Patent Application
20230411854
This patent application relates to stacked patch antenna elements and more particularly to providing for lower frequency operation for a given size of stacked patch antenna elements and reducing the size of antennas that employ stacked patch antenna elements.
Global satellite navigation systems or global navigation satellite systems (GNSS) employ a network of geo-spatially positioned satellites to broadcast precisely synchronized navigation messages, thereby providing for determination of a network time and a geolocation by dedicated GNSS receivers. Such receivers provide for a ubiquitous and global time reference, in addition to a host of geolocation uses, ranging from consumer navigation devices to means to monitor global warming to precision agriculture and of course, military applications.
Modern Global Navigation Satellite Systems (GNSS) receivers are commonly designed and configured to receive signals from multiple constellations, such as the European Galileo, Russian GLONASS, US GPS, and Chinese Beidou Global Navigation Systems, plus at least two regional positioning and timing systems such as the Indian NAVIC and Japanese QZSS systems.
Low cost navigation receivers such as those employed in consumer grade navigators (“SatNav” devices) largely, if not entirely, make use of navigation signals broadcast in the upper GNSS band only (typically the GPS L1 and GLONASS G2 signals). Higher precision positioning systems may also take advantage of navigation signals broadcast in at least two well separated frequency bands to take advantage of predictable signal dispersion to better estimate ionospheric effects, and to thereby improve “fix” accuracy. Further improvements in accuracy of up to an order of magnitude can be achieved by means of Precise Point Positioning (PPP) or ‘Real Time Kinematic (‘RTK’) systems that provide corrections data to compatible receivers to enable carrier phase lock onto individual space vehicle signals. This allows estimation of satellite ranges in measures of carrier wavelengths rather than the plain course acquisition code (“C/A”) or similar messages transmitted within most of the new GNSS signals. PPP and RTK corrections systems are commonly referred to as state space and observation space corrections data, respectively, and both rely upon delivery of corrections data through an independent communications channel. RTK corrections primarily rely upon cancellation of common errors between a reference receiver (the Base station) and a roving positioning receiver (the ‘Rover’), that are relatively close compared to the signal path length from the satellite. PPP corrections data is used to precisely correct clock and orbital ephemeris data broadcast by each satellite, computed from data received from a distributed network of precision reference receivers installed at precisely known locations, over large geographic regions.
Patch antenna elements are typically square or circular blocks of very low loss dielectric material having a first lower surface fully metalized so as to provide a ground plane, and a second upper surface at least partially metalized, so as to provide a resonant cavity within the dielectric block. Currents associated with electric fields within the cavity are conducted on the metallic surfaces directly in contact with the dielectric block. The element provides for reception or transmission of signals at frequencies at or close to the resonant frequency of the cavity by virtue of fringing fields between the resonant metallization and the ground metallization at the perimeter of the patch antenna element. The current state of the art provides for antenna elements with a circularly polarized response in either rotational sense using symmetrical or near symmetrical dielectric blocks with either a single feed pin or with dual feed pins.
It is also well known in the art that a pair of dielectric blocks metallized to provide different and distinct resonant frequencies, may be “stacked” concentrically or nearly concentrically, one physically upon the other, to provide an antenna element with resonant responses corresponding or close to the resonant frequencies of the two resonant dielectric elements. In this structure, the lower dielectric block has a lower metallization acting as a ground plane, covering most of the lower surface of the lower element, and a resonant metallization pattern covering at least a part of the upper surface of the lower element, to realize a resonant response at a first frequency. The upper dielectric block similarly has a portion of its lower surface metalized to act as a ground plane and a metallization patter resonant metallization covering at least a portion of the upper surface of the upper dielectric block to provide a resonant response at a second frequency. One or more feed pins are commonly used to connect an external feed circuit either to the upper surface of the upper patch alone or to the upper surfaces of both patches. As is well known in the art, the dielectric blocks have physical holes through which the feed pins pass, with openings in the metallization patterns to allow the feed pins to pass through metallization layers not designed to be connected to the feed pins. For stacked patch structures wherein the electrical feed pins are connected to the upper surface metallization of the upper patch antenna element only, coupling to the lower patch antenna element is achieved through near field electromagnetic coupling of the two patch antenna elements.
The stacked dielectric blocks may be equal in size and shape or quite different in both respects, however, to maintain the independence between the first and second resonant response frequencies of the lower and upper patches respectively, it is a requirement, within the prior art, that the dimensions of the ground plane metallization of the upper patch be smaller than, and contained within the perimeter of the resonant metallization of the lower patch, so that the perimeter of the ground plane metallization of the upper block lies entirely within the perimeter of the resonant metallization of the lower block.
Accordingly, in the art it is commonly arranged that the resonant frequency of the upper element correspond to the upper frequency of the two resonances and the resonant frequency of the lower element to that of the lower resonant frequency.
