EP3482448B1 - Controllable phase control element for electromagnetic waves - Google Patents

Description

The invention relates to a controllable phase actuator for electromagnetic waves, in particular for the GHz frequency range and in particular for antennas.

Controllable phase shifters are used in a variety of RF systems for signal processing. An important field of application are antennas or antenna systems, where the main concern is the phase-coherent superimposition of signals.

It is known, for example, that the antenna pattern of stationary antenna groups can be spatially changed with the aid of controllable phase shifters. For example, the main beam swings in different directions. The phase actuators change the relative phase position of the signals that are received or sent by different individual antennas of a group antenna. If the relative phase position of the signals of the individual antennas is set accordingly with the aid of the phase actuators, then the main beam of the antenna directional diagram of the group antenna points in the desired direction.

For group antennas on mobile carriers such as vehicles, airplanes or ships, for example, the phase control has that Task to always optimally align the main beam of the group antennas to a target during the spatial movement of the mobile carrier.

Conversely, as with stationary radar antennas, a moving target can be tracked using phase control.

The currently known phase actuators are mostly made up of non-linear solid bodies (“solid state phase shifters”), mostly ferrites, microswitches (MEMS technology, binary switches), or liquid crystals (“liquid crystals”).

However, all of these technologies have the disadvantage that they often lead to considerable signal loss, since part of the high-frequency power is dissipated in the phase actuators. The antenna efficiency of the group antennas drops sharply, particularly in applications in the GHz range.

In addition, phase controlled array antennas using conventional phase actuators are very expensive. This prevents use, particularly for civil applications above 10 GHz.

Another problem is the requirements for the precise control of the antenna pattern of the group antennas. If the group antennas are used in directional radio applications with satellites, then there are strict requirements for the regulatory conformity of the antenna pattern. For each main beam direction, the diagram of the regulatory mask must obey in transmission mode. This can only be reliably ensured that at any time both the amplitude and the phase of each individual antenna element of the group antenna is known.

However, none of the currently known technologies for phase actuators allow reliable instantaneous, i.e. Immediate determination of the phase position of the signal after the phase actuator possible without additional calculation. For this it would be necessary to be able to reliably determine the state of the phase actuator at any time. However, this is practically not possible with solid-state, MEMS or liquid crystal phase shifters.

From the DE 37 41 501 C1 is known feed system for an antenna that can transmit different polarized waves. The feed system uses a fixed 90 ° phase shifter and a movable 180 ° phase shifter so that the phase relationship of the two shafts can be adjusted to each other. The EP 0 196 081 A2 shows a high-frequency coupler with several sequentially arranged phase shifters. From the DE 39 20 563 A1 is a feed system for a parabolic antenna, which is mounted on a rotatable holder and contains a polarizer and a polarization switch.

The U.S. patent US 2,438,119 A discloses a phase converter for a linearly polarized wave by means of a plurality of webs in a cavity structure.

The JP S55 102901 A discloses the possibility of a phase shift of a high-frequency signal by means of a rotatable dielectric plate within a waveguide arrangement.

According to the US 2,546,840 A proposes a phase shifter within a hollow tubular waveguide in which a plurality of webs are arranged in the longitudinal direction, so that a phase shift of a linearly polarized wave is generated within the waveguide.

1. 1. die exakte Steuerung der relativen Phasenlage von Signalen erlaubt,
2. 2. keine, oder nur sehr geringe Verluste induziert,
3. 3. zu jedem Zeitpunkt die instantane Bestimmung der Phasenlage eines anliegenden Signals zulässt und
4. 4. kostengünstig realisierbar ist.

The scientific paper by GF Brand "A new millimeter wave gemometric phase demonstration", Int. Journal of infrared and milimeter waves, April 2000 examines the influence of a microwave phase shifter on the phase shift. The object of the invention is therefore to provide a controllable phase actuator, in particular in the GHz frequency range and in particular for antennas, which

1. 1. allows the precise control of the relative phase position of signals,
2. 2. induces no or only very small losses,
3. 3. Allows instantaneous determination of the phase position of an applied signal at any time and
4. 4. is inexpensive to implement.

