An antenna (such as a dipole antenna) typically generates radiation in a pattern that has a preferred direction. For example, the generated radiation pattern is stronger in some directions and weaker in other directions. Likewise, when receiving electromagnetic signals, the antenna has the same preferred direction. Signal quality (e.g., signal to noise ratio or SNR), whether in transmitting or receiving scenarios, can be improved by aligning the preferred direction of the antenna with a direction of the target or source of the signal. However, it is often impractical to physically reorient the antenna with respect to the target or source of the signal. Additionally, the exact location of the source/target may not be known. To overcome some of the above shortcomings of the antenna, a phased array antenna can be formed from a set of antenna elements to simulate a large directional antenna. An advantage of a phased array antenna is its ability to transmit and/or receive signals in a preferred direction (e.g., the antenna's beamforming ability) without physical repositioning or reorientating.
It would be advantageous to configure phased array antennas having increased bandwidth while maintaining a high ratio of the main lobe power to the side lobe power. Likewise, it would be advantageous to configure phased array antennas having reduced weight, reduced size, lower manufacturing cost, and/or lower power requirements. Accordingly, embodiments of the present disclosure are directed to these and other improvements in phase array antennas or portions thereof.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In accordance with one embodiment of the present disclosure, a self-multiplexing antenna is provided. The self-multiplexing antenna includes: a substrate; a first antenna element carried by the substrate, the first antenna element including a first antenna patch, and a first antenna reflector; a first signal feed connected with the first antenna patch; a second antenna element carried by the substrate, wherein the second antenna element is stacked with the first antenna element, the second antenna element including a second antenna patch, and a second antenna reflector; a second signal feed connected with the second antenna patch; and a first isolator cavity between the second antenna reflector and the first antenna patch.
In accordance with another embodiment of the present disclosure, a self-multiplexing antenna is provided. The self-multiplexing antenna includes: a substrate; a first antenna element carried by the substrate, the first antenna including a first antenna patch, and a first antenna reflector; a first signal feed connected with the first antenna patch; a second antenna element carried by the substrate, wherein the second antenna is stacked with the first antenna element, the second antenna element including a second antenna patch, and a second antenna reflector; a second signal feed connected with the second antenna patch; a first isolator cavity between the first antenna reflector and the second antenna patch, wherein the first isolator cavity is dimensioned to suppress coupling of RF radiation between the first antenna element and the second antenna element at the second frequency; and a notch filter connected to the first signal feed of the first antenna and disposed in the first isolator cavity, the notch filter line having a length sized to filter out the first frequency.
In accordance with another embodiment of the present disclosure, a phased array antenna is provided. The phased array antenna includes: a carrier; and a plurality of self-multiplexing antenna element stacks, each stack including a first antenna element configured to transmit and/or receive signals at a first value of a parameter, a second antenna element configured to transmit and/or receive signals at a second value of a parameter, and an isolator cavity between the first and second antenna elements.
In accordance with another embodiment of the present disclosure, a self-multiplexing antenna is provided. The phased array antenna includes: a substrate; a first antenna element carried by the substrate; a second antenna element carried by the substrate; and an isolator cavity disposed between the first antenna element and the second antenna element.
In any of the embodiments described herein, the first antenna element may be configured to operate at a first frequency, and the second antenna element may be configured to operate at a second frequency different from the first frequency.
In any of the embodiments described herein, the second frequency may be greater than the first frequency.
In any of the embodiments described herein, the fractional guard-band (edge-to-edge) may be selected from the group consisting of greater than 4.5%, greater than 5%, greater, than 6%, and greater than 7%.
In any of the embodiments described herein, the first signal feed is a center conductor of a first coaxial line, wherein the first coaxial line may include a first shielding connected to the first antenna reflector, wherein the second signal feed is a center conductor of a second coaxial line, and wherein the second coaxial line may include a second shielding connected to the second antenna reflector.
In any of the embodiments described herein, the first shielding and the second shielding may include a plurality of metal vias in the substrate.
In any of the embodiments described herein, the second signal feed may be substantially centrally located with respect to the first antenna patch.
In any of the embodiments described herein, the self-multiplexing antenna may further include a third antenna element carried by the substrate, wherein the third antenna is at least partially vertically aligned with the first and second antenna elements, the third antenna element including a third antenna patch, and a third antenna reflector; a third signal feed connected with the third antenna patch; and a second isolator cavity between the second antenna patch and the third antenna reflector.
