Slot feed patch antenna for GNSS applications

Abstract

A broadband GNSS antenna has a broadband patch radiator with top slot excitation and a groove slot type vertical choke structure surrounding the patch radiator. The patch radiator includes a radiator ground plane, a slot feed radiation patch, a broadband feed network, and a set of elements having a vertical current. The vertical choke structure includes a top conductive surface having a set of slits, a bottom conductive surface, and an adjacent vertical conductive pillar.

Description

Technical Field

[0001] The present invention generally relates to antennas, and more particularly to a broadband circularly polarized antenna with improved multipath suppression for receiving signals from a Global Navigation Satellite System (GNSS). Background Art

[0002] One factor that affects the quality of positioning information determined based on data from Global Navigation Satellite System (GNSS) satellites is the performance of the receiving antenna. One source of positioning error is multipath signals. Multipath signals are signals from GNSS satellites received by the antenna via paths other than the direct path from the GNSS satellite to the antenna. Such signals may be caused by reflection of signals from GNSS satellites on objects near the antenna. For example, an object located below the antenna may generate a reflected signal. Multipath signals are classified as far-field multipath signals and near-field multipath signals. Far-field multipath signals result from reflection from an object located at a distance of several wavelengths (e.g., five wavelengths) or more. The surface of the ground below the antenna can be considered an object located at a distance of several wavelengths. Near-field multipath signals are generated by an object located no more than a few wavelengths away from the antenna. Such objects are mainly antenna accessories, such as, for example, a tripod base. GNSS base station antennas require an effective level of multipath signal suppression.

[0003] Qualitative parameters related to the suppression of far-field multipath signals include the radiation pattern (RP), and particularly the level of the back lobe or the ratio of the level of the front lobe to the level of the back lobe. Qualitative parameters related to the suppression of near-field multipath signals can be represented by the amplitude in the near field, and particularly by the distribution of the horizontal component of the electric field vector of the near field that appears along the symmetry axis of the antenna below the antenna.

[0004] Signals broadcast by GNSS satellites typically have right-hand circular polarization (RHCP). The entire GNSS frequency band is divided into two smaller frequency bands: a low frequency (LF) (about 1165 MHz to 1300 MHz) and a high frequency (HF) (about 1525 MHz to 1605 MHz).

[0005] GNSS antennas should provide stability of the phase center and azimuth RP symmetry within the required bandwidth. This can be achieved by using four feed points. A microstrip patch antenna excited by a probe or a slot can be used in this application. Slot excitation allows the use of a compact feed network.

[0006] The positioning information generated using signals from GNSS satellites can be achieved by an antenna that receives RHCP signals from directions above the horizon and suppresses multipath signals from directions below the horizon. Such an antenna should have a feeding network that provides four feeding points, and the feeding network should operate over the entire GNSS frequency band.

[0007] For GNSS antenna applications, a conventional patch antenna with a flat ground plane is not sufficient to suppress multipath signals. If the size of the ground plane is equal to the size of the radiating patch, the back-lobe signal level is the same as the main-lobe signal level. To reduce the back-lobe level, the patch antenna can be mounted on a special ground plane. For example, the patch antenna can be mounted on a choke.

[0008] Figure 1 shows a prior art antenna described in U.S. Patent No. 6,940,457, which is configured to receive GNSS signals. The multi-frequency slot-fed antenna 101 has an edge diffraction reflector 102 attached to its rear side. A lossy dielectric magnetic material 103 surrounds the opposite and rear sides of the antenna 101 to reduce multipath signals. The edge diffraction reflector 102 includes stacked groups of grooves 104, 105, 106, 107 formed by adjacent plates and a central columnar member. This type of edge diffraction reflector design is commonly referred to as a vertical choke. The multi-frequency antenna is a stacked patch antenna in the form of two groups of patch radiators 108, 109, one above the other. The lower patch radiator has groups of excitation slots excited by microstrip lines. The diagrams shown in U.S. Patent No. 6,940,457 indicate that to achieve a front-to-back ratio level of 20 dB or greater, an edge diffraction reflector with at least two stacked grooves needs to be designed. For the LF band, a pair of stacked grooves 104, 105 with specific depths are used. For the HF band, a pair of stacked grooves 106, 107 with depths different from the specific depths of the stacked grooves 104, 105 are used. To provide the required front-to-back ratio levels in the LF band and HF section, at least four stacked grooves 104, 105, 106, 107 with different depths are used. The availability of the groups of stacked patch radiators 108, 109 and the groups of stacked grooves 104, 105, 106, 107 makes the antenna complex and difficult to manufacture.

[0009] The prior art antenna shown and described in U.S. Patent No. 10,197,679 relates to an antenna design that has good suppression of both far-field and near-field multipath signals. The antenna ground plane is a printed circuit board ("PCB") with inductance and resistance, and the antenna ground plane includes slots. To suppress near-field multipath signals, there are additional vertical mushroom-shaped elements. These properties make this antenna complex and difficult to manufacture.

