RU2566970C2 - Directed scanning planar portable lens antenna - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to the design of small-size scanning antennae. The directed scanning planar portable lens antenna includes: an upper (1) and a lower (2) lens structure in the form of a set of conducting cylinders (3), placed between two conducting screens - an outer screen (4) and an inner screen (5); unipolar radiators (6); reflectors (7); and a switch (8), wherein each port of the switch is connected to the corresponding radiator (6), and each input port is connected to a separate port of an external eight-channel receiving-transmitting device (9).

EFFECT: designing an antenna structure with wide beam scanning and enabling production using a printing technique.

7 cl, 14 dwg

Description

The invention relates to the field of telecommunications, and more specifically to the design of small-sized scanning antennas that can be used in portable mobile communication devices.

Directional scanning antennas are currently gaining ground not only in radar technology and complex special communication systems, but also in public electronic devices. The use of such functionally complex antennas in relatively inexpensive devices imposes certain restrictions on the choice of antenna type. Such restrictions as the dimensions and price of the antenna device come to the fore.

Based on such considerations, the most attractive are flat and linear antenna arrays, as well as switched antennas.

In designs based on a multi-channel transmitting and receiving microcircuit, the use of antenna arrays seems very promising, however, such antennas have a limitation in beam scanning angles, and at the maximum deviation there is a significant decrease in antenna gain.

Antennas with beam scanning by switching emitters forming a directivity in one direction or another are free from this drawback.

The most suitable in such constructions may be an axisymmetric lens antenna, which allows scanning the beam up to 360 degrees in a very wide range without significantly reducing the gain, and the scanning can be either spatial or planar.

Spatial scan lenses are large in size and unsuitable for use in compact portable devices, while planar scan lenses can be very small in height, which allows them to be placed in portable devices.

Known from the prior art directional antennas with wide circular scanning of the beam have a common significant drawback, namely, the difficulty in manufacturing and assembly in combination with the need to use a complex switching device to control the directivity.

In particular, the antenna described by Liang Xue, Vincent Fusco - Electronically Reconflgurable Microwave Lens Antennas; EOARD FA8655-04-1-3076; 2nd Six Monthly Report; www.ecit.qub.ac.uk [1], is implemented on the basis of a cylindrical planar lens, in which, due to a decrease in the dielectric constant from the center of the cylinder to the periphery, radiation directivity is formed. In this case, an artificial decrease in the dielectric constant is carried out by drilling a part of the dielectric and thus replacing it with air.

As noted earlier, this type of lens antenna has certain disadvantages. In particular, although a lens structure of this type is easily realizable, this is true only when the size of the lens is relatively large. And if the diameter of the lens is small, then its walls, separating the holes, become very fragile due to the high density of the latter. Implementing such a structure is technologically difficult. In addition, during the manufacturing process, an additional operation is required, namely, after making holes on the top and bottom of the lens, installation of metal screens is necessary. And additional refinement of the shape of the side surface of the lens is also needed.

Another prior art lens antenna design is described in US Pat. No. 6,982,676 [2]. It has the advantage that its manufacture is entirely based on the technology of multilayer printed circuit boards, however, it should be pointed out that such an antenna consists of two printed circuit boards located perpendicular to one another, and the multi-contact electrical connection of such parts is very difficult. In addition, the scanning angle has a significant limitation due to the flat aperture of the antenna.

The antenna presented in US patent No. 5,966,103 [3], is characterized by the fact that its main components are performed by printed circuit mounting, however, the lens itself is manufactured separately and also has a complex profile. The manufacture of the antenna involves mechanical assembly. In mass production, this disadvantage is significant.

The same disadvantage is inherent in the antenna described in US patent No. 3,958,246 [4]. The antenna requires a separate manufacture of components with subsequent assembly.

Closest to the claimed invention features a lens antenna described in US patent No. 6,317,092 [5] and presented in Figure 1. Here, the retarding structure is formed similarly, by installing a set of identical metal pins with the same height, evenly distributed inside the cylinder. This structure, however, assumes the presence of air in a space filled with metal pins. In this regard, the design does not imply the implementation of the lens in the environment of a multilayer printed circuit board. In addition, this antenna uses a complex switch with active attachments, which leads to significant losses and requires energy to manage.