In any of the embodiments described herein, the substrate may be a printed circuit board (PCB) or a ceramic board.
In any of the embodiments described herein, the first isolator cavity may be dimensioned to suppress coupling of RF radiation between the first antenna element and the second antenna element at the second frequency.
In any of the embodiments described herein, the second antenna element may further include one or more parasitic elements configured to operate at the second frequency.
In any of the embodiments described herein, the one or more parasitic elements may be one or more resonator patches.
In any of the embodiments described herein, the parasitic elements may have the same shape as the second antenna patch.
In any of the embodiments described herein, the self-multiplexing antenna further may include a notch filter connected to the second signal feed of the second antenna and disposed in the first isolator cavity, the notch filter line having a length sized to filter out the first frequency.
In any of the embodiments described herein, the notch filter may be a trace line.
In any of the embodiments described herein, the first trace line may be wound in the first isolator cavity.
In any of the embodiments described herein, the self-multiplexing antenna further may include a tuning stub connected to the notch filter.
The foregoing aspects and many of the attendant advantages of this disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Embodiments of the present disclosure are directed to apparatuses and methods relating to self-multiplexing antennas and self-multiplexing antennas in phased array antenna systems. In one embodiment of the present disclosure, a self-multiplexing antenna includes a substrate, first and second antenna elements carried by the substrate, and an isolator cavity disposed between the first antenna element and the second antenna element. These and other aspects of the present disclosure will be more fully described below.
While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described herein in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives consistent with the present disclosure and the appended claims.
References in the specification to “one embodiment,” “an embodiment,” “an illustrative embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may or may not necessarily include that particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Additionally, it should be appreciated that items included in a list in the form of “at least one A, B, and C” can mean (A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C). Similarly, items listed in the form of “at least one of A, B, or C” can mean (A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C).
Language such as “top”, “bottom”, “top surface”, “bottom surface”, “vertical”, “horizontal”, and “lateral” in the present disclosure is meant to provide orientation for the reader with reference to the drawings and is not intended to be the required orientation of the components or to impart orientation limitations into the claims.
In the drawings, some structural or method features may be shown in specific arrangements and/or orderings. However, it should be appreciated that such specific arrangements and/or orderings may not be required. Rather, in some embodiments, such features may be arranged in a different manner and/or order than shown in the illustrative figures. Additionally, the inclusion of a structural or method feature in a particular figure is not meant to imply that such feature is required in all embodiments and, in some embodiments, it may not be included or may be combined with other features.
Many embodiments of the technology described herein may take the form of computer- or controller-executable instructions, including routines executed by a programmable computer or controller. Those skilled in the relevant art will appreciate that the technology can be practiced on computer/controller systems other than those shown and described above. The technology can be embodied in a special-purpose computer, controller or data processor that is specifically programmed, configured or constructed to perform one or more of the computer-executable instructions described above. Accordingly, the terms “computer” and “controller” as generally used herein refer to any data processor and can include Internet appliances and hand-held devices (including palm-top computers, wearable computers, cellular or mobile phones, multi-processor systems, processor-based or programmable consumer electronics, network computers, mini computers and the like). Information handled by these computers can be presented at any suitable display medium, including a CRT display or LCD.
Referring to
In accordance with embodiments of the present disclosure, the phased array antenna system 100 may be a multi-beam phased array antenna system, in which each beam of the multiple beams may be configured to be at different angles, different frequency, and/or different polarization.
In the illustrated embodiment, the antenna lattice 120 includes a plurality of antenna elements 122i. A corresponding plurality of amplifiers 124i are coupled to the plurality of antenna elements 122i. The amplifiers 124i may be low noise amplifiers (LNAs) in the receiving direction RX or power amplifiers (PAs) in the transmitting direction TX. The plurality of amplifiers 124i may be combined with the plurality of antenna elements 122i in for example, an antenna module or antenna package. In some embodiments, the plurality of amplifiers 124i may be located in another lattice separate from the antenna lattice 120.
Multiple antenna elements 122i in the antenna lattice 120 are configured for transmitting signals (see the direction of arrow TX in
Referring to
The beamformer lattice 140 includes a plurality of beamformers 142i including a plurality of phase shifters 145i. In the receiving direction RX, the beamformer function is to delay the signals arriving from each antenna element so the signals all arrive to the combining network at the same time. In the transmitting direction TX, the beamformer function is to delay the signal sent to each antenna element such that all signals arrive at the target location at the same time. This delay can be accomplished by using “true time delay” or a phase shift at a specific frequency.
