The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to antennas, in particular, to patch antennas used in global navigation satellite systems (GNSS).
"Patch antenna systems are used in different radio electronic devices. They are widely applicable in ground satellite navigation systems (GPS, GLONASS, Galileo etc.), with the help of which a position of an object can be quickly and accurately determined at any point of the world. One of the main reasons for reduced GNSS positioning accuracy of land objects is related to receiving not only the line-of-sight satellite signal but also signals reflected from surrounding objects, and especially from the Earth's surface. The strength of such signals depends directly on the antenna's directional diagram (DD) in the rear hemisphere.
"A right-hand circularly polarized signal (RHCP) is used as a working signal in navigation systems. Signals reflected from the Earth's surface, when there are no major surface features, are mostly left-hand circularly polarized signals (LHCP). This also holds true for signals of satellites that are at an angle over the horizon that is higher than Brewster's angle, that is, for typical soils, about 10-15 degrees over the horizon plane. Considering this, a GNSS antenna systems need to have a lower DD level in the rear hemisphere, and primarily, a lower component of the LHCP (cross-polarized) signal. A reduction in antenna weight and dimensional characteristics is also required.
"The simplest method of reducing DD level in the rear hemisphere is mounting the antenna directly on a metal or impedance ground plane. However, this results in increasing antenna dimensions. Another method is the use of an additional antenna, the field of which is anti-phase-added to the main antenna field. This provides a reduction in the radiation level of the rear hemisphere. U.S. Pat. No. 6,836,247 B2 shows a design of a circularly-polarized antenna in the form of two patch (MP) radiators axial-symmetrically disposed one under another (see FIG. 1a). A ground plane of the top radiator is under a radiating patch, and a ground plane of the bottom radiator is over the radiating patch. In an isolated cavity of the ground planes, there is a low-noise amplifier (LNA). The top radiator is actively excited by pins; the bottom radiator is passively excited. Such a design provides a noticeable reduction in LHCP field only in the vicinity of anti-normal direction, while the antenna's vertical dimension still remains very large.
"Modern high-precision positioning receivers employ signals of different frequencies. Operating GPS frequencies are 1575 MHz (L1-band), 1227 MHz (L2-band) and a frequency of 1175 MHz (L5-band) was recently added. GLONASS and GALILEO satellite systems also broadcast some operating frequencies. In total, the operating frequencies of GNSS systems lie in two frequency ranges: low-frequency (LF 1165-1300 MHz) and high-frequency (HF 1525-1605 MHz). Antennas of high-precision navigation devices need to operate in the both frequency bands. In most cases, antenna designs include two radiators operating at their own frequencies. U.S. Pat. 6,836,247 B2 describes a dual-band stacked antenna (FIG. 1b). Such a combined antenna includes two active MP radiators disposed one over the other, and two passive ones. The radiating patch of the low-frequency radiator serves as a ground plane of the high-frequency radiator. Bandwidth expansion of each radiator is normally attained by increasing the distance between the radiating patch and ground plane, i.e., increasing the thickness of MP radiator. Note that an increase in LF radiator thickness results in increasing the distance between active and passive HF radiators. This, in turn, causes reduction in their coupling and excitation level of the passive radiator, and, hence in the antenna's less efficient operation.
"The proposed technical solution is intended at solving cross-polarized (LHCP) field suppression problems in a wide angle sector of the rear hemisphere, enhancing the operation of the passive HF radiator in the dual-band antenna, and reducing antenna dimensions."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "An antenna system for receiving navigation satellite signals is proposed, comprising a patch radiator consisting of a radiating patch disposed over a ground plane which is excited by, for example, exciting electric pins or slots, from a connected power circuit of the MP radiator, and a horizontal loop radiator axially disposed around the MP radiator. The radiating patch and ground patch can have the same dimensions, or the radiating patch can be larger or smaller than the ground patch. A cavity can be made directly under the ground patch, where power circuits of the loop radiator and the MP radiator can be located.
"The loop radiator is a conducting ring, for example, made of wire or conductive film; its vertical axis matches the symmetry axis of the MP radiator. In another embodiment, the loop radiator can be disposed at the same distance from the surface of the radiating and ground patches, or it can be shifted toward the ground plane. Inductive elements can be sequentially connected with the loop radiator.
"The loop radiator is excited by transmission lines at least at one point, for example, by two-wire transmission lines connected to the power supply circuit of the loop radiator. The power supply lines provide excitation of right hand circularly-polarized waves in the direction of DD maximum. The antenna system also includes a dividing circuit, whose input is the input of the antenna, and the power supply circuits of MP and loop radiators are connected to the outputs. The power supply circuits provide anti-phase excitation of LHCP waves for the MP and loop radiators in the rear hemisphere. The proposed combination of MP and loop radiators compensates for LHCP field in a wide angle sector.
