Patent Grant
12278429
This application claims priority to European Application No. EP21173870.3, filed on May 14, 2021, the contents of which are incorporated herein by reference in their entirety.
The present invention relates to antennas. In particular, it relates to antennas suitable for a global navigation satellite system (GNSS) receiver.
Antennas that are suitable for a global navigation satellite system (GNSS) receiver are known. A GNSS receiver receives satellite signals transmitted from a GNSS satellite constellation through such an antenna. Next-generation GNSS receivers operate at two (or more) frequency bands to mitigate multipath and atmospheric distortion errors. Hence, it is desirable for antennas to be compatible with dual-band GNSS technology.
In general, the cost and size of an antenna are important factors. It is desirable for the antenna to be as small as possible, and it is desirable for the antenna to be as economical as possible to manufacture on a large scale. Traditionally, reductions in antenna size have been achieved by increasing the dielectric constant of the substrate on which the antenna is fabricated. However, substrates with a high dielectric constant tend to be more expensive.
The present inventors have recognised that it would be desirable to provide a smaller antenna—for example, a smaller antenna for a GNSS receiver—without resorting to high cost, high dielectric constant materials.
The invention is defined by the claims. According to a first aspect, there is provided an antenna comprising a plurality of like antenna elements,
Antennas according to embodiments may facilitate size reduction, and may be manufactured at relatively low cost, without the need for specialised, high dielectric constant materials.
The antenna elements are substantially similar, preferably identical. The antenna elements may be spaced and oriented with regular intervals between them, in a rotationally symmetric arrangement. This means that the set of antenna elements looks the same when rotated by a partial turn. The degree of rotational symmetry (that is, the number of distinct orientations in which the set of antenna elements looks the same) may be identical to the number of antenna elements.
There may be at least three antenna elements, or at least four antenna elements. Such configurations may be suitable for transmitting/receiving circularly polarised signals. In particular, they may facilitate reception of right-hand circularly polarised GNSS signals.
The radiating element and the short to ground are conductive elements.
The ground plane may be provided separately from the antenna—in particular, separately from the antenna elements. For example, the ground plane may be formed on a substrate that is different from a substrate on which any of the antenna elements is formed.
Antenna elements like those presently disclosed, having a radiating element, a feed point, and short to ground, are sometimes described as “inverted-F” antennas.
The antenna elements may be configured to transmit/receive different versions of the same signal, with a phase shift between the versions of the signal that are transmitted/received by neighbouring antenna elements.
In other words, the different versions of the same signal may be phase-shifted versions of the signal—copies of the same signal at different phase shifts. In this way, the antenna elements are configured to act as a single radiating element.
The antenna elements may be collectively configured to transmit/receive a circularly polarised signal.
The radiating element of each antenna element may extend in a plane parallel to the ground plane, and the short to ground may extend perpendicular to the ground plane.
Each radiating element may lie in a notional plane that is parallel to the ground plane. This means that each radiating element extends parallel to the ground plane, and is spaced a certain fixed distance from the ground plane. Each radiating element may describe a line or an arc in the notional plane.
Each short to ground may extend between the ground plane and the radiating element such that it is perpendicular to the ground plane and perpendicular to the notional plane in which the radiating element lies. In a normal upright orientation of the antenna, both the ground plane and this notional plane may be horizontal planes.
In each antenna element, the radiating element may comprise an elongate element and the feed point may be arranged at an intermediate point along the elongate element.
In each antenna element, the short to ground may be arranged at one end of the radiating element.
The antenna may be a multi-band antenna or dual band antenna.
A multi-band antenna is configured to have resonant frequencies in more than one frequency band. A dual band antenna is an example of a multi-band antenna, which is configured to have exactly two resonant frequencies, in respective different frequency bands.
The antenna may have a first resonant frequency in a first frequency band and a second resonant frequency in a second frequency band, different from the first frequency band. A ratio of the first resonant frequency to the second resonant frequency may be in the range 1.2:1 to 1.4:1, optionally 1.3:1 to 1.35:1. In some embodiments, the first resonant frequency may be in the L1 band and the second resonant frequency may be in the L5 band.
In each antenna element, the radiating element optionally comprises a first part and a second part, wherein the first part is spaced a first distance from the ground plane and the second part is spaced a second distance from the ground plane, wherein the second distance is greater than the first distance.
Providing the first part and second part in this way may offer one convenient way to achieve dual-band or multi-band functionality.
Each of the first part and the second part may comprise an elongate element, wherein the first part has a first length and the second part has a second length, different from the first length.
The second length may be longer than the first length.