It is also known in the art that the resonant frequency of a dielectric block with a first lower surface metallized as a ground plane and a second upper surface metallized with a resonant pattern may be reduced through castellation of the perimeter of the second upper surface metallization. This allows for the resonant frequency of a patch antenna element to be reduced without increasing the patch antenna element dimensions provided that the castellations are small reductions in the outer dimensions of the resonant metallization of the dielectric block which is otherwise sized to the maximum available dimensions.
These design considerations are particularly important with prior art stacked patch antennas wherein a first patch antenna is mounted on top of a second patch antenna. Provided that the ground plane metallization on the lower surface of upper patch element is smaller than the resonant metallization on the upper surface of the lower element, then the frequencies of the pair of patch antennas may be determined largely independently of each other. Without castellations, the lowest achievable resonant frequency of the lower patch element is limited by the dimensions of the ground plane (lower) metallization on the upper patch element. Any castellation depth applied to the upper resonant metallization of the lower patch to reduce the resonant frequency of the lower patch element is limited to the outer dimensions of the lower ground plane metallization of the upper element, if the two are in contact because the larger metallization size in essence “shorts out” the smaller. Thus, the dimensions of the composite stacked patch element is limited to that required to achieve the desired resonant frequency of the lower patch.
It would be advantageous to provide a structure where the size of the ground plane on the lower surface of the upper patch element is not limited by the geometry of the castellations on the resonant upper metallization of the lower patch element. Alternatively, it would be advantageous to provide a structure whereby the geometry of the castellations on the resonant patch of the upper metallization of the lower patch element is not limited by the ground plane metallization on the lower surface of the first upper patch element. Accordingly, it would be beneficial to provide antenna designers with a design solution allowing the lower frequency performance of the first, lower patch within a stacked patch antenna to be lowered without compromising footprint of the resulting antenna.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
It is an object of the present invention to mitigate limitations within the prior art relating to stacked patch antenna elements and more particularly to providing for lower frequency operation for a given size of stacked patch antenna elements and reducing the size of antennas that employ stacked patch antenna elements.
In accordance with an embodiment of the invention there is provided an antenna comprising:
In accordance with an embodiment of the invention there is provided a method comprising: providing a first patch antenna element comprising a first dielectric body formed from a first dielectric material having a first predetermined geometry comprising a first upper surface with a first metallization on the first upper surface of the first dielectric body having a second predetermined geometry and a distal first lower surface with a second metallization on the distal first lower surface of the first dielectric body having a third predetermined geometry;
In accordance with an embodiment of the invention there is provided a method comprising: providing an upper patch antenna element having a first resonant frequency;
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:
The present invention is directed to stacked patch antenna elements and more particularly to providing for lower frequency operation for a given size of stacked patch antenna elements and reducing the size of antennas that employ stacked patch antenna elements.
The ensuing description provides representative embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the embodiment(s) will provide those skilled in the art with an enabling description for implementing an embodiment or embodiments of the invention. It being understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims. Accordingly, an embodiment is an example or implementation of the inventions and not the sole implementation. Various appearances of “one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention can also be implemented in a single embodiment or any combination of embodiments.
Reference in the specification to “one embodiment”, “an embodiment”, “some embodiments” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment, but not necessarily all embodiments, of the inventions. The phraseology and terminology employed herein is not to be construed as limiting but is for descriptive purposes only. It is to be understood that where the claims or specification refer to “a” or “an” element, such reference is not to be construed as there being only one of that element. It is to be understood that where the specification states that a component feature, structure, or characteristic “may”, “might”, “can” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included.
Reference to terms such as “left”, “right”, “top”, “bottom”, “front” and “back” are intended for use in respect to the orientation of the particular feature, structure, or element within the figures depicting embodiments of the invention. It would be evident that such directional terminology with respect to the actual use of a device has no specific meaning as the device can be employed in a multiplicity of orientations by the user or users.
Reference to terms “including”, “comprising”, “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, integers or groups thereof and that the terms are not to be construed as specifying components, features, steps or integers. Likewise, the phrase “consisting essentially of”, and grammatical variants thereof, when used herein is not to be construed as excluding additional components, steps, features integers or groups thereof but rather that the additional features, integers, steps, components or groups thereof do not materially alter the basic and novel characteristics of the claimed composition, device or method. If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element.
Reference to terms such as “perpendicular”, “along”, “parallel” and grammatical variants thereof in respect to alignment and/or direction should be considered not as absolute but as having a tolerance to variation thereof such that these directions and/or alignments are “substantially” as indicated. Tolerances to these being as established, for example, through manufacturing tolerances, performance tolerances, manufacturing costs etc.
