrangement according to any one of the preceding claims, wherein the at least one branch line is connected to the at least one column (21,22,23) of antenna element The antenna (20) of claim 13, comprising at least two substantially vertical columns of antenna elements for transmitting and receiving a composite microwave beam, the phase shifter (27) causing a change of the beam in azimuth and operating in conjunction with another phase shifter (24,25). , 26) which controls the height of the microwave beam.