Following the transmitting direction of arrow TX in the schematic illustration of
For example, the phases of the common RF signal can be shifted by 0° at the bottom phase shifter 145i in
Because of the phase offsets, the RF signals from individual antenna elements 122i are combined into outgoing wave fronts that are inclined at angle ϕ from the antenna aperture 110 formed by the lattice of antenna elements 122i. The angle ϕ is called an angle of arrival (AoA) or a beamforming angle. Therefore, the choice of the phase offset Δα determines the radiation pattern of the combined signals S defining the wave front. In
Following the receiving direction of arrow RX in the schematic illustration of
Still referring to
In accordance with some embodiments of the present disclosure, the antenna elements 122i and other components of the phased array antenna system 100 may be contained in an antenna module to be carried by the carrier 112. (See, for example, antenna modules 226a and 226b in
Referring to
The system 100 includes a first portion carrying the antenna lattice 120 and a second portion carrying a beamformer lattice 140 including a plurality of beamformer elements. As seen in the cross-sectional view of
Referring to
One approach for reducing side lobes Ls is arranging elements 122i in the antenna lattice 120 with the antenna elements 122i being phase offset such that the phased array antenna system 100 emits a waveform in a preferred direction D with reduced side lobes. Another approach for reducing side lobes Ls is power tapering. However, power tapering is generally undesirable because by reducing the power of the side lobe Ls, the system has increased design complexity of requiring of “tunable and/or lower output” power amplifiers.
In addition, a tunable amplifier 124i for output power has reduced efficiency compared to a non-tunable amplifier. Alternatively, designing different amplifiers having different gains increases the overall design complexity and cost of the system.
Yet another approach for reducing side lobes Ls in accordance with embodiments of the present disclosure is a space tapered configuration for the antenna elements 122i of the antenna lattice 120. (See the antenna element 122i configuration in
In addition to undesirable side lobe reduction, space tapering may also be used in accordance with embodiments of the present disclosure to reduce the number of antenna elements 122i in a phased array antenna system 100 while still achieving an acceptable beam B from the phased array antenna system 100 depending on the application of the system 100. (For example, compare in
Although not shown, one or more additional layers may be disposed between layers 180a and 180b, between layers 180b and 180c, between layers 180c and 180d, above layer 180a, and/or below layer 180d. Each of the layers 180a, 180b, 180c, and 180d may comprise one or more PCB sub-layers. In other embodiments, the order of the layers 180a, 180b, 180c, and 180d relative to each other may differ from the arrangement shown in
Layers 180a, 180b, 180c, and 180d may include electrically conductive traces (such as metal traces that are mutually separated by electrically isolating polymer or ceramic), electrical components, mechanical components, optical components, wireless components, electrical coupling structures, electrical grounding structures, and/or other structures configured to facilitate functionalities associated with the phase array antenna system 100. Structures located on a particular layer, such as layer 180a, may be electrically interconnected with vertical vias (e.g., vias extending along the z-direction of a Cartesian coordinate system) to establish electrical connection with particular structures located on another layer, such as layer 180d.
Antenna layer 180a may include, without limitation, the plurality of antenna elements 122i arranged in a particular arrangement (e.g., a space taper arrangement) as an antenna lattice 120 on the carrier 112. Antenna layer 180a may also include one or more other components, such as corresponding amplifiers 124i. Alternatively, corresponding amplifiers 124i may be configured on a separate layer. Mapping layer 180b may include, without limitation, the mapping system 130 and associated carrier and electrical coupling structures. Multiplex feed network layer 180c may include, without limitation, the multiplex feed network 150 and associated carrier and electrical coupling structures. Beamformer layer 180d may include, without limitation, the plurality of phase shifters 145i, other components of the beamformer lattice 140, and associated carrier and electrical coupling structures. Beamformer layer 180d may also include, in some embodiments, modulator/demodulator 170 and/or coupler structures. In the illustrated embodiment of
Although not shown, one or more of layers 180a, 180b, 180c, or 180d may itself comprise more than one layer. For example, mapping layer 180b may comprise two or more layers, which in combination may be configured to provide the routing functionality discussed above. As another example, multiplex feed network layer 180c may comprise two or more layers, depending upon the total number of multiplex feed networks included in the multiplex feed network 150.