[0010] There is a need for a patch antenna for GNSS applications with far-field multipath suppression and near-field multipath suppression, which has the minimum number of components and is easy to manufacture. Summary of the Invention

[0011] The antenna according to one embodiment has a vertical axis, and the antenna includes: a patch radiator, a ground plane, a dielectric part, a plurality of vertical conductors, and a choke structure. The patch radiator includes: a printed circuit board (“PCB”), the printed circuit board includes: a feed network and a slot-fed radiation patch, the slot-fed radiation patch is perpendicular to the vertical axis, and the slot-fed radiation patch includes a set of four excited slots, and the set of four excited slots are connected to the feed network through microstrip lines. The dielectric part and / or the plurality of vertical conductors are located between the ground plane and the slot-fed radiation patch, and the dielectric part and / or the plurality of vertical conductors are configured to carry one or both of a conduction current and / or a polarization current flowing in the direction of the vertical axis. The feed network is configured to ensure the reception or transmission of right-hand circular polarization (“RHCP”) waves. The choke structure includes a top conductive surface, a bottom conductive surface, and a conductive columnar member. The top conductive surface includes a set of extending slots, and each slot has an end located on the outer periphery of the top conductive surface. The conductive columnar member includes a top edge and a bottom edge, the top edge is connected to the top conductive surface, and the bottom edge is connected to the bottom conductive surface, and the ground plane is connected to the conductive columnar member along the outer edge of the ground plane.

[0012] In one embodiment, the antenna further includes four capacitor circuits located on the PCB and outside the outer periphery of the slot-fed radiation patch, wherein each of the circuits has a first end, a second end, and at least three capacitors connected in series. In one embodiment, the first end of each of the four capacitor circuits is connected to a corresponding first point located on the peripheral portion of the slot-fed radiation patch, the second end of each capacitor circuit is connected to a corresponding second point located on the peripheral portion of the slot-fed radiation patch, the corresponding first point and the corresponding second point are located on opposite sides of a corresponding one of the set of four excited slots, the first capacitor of the at least three capacitors is located near the first point, the second capacitor of the at least three capacitors is located near the second point, and the third capacitor of the at least three capacitors is positioned opposite to the corresponding excited slot.

[0013] In one embodiment, the three capacitors are formed using lumped elements. In one embodiment, the third capacitor of the at least three capacitors is formed as a distributed element, the distributed element including: three conductors located on a first side of the PCB, and a set of compensating conductors located on a second side of the PCB, wherein a first conductor of the three conductors includes: a first end connected to a first capacitive element; and an insulated second end, a second conductor of the three conductors includes: a first end connected to a second capacitive element; and an insulated second end, a third conductor is positioned opposite the excitation slot, both ends of the third conductor being insulated, the set of compensating conductors being located between the third conductor and the first conductor and between the third conductor and the second conductor, and a first end of the third conductor overlapping a second end of the first conductor, and a second end of the third conductor overlapping a second end of the second conductor.

[0014] In one embodiment, the dielectric portion includes a dielectric columnar member having a top surface and a bottom surface, the top surface being adjacent to the PCB and the bottom surface being adjacent to the ground plane. Each of the plurality of conductors located between the ground plane and the slot-fed radiating patch may include pins that are connected to the ground plane and are within the outer periphery of the PCB. Each of the excitation slots may be substantially straight and have an end located at the outer periphery of the slot-fed radiating patch, or each of the excitation slots may be T-shaped and have an end located at the outer periphery of the slot-fed radiating patch. A set of conductive rib members may be connected to the ground plane and are outside the outer periphery of the PCB. In one embodiment, each of the set of extended slots on the top conductive surface is rotated by an angle. In one embodiment, the bottom conductive surface includes a set of extended slots, each of the set of extended slots having an end located on the outer periphery of the bottom conductive surface. In one embodiment, the bottom conductive surface, the conductive columnar member, the ground plane, and the set of conductive rib members are formed as a single piece.

[0015] In one embodiment, the antenna has a vertical axis and the antenna includes: a grooved slot vertical choke structure having a top conductive slot surface; an integral component attached to the top conductive slot surface; and a patch radiator connected to the integral component. Description of the Drawings

[0016] In the drawings, like reference numerals describe like components in different figures. Like reference numerals with different letter suffixes represent different instances of like components and / or signals.