The problem to which the invention is directed, is to develop the design of a small planar lens antenna with wide beam scanning and with the possibility of manufacturing based on printing technology.

The technical result is achieved through the development of an improved design of a directional scanning planar portable lens antenna, which includes:

- the upper and lower lens structures in the form of a set of conductive cylinders located between two conductive screens - the outer screen and the inner screen, perpendicular to them and in contact with the inner screen, while the cylinders of each lens structure have a variable height and are placed so that the distance between cylinders is approximately equal to a quarter of the wavelength in the surrounding dielectric, and in the central part the height of the cylinders is maximum and decreases to the periphery; the area occupied by the cylinders has a circular shape with axial symmetry, the lower lens structure being a mirror image of the upper lens structure;

- monopoly emitters, of which the upper ones are located on the periphery of the upper lens structure, and the lower ones are located on the periphery of the lower lens structure of collinearly conducting cylinders at equal angular distances from each other at 45 degrees from the center, with the group of upper emitters located diametrically opposite to the group of lower emitters; emitters are configured to generate a cylindrical wave propagating in a planar waveguide formed by the outer screen and the inner screen toward the lens structures;

- reflectors in the form of three conductive cylinders located on the opposite side of the lens structures of each emitter at a distance approximately equal to a quarter of the wavelength in the filled dielectric, and the reflectors are configured to form a directional wave propagation towards the center of the lens structures;

- a switch located in the middle part of the entire system between the upper lens structure and the lower lens structure in the form of a passive sixteen-pole device made on the basis of a two-feeder offset symmetrical line, with each output port of the switch connected to a corresponding emitter, and each input port connected to a separate port of the external eight-channel transceiver; the switch is configured to sum the power of eight input signals on one or two emitters in scan mode.

The main idea is that all the elements of the lens switchable antenna and the lens itself are made in print. Moreover, the slowing-down properties of the lens are realized by the field of conductive cylinders in the thickness of the multilayer printed circuit board, and the channel switch is a fully passive sixteen-pole strip device in which the channel switching is carried out by changing the phases of the input signals. The result is a compact planar antenna with directional controlled radiation, in which switching losses are minimal due to the absence of active elements. All elements of the antenna are made by high-performance printing method.

The design underlying the claimed invention is a three-section planar structure made on a layered metallized dielectric. The lower and upper sections are dielectric layers bounded on the outer upper and lower sides by round metal screens. In the environment of each dielectric layer between the screens there are many conductive cylinders formed by metallization of holes made in a multilayer dielectric with an axisymmetric distribution and with different heights of the cylinders, decreasing from the center to the edge. The distance between the cylinders is approximately equal to a quarter of the wavelength in the medium of the dielectric layer. The combination of these cylinders acts as a planar diagram-forming lens structure. On the periphery of each such structure, four metallized holes that serve as elementary emitters are located at an equal distance. The central angle defined by the extreme emitters is 135 degrees. On the opposite side from the center of each emitter has a reflector made in the form of three metallized holes. Both groups of emitters with their reflectors of the upper and lower sections are located diametrically opposite to the central axis, and the structure of the lower section is a mirror image of the upper relative to the middle section. The middle section is a multilayer strip connection that acts as a commutator of emitters. The outputs of the switch are connected to the respective emitters, and the inputs are connected to an external eight-channel transceiver.