In accordance with embodiments of the present disclosure, the phased array antenna system 100 may be a multi-beam phased array antenna system. In a multi-beam phased array antenna configuration, each beamformer 142i may be electrically coupled to more than one antenna element 122i. The total number of beamformer 142i may be smaller than the total number of antenna elements 122i. For example, each beamformer 142i may be electrically coupled to four antenna elements 122i or to eight antenna elements 122i.
In the illustrated embodiment of
Signals are detected by the individual antenna elements 222a and 222b, shown in the illustrated embodiment as being carried by antenna modules 226a and 226b on the top surface of the antenna lattice layer 280a. After being received by the antenna elements 222a and 222b, the signals are amplified by the corresponding low noise amplifiers (LNAs) 224a and 224b, which are also shown in the illustrated embodiment as being carried by antenna modules 226a and 226b on a top surface of the antenna lattice layer 280a.
In the illustrated embodiment of
In the illustrated embodiment of
In the illustrated embodiment, the antenna elements 222i and the beamformer elements 242i are configured to be on opposite surfaces of the lay-up of PCB layers 280. In other embodiments, beamformer elements may be co-located with antenna elements on the same surface of the lay-up. In other embodiments, beamformers may be located within an antenna module or antenna package.
As previously described, electrical connections coupling the antenna elements 222a and 222b of the antenna lattice 220 on the antenna layer 280a to the beamformer elements 242a of the beamformer lattice 240 on the beamformer layer 280d are routed on surfaces of one or more mapping layers 280b1 and 280b2 using electrically conductive traces. Exemplary mapping trace configurations for a mapping layer are provided in layer 130 of
In the illustrated embodiment, the mapping is shown on top surfaces of two mapping layers 280b1 and 280b2. However, any number of mapping layers may be used in accordance with embodiments of the present disclosure, including a single mapping layer. Mapping traces on a single mapping layer cannot cross other mapping traces. Therefore, the use of more than one mapping layer can be advantageous in reducing the lengths of the electrically conductive mapping traces by allowing mapping traces in horizontal planes to cross an imaginary line extending through the lay-up 280 normal to the mapping layers and in selecting the placement of the intermediate vias between the mapping traces.
In addition to mapping traces on the surfaces of layers 280b1 and 280b2, mapping from the antenna lattice 220 to the beamformer lattice 240 further includes one or more electrically conductive vias extending vertically through one or more of the plurality of PCB layers 280.
In the illustrated embodiment of
Of note, via 248a corresponds to via 148a and filter 244a corresponds to filter 144a, both shown on the surface of the beamformer layer 180d in the previous embodiment of
Similar mapping connects the second antenna element 222b to RF filter 244b and then to the beamformer element 242a. The second antenna element 222b may operate at the same or at a different value of a parameter than the first antenna element 222a (for example at different frequencies). If the first and second antenna elements 222a and 222b operate at the same value of a parameter, the RF filters 244a and 244b may be the same. If the first and second antenna elements 222a and 222b operate at different values, the RF filters 244a and 244b may be different.
Mapping traces and vias may be formed in accordance with any suitable methods. In one embodiment of the present disclosure, the lay-up of PCB layers 280 is formed after the multiple individual layers 280a, 280b, 280c, and 280d have been formed. For example, during the manufacture of layer 280a, electrically conductive via 228a may be formed through layer 280a. Likewise, during the manufacture of layer 280d, electrically conductive via 248a may be formed through layer 280d. When the multiple individual layers 280a, 280b, 280c, and 280d are assembled and laminated together, the electrically conductive via 228a through layer 280a electrically couples with the trace 232a on the surface of layer 280b1, and the electrically conductive via 248a through layer 280d electrically couples with the trace 234a on the surface of layer 280b2.
Other electrically conductive vias, such as via 238a coupling trace 232a on the surface of layer 280b1 and trace 234a on the surface of layer 280b2 can be formed after the multiple individual layers 280a, 280b, 280c, and 280d are assembled and laminated together. In this construction method, a hole may be drilled through the entire lay-up 280 to form the via, metal is deposited in the entirety of the hole forming an electrically connection between the traces 232a and 234a. In some embodiments of the present disclosure, excess metal in the via not needed in forming the electrical connection between traces 232a and 234a can be removed by back-drilling the metal at the top and/or bottom portions of the via. In some embodiments, back-drilling of the metal is not performed completely, leaving a via “stub”. Tuning may be performed for a lay-up design with a remaining via “stub”. In other embodiments, a different manufacturing process may produce a via that does not span more than the needed vertical direction.