[0017] Figure 1 shows an antenna of the prior art;

[0018] Figure 2A shows a side view of an antenna according to one embodiment;

[0019] Figure 2B shows Figure 2A an isometric view of the antenna shown in

[0020] Figure 2C shows an isometric view of an antenna according to one embodiment, which is a Figure 2B variant of the antenna shown in

[0021] Figure 3 shows a patch radiator with top slot excitation according to an embodiment;

[0022] Figure 4 shows the arrangement of the radiator ground plane and vertical pins according to one embodiment;

[0023] Figure 5 shows a slot-fed radiating patch according to one embodiment;

[0024] Figures 6A to 6B shows a printed circuit board ("PCB") with a slot-fed radiating patch according to one embodiment;

[0025] Figure 6C shows a capacitive circuit according to one embodiment;

[0026] Figure 6D shows a cross-section of a PCB with a capacitive circuit and a compensating conductor of an equivalent capacitor according to one embodiment;

[0027] Figure 7 shows a schematic diagram of the limiting case of the size of a patch radiator according to an embodiment;

[0028] Figure 8 shows a graph of the normalized radiation pattern;

[0029] Figure 9 shows a signal propagation diagram showing the operation of an antenna according to one embodiment;

[0030] Figure 10 shows a graph related to the experimental graph of the front-to-back ratio, which shows the relationship between decibels (dB) and frequency;

[0031] Figure 11 shows a graph related to the horizontal component of the E-field in the near-field region of the rear area;

[0032] Figure 12Graph showing experimental graphs of radiation patterns for different slot angles;

[0033] Figure 13 Graph showing the dependence of the voltage standing wave ratio (“VSWR”) on frequency, which shows the relationship between VSWR and frequency (in MHz); and

[0034] Figure 14 Antenna according to one embodiment is shown. Detailed Description

[0035] A broadband right - hand circularly polarized (RHCP) antenna for global navigation satellite system (GNSS) applications is described herein. The antenna has a radiating patch and a grooved vertical choke structure. In one embodiment, the antenna has only one radiating patch and one groove in the vertical choke structure. This antenna design can suppress multipath signals and provide a front - to - back ratio of more than 20 dB for all frequencies within the GNSS frequency range.

[0036] Figure 2A Side view of antenna 200 according to one embodiment is shown. Figure 2B Isometric view of antenna 200 is shown. Figure 2C Shown as Figure 2A and Figure 2B An antenna which is a variant of the antenna shown in. Antenna 200 has a four - fold rotational symmetry about the symmetry axis 201 (i.e., each quarter of the antenna is symmetric about the symmetry axis 201). The direction of the symmetry axis 201 is aligned with the zenith direction. The direction along the symmetry axis 201 will be referred to as the vertical direction, and the plane perpendicular to the symmetry axis 201 will be referred to as the horizontal direction. Antenna 200 includes a patch radiator 21 with top - slot excitation and a grooved - slot vertical choke structure 22.

[0037] The patch radiator 21 with top - slot excitation includes: a radiator ground plane 211, a slot - fed radiating patch 212, a feed network 214, and an element in which vertical current (i.e., conduction current and / or polarization current flowing in the vertical direction) flows, which may include a vertical pin conductor 213 and / or a dielectric part 220. Compared with a conventional patch radiator, a remarkable feature of the patch radiator 21 with top - slot excitation is that even if its ground plane is small, the patch radiator 21 with top - slot excitation can suppress signals from the lower hemisphere.

[0038] The slot - fed radiating patch 212 is located above the radiator ground plane 211. The slot - fed radiating patch 212 can use, for example, plastic spacers ( Figure 2A or Figure 2Bis fixed (not shown in the figure). The slot-fed radiating patch 212 is a conductive surface having a set of exciting slots 215. In one embodiment, the input of the feed network 214 is connected to the exciting slots 215.

[0039] The structure in which the vertical current flows provides the required level of antenna gain and axial ratio over the entire upper hemisphere, particularly for elevation angles close to the horizon. To receive signals from low-altitude satellites with high quality, the antenna gain of the antenna in the horizontal direction should be no less than -8 dBic (i.e., dB of an isotropic circular antenna). In one embodiment, the conductor and dielectric parts in which the vertical current flows are placed in the space between the slot-fed radiating patch 212 and the radiator ground plane 211. For example, Figure 2A shows a set of vertical pin conductors 213 connected to the radiator ground plane 211 and a dielectric part 220 shown as a dielectric columnar member. In one embodiment, the feed network 214 is a power divider configured to ensure the optimal reception of RHCP waves.

[0040] In one embodiment, a grooved slot-type vertical choke structure 22 includes a groove 216 of a certain depth, which is formed by a top conductive slot-type surface 217 (also referred to as the top conductive surface), a bottom conductive surface 218, and a vertical conductive columnar member 219, and the vertical conductive columnar member 219 is adjacent to the top conductive slot-type surface 21 and the bottom conductive surface 218. The vertical conductive columnar member 219 is connected to the outer periphery of the radiator ground plane 211. In one embodiment, the radiator ground plane 211 and the top conductive slot-type surface 217 can be in the same plane. In other embodiments, the radiator ground plane 211 and the top conductive slot-type surface 217 can be in different planes. The top conductive slot-type surface 217 contains a set of extended (i.e., elongated) slots 221. Each of the slots 221 has an end located on the outer periphery of the top conductive slot-type surface 217. The slots 221 can be positioned radially (as Figure 2B shown in) or at an angle α with respect to the radial direction 224 (as Figure 2C shown in). By changing the angle α of the slots 221, the level of antenna gain can be changed. If the angle α is positive, the antenna gain in the horizontal direction decreases. If the angle α is negative, the antenna gain in the horizontal direction increases. Figure 2C shows an embodiment with a positive angle α. It should be noted that the bottom conductive surface 218 can also contain a set of slots 222, as Figure 2B shown in. These slots make it possible to reduce near-field multipath.