The eight-channel signal enters the middle section of the antenna device, which is a sixteen-pole distributor and acts as a switch. Due to phase relationships, the power of all signals is summed up on one or two adjacent output ports of the switch. Next, the signal is supplied to the corresponding one or two adjacent emitters of the upper or lower sections of the antenna, which are a planar lens, and radiated by them towards the center of the planar lens in the form of a cylindrical wave directed by the upper and lower conductive screens. A cylindrical wave formed by the emitter and guided by the upper and lower conducting screens propagates in the direction of the center of the planar lens. Passing further through the set of reactive elements made in the form of metallized holes, the cylindrical wave front is converted into a shape close to a flat front. Thus, the field of reactive elements implements the function of the lens, which forms a directed radiation. Further, the electromagnetic wave is emitted by the end part of the antenna in one direction or another, depending on the specific emitter. Thanks to the switch, a flat scan takes place within 360 degrees, with four emitters of the upper or lower sections overlapping an angle of 180 degrees each, complementing one another to a full 360 degrees.

All reactive elements, emitters, as well as reflectors are metallized holes in the body of a multilayer dielectric made using printed circuit board technology.

Figure 1 is a drawing from a patent prototype [5].

Figure 2 - is a General view of the inventive antenna,

where 1 is the upper lens structure,

2 - lower lens structure,

4 - upper conductive screen,

5 - lower conductive screen,

6 - emitter

7 - reflector,

8 - switch

9 - external transceiver.

Figure 3 - shows a set of conductive cylinders forming a lens structure,

where 3 is a conductive cylinder,

4 - upper conductive screen,

5 - lower conductive screen.

Figure 4 - shows a planar dielectric lens located in a planar waveguide,

where 10 is a conducting plane,

11 - unit cell.

5 - illustrates the process of aligning the front of the wave passing through the lens.

6 - depicts the heterogeneity as a unit cell,

where 3 is a conductive cylinder.

7 - shows a transverse configuration of the lens structure.

Fig. 8 is an equivalent diagram of a lens structure.

Fig.9 - shows a partial radiation pattern.

Figure 10 - depicts the topology of the switch,

where 12 is a tandem directional coupler,

13 - phase shifter.

11 is a structure of a tandem directional coupler.

Fig - depicts the transverse structure of the entire antenna,

where 1 is the upper lens structure,

2 - lower lens structure,

3 - conductive cylinder,

4 - upper conductive screen,

5 - lower conductive screen,

6 - emitter

7 - reflector,

8 - switch.

Fig - contains a table of phase relationships of the input signals.

Fig - shows a method of excitation by means of a double-slot emitter,

where 1 is the upper lens structure,

4 - upper conductive screen,

5 - lower conductive screen,

14 - slot emitter

15 is a symmetrical feed line.

A general view of the antenna is shown in FIG. 2. The antenna is based on the upper (1) and lower (2) lens structures with four monopole emitters (6) each.

The emitters (6) are located at the periphery of the lateral surface of the lens structure (1), (2) at the same distance from each other. Each emitter individually forms a cylindrical wave propagating in the space between the upper (4) and lower (5) screens with a polarization perpendicular to the screens. Due to the reflectors (7) located behind the emitters (6) at a distance of approximately equal to a quarter of the wavelength in the dielectric medium, the wave propagation to the outside of the lens structure (1), (2) is significantly attenuated and concentrated towards the center. In the process of propagation, when passing through the retarding lens structure (1), (2), the cylindrical wave front is transformed to close to plane.

The role of the slowing-down structure of the lens (1), (2) is played by a set of reactive elements in the form of conductive cylinders (3) in FIG. 3. A method of forming a retarding diagram-forming lens structure is shown in FIG. 4. Here, two conducting planes (10) act as a plane waveguide partially filled with a dielectric. Due to the variable filling density, the wave propagation velocity will be different in individual parts of the waveguide. If we divide the entire filling region into homogeneous cells (11), then the phase delay for the peripheral cells will be less than for the central ones.

The phase delay is determined by the expression

$$\varphi =\frac{2\pi \sqrt{{\epsilon }_{e\mathrm{<figure-callout\; id="0"\; label="f\; \lambda "\; filenames="00000023.png"\; state="\{\{state\}\}">f\; </figure-callout>}}}}{{\lambda }_{}}\Delta l$$

where ε _ef is the effective dielectric constant of the unit cell,

Δl is the cell length,

λ ₀ is the wavelength.