This object is achieved by a controllable phase actuator according to the invention. Advantageous developments of the invention can be found in the dependent claims, the description and the figures.

Figur 2

eine Phasenverschiebung einer zirkularen Welle,

Figur 3

einen Polarisator in Draufsicht,

Figur 4

ein Phasenstellglied in einem Hohlleiter,

Figur 5

mehreren Phasenstellglieder innerhalb einer Antenne,

Figur 6

ein weiteres Beispiel eines Phasenstellgliedes mit seitlich angeordneten Antrieb,

Figur 7,8

weitere Ausführungsbeispiele eines Phasenstellgliedes mit Polarisatorpaaren,

Figur 9-11

weitere Ausführungsbeispiele eines Phasenstellgliedes mit zusätzlichen Polarisatoren und einer Phasenverschiebung einer zirkularen Welle.

A controllable phase actuator according to the invention comprises a drive unit (2) and a holder (3) on which at least two polarizers (4) arranged one behind the other in the direction of incidence of a shaft are attached. Each polarizer (4) is designed in such a way that it can convert a circularly polarized signal into a linearly polarized signal. The drive unit (2) is designed so that the bracket (3) can be rotated. This also rotates the polarizers (4) by an angle that can be freely selected and adjusts the phase of the signal as desired. The principle of operation is in Figure 1 explained, the remaining figures showing:

Figure 2

a phase shift of a circular wave,

Figure 3

a polarizer in top view,

Figure 4

a phase actuator in a waveguide,

Figure 5

several phase actuators within an antenna,

Figure 6

another example of a phase actuator with laterally arranged drive,

Figure 7.8

further exemplary embodiments of a phase control element with polarizer pairs,

Figure 9-11

further embodiments of a phase actuator with additional polarizers and a phase shift of a circular wave.

The principle of operation of the invention is in Fig. 2 shown. An incident wave (5a) with circular polarization and phase position ϕ is transformed by the first polarizer (4a) into a wave with linear polarization (5b). These are converted back into a wave with circular polarization (5c) by the second polarizer (4b).

If the phase actuator (1) is now rotated by an angle Δθ with the aid of the drive unit (2), then the polarization vector (5b) of the linear wave rotates between the two polarizers (4a) and (4b) in a plane perpendicular to the direction of propagation. Since the polarizers (4a) and (4b) also rotate, the circular shaft (5c), which is generated by the second polarizer (4b), now has a phase position of ϕ + 2 Δθ, as from Figure 2 can be seen.

Due to the construction of the controllable phase actuator according to the invention, the dependence of the phase angle difference between the outgoing (5c) and incoming (5b) circular wave on the rotation of the phase actuator (1) is strictly linear, continuous and strictly 2π periodic. In addition, any phase rotation or phase shift can be set continuously by the drive unit (2).

Since the phase actuator (1), viewed electrodynamically, is advantageously a purely passive component that does not have to contain any nonlinear components, its function is completely reciprocal. This means that a shaft that runs through the phase actuator (1) from bottom to top is rotated in phase in the same way as a shaft that runs through the phase actuator (1) from top to bottom.

Due to the design, the wave impedance of the arrangement is also completely independent of the relative phase position of the incoming and outgoing wave, which is not the case with non-linear phase shifters such as semiconductor phase shifters or liquid crystal phase shifters. There the wave impedance depends on the relative phase position, which makes these components difficult to control.

The at least two polarizers (4a) and (4b) are preferably mounted perpendicular to the direction of propagation of the incident wave and parallel to one another in the holder (3). The axis of rotation (6) is preferably in the direction of propagation of the incident wave.