[0041] To ensure maximum power transfer to the antenna, high-quality matching is necessary. The VSWR (Voltage Standing Wave Ratio) level is a measure used to evaluate the degree of antenna matching. Antenna matching is mainly provided by the design of the patch radiator 21. Changing the height of the vertical pin conductor 213 affects the radiation pattern and matching. In Figure 2A and Figure 2B In the embodiments shown, to adjust the radiation pattern without affecting the matching, a group of conductive rib-like members 223 are positioned on the surface of the radiator ground plane 211. Since the conductive rib-like members 223 are located outside the peripheral portion of the slot-fed radiation patch 212, this group of rib-like members 223 only slightly affects the matching of the patch radiator 21 (compared to the vertical pin conductor 213), but allows an increase in the radiation pattern (RP) level in a direction perpendicular to the axis 201. In addition, changing the height of one of the rib-like members in this group of rib-like members 223 allows adjustment of the horizontal phase center of the antenna.

[0042] Figure 3 An embodiment of a patch radiator 21 with top slot excitation is shown. In this embodiment, the patch radiator 21 includes a PCB 301 and a metal component 302. These components are positioned one above the other using, for example, plastic spacers ( Figure 3 not shown in). In this embodiment, the slot-fed radiation patch 212 and the feed network 214 (as Figure 2A shown in) are formed in the form of a metallization layer of the PCB 301. In this embodiment, a low-noise amplifier ("LNA") can be located on the PCB 301 covered with a shield 303. The LNA output is connected to an output cable 304, which is vertically located at the center of the antenna.

[0043] Figure 4 A radiator ground plane 211 and vertical pin conductors 213 (shown as a group of vertical pins 213 in Figure 2A ) formed in the form of a metal component 302 according to an embodiment are shown. In this embodiment, the vertical pin conductors 213 are positioned along the peripheral portion of the horizontal plane 401, and the vertical pin conductors 213 carry conduction current and / or polarization current. In this embodiment, the horizontal plane 401 is part of the radiator ground plane 211 (as Figure 2A shown in). The metal component 302 can be made by stamping any sheet material and then bending it to form the vertical pin conductors 213.

[0044] Figure 5 A slot-fed radiation patch 212 configured in the form of a metallization layer according to an embodiment is shown (as Figure 2AAs shown in). In this embodiment, the metallization layer is the PCB 301, and the antenna design has four-fold rotational symmetry. In this embodiment, the slot-fed radiating patch 212 includes a conductive disk-shaped member 501 having four substantially straight excitation slots 215. Each of the excitation slots 215 has an end 502 located on the outer periphery of the disk-shaped member 501. Connected to the conductive disk-shaped member 501 are four capacitive circuits 505 that are located outside the outer periphery of the conductive disk-shaped member 501. In one embodiment, each of the capacitive circuits 505 is positioned at the same distance from the outer periphery of the conductive disk-shaped member 501. Each of the capacitive circuits 505 includes a series of conductors and capacitors. Any capacitor can be made as a lumped element or a distributed element. In one embodiment, the capacitive circuits 505 are configured to present an arc-shaped member terminated by radial segments 511 and 512. Each capacitive circuit 505 wraps around its respective excitation slot 215. Each capacitive circuit has a first end 503 and a second end 504 connected to the conductive disk-shaped member 501. The points of end 503 and the points of end 504 are respectively located on opposite sides of the corresponding excitation slot 215. Each capacitive circuit 505 includes at least three capacitors 506, 507, and 508 connected in series and the at least three capacitors 506, 507, and 508 are positioned opposite their respective excitation slots 215. Capacitors 506 and 507 are connected to the capacitive circuit 505 near the point where the capacitive circuit 505 is connected to the disk-shaped member 501. Capacitor 508 is located at a position in the capacitive circuit 505 opposite the excitation slot 215.

[0045] The antenna 200 (such as Figure 2A and Figure 2B shown in) has two resonances: a low frequency ("LF") and a high frequency ("HF"). The resonant frequency of the LF band is determined by the size of the radiating patch 212, the height of the vertical pin conductor 213, and the capacitance values of the capacitors 506 and 507 (such as Figure 5 shown in). Return Figure 5 , and the high-frequency resonance is achieved using the capacitive circuits 505. The resonant frequency of the HF band is mainly determined by the capacitance of the capacitor 508. Thus, although the antenna design only includes one PCB 301, dual-band antenna operation is achieved with good matching over the entire desired frequency band.