As compared to the use of one mapping layer, the use of two mapping layers 280b1 and 280b2 separated by intermediate vias 238a and 238b as seen in the illustrated embodiment of
In the illustrated embodiment of
In some embodiments of the present disclosure, the individual antenna elements 322a and 322b may be configured to receive and/or transmit data at different values of one or more parameters (e.g., frequency, polarization, beam orientation, data streams, receive (RX)/transmit (TX) functions, time multiplexing segments, etc.). These different values may be associated with different groups of the antenna elements. For example, a first plurality of antenna elements carried by the carrier is configured to transmit and/or receive signals at a first value of a parameter. A second plurality of antenna elements carried by the carrier are configured to transmit and/or receive signals at a second value of the parameter different from the first value of the parameter, and the individual antenna elements of the first plurality of antenna elements are interspersed with individual antenna elements of the second plurality of antenna elements.
As a non-limiting example, a first group of antenna elements may receive data at frequency f1, while a second group of antenna elements may receive data at frequency f2.
The placement on the same carrier of the antenna elements operating at one value of the parameter (e.g., first frequency or wavelength) together with the antenna elements operating at another value of the parameter (e.g., second frequency or wavelength) is referred to herein as “interspersing”. In some embodiments, the groups of antenna elements operating at different values of parameter or parameters may be placed over separate areas of the carrier in a phased array antenna. In some embodiments, at least some of the antenna elements of the groups of antenna elements operating at different values of at least one parameter are adjacent or neighboring one another. In other embodiments, most or all of the antenna elements of the groups of antenna elements operating at different values of at least one parameter are adjacent or neighboring one another.
In the illustrated embodiment of
Although shown in
In the illustrated embodiment of
The mapping layers and vias can be arranged in many other configurations and on other sub-layers of the lay-up 180 than the configurations shown in
To increase the number of beams transmitted or received from an antenna aperture, embodiments of the present disclosure include phased array antenna systems including a plurality of vertically stacked antenna elements. A vertical stack of individual antenna elements may also be referred to as a “self-multiplexing antenna.” In some embodiments of the present disclosure, a second antenna element is stacked with the first antenna element to be at least partially vertically aligned with a first antenna element. In some embodiments of the present disclosure, the second antenna element is stacked and concentric with the first antenna element.
Each antenna element in the stack may include an antenna patch and a ground plane or ground reflector. A patch antenna (also known as a microstrip antenna) is a type of radio antenna with a low profile, which can be mounted on a flat surface. A patch antenna may be a flat sheet or “patch” of metal, mounted over a larger sheet of a metal ground reflector.
In some embodiments, antenna patches can be mounted on a carrier, for example, on a printed circuit board (PCB), with the substrate defining the dielectric of the patch. In other embodiments, antenna patches may be mounted on or within an antenna package (such as an antenna module 226 as shown in
In each antenna element, the distance between the patch and the ground reflector—dielectric height h—determines the bandwidth of the antenna. The ground reflector generally extends beyond the edges of the patch for proper operation. A ground reflector that is too small will result in a reduced front to back ratio. The center conductor of a coaxial line serves as the feed probe to couple electromagnetic energy in and/or out of the patch.
In operation, the individual antenna elements in the stack may receive and/or transmit data at different parameters (e.g., different frequencies, polarization angles, time multiplexing segments, etc.) to decrease coupling between antenna elements. For example, a first antenna element in the stack may transmit data at frequency f1, while a second antenna element in the stack may transmit data at frequency f2.
In general, some power may leak from one antenna element to another antenna element in a stack operating at nominally different values of a parameter (for example, operating at different frequencies). Even when an individual antenna in the stack primarily operates at one value of the parameter, e.g., frequency f1, that antenna may retain some sensitivity to another value of the parameter that is primarily associated with another antenna in the stack, e.g., frequency f2. Therefore, in some embodiments, filters are used to limit the cross-talk between the individual antenna elements in the stack, as described in greater detail below. In some embodiments, the filters may be constructed within the same footprint that is already occupied by the stack, which further minimizes the overall size of the phased array antenna.
In operation, the antenna patch 423 receives radio frequency (RF) signals through an antenna feed 435 and emits RF signals (thorough the resonator formed by the antenna patch 423 and the ground reflector 425). Generally, the characteristic dimension of the antenna patch 423 is selected to promote a specific radio frequency (RF) of the signal. The antenna feed 435 can be a coaxial line including a center conductor 436 placed with respect to an outer shielding 437 to reduce noise coming into the antenna feed 435.