The controllable phase control element works practically without loss, since the losses induced by the polarizers (4a, b) and the dielectric holder (3) are very small with a corresponding design. At frequencies of 20 GHz, for example, the total losses are less than 0.2 dB, which corresponds to an efficiency of more than 95%. Conventional phase shifters, on the other hand, typically already have losses of several dB at these frequencies.

If the drive unit (2) is also equipped with an angular position encoder or if it already gives the angular position (as is the case with some piezomotors), then the phase position of the outgoing shaft (5c) can be instantly determined exactly at any time.

Because of the simple construction of the phase actuator (1) and the fact that only very simple drives (2) are required, the phase control can be implemented very inexpensively. Reproduction in large numbers is also easily possible.

Possible drive units (2) are, for example, both inexpensive electric motors, as well as piezomotors, or simple actuators which are constructed from electroactive materials.

The polarizers (4a, b) can consist, for example, of simple, flat meandering polarizers, which are applied to a carrier material, for example a high-frequency circuit board. Manufactured these polarizers can be made by known etching processes or by additive processes ("circuit printing").

As in Fig. 3 shown, the at least two polarizers (4a) and (4b) preferably have a shape symmetrical to the axis (5).

The in Fig. 3 The polarizer (4a, b) shown is designed as a meander polarizer. However, as is known to the person skilled in the art, there are also a large number of other possible embodiments of polarizers for electromagnetic waves which can transform a wave of circular polarization into a wave of linear polarization.

Dielectric materials such as e.g. closed-cell foams with low density, which have very low HF losses, but also plastic materials such as polytetrafluoroethylene (Teflon) or polyimides are used. Because of the small size of the phase control element in the region of a wavelength, particularly at frequencies above 10 GHz, the RF losses remain very small here, with appropriate impedance matching.

The mode of operation of the invention is explained by means of several exemplary embodiments on the basis of the following figures.

In Fig. 4 An antenna element (6) is shown schematically in an exemplary application, which is preceded by a phase control according to the invention.

In transmission mode, the signal is fed into the waveguide section (2) via a coupling (31). The signal then happens Phase actuator (1) and is passed via the coupling (32) to the antenna element (6). With the help of the drive (2), which rotates the phase actuator (1) in the waveguide with the aid of the connecting element (33), the phase position of the signal emitted by the antenna element (6) can be set as desired.

Since the phase control according to the invention is completely reciprocal due to its construction, the processing of a received signal takes place in the same way: the signal received by the antenna element (6) is fed into the waveguide with the aid of the coupling (31). The signal then passes through the phase actuator (1) and is coupled out of the waveguide with the coupling (32). The phase of the received signal can be set as desired using the drive (2). A receiving amplifier can also be attached directly to the coupling (32), e.g. Compensate for network losses.

The connecting element (33) is designed as an axis and preferably consists of a non-metallic, dielectric material such as e.g. Plastic. This has the advantage that cylindrical cavity modes are not disturbed, or only very little, if the axis is mounted symmetrically in the waveguide.

The coupling structure (31) or the coupling structure (32) can be as in Fig. 4 shown as a loop, so that a cylindrical cavity mode is directly excited. However, embodiments are also conceivable in which two signals are coupled in or out with orthogonal pins. The phase relationship of the two signals is then such that a cylindrical cavity mode is also excited. The shape of the waveguide is preferably a hollow cylinder. Another example for explaining the invention is in Fig. 5 shown schematically. The phase actuator (1) consists of the two polarization plates (4a, 4b) and the holder (3) and is mounted in a cylindrical waveguide piece (50). The holder (3) is firmly connected to the waveguide piece (50). The waveguide piece (50) is introduced into a further cylindrical waveguide (51) in such a way that the waveguide piece (50) in which the phase actuator (1) is located can rotate freely about the waveguide axis (52). A drive unit (2) has a roller (53) so that the waveguide section (50) and thus also the phase actuator (1) can be rotated by the drive unit (2).