The region of partial filling with a dielectric has axial symmetry. Part of the front of the cylindrical wave, propagating from the monopole emitter (6), passing through the central region of the lens structure (1), (2), experiences a greater deceleration than the part passing along the periphery. As a result, the common wave front receives a significant alignment, shown in Figure 5, which leads to an increase in the directivity of the antenna.

In addition to a real dielectric, a slowdown in the propagation velocity can also be realized by introducing special inhomogeneities in the form of reactive elements into the structure. So the heterogeneity in the form of a conductive cylinder (3), depicted in Fig.6, is a parallel capacitor giving a phase delay:

$$C=f(h;d)$$

$$\varphi =\arctan \left(\frac{2}{\omega C}\right)$$

$$B=\omega C$$

$$\begin{array}{l}\phi \text{- phase shift}\text{given by the conductive cylinder}\text{,}\\ \text{C is the equivalent capacity of the heterogeneity}\text{,}\\ \text{h - cylinder height}\text{,}\\ \text{d - cylinder diameter}\text{.}\end{array}$$

Thus, the conducting cylinder (3) can be represented as a unit cell of length Δl filled with a dielectric with an effective dielectric constant giving the same phase shift as the cylinder. 6, the boundary planes of the equivalent cell are designated as T1 and T2. As a result, the conducting cylinder (3) can be represented as a cell (11) filled with an artificial dielectric. Obviously, the effective dielectric constant of such a dielectric depends on the height of the cylinder and its diameter, as well as on the height of the plane waveguide. Therefore, in order to form the lens structure (1), (2), which aligns the wave front, it is required that the height of the cylinders be maximum in the center and decrease towards the periphery. The structure of such a lens structure (1), (2) should also be axisymmetric. 7 shows a cross section of the lens structure (1), (2). The height of the cylinders should be changed so that the following condition is approximately satisfied:

$${\epsilon }_{ef}(r)=2-\frac{r^2}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="00000015.png,00000020.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}$$

where ε _ef (r) is the effective dielectric constant of an artificial dielectric made on the basis of metal cylinders, reduced to the permeability of the medium surrounding the lens.

r is the current radius of the lens,

R is the outer radius of the lens.

On Fig presents an equivalent diagram of the lens structures (1), (2). The values of reactive conductivities are determined experimentally or analytically. In order for the elements of the lens structures (1), (2) not to cause significant reflections of the incident wave, the distance between adjacent conducting cylinders (3) (length of the matching transformer Tr) must be such that the condition is satisfied:

$$B_n+B_{n-\mathrm{one}}^{\text{'}\text{'}}=\min ;$$

$$B_{n-\mathrm{one}}^{\text{'}\text{'}}=\mathrm{Im}\left(\frac{Y_{n-\mathrm{one}}+\tanh (k{l}_{tr})}{\mathrm{one}+Y_{n-\mathrm{one}}\tanh (k{l}_{tr})}\right)$$

$$Y_{n-\mathrm{one}}=\mathrm{one}+j{B}_{n-\mathrm{one}}$$

where l _tr is the length of the transformer.

On Fig presents a partial radiation pattern of the antenna in the plane of beam formation (plane of the vector H) taking into account losses in the dielectric. Scanning is carried out by switching elementary emitters.

Due to the axial symmetry of the entire system, identical diagrams will be located at equal angles from one another. For smooth overlapping of a given area without significant deviation of the gain level, the partial radiation pattern should be of sufficient width. Since the width of the chart is determined primarily by the size of the lens, there are restrictions on its size. In this case, the diameter of the lens should not exceed 2λ, to ensure that adjacent diagrams overlap at a level of 3 dB. The height of the lens is limited by design and technological requirements, as well as the condition for the absence of higher types of waves.

$$h<\frac{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="00000015.png,00000020.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}{2\sqrt{{\epsilon }_{fil}}}$$

where ε _fil is the dielectric constant of the lens filling material.