In some applications, a plurality of antenna elements can be used to increase power of the main lobe and/or decrease power of the side lobes and to increase the number of beams (communication links) of a phased array antenna system. As a result, the overall size of the phased array antenna and the number of antenna elements can become significant, which drives up the cost and size of the phased array antenna system. Therefore, in some phased array antenna systems, the individual antenna elements can be stacked on top of each other to reduce the overall area of the carrier and to increase the capacity of the system by increasing the number of beams transmitted and/or received by the system. An example of the conventional stacking of the antenna elements is described with reference to
The second antenna element 522-2 is stacked over the first antenna element 522-1. The antenna patch 543 of the second antenna element 522-2 uses the antenna patch 523 of the first antenna element as its ground reflector.
The individual antennas 522-1 and 522-2 receive their corresponding RF signals through signal feeds 535 and 555. Typically, the first (lower and larger) antenna element 522-1 operates at an RF frequency that is lower than that of the second (upper and smaller) antenna element 522-2, because the size of the antenna patch of the antenna scales inversely proportionally with the operating frequency of the antenna element.
In view of the stacking of antenna elements, the increase in the number of antenna elements does not require an incremental increase of the surface area of the carrier (also referred to as “footprint” or “real estate” in the industry). However, stacking individual antenna elements may cause electromagnetic interference or power coupling between the antennas in the stack (also referred to as “cross-talk” or “leakage”). Generally, such electromagnetic interference reduces the efficiency of the antenna elements. Accordingly, it would be advantageous to provide stacks of the individual antenna elements that result in reduced interference and reduced power dissipation from the antenna elements. Furthermore, it would be advantageous to provide improved phased array antennas having an increased number of beams without an increase in surface area of the carrier.
Such interference can be problematic at low fractional bandwidth. For example, when you have two resonant antennas on the same side of a carrier (side by side or having a vertical overlay) having center frequencies f1 and f2. As the fractional bandwidth [2(f1−f2)/(f1+f2)] gets larger, the coupling between the antennas can become smaller. Therefore, filtering techniques can be used for one or both of the antennas to further suppress the coupling. Moreover, frequency planning can be used to increase the fractional bandwidth between interspersed antenna elements on the same side of a carrier.
In a non-limiting exemplary, TABLE 1 below provides an exemplary channel configuration a Ku-Band downlink of 10.7 GHz to 12.7 GHz, having a total band spread of 2 GHz. When divided into eight channels with each channel representing 250 MHz, and each channel having respective center frequencies (fc) listed in TABLE 2 below.
In a non-limiting example, the antenna elements may be divided between two panels, Panel 1 and Panel 2, each having two different types of antenna modules, AIP1 and AIP2 on panel 1 and AIP3 and AIP4 on panel 2. In the illustrated example, each antenna module includes two self-diplexing antenna elements.
Frequency planning can be used to increase the fractional bandwidth between vertically stacked antenna elements on the same side of a carrier. In the illustrated example (8-channel case, TABLE 1), the following frequency planning set out in TABLE 2 below can be used to establish at least a 750 MHz guard-band (edge-to-edge) difference between operational bands of antenna elements on the same side of a carrier having a vertical overlay. In this example (e.g. Ch-1 & Ch-5 on AIP-1), the fractional guard-band is 750 MHz divided by the center frequency (11.325 GHz) of the channel pair, which equals a fractional bandwidth of 6.6%. Such fractional bandwidth
In one embodiment of the present disclosure, the fractional guard-band is greater than 4.5%. In one embodiment of the present disclosure, the fractional guard-band is greater than 5%. In another embodiment of the present disclosure, the fractional guard-band is greater than 6%. In another embodiment of the present disclosure, the fractional guard-band is greater than 7%.
In one embodiment, the guard-band maintains about 2% operational bandwidth for the first and second antennas around first frequency and second frequency, respectively. In other embodiment, the guard-band maintains up to 5% of the operational bandwidth for the first and second antennas around first frequency and second frequency, respectively.
The first antenna element 622-1 includes an antenna patch 623 and a ground reflector 625 spaced from the antenna patch 623 by a distance h1. Likewise, the second antenna element 622-2 includes an antenna patch 643 and a ground reflector 645 spaced from the antenna patch 643 by a distance h2. An isolator cavity 631, as discussed in greater detail below, is defined between the first and second antenna elements 622-1 and 622-2. The antenna patches and the ground reflectors may be portions of the routing layers (e.g., metal layers) between the pairs of the insulation layers (e.g., polymer, ceramic, etc.) of the carrier 633.