If a cylindrical waveguide mode now runs through the waveguide (51), the direction of propagation not being important because of the reciprocity of the function of the phase control according to the invention, this waveguide mode is impressed with a phase angle which is linearly dependent on the angular position of the phase actuator. By rotating the waveguide section (50) and thus the phase actuator (1) with the aid of the drive unit (2), this phase angle can be set as desired.

In the in Fig. 6 Example shown to explain the invention, the holder (3) is designed as a dielectric filler, which completely fills the waveguide section (50) and in which the polarizers (4a, 4b) are embedded. The waveguide section (50) is equipped with an outer ring gear (54) so that the drive unit (2) can rotate the waveguide section (50) together with the phase actuator (1) via the gear coupling (55).

The polarizers (4a, 4b) are designed here as two pairs. This can have the advantage of higher polarization decoupling and / or have a larger frequency bandwidth. The polarizers of a pair are at a distance from each other that is significantly smaller than a wavelength. The two pairs are spaced from each other by approximately half the wavelength in order to reduce coupling of the two polarizers.

For applications in the frequency range greater than 20 GHz, embodiments which have more than 4 polarizers can also be advantageous.

If the holder is designed as a dielectric filler that completely fills a waveguide piece, then it is also conceivable to metallize the dielectric filler on its outside, where it contacts the waveguide piece (50). This is advantageous if the component is to be very light, because then the waveguide section (50) can be omitted.

Embodiments are also conceivable in which the conversion of the signal polarization is not carried out by plane polarizers or polarization plates, but e.g. by means of structures distributed spatially in the holder (e.g. septum polaristors). For the function of the invention it is only important that these structures can first transform an incident wave with circular polarization into a wave with linear polarization and then transform it back into a wave with circular polarization.

The in the Figures 4 , 5 and 6 The examples shown can typically be easily integrated into the feed networks of group antennas due to their small space requirement. At a frequency of 20 GHz, for example, the dimensions are typically in the range of less than one wavelength, ie approx. 1cm x 1cm. If the holder (3) is designed as a dielectric filler and the dielectric constant is chosen to be correspondingly large, then much smaller construction volumes can also be achieved. The ohmic losses then increase slightly, but are still only in the percentage range.

The weight of the controllable phase actuator is also typically very small. If the polarizers are made using thin-film technology on thin HF substrates and the holder is made of closed-cell foam, the weight of the phase actuator is typically only a few grams. Therefore, only very small and light actuators, such as micro-electric motors, are required for the drive unit. The weight of such micro-electric motors is also in the gram range. The weight of an individual phase control, in particular in the frequency range above 10 GHz, is then typically only a few grams.

Added to this is the very low dissipation of the phase controls according to the invention. The heat input from the phase actuators is negligible due to the very low ohmic losses. If electric motors are used as drive units, their efficiency is typically> 95%, so that the drive units also produce practically no heat input. In addition, the power consumption of micro motors, for example, is only in the mW range.

Another advantageous embodiment of the invention is in Fig. 7 shown. The holder (3) is designed here as a star-shaped filler body with a cylindrical outer contour. In addition, four slots are provided for the pairs of polarizers (4a, 4b) and a central bore for the axis (56).

The advantage lies in the simple manufacture. The polarizers (4a, 4b) can be glued directly into the slots of the holder (3), which results in a phase actuator (1) according to the invention without further process steps. The axis (56) can also be glued directly into a hole in the holder (3) and connected to the drive unit (2).

It is also conceivable that the axis (56) is directly the axis of an electric motor, which thus directly establishes the required connection with the phase actuator (1) and can therefore meet all functional requirements.

Others, e.g. Cylindrical or triangular or cross-shaped dielectric fillers are conceivable.

A further development of the invention for the direct processing of signals with linear polarization is in Fig. 8 shown. The further development provides that at least one further polarizer (41), which can transform signals with linear polarization into signals with circular polarization, is attached in front of the phase actuator (1), and at least one further polarizer (42) is attached after the phase actuator (1) is which signals of circular polarization can transform into signals of linear polarization.