[0046] The excitation slot 215 includes an excitation probe 509, which is such as Figure 5As shown by the arrow in []. The excitation probe 509 is connected to the feed network 214. The feed network 214 is designed such that pairs of excitation slots 215 opposite to each other are excited in phase. The in-phase excitation of the opposite slots 215 is conditionally shown by arrows in the same direction, and pairs of excitation slots 215 positioned at a 90-degree angle to each other are excited with a 90-degree phase shift. This ensures the excitation of RHCP waves. This excitation is achieved by the feed network 214.

[0047] In one embodiment, the excitation slot 215 can be shaped in different forms, such as T-shaped. In one embodiment, the radius where the group of vertical pin conductors 213 is located does not exceed the radius of the capacitive circuit 505.

[0048] Figures 6A to 6D A variant of the printed circuit board (“PCB”) 301 is shown, where the capacitor 508 is configured to be located in the distributed elements. Figure 6A The top metallization layer of the PCB 301 is shown, and Figure 6B The bottom metallization layer of the PCB 301 is shown. In this embodiment, as combined with Figure 6A and Figure 6B described, the slot-fed radiating patch 212 (as shown in Figure 2A ) is a conductive disk-shaped member 601 located in the top metallization layer of the PCB 301. In this embodiment, the excitation slot 215 located in the disk-shaped member 601 is T-shaped. To accommodate this, each of the slots 215 has a radial portion 602 and an arc portion 603. One end of the radial portion 602 of the slot 215 contacts the periphery of the conductive disk-shaped member 601, and the other end contacts the arc portion 603.

[0049] The probe 509 is located in the lower metallization layer. The probe 509 is configured such that the electromagnetic field of the incident wave from the satellite induced in the excitation slot 215 enters the feed network 214 (as shown in Figure 2A ). The probe 509 is a continuation of the microstrip line passing through the excitation slot 215. The excitation technique of the slot 215 using these types of probes 509 is well known. The probe 509 is connected to the feed network 214 via a microstrip line (as shown in Figure 2A ). In one embodiment, the feed network 214 is a group of power dividers, and the group of power dividers is designed to excite RHCP waves. The feed network 214 can be located on the PCB 301.

[0050] The capacitive circuit 505 is formed on the lower metallization layer of the PCB 301. Figure 6CShows one of four capacitive circuits located on the lower metallization layer of the PCB 301. Each capacitive circuit 505 includes capacitors 506 and 507 and conductors 606, 607, and 608. Capacitors 506 and 507 are implemented as lumped elements. Conductors 606, 607, and 608 are located outside the outer periphery of the disc-shaped member 601 (as shown in Figure 6A ). One end of capacitors 506 and 507 is connected to the conductive disc-shaped member 601 through metallized holes 604 and 605. The other ends of capacitors 506 and 507 are connected to conductors 606 and 607 respectively. Conductor 608 is positioned opposite to conductors 606 and 607. There is a gap between conductor 608 and 606. Similarly, there is also a gap between conductor 608 and 607. Therefore, conductor 608 and 607 are capacitively coupled, and conductor 608 and 606 are also capacitively coupled. Therefore, the equivalent capacitor 508 is implemented by a distributed circuit including conductors 606, 607, 608.

[0051] In one embodiment, a group of compensating conductors 609 are located in the upper metallization layer of the PCB 301. These conductors are located in the gap between conductor 608 and 606 and in the gap between conductor 608 and 607.

[0052] Figure 6D Shows a cross-section of the region in the PCB 301 where conductors 607, 608, and 609 are located. Capacitor 610 is formed by conductors 607 and 608. Compensating capacitor 611 is formed by conductors 607 and 609. Compensating capacitor 612 is formed by conductors 608 and 609. An increase in the height h of the dielectric substrate 613 increases the capacitance of capacitor 610 while decreasing the capacitance of capacitors 611 and 612. Therefore, the total capacitance of all three capacitors changes only slightly. In this configuration, the compensating conductor 609 reduces the impact of changes in the thickness "h" value of the dielectric substrate 613 of the PCB 301 on the capacitance values formed by conductors 606 and 608 and 607 and 608.

[0053] Changing the lengths of conductors 606 and 607 allows the antenna to be tuned in the LF band, and the antenna can be tuned in the HF band by changing the length of conductor 608.

[0054] The patch radiator 21 with top slot excitation has advantages over traditional patch radiators. The advantage is that using the patch radiator 21 with top slot excitation simplifies the design of the vertical choke structure. To demonstrate this advantage, the performance of the patch radiator 21 itself (i.e., without the vertical choke structure) is described here. Figure 7 Is a diagram showing the size of the slot-fed radiating patch 212 (as determined by the length L RP) is equal to the size of the radiator ground plane 211 (as indicated by the length L GP Schematic diagram of a patch radiator 21 without a vertical choke structure in the limiting case of FIG. 21 . This limiting case is indicative because in this case the ground plane 211 does not affect the level of the back lobe. Figure 7 As shown in , the angle θ is the elevation angle from a particular direction to the horizon.