Channel switching during the scanning process is carried out by a special passive switch located between the upper and lower lenses. The topology of the switch is shown in FIG. 10. All elements of the switch are made in two adjacent layers of the dielectric based on a symmetrical strip line. The main element of the switch is a tandem directional coupler (12) with full communication, shown in Fig.11. The whole circuit allows summing the signals arriving simultaneously at eight input ports on any one output port connected to the corresponding elementary emitter (6). The output number depends on the phase relationships of the input signals. Using additional phase shifters (13), a mixed mode is provided when it is possible to apply an equiphase signal simultaneously to two neighboring elementary radiators. In this case, a radiation pattern is formed that occupies an intermediate position between the two main ones, while the scanning area will have a more uniform coverage. The switch has direct losses of about 1.5 dB and the isolation between the switched off channels is not worse than 20 dB.

The table in FIG. 13.1 shows the phase values of the input signals for transmitting all the power to one or another output port of the switch.

The table in FIG. 13.2 shows the phase values of the input signals for mixed mode, when the power is divided between two ports to excite a pair of adjacent emitters.

A general cross-section of an antenna structure is shown in FIG.

The claimed invention can be used in portable means of communication, namely, where it is required to carry out reliable reception from a changing direction and spatial suppression of interfering directions. Examples include WiFi and WiGig communications; television reception for moving objects; radars for cars, providing a circular view.

Claims (7)

1. Directional scanning planar portable lens antenna, including:
the upper (1) and lower (2) lens structures in the form of a set of conductive cylinders (3) located between two conductive screens - the outer screen (4) and the inner screen (5),
perpendicular to them and in contact with the inner screen, while the cylinders of each lens structure have a variable height and are placed in such a way that the distance between the cylinders is approximately equal to a quarter of the wavelength in the surrounding dielectric, and in the central part the height of the cylinders is maximum and decreases to the periphery; the area occupied by the cylinders has a circular shape with axial symmetry, and the lower lens structure (2) is a mirror image of the upper lens structure (1);
monopoly emitters (6), of which the upper ones are located on the periphery of the upper lens structure (1), and the lower ones are located on the periphery of the lower lens structure (2) collinearly conducting cylinders (3) at equal angular distances from each other at 45 degrees from the center, and the group of upper emitters is located diametrically opposite to the group of lower emitters; emitters (6) are configured to generate a cylindrical wave propagating in a plane waveguide formed by the outer shield (4) and the inner shield (5) towards the lens structures (1) and (2);
reflectors (7) in the form of three conductive cylinders located on the opposite side of the lens structures (1), (2) of each emitter at a distance of approximately a quarter of the wavelength in the filled dielectric, and reflectors (7) are configured to form a directional wave propagation towards the center of the lens structures (1) and (2);
a switch (8) located in the middle part of the entire system between the upper lens structure (1) and the lower lens structure (2) in the form of a passive sixteen-pole device made on the basis of a two-feed offset symmetrical line, with each output port of the switch connected to a corresponding emitter (6 ), and each input port is connected to a separate port of an external eight-channel transceiver (9); the switch (8) is configured to sum the power of eight input signals on one or two emitters (b) in the scanning mode. 2. The antenna according to claim 1, characterized in that the inner screens (5) are provided with active slots (14) configured to excite a cylindrical directed wave in the space between the conducting screens (4) and (5). 3. The antenna according to claim 2, characterized in that the slots are located on the periphery of the lens structures (1) and (2) with axes parallel to the tangent to the boundary of the lens structures (1) and (2), and the distance between the slits is approximately a quarter of the length waves in the filling medium. 4. The antenna according to claim 2 or 3, characterized in that the slots are fed by a symmetrical line (15) connected to the corresponding output port of the switch (8), so that the phase of the excited signal for the slot located closer to the center of the system lags behind 90 degrees from the phase of the signal for the second slit. 5. The antenna according to claim 1, characterized in that the connection between the lens structures (1) and (2) and the switch is non-contact. 6. The antenna according to claim 1, characterized in that each output port of the switch has its own number, which is determined by the phase relationships between the input signals. 7. The antenna according to claim 1, characterized in that all elements of the antenna are made on the basis of the manufacturing technology of multilayer printed circuit boards in the form of strip conductors or metallized holes.

Images