According to the invention, the phase actuator (1) also consists of the holder (3) and the polarizers (4) and has a drive unit (2) which is designed in this way and is connected to the phase actuator (1) or the holder (3) in this way that the holder (3) or the phase actuator (1) can be rotated.

The functioning of the further development of the invention is in Fig. 9 shown. An incident wave of linear polarization (7a) with phase position ϕ is transformed into a signal with circular polarization (7b) by the polarizer (41) attached in front of the phase actuator (1). The wave with circular polarization (7b) then falls on the rotatable phase actuator (1) and is transformed by the polarizer (4a) into a wave of linear polarization (7c). If the phase actuator is rotated, then the field vector (or the E and H field vectors) rotates according to the linear polarization (7c) in a plane perpendicular to the direction of propagation of the wave. The signal of linear polarization rotated in this way is then transformed by the polarizer (4b) into a signal of circular polarization (7d), the phase position of which now depends in a linear manner on the rotation of the phase actuator. If the phase actuator is rotated by an angle Δθ, then the circular shaft (7d) has the phase position ϕ + 2 Δθ. The double change 2 Δθ is caused by the rotation of the polarizers (4a) and (4b). The signal of circular polarization (7d) with phase angle ϕ + 2 Δθ is finally transformed back by the polarizer (42) into a signal with linear polarization (7e), which then also has the phase position ϕ + 2 Δθ.

The position of the vector of the linear polarization of the wave (7e) relative to the position of the polarization vector of the incident wave (7a) in the plane perpendicular to the direction of propagation depends on the relative orientation of the two polarizers (5) and (6). If these are oriented the same, then the polarization vectors of the waves (7a) and (7e) are the same. If, on the other hand, the polarizers (5) and (6) are oriented differently, then the polarization vectors of the waves (7a) and (7e) an angle determined by the relative orientation of the polarizers (41) and (42).

It is therefore conceivable, e.g. when the signal polarization has to be tracked, which can occur in certain mobile antenna applications, to design one or both polarizers (41) or (42) so as to be rotatable and to provide them with their own drive unit.

E.g. the polarizer (41) is designed to be rotatable with its own drive unit, the polarizer (42) is not designed to be rotatable, and if the polarizer (41) can be rotated independently of the phase actuator (1), then the polarizer (41) can rotate the linear polarization ( 7a) follow the incident wave. This creates a new arrangement, with the help of which the signal polarization can be tracked simultaneously and the phase position of the signal can be adjusted.

As in Fig. 10 shown, the further development of the invention also works for two signals with orthogonal linear polarization. All that needs to be considered here is the definition of the convention for the direction of rotation of the phase angle for the right- or left-polarized shaft.

Out Fig. 10 it is also clear that the function of the phase control after Fig. 1 regardless of whether a left or right circular wave is incident. Because of the reciprocity and the linearity of the function, this also applies to any superposition or even if waves of different circularity are incident simultaneously.

In Fig. 11 a phase-controlled group antenna with 4 antenna elements is shown as an example, which contains controllable phase actuators in its feed network (10).

The signals from all four antenna elements are brought together via the feed network (10). The drives of the individual phase controls are controlled e.g. by a microprocessor (11). If the phase controls are now set with the help of the microprocessor (11) so that there is a constant relative phase difference Δϕ between the signals of the individual elements, then the main beam of the array antenna points in a specific direction which is dependent on the phase difference Δϕ.

Since the amplitude relationships of the transmitted or received signals of the individual antennas are precisely known via the feed network (10) and the phase position of each of these signals can also be precisely determined via the phase controls, the antenna diagram of the group antenna is in every state of the group antenna (i.e. also to any one Time) determined completely deterministically.