[0055] Figure 8 The slot-fed radiating patch 212 and the radiator ground plane 211 (eg Figure 2A Graphs of normalized radiation patterns calculated based on an elevation angle θ in a configuration with an indication length of 0.42λ (shown in ). In these configurations, λ is the signal wavelength in a vacuum. In this configuration, a dielectric portion with a relative dielectric constant of 4 is used as a dielectric substrate 220, in which a vertically polarized current flows. Curve 801 corresponds to a configuration of a patch radiator with top slot excitation. Curve 802 corresponds to a configuration of a conventional patch radiator. In one embodiment, when curve 802 is calculated, probe feeding is used. In the case of curve 802 for a conventional patch radiator, the back lobe level is equal to the main lobe level. Whereas in the case of curve 801 for a patch radiator with top slot excitation, the back lobe level is 13 dB lower than the main lobe level. This is because, in the case of a patch radiator with top slot excitation, the excitation slot 215 and the side slots 701 and 702 radiate. The side slots 701 and 702 are opposing legs of the cylindrical peripheral slot formed by the edge of the slot-fed radiating patch 212 and the radiator ground plane 211. The fields formed by the side slots 701, 702 and the excitation slot 215 in the θ=90 degree direction are added, and the fields formed by the side slots 701, 702 and the excitation slot 215 in the θ=-90 degree direction are subtracted. Figure 8 The front-to-back ratio is shown to be about 13 dB. In the case of a conventional patch radiator, only the side slots are radiating. RP =L GP In the case of θ = 90 degrees and θ = -90 degrees, the side slots radiate in the same way, that is, the front-to-back ratio is 0 dB.

[0056] When the size of the radiating patch 212 is about 0.5λ, the patch radiator 21 with top slot excitation has no deep beam dips in the horizontal direction. The radiation pattern of a conventional patch antenna usually has deep beam dips in the horizontal direction. This is due to the L RP= 0.5λ (i.e., the distance between the side slits 701 and 702 is 0.5λ). In the case of a conventional patch antenna without the excitation slit 215, the electromagnetic fields formed by the side slits 701 and 702 in the horizontal direction are opposite in phase and cancel each other out. The patch radiator 21 with top slit excitation also has radiation formed by the excitation slit 215. Its field is not subtracted, so there is no deep beam dip in the horizontal direction in this case.

[0057] As Figure 8 shown in, at θ = 0 degrees, the curve 802 has a deep beam dip, where the level of the curve 801 is approximately -10 dB. This level is acceptable for receiving signals from satellites located near the horizon. Therefore, the patch radiator 21 with top slit excitation can have a diameter up to 0.5λ, which allows expanding its operating frequency band, as well as placing the feed network 214, LNA, and a set of filters on the slit-fed radiation patch 212, and these components can occupy a considerable area. The diameter of the radiation patch of a conventional patch antenna typically does not exceed 0.3λ.

[0058] As described above, the patch radiator 21 with top slit excitation itself has the ability to suppress multipath signals. Therefore, in order to achieve a required front-to-back ratio of about 20 dB and higher, it is only necessary to mount it on the vertical choke structure 22 with only one groove 216.

[0059] Figure 9 A signal propagation diagram is shown, which illustrates the operation of the antenna 200 according to one embodiment. Although the GNSS antenna is a receiving antenna configured to operate in the receiving mode, for convenience, Figure 9 the transmit mode is shown in. It should be noted that the reciprocity theorem states that the parameters related to the transmit operation mode and the receive operation mode are equivalent. The excitation slit 215 radiates an electromagnetic field, which propagates towards the horizon along two paths 901 and 902. Path 901 passes through the slit-fed radiation patch 212, and path 902 passes between the slit-fed radiation patch 212 and the radiator ground plane 211. The presence of the vertical pin conductor 213 or the dielectric substrate 220 causes a phase change in the wave propagating along path 902. The parameters of the vertical pin conductor 213 or the dielectric substrate 220 can be selected such that the waves traveling along paths 901 and 902 are opposite in phase and cancel each other out. As a result, the attenuated wave 903 approaches the groove 216 of the vertical choke structure. The wave 903 passing along the groove 216 is further attenuated due to interference with the wave 904 reflected from the groove 216. As a result, the wave 905 propagating to the rear hemisphere is significantly attenuated.