"To reduce overall dimensions, the space between the radiating patch and the ground patch of the MP radiator can be filled with a dielectric, or a slowing structure can be installed, for example, made as a set of conductive periodic elements, or a set of capacitive impedance elements can be used, which are arranged along the perimeter of the ground patch and/or the radiating patch of the MP radiator. The elements of the slowing structure can be a set of separate ribs, or combs, or teeth, or pins. Capacitive elements are also a set of separate ribs, or combs, or teeth, or pins. As another embodiment, the dielectric filler can have grooves/slots where two-wire transmission lines are located to connect the power circuit to the loop radiator, or it can be made in the form of two dielectric segments between which power lines are located.
"A compact dual-band antenna system is proposed to receive signals from two frequency bands, comprising an active high-frequency MP radiator, under which there is an active low-frequency radiator. Each of the active radiators includes a radiating patch disposed under the corresponding ground plane. MP radiators are excited, for example, by electric pins or slots powered by power circuits of the corresponding frequency band. The radiating patch of the active LF band serves as a ground plane of the active HF MP radiator, and in the vicinity of the active HF radiator, there is a loop HF radiator, which is in axial alignment with the active HF radiator. Under the ground patch of the active LF radiator, there is a passive LF radiator at a certain distance from the ground plane, which is an MP radiator as well. This MP radiator is excited by electromagnetic coupling with the active LF MP radiator.
"Another embodiment has an active HF loop radiator which is excited by two-wire lines connected to the HF loop radiator power circuit at least at one point. To provide a uniform excitation field, four excitation points are preferably used. The power circuits excite two-wire lines with equal amplitudes, with a sequential phase shift of -90.degree. ensuring excitation of RHCP waves in the front hemisphere. The antenna system also includes an HF dividing circuit, the input of which is the HF antenna input, and the power circuits of HF MP and loop radiators are connected to the outputs. The power circuits provide anti-phase excitation of LHCP waves for HF MP and loop radiators in the rear hemisphere. The LF active radiator input is the LF antenna input.
"In another embodiment, the LF passive radiator can be a loop coaxially disposed at a certain distance from the bottom active LF radiator.
"In another embodiment, the LF loop radiator can also be active and excited similarly to the active HF loop radiator described above.
"The HF or LF loop radiator is a conductive ring to which inductive elements can be sequentially connected. The vertical symmetry axis of the LF or HF loop radiator coincides with the symmetry axis of the corresponding HF or LF MP radiators.
"In another embodiment, HF or LF loop radiator can be arranged at an equal distance from the surface of the corresponding radiating and ground patches or be shifted toward the ground patch, for example, be in the same plane as the ground patch or lower than the ground patch.
"A cavity where power circuits of loop radiators and MP radiator of the corresponding band are easily installed can be directly under the ground patch of the LF radiator.
"In another embodiment, slot excitation can be used to excite MP radiators in the above-said structures.
"Additional features and advantages of the invention will be set forth in the description that follows. Yet further features and advantages will be apparent to a person skilled in the art based on the description set forth herein or may be learned by practice of the invention.
"The advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
"It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS
"The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
"In the drawings:
"FIG. 1a shows a conventional antenna system.
"FIG. 1b shows a conventional dual-band antenna based on a stacked construction.
"FIG. 2 shows a section view above the proposed antenna system comprising a MP radiator, and a loop radiator in the form of a wire ring.
"FIG. 3 shows a proposed antenna with capacitive elements in the form of conductive petals/lobes.
"FIG. 4 shows a proposed antenna system with inductive elements.
"FIG. 5 shows a section view above of the proposed antenna system with a loop radiator shifted towards the ground patch of the MP radiator.
"FIG. 6 shows a proposed antenna system with passive excitation, where the diameter of the radiating patch is larger than the ground patch diameter.
"FIG. 7 shows a proposed dual-band antenna with a passive HF loop radiator and a passive LF MP radiator.
"FIG. 8 shows a proposed dual-band antenna with an active loop radiator of HF band and a passive MP radiator of LF band.
"FIG. 9 shows a proposed dual-band antenna with passive loop radiators of the LF and HF bands.
"FIG. 10 illustrates DD calculation results for the proposed antenna system.
"FIG. 11 illustrates DD calculation results for the case of a shifted loop radiator (i.e., shifted towards the ground plane)."
For additional information on this patent application, see: Tatarnikov, Dmitry Vitalievich; Astakhov, Andrey Vitalievich. Compact Circular Polarization Antenna System with Reduced Cross-Polarization Component. Filed
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