In some embodiments, the individual antennas may have different sizes. For example, the second antenna element 622-2 (which is the top antenna element in the configuration shown in
The first and second antenna elements operate at different parameters. For example, the first antenna element 622-1 may receive signals at frequency f1 through a first antenna feed 635, and the second antenna element 622-2 may receive signals at frequency f2 through a second antenna feed 655.
In some embodiments, the antenna feeds (also referred to as “signal feeds”) may include co-axial cables. For example, the antenna feed 635 for the first antenna element 622-1 in the illustrated embodiment includes a center conductor 636 which is shielded by 637. The shielding 637 may be connected to the ground reflector 625 for the first antenna element 622-1. Likewise, the shielding 657 may be connected to the ground reflector 645 for the second antenna element 622-2. In some embodiments, the shielding portions 637 and 657 may be metal-plated vias in the substrate 633 (see, e.g., exemplary shielding 1257 in
The first and second antenna elements 622-1 and 622-2 may simultaneously operate at frequencies f1 and f2 to or from a remote receiver and/or transmitter. As a result, the overall data bandwidth of the stack 600 is increased, while the footprint of the stacked antenna remains generally the same as it would be for a non-stacked antenna design.
The isolator cavity 631 between the first and second antenna elements 622-1 and 622-2 provides an RF choke (resonant type) to isolate the antenna elements and reduce electromagnetic coupling between the first and second antenna feeds 635 and 655. The isolation frequency of the cavity 631 is a function of the volume (as shown by “L” in
Typically, the resonant field inside the RF-choke is similar to the resonant field of a conventional patch antenna with equal cavity size operating at its first dominant mode. As a first order approximation; we can ignore the thickness of coaxial shield 657 of top antenna and the fringing effect between the second antenna reflector 645 and the first antenna patch 623. Assuming the second (top) antenna reflector 645 is of circular shape, L becomes the radius of the second antenna reflector 645 and the resonance frequency, fc, of the cavity can be found as follows;
ϵr is the dielectric constant of the cavity medium
For a practical implementation, the coaxial shield 657 will occupy a finite volume inside the isolator cavity 631 and fc will be slightly above the value suggested by the equation, due to reduced cavity volume. Also for increasing thickness of the isolator cavity 631, the fringing effect around the perimeter of the isolator cavity 631 will decrease the resonance frequency, fc, slightly below the value suggested by the equation. The exact resonant frequency will also depend on the size of the first antenna patch 623 when it is close in diameter to the isolator cavity 631 in size/diameter.
The solid line S11 curves for the first and second antenna elements 622-1 and 622-2 are exemplary S11 curves for an antenna stack without any filtering. In view of the filtering provided by the isolator cavity 631 shown and described with reference to
A relatively narrow r (reflection coefficient) for the individual antenna operating at frequency f1 indicates a high selectivity of that antenna for the signals at f1, and high rejection of the signals outside of the relatively narrow frequency range around f1. As a result, the individual antenna element operating at frequency f1 is less receptive to the frequencies away from f1. Generally, the relatively high selectivity of an individual antenna for its operating frequency makes the individual antenna element more immune to the frequencies outside of the preferred range. Accordingly, separation can be achieved between the resonators in the non-limiting example of the first antenna element 622-1 operating at frequency f1=10.7 GHz, and the second antenna element 622-2 operating at frequency f2=11.7 GHz. With improved separation, the overall signal-to-noise ratio (SNR) and the total efficiency of the antenna stack may be improved. In a non-limiting example of
The RF choke (cavity 631), shown in
In operation, the individual antenna elements create an electrical field (E) in response to the excitation provided by the antenna feeds. For example, the first antenna element 722-1 creates an electrical field E inside the volume the first antenna patch 723 and the first antenna reflector 725 that, at the time of sampling, ranges from E=E+ at one side of the antenna, through E=0 at the geometrical center, to E=E− at the opposite side of the antenna. Even as the electrical field E changes as a function of time, the electrical field E may generally remain zero or close to zero at the geometrical center or close to the geometrical center of the antenna.