[0060] Figure 10shows a graph related to the experimental graph of the front-to-back ratio, which shows the relationship between decibels (dB) and frequency. For generating Figure 10 The antenna design for the graph shown in Figure 9 has the following dimensions (see the dimension labels shown in Figure 10 ): D = 250 mm, h2 = 22 mm, h1 = 22 mm, d2 = 47 mm. Curve 1001 corresponds to the antenna design according to an embodiment, in which a patch radiator 21 with top slot excitation is mounted on a grooved slot vertical choke structure 22. As Figure 10 shown, in this case, the value of the front-to-back ratio in the entire operating frequency band of the GNSS range is not less than 25 dB. Curve 1002 is measured using a conventional stacked patch antenna mounted on the same grooved slot vertical choke structure 22. As

[0061] shown, in this case, the value of the front-to-back ratio in the high-frequency GNSS range is significantly lower and is about 17 dB. Figure 2A and Figure 2B shown, the presence of the slot 221 on the top conductive slot surface 217 results in a reduction in the intensity of the near-field multipath signal. The intensity of the unwanted near-field in the rear hemisphere can be estimated based on the electric field intensity on the axis of symmetry of the antenna.

[0062] Figure 11 shows a graph related to the horizontal component of the E-field in the near-field range of the rear region, which shows the relationship between the voltage per meter and the distance of the antenna in the nadir direction (in millimeters). This distance is calculated from the radiator ground plane in the direction opposite to the axis 201 (as Figure 2A shown), i.e., in the nadir direction. Curve 1101 corresponds to the case where the slot 221 (shown in Figure 2B ) is present, while curve 1102 corresponds to the case where the slot 221 is absent. As Figure 11 shown, the availability of the slot 221 on the top conductive slot surface 217 results in a reduction of the unwanted near-field by approximately a factor of 2.

[0063] As described above, changing the rotation angle α of the slot 221 on the top conductive slot surface 217 allows changing the antenna gain for the zenith direction and the horizontal direction. The direction of the angle α is as Figure 2C shown.

[0064] Figure 12A graph showing experimental graphs of radiation patterns for different slot angles α is presented, which shows the relationship between dBic (i.e., dB of an isotropic circular antenna) and the elevation angle θ (in degrees). It can be seen that by changing the angle α from -10° to +20°, the antenna gain can be changed by 3 dB towards the horizontal direction (θ = 0 degrees).

[0065] Figure 13 A graph showing the dependence of the voltage standing wave ratio (“VSWR”) on frequency is presented, which shows the relationship between VSWR and frequency (in MHz). Curve 1301 shows the case where the capacitive circuit 505 (as Figure 5 、 Figure 6B 、and Figure 6C shown) is connected to the radiating patch, and curve 1302 shows the case without the capacitive circuit 505. In one embodiment, the diameter of the PCB 301 having the slot-fed radiating patch 212 and the capacitive circuit 505 is 80 mm, and the distance between the radiating patch PCB 301 and the radiator ground plane is 22 mm. It can be seen that the antenna according to one embodiment provides a VSWR level of less than 2 over the entire GNSS range in the presence of the capacitive circuit 505.

[0066] Figure 14 An embodiment of an antenna formed using three main components is shown. As Figure 14 shown, the bottom conductive surface 218, the vertical conductive columnar member 219, the radiator ground plane 211, and the group of conductive rib-like members 223 are formed as an integral part 1401, which can be made of metallized plastic. The top conductive slot surface 217 is tightened to the part 1401 by screws 1402. In one embodiment, the top conductive slot surface 217 can be made of a sheet material, for example, by laser cutting. Thus, in one embodiment, a grooved slot vertical choke structure 22 includes only two parts. The patch radiator 21 with top slot excitation is mounted on the radiator ground plane 211, and in this embodiment, the horizontal surface 401 of the part 302 is in contact with the radiator ground plane 211. The vertical conductive columnar member 219 can have a vertical portion 1403 and a tapered portion 1404.

[0067] The foregoing detailed description is to be understood as illustrative and exemplary in every respect and not restrictive, and the scope of the inventive concept disclosed herein is to be construed in accordance with the full scope permitted by patent law. It is to be understood that the embodiments shown and described herein are only for illustrative purposes of the principles of the inventive concept, and various modifications can be made by those skilled in the art without departing from the scope and spirit of the inventive concept. Those skilled in the art can achieve various other combinations of features without departing from the scope and spirit of the inventive concept.

Claims

1. An antenna having a vertical axis, the antenna comprising: a patch radiator, the patch radiator comprising: a printed circuit board ("PCB"), the printed circuit board comprising: a feed network configured for reception or transmission of right-hand circularly polarized ("RHCP") waves; and a slot-fed radiating patch perpendicular to the vertical axis, the slot-fed radiating patch comprising: a group of four excitation slots connected to the feed network by microstrip lines; a ground plane; a dielectric portion located between the ground plane and the slot-fed radiating patch; a plurality of vertical conductors located between the ground plane and the slot-fed radiating patch, the dielectric portion and the plurality of vertical conductors being configured to carry one or both of a conduction current and a polarization current in a direction along the vertical axis; and a vertical choke structure, the vertical choke structure comprising: a top conductive surface including a group of extending slots, each slot including an end located on the outer periphery of the top conductive surface; a bottom conductive surface; and a conductive columnar member including a top edge and a bottom edge, the top edge being connected to the top conductive surface and the bottom edge being connected to the bottom conductive surface, the ground plane being connected to the conductive columnar member along an outer edge of the ground plane.