Each elongate element may extend in a plane parallel to the ground plane. The first length and the second length may be measured parallel to the ground plane.
The feed point may be arranged at an intermediate point along the first part, and wherein the short to ground is arranged at one end of both the first part and the second part, for galvanically connecting the first part and the second part to the ground plane.
The length of each part may be measured (parallel to the ground plane) starting from the short to ground.
Each antenna element may be formed on a printed circuit board (PCB). In some embodiments, the antenna elements may all be formed on different PCBs.
The antenna elements may be formed on a single, unitary substrate.
Each antenna element may be formed on a printed circuit board (PCB). The antenna elements may all be formed on the same PCB.
The use of a PCB substrate may help to reduce cost and weight, especially in comparison with antennas that require a substrate with a high dielectric constant. Reduction in weight can help to make the antenna less susceptible to damage due to mechanical vibration and impacts.
The substrate may be flexible, and may be bent, curved or folded to arrange the antenna elements in their respective positions and orient them in their respective directions.
The substrate may be bent, curved or folded, such that an edge of the substrate, parallel to the ground plane, may form one of the following shapes: a circle; an ellipse; a polygon; a polygon with rounded corners; a rectangle; and a rectangle with rounded corners.
Here, it should be understood that a “rectangle” includes a square, as a special case in which the rectangle has sides of equal length. Alternatively, the rectangle may have sides of unequal length.
The substrate may comprise a flexible PCB.
The antenna may have a length and a width, or a diameter, in the range 25 to 30 mm, with the length and the width optionally being equal, and a height in the range 5 to 7 mm.
The antenna may further comprise a phase shifting network, coupled to the feed points of the antenna elements and configured to provide a phase shift between the feed points of neighbouring antenna elements.
The phase shifting network may be configured to apply a phase shift between the antenna elements such that the antenna is configured to transmit/receive circularly polarised signals, in particular, right-hand circularly polarised signals. The phase shifts may all be substantially equal to one another. The phase shifts may be chosen in correspondence with the number and angular positions of the antenna elements. For example, where the antenna comprises N antenna elements, arranged at intervals of 360°/N, the phase shifts may be equal to 360°/N. The phase shifting network may avoid the need for a hybrid coupler to couple the feed points to the transmitter/receiver. This may help to reduce the cost of the overall system.
In general, the phase shifting network may be provided separately from the antenna elements, or may be formed integrally with the antenna elements. However, the latter arrangement may facilitate a reduction in the number of separate components, and potentially a consequent reduction in the size and cost of the antenna.
The antenna elements may be formed on a single, unitary substrate and the phase shifting network may be formed on the same substrate as the antenna elements. This can provide a compact, efficient, and cost effective way to form the phase shifting network. As noted above, the substrate may comprise a PCB, in particular, a flexible PCB.
The phase shifting network may comprise one or more inductive or capacitive elements between each pair of neighbouring antenna elements. The use of one or more inductive/capacitive (L/C) elements in the phase shifting network can facilitate a size reduction of the phase shifting network, thereby making the overall system more compact.
Each antenna element may comprise one or more inductive or capacitive elements.
The one or more L/C elements in each antenna element may be configured to increase an electrical length of at least a portion of the antenna element. This can facilitate a reduction in the size of the antenna element (for a given frequency band of operation), and thereby a reduction in the size of the antenna, making it more compact. The one or more L/C elements can also assist in tuning at least one resonant frequency of the antenna.
At least one of the inductive or capacitive elements may be formed as a distributed element. This applies to the one or more L/C elements of the antenna elements and/or those of the phase shifting network. If the antenna elements are formed on a unitary substrate, the distributed element(s) may comprise conductive tracks on the substrate.
In alternative embodiments, the L/C elements may be formed as discrete elements—for example, surface mount elements on a PCB. However, distributed elements may have the advantage of lower cost.
Distributed elements formed on a flexible PCB can offer accurate control of fine dimensions of the elements, facilitating reduction in size as well as improved manufacturing yield.
Also provided is a GNSS receiver module, comprising: an antenna as summarised above and/or according to of any one of the appended claims; and a GNSS receiver, coupled to the antenna.
The antenna may be coupled to the GNSS receiver via one or more filters and/or amplifiers.
The GNSS receiver may be configured to receive signals in both the L1 and L5 bands, via the antenna.
According to another aspect, there is provided a method of manufacturing an antenna, the method comprising:
providing a flexible substrate;
disposing a plurality of like antenna elements on the flexible substrate, each antenna element comprising:
bending the flexible substrate such that the antenna elements are spaced apart in different positions and oriented in different directions.