In some embodiments, the antenna feed for a subsequent second antenna may be routed at least partially through the areas of E=0 to minimize to mitigate the interference with the E-field profile and distribution of the first antenna 722-1. For example, in the illustrated embodiment of
In some embodiments, the center conductors may be connected to their respective antenna patches away from the center of the antenna patches to promote excitation of the antenna elements. For example, in the illustrated stack 700 in
As discussed above with reference to
In addition to reducing the leakage between the antenna pair 622-1 and 622-2 at the high band (f2) in the illustrated embodiment of
In operation, the parasitic patches can be used to control the frequency response of the second (top) antenna 922-2 in the stack, as explained with reference to
In the illustrated embodiment of
In the illustrated embodiment, the sizes of the parasitic patches 973, 975, 977 can be chosen to get a specific frequency response from the second antenna element 922-2 but is typically smaller than the second antenna patch 943. As a result, the parasitic patches 973, 975, 977 do not require additional footprint of the carrier. However, other sizing for parasitic patches is within the scope of the present disclosure.
In the illustrated embodiment of
The solid line S11 curves for the first and second antenna elements 922-1 and 922-2 are exemplary S11 curves for an antenna stack without any filtering. The antennas are still impedance matched in the other's operational band, resulting in resistive loading to each other, and therefore, decreased efficiency. In view of the filtering provided by the isolator cavity 931, the S11 curve for the first (bottom) antenna element 922-1 becomes narrower around f1 by increasing the roll-off of the S11 away from f2, the high band as indicated by the arrow A1. The S11 curve of the second (top) antenna element 922-2 can be shaped in a similar way (shown by arrows A2 and A3) by using the patches 943, 973, 975, 977 and the dielectric material filling between those patches. A relatively narrower band response for each antenna element prevents them from resistively loading each other during their operation, resulting in higher radiation efficiency.
As described with reference to the simulation results in
As discussed above with reference to
In
In
In some embodiments, the trace filter 1181 may be wound inside the space or cavity 1131 between the two individual antennas elements 1122-1 and 1122-2, therefore not requiring additional footprint on the carrier 1233. In some embodiments, the trace filter 1181 can be a conductive trace laid within a routing layer of the carrier 1133 (e.g., PCB or a ceramic carrier).
In some embodiments, the length of the trace filter 1181 can be selected to filter out undesired frequencies. For example, the trace filter 1181 may filter the frequency f1 emitted by the first (bottom) antenna element 1122-1, while not filtering frequency f2 of the second (top) antenna element 1122-2.
In some embodiments, the illustrated trace filter 1181 has a length L:
L=(2N+1)λg/4 Eq. (1)
where λg is the guided wavelength of the RF signal transmitted/received by the first antenna elements 1122-1 inside the dielectric volume 1131, and N is a whole number.
In the illustrated embodiment of
In the illustrated embodiment, the first central conductor 1236 (the coaxial line leading from below the stack is not shown) provides signals to the first antenna patch 1223, and the second central conductor 1256 (the coaxial line leading from below the stack is not shown) provides signals to the second antenna patch 1243. Shielding vias 1257 around the second central conductor 1256 make up the outer conductor surrounding the second central conductor 1256. The total diameter of the circular area occupied by shielding vias 1257 and can be used to tune the frequency of the first (bottom_antenna element 1222-1 and the isolator choke 1240. The shielding vias 1257 that are closest to the central conductor 1256 of the second (top) antenna element 1222-2 can be used to impedance tune the second (top) antenna element 1222-2.
In the illustrated embodiment, the stack 1200 includes a plurality of tuning pins 1285 and 1287, designed, for example, for frequency tuning of the respective antenna elements 1222-1 and the RF choke 1240. The tuning pins can be used to lower the resonance of the cavities they are placed inside. For example pins 1287 can be used to tune the resonance frequency of the isolator cavity, without the need to change the sizing of the isolator cavity as determined by the sizing of the second reflector 1245 and the first antenna patch 1223, hence not perturbing the resonance frequencies of the top and bottom antenna cavities. Same applies to the pins 1285, which can be used to tune the resonance frequency of the bottom antenna cavity, without changing the sizing of 1225 and 1223, hence not perturbing the resonance frequency of the isolator and/or top antenna cavity
In the illustrated embodiment, the stack 1200 includes a trace filter 1281 and a tuning stub 1282, as explained with reference to
While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosure.
This application claims the benefit of U.S. Provisional Application Nos. 62/631,195, filed Feb. 15, 2018, and 62/631,685, filed Feb. 17, 2018, the disclosures of which are hereby incorporated by reference herein in their entirety.
Number | Date | Country | |
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62631685 | Feb 2018 | US | |
62631195 | Feb 2018 | US |