2. The antenna according to claim 1, the antenna further comprising: four capacitor circuits located on the PCB and extending beyond an outer periphery of the slot-fed radiating patch, each of the four capacitor circuits comprising: a first end; and a second end; and at least three capacitors connected in series together, wherein a first end of each of the four capacitor circuits is connected to a respective first point located on a peripheral portion of the slot-fed radiating patch, a second end of each capacitor circuit is connected to a respective second point located on the peripheral portion of the slot-fed radiating patch, the respective first point and the respective second point being located on opposite sides of a corresponding one of the group of four excitation slots, a first capacitor of the at least three capacitors being located near the first point, a second capacitor of the at least three capacitors being located near the second point, and a third capacitor of the at least three capacitors being positioned opposite the corresponding excitation slot.

3. The antenna according to claim 2, wherein, the at least three capacitors are formed using lumped elements.

4. The antenna according to claim 2, wherein, the third capacitor of the at least three capacitors is formed as a distributed element, the distributed element comprising: three conductors located on a first side of the PCB; and a group of compensating conductors located on a second side of the PCB, wherein a first conductor of the three conductors includes: a first end connected to a first capacitive element; and an insulated second end, The second conductor of the three conductors includes: a first end connected to the second capacitive element; and an insulated second end, The third conductor is positioned opposite the excitation slot, and both ends of the third conductor are insulated, The set of compensating conductors is located between the third conductor and the first conductor and between the third conductor and the second conductor, and The first end of the third conductor overlaps with the second end of the first conductor, and the second end of the third conductor overlaps with the second end of the second conductor.

5. The antenna according to claim 1, wherein, The dielectric part includes a dielectric columnar member having a top surface and a bottom surface, the top surface being adjacent to the PCB and the bottom surface being adjacent to the ground plane.

6. The antenna according to claim 1, wherein, Each of the plurality of conductors located between the ground plane and the slot-fed radiating patch includes a pin that is connected to the ground plane and is located within the outer periphery of the PCB.

7. The antenna according to claim 1, wherein, Each of the excitation slots is substantially straight and has an end located at the outer periphery of the slot-fed radiating patch.

8. The antenna according to claim 1, wherein, Each of the excitation slots is T-shaped and has an end located at the outer periphery of the slot-fed radiating patch.

9. The antenna according to claim 1, the antenna further comprises: A set of conductive rib members that are connected to the ground plane and are located outside the outer periphery of the PCB.

10. The antenna according to claim 1, wherein, Each of the set of extended slots on the top conductive surface is rotated by an angle.

11. The antenna according to claim 1, wherein, The bottom conductive surface includes a set of extended slots, and each of the set of extended slots has an end located on the outer periphery of the bottom conductive surface.

12. The antenna according to claim 9, wherein, The bottom conductive surface, the conductive columnar member, the ground plane, and the set of conductive rib members are formed as a single piece.

13. An antenna having a vertical axis, the antenna comprises: A grooved slot type vertical choke structure, the grooved slot type vertical choke structure includes: A top conductive slot surface; An integral component attached to the top conductive slot surface, the integral component includes: A bottom conductive surface; A vertical conductive columnar member connected to the bottom conductive surface; A radiator ground plane connected to the vertical conductive columnar member; and A set of conductive rib members connected to the radiator ground plane; and A patch radiator connected to the integral component.

14. The antenna according to claim 13, the patch radiator comprises: A printed circuit board ("PCB"), the printed circuit board includes: A feed network; and A slot-fed radiating patch, the slot-fed radiating patch being perpendicular to the vertical axis, the slot-fed radiating patch comprising: A set of four exciting slots, the set of four exciting slots being connected to the feed network by microstrip lines, each of the exciting slots having an end located at the outer periphery of the slot-fed radiating patch.

15. The antenna according to claim 14, the top conductive slot-type surface comprising: A set of extending slots, each slot comprising an end located on the outer periphery of the top conductive slot-type surface.

16. The antenna according to claim 14, wherein, The antenna has a four-fold symmetry about the vertical axis, and the antenna has a front-to-back ratio level of at least 20 dB in the operating frequency band.

17. The antenna according to claim 14, wherein, Each of the set of four exciting slots is substantially straight.

18. The antenna according to claim 14, wherein, Each of the set of four exciting slots is T-shaped.

19. The antenna according to claim 15, wherein, Each of the set of extending slots on the top conductive surface is rotated by an angle.

20. The antenna according to claim 14, wherein, The bottom conductive surface includes a set of extending slots, each of the set of extending slots having an end located on the outer periphery of the bottom conductive surface.

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