The method may further comprise disposing a phase shifting network for the antenna on the flexible substrate. Optionally, this may be done in the same step as disposing the antenna elements on the substrate.
Also provided is a method of transmitting or receiving a circularly polarised signal using an antenna as summarised above or as recited in any one of the appended claims.
The invention will now be described by way of example with reference to the accompanying drawings, in which:
It should be noted that these figures are diagrammatic and not drawn to scale. Relative dimensions and proportions of parts of these figures have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings.
Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings. The described embodiments should not be construed as being limited to the descriptions given in this section; the embodiments may have different forms. In the embodiments below, an antenna comprising a plurality of like antenna elements, a GNSS receiver module incorporating the antenna, and a method of manufacturing such an antenna shall be described.
In the example shown in
The antenna elements 10 are all identical. They are arranged in a circular configuration, at regular angular intervals of 90°. Consequently, the antenna is rotationally symmetric, with a degree of rotational symmetry equal to 4. This antenna is well-suited to transmitting—or, in particular, receiving—right-hand circularly polarised (RHCP) GPS signals. Designing the antenna to receive RHCP GPS signals using such a configuration of antenna elements may assist with rejection of reflected (multipath) GPS signals, and may improve the gain of the antenna.
The antenna elements 10 are formed on a unitary substrate. Specifically, in this example, the antenna elements 10 are formed by metallization on a flexible printed circuit board (PCB) 30. That is, the flexible PCB 30 is a unitary substrate on which the antenna elements 10 are formed. The height of the flexible PCB 30, and hence the height of the antenna 100 itself, is measured along the z-axis. This flexible PCB 30 is bent 360° around the z-axis into a cylindrical shell with open circular ends. The height of the antenna is less (preferably significantly less) than the diameter of the antenna, measured parallel to the x-y plane. For example, the antenna may have a height of approximately 5 mm and a diameter of approximately 25 mm.
In the example illustrated in
The ground plane 20 is provided on a separate flat substrate, which mechanically supports the flexible PCB 30 from below. The ground plane 20 is shown partially and schematically in
It will be understood that the parts associated with different antenna elements are distinguished by the use of suffixes -1 to -4 in the reference numerals. Thus, a first antenna element 10-1 has a feed point 14-1 above an opening 18-1 in the ground plane 20, and so forth. Likewise, a second antenna element 10-2 is positioned above an opening 18-2 in the ground plane. As mentioned above, a third antenna element 10-3 and a fourth antenna element 10-4 are hidden from view in
Since the antenna elements 10 are evenly distributed around the cylindrical shell, with regular angular shifts of 90° between them, the openings 18 in the ground plane are distributed in the same rotationally symmetric pattern.
Each antenna element 10 comprises a radiating element formed of parts 12 and 13, a feed point 14, and a short to ground 16. The feed point 14 is used to couple the radiating element 12, 13 to a GPS receiver 50 as part of the GPS receiver module 150. (The GPS receiver and GPS receiver module are illustrated in
According to the example illustrated in
The parts of each individual antenna element 10 will now be described in greater detail, with reference to
It can be seen that each antenna element 10 comprises a radiating element formed of parts 12 and 13, a feed point 14, and a short to ground 16. The feed point 14 is used to couple the radiating element 12, 13 to the GPS receiver 50 (illustrated in
As can be deduced from
The short to ground 16 extends vertically downward from one end of the radiating element 12, 13, towards the lower edge of the flexible PCB 32, where, in the example of
The feed point 14 is arranged at an intermediate point along the radiating element 12, 13. This combination of features provides the antenna element 10 with an inverted-F configuration.
In the examples shown in
The feed point 14 is arranged at an intermediate position along an elongate element of the radiating element. In particular, in the example shown in
The transmission line 35 extends parallel to the x-y plane on the outer surface of the bent PCB 32. A first vertical gap exists between the lower edge of the flexible PCB 32 and a lower edge of the transmission line 35, such that the lower edge of the flexible PCB 32 is below the lower edge of the transmission line 35. The first vertical gap ensures the transmission line 35 is not in contact with the ground plane 40. A second vertical gap exists between an upper edge of the transmission line 35 and an upper edge of the ground strip 21, such that the upper edge of the transmission line 35 is below the upper edge of the ground strip 21. The second vertical gap ensures that the transmission line avoids crossing over the short to ground 16, to avoid adding an undesired and/or unknown loading to the transmission line 35. Such an undesired/unknown loading may cause the performance of the micro-strip feed network to deteriorate.