If the required computing power is available in the microprocessor (11) or at another location in the antenna system, it is therefore even possible to calculate the entire antenna pattern analytically at any time with very high accuracy. This represents a significant advantage of arrangements according to the invention, in particular with regard to the regulatory conformity of the antenna pattern typically required in civil applications.

Even if the group antennas contain several thousand individual antennas, e.g. is typically the case in the frequency range above 10 GHz, the corresponding antenna pattern can be calculated very precisely with relatively low computing power using a Fast Fourier Transformation (FFT). Correspondingly fast FFT algorithms are well known.

The described examples of 1 to 7 apply analogously to the in 8-10 shown further development of the invention, so that a variety of variations and combinations is possible. Reference numerals Phase actuator 1 Drive unit 2nd bracket 3rd Polarizers 4, 4a, 4b Axis of rotation 5 Antenna element 6 Dining network 10th microprocessor 11 Decoupling 31 Coupling 32 Fastener 33 Additional polarizers 41, 42 Waveguide piece 50 Waveguide 51 Waveguide axis 52 roller 53 Sprocket 54 Gear clutch 55 axis 56

Claims (11)

1. Controllable phase control element (1) for electromagnetic waves for a feed structure of an antenna, comprising
   a drive unit (2),
   a holder (3) which has a connecting element (33) which can be rotated about an axis, and the holder (3) is mounted in a cylindrical waveguide of the controllable phase control element (1), and
   at least two meander-line polarizers (4), wherein the meander-line polarizers (4) are mounted on the holder (3) and each meander-line polarizer (4) is designed for converting a circularly polarized signal into a linearly polarized signal, and
   the drive unit (2) is connected to the holder (3) by means of the rotatable connecting element (33) in such a way that the meander-line polarizers (4) can be rotated, wherein the holder (3) is fixedly connected to the waveguide, and the waveguide is connected in a rotatable manner and to the drive unit (2), which is situated outside the waveguide, in such a way that the drive unit rotates the waveguide and the inner holder (3).
2. Controllable phase control element (1) according to Claim 1, wherein the meander-line polarizers (4) are mounted on the holder (3) perpendicularly in relation to the propagation direction of an incident wave and parallel in relation to one another.
3. Controllable phase control element (1) according to either of the preceding claims, wherein the meander-line polarizers (4) and/or the holder (3) have/has a shape which is rotationally symmetrical in relation to the rotation axis of the rotatable connecting element (33) of the holder (3).
4. Controllable phase control element (1) according to one of the preceding claims, wherein the holder (3) consists of a plastic and/or of closed-cell foam.
5. Controllable phase control element (1) according to one of the preceding claims, wherein the drive unit (2) contains an electric motor or a piezo motor or an actuator, wherein the actuator contains electroactive materials.
6. Controllable phase control element (1) according to one of the preceding claims, comprising an angle position sensor which determines the angular position of the holder (3).
7. Controllable phase control element (1) according to one of the preceding claims, wherein the meander-line polarizers (4) consist of in each case at least one polarization pair (4a, 4b) which are arranged parallel in relation to one another, wherein the distance between the meander-line polarizers (4) is less than the wavelength λ.
8. Controllable phase control element (1) according to Claim 7, wherein the distance between the meander-line polarizers (4) is half the wavelength λ.
9. Controllable phase control element (1) according to one of the preceding claims, wherein the holder (3) is a dielectric filler which is metallized on its outer sides.
10. Controllable phase control element (1) for electromagnetic waves according to one of the preceding claims, comprising two additional polarizers (41, 42) which are mounted upstream and, respectively, downstream of the meander-line polarizers (4) in the propagation direction of an incident wave, and each of the additional polarizers (41, 42) is designed in such a way that it can convert a circularly polarized signal into a linearly polarized signal.
11. Controllable phase control element (1) according to Claim 10, wherein at least one of the additional polarizers (41, 42) is configured in a rotatable manner and has a drive unit by way of which it can be rotated independently of the holder (3).

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