As discussed above GNSS receivers are employed within a wide range of applications within both the civil and military markets. Accordingly, these may range from small footprint low cost consumer receivers for smartphones, fitness trackers etc. through to high accuracy high gain receivers specifically designed for timing and/or location. Referring to
Within most applications the GNSS antenna is housed within a housing or cover, commonly referred to as a radome, which is transparent to wireless signals in the frequencies of interest as listed in Table 1 below. Accordingly, GNSS antennas such as those depicted within first to third images 110 to 130 of
An example of such a radome being depicted within
At present, a dominant configuration for dual band receivers for civilian applications is the use of the L1+L2 bands of the GPS system (formerly Naystar GPS) which is owned by the United States of America government and operated by the United States Air Force since the 1970s for military use and the 1980s for civilian use. The operating frequency bands for GPS L1 and GPS L2 being listed below in Table 1 together with the frequency bands of the other major GNSS systems introduced in the 2000s, namely Beidou, Galileo, GLONASS, GPS, and NAVIC.
There is an increasing deployment of satellites which also provide a navigation signal on the L5 band. Accordingly, there is also a market drive to replace L1+L2 GPS receivers with L1+L5 GPS receivers. This arises from several factors including, but not limited to:
Additionally, in 2020 the US Department of Defense will cease to support codeless/semicodeless tracking of GPS L2 signals in favor of a new L2C signal that includes an updated and more refined C/A acquisition signal, transmitted on the existing L2 frequency. The updated GPS signal set includes the new L5 signal which provides an updated C/A signal, and which is broadcast at approximately 3 dB higher EIRP than the L1 and L2 signals. These updates will offer great opportunities to reduce the cost of precision multiband receivers.
Accordingly, there is a requirement to provide L1+L5 stacked patch antennas to meet these evolving requirements either to provide form-fit antennas for retrofitting equipment already deployed allowing them to be upgraded for ongoing L1+L5 operation or to provide form-fit antennas to products in ongoing production to eliminate a requirement for product redesign.
Accordingly, it would be beneficial for the L1+L5 stacked patch antenna to provide the same footprint as the L1+L2 stacked patch antenna. However, as noted from Table 1 the L2 carrier frequency is 1.22760 GHz (wavelength in air 24.45 cm) whilst the L5 carrier frequency is 1.17645 GHz. The diameter of a patch antenna resonant element is inversely proportional to the resonant frequency. Accordingly, the dimensions of an L5 patch antenna are larger than those of an L2 patch antenna which is undesirable. There is significant given demand for reducing antenna footprints generally or providing form-fit replacements in other applications.
Referring to
Referring to
Accordingly, the inventors provide a spacer 410 having a dielectric constant lower than either of the dielectric constants of upper element 300C and 400D, disposed between the upper element 300C and the lower element 400D. By this means the microwave signals propagating within lower element 400D and flowing on second upper metallization 420 are decoupled from first lower metallization 330. Accordingly, the geometrically varying periphery comprising castellations defined by first and second notches 430 and 440 respectively in the first and second plan views 400B and 400C respectively can now extend under the upper patch antenna element 300C allowing the lower patch antenna element 400D to operate at lower frequencies than prior art DB-SPAs. The coupling between the microwave signals propagating within the upper metallization 420 of the lower patch antenna element 400D to the upper patch antenna element being reduced to below a threshold such that the resonant frequency of the lower patch antenna element is determined by the cavity resonator comprised of the castellated upper metallization 420 and the ground plane metallization 360 of the second dielectric 350. The dielectric spacer 410 is manufactured from a material having a lower effective dielectric constant so that the decoupling between the lower metallization 330 of the upper patch antenna element 300C and upper metallization 420 of the lower patch antenna element 400D is achieved for a small or low thickness of the dielectric spacer 410.
Referring to
It would be evident from first to third images 600A to 600C respectively and
Referring to
A similar situation is evident in
Within the descriptions supra in respect of
Two examples being depicted in
Specific details are given in the above description to provide a thorough understanding of the embodiments. However, it is understood that the embodiments may be practiced without these specific details.
The foregoing disclosure of the exemplary embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents.
This patent application claims the benefit of priority as a continuation of U.S. patent application Ser. No. 17/812,681 filed Jul. 14, 2022; which itself claims the benefit of priority from U.S. patent Ser. No. 16/943,209 filed Jul. 30, 2020 which has issued as U.S. Pat. No. 11,417,961; which itself claims the benefit of priority from U.S. Provisional Patent Application 62/880,237 filed Jul. 30, 2019; the entire contents of each being incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62880237 | Jul 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17812681 | Jul 2022 | US |
| Child | 18450220 | US | |
| Parent | 16943209 | Jul 2020 | US |
| Child | 17812681 | US |