Forming the radiating element of two parts 12 and 13 having different dimensions and arranged at different distances from the ground plane 20 or 40, as illustrated in
In the examples of
In the example illustrated in
In the second example illustrated in
In another example, the phase shifting network may comprise a single feed pin extending to the feed point of the fourth antenna element 10-4, to couple the GPS receiver 50 to this element. The feed points of the first, second, and third antenna elements 10-1, 10-2, and 10-3 may be coupled to the feed point of the fourth antenna element 10-4 by successive phase shifting circuits 46, 44, and 42, implemented on the flexible PCB itself.
The exemplary phase shifting network illustrated in
Note that, since the phase shift of an L/C phase shifting circuit will inevitably be a variable function of frequency, it is not possible, in practice, to provide a phase shift of exactly 90° uniformly over the entire frequency range. However, it has been found that reception of RHCP signals may be enhanced by providing approximately the correct phase shifts over the relevant frequency range—for example, by providing that the average phase shift over the frequency range has the targeted value.
In some examples, distributed L/C elements may also be provided in the antenna elements 10. Here, they may be used to change the electrical length of one or more portions of the antenna element. This may help to reduce the size of the antenna element (and potentially also the antenna) for a given desired frequency range of operation. The L/C elements can also be used as part of the antenna elements in order to tune one or more resonant frequencies of the antenna.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.
The antennas in
Antennas according to some embodiments may receive GPS signals but may have a first and second resonant frequency different to the resonant frequencies stated above. For example, the antenna may have a first resonant frequency in the L2 band, and a second resonant frequency in the L1 band. More generally, for an antenna designed to receive GNSS signals, the ratio of the first resonant frequency to the second resonant frequency may be in the range 1.2:1 to 1.4:1, optionally 1.3:1 to 1.35:1.
In general, a GNSS receiver module according to the present disclosure comprises an antenna according to the present disclosure and a GNSS receiver. The GNSS receiver module further comprises a phase shifting network for the antenna. The phase shifting network may be formed integrally with, or separately from, the antenna.
It should be understood that, although in the examples above the antenna was a GNSS antenna, antennas according to the present disclosure may be used for other applications/purposes.
In the example of
Of course, in still other examples of antennas according to the present disclosure, the antenna elements need not be formed on a single unitary flexible substrate. Although potentially convenient, it is not essential that all of the antenna elements are formed on a single unitary substrate that is folded or bent into shape. In some examples, the different antenna elements of the antenna could be provided on separate substrates—for example, separate pieces of rigid PCB.
Although the phase shifting network described above may offer a convenient and economical way to provide the desired phase shifts between the respective adjacent antenna elements, equivalent results may be achieved in other ways. For instance, the phase shifting network could be replaced by a hybrid coupler in some examples.
Similarly, although the foregoing description has focused on examples in which L/C elements were formed as distributed elements, some or all of the L/C elements could be replaced by discrete elements, for example surface mount elements.
The phase shifting network is not limited to the configuration illustrated in
In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The embodiments may be implemented by means of hardware comprising several distinct elements. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Furthermore, in the appended claims lists comprising “at least one of: A; B; and C” should be interpreted as (A and/or B) and/or C.
In flowcharts, summaries, claims, and descriptions relating to methods, the sequence in which steps are listed is not, in general, intended to be limiting on the order in which they are carried out. The steps may be performed in a different order to that indicated (except where specifically indicated, or where a subsequent step relies on the product of a preceding step). Nevertheless, the order in which the steps are described may in some cases reflect a preferred sequence of operations.
Furthermore, in general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor or other computing device, although these are not limiting examples. While various aspects described herein may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
The embodiments described herein may be implemented by computer software executable by a data processor of the apparatus, such as in the processor entity, or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD.
The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi-core processor architecture, as non-limiting examples.
Embodiments as discussed herein may be practiced in various components such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21173870 | May 2021 | EP | regional |
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| 7450072 | Kim | Nov 2008 | B2 |
| 7812783 | Mak | Oct 2010 | B2 |
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| 20130285857 | Schultz | Oct 2013 | A1 |
| 20130321240 | O'Shea | Dec 2013 | A1 |
| 20140253393 | Nissinen | Sep 2014 | A1 |
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| 20170324146 | Karlsson | Nov 2017 | A1 |
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| Number | Date | Country |
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| 108172984 | Jun 2018 | CN |
| 2846398 | Mar 2015 | EP |
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| EP Extended Search Report in European Appln. No. 21173870.3, dated Jan. 4, 2022, 9 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220368032 A1 | Nov 2022 | US |
