Hybrid RF beamforming with multiport antenna with parasitic array

A method for hybrid RF beamforming comprising: providing an antenna structure which comprises: a driven element, parasitic elements configured to couple/decouple a linearly polarized radiation pattern and arranged around the driven elements, a feed system comprising four ports that are 90 degrees out of phase with each other and are connected to the driven element, RF switches electrically connected to the parasitic elements and the four ports, and a controller operatively connected to the RF switches; selectively attenuating an output of each of the four ports with the controller according to a stored configuration, which is stored in a memory, by changing the four ports' respective phase or attenuation; and selectively changing a loading of each parasitic element by activating each parasitic element's corresponding RF switch with the controller according to the stored configuration so as to produce a desired null/beamforming of a main RF beam.

BACKGROUND OF THE INVENTION

Antenna null forming or beamforming can be achieved using a variety of existing architectures. Examples of prior art architectures are depicted inFIGS.1A through1E. The aerial beamforming architecture shown inFIG.1Dhas the advantage of requiring only input/output path from a single antenna. However, parallel processing is impossible when using the aerial beamforming architecture because only a single input/output path can be processed at a time.

Digital beamforming antennas, depicted inFIG.1A, are widely used. Digital beamforming (DBF) are good adaptive antennas, and are supported by a wealth of control algorithms. However, digital beamforming antennas are very expensive because of the multiplicity of paths and subsequent components required in each of their radio frequency (RF) chains. These components typically include transmission lines, amplifiers, filters, analog-to-digital converters, weight circuitry, and other components. Each element requires a dedicated path with a set of components. Similarly, the microwave beamforming (MBF) depicted inFIG.1B, local beamforming (LBF) depicted inFIG.1C, and optical beamforming (OBF) depicted inFIG.1Erequire additional components for each RF path/chain as well. The single input/output of ABF is simple and inexpensive, but not too capable. The multiple input/output paths of parallel processing is more capable, but complex and expensive. There is a need for an improved method, a compromise between the two, a hybrid RF beamforming.

SUMMARY

Disclosed herein is a method for hybrid RF beamforming comprising the following steps. The first step entails providing an antenna structure which comprises: a driven element, a plurality of parasitic elements, a first plurality of RF switches, a feed system, a second plurality of RF switches, and a controller. The plurality of parasitic elements are arranged around the driven element and each of the plurality of parasitic elements is configured to couple/decouple a linearly polarized radiation pattern. The first plurality of RF switches is electrically connected to the plurality of parasitic elements. The feed system comprises four ports that are 90 degrees out of phase with each other. The four ports are connected to the driven element. The second plurality of RF switches are connected to the four ports. The controller is operatively connected to the first and second pluralities of RF switches. Another step provides for selectively attenuating an output of each of the four ports with the controller according to a stored configuration, which is stored in a memory, by changing the four ports' respective phase or attenuation. Another step provides for selectively changing a loading of each parasitic element by activating each parasitic element's corresponding RF switch with the controller according to the stored configuration so as to produce a desired null/beamforming of a main RF beam.

An embodiment of the hybrid beamforming method is also disclosed herein as comprising the following steps. The first step entails providing an antenna structure that comprises a driven element, a plurality of parasitic elements, first and second pluralities of RF switches, four ports, and a controller. The plurality of parasitic elements are arranged around the driven element, and each of the plurality of parasitic elements is configured to couple/decouple a linearly polarized radiation pattern. The first plurality of RF switches electrically are connected to the plurality of parasitic elements. The four ports, which are 90 degrees out of phase with each other, are configured to feed the driven element. The second plurality of RF switches are connected to the four ports. The controller is operatively connected to the first plurality of RF switches and to the second plurality of RF switches. Another step provides for using the controller to selectively disconnect an one, two or up to three outputs of a given feed port according to a stored configuration, which is stored in a memory, by switching a state of the given feed port's corresponding RF switch, thereby changing the feed ports' respective phase or attenuation. Another step provides for selectively changing a loading of each parasitic element by activating each parasitic element's corresponding RF switch with the controller according to the stored configuration so as to produce a desired null/beamforming of a main RF beam.

DETAILED DESCRIPTION OF EMBODIMENTS

The disclosed methods and antenna below may be described generally, as well as in terms of specific examples and/or specific embodiments. For instances where references are made to detailed examples and/or embodiments, it should be appreciated that any of the underlying principles described are not to be limited to a single embodiment, but may be expanded for use with any of the other methods and antenna described herein as will be understood by one of ordinary skill in the art unless otherwise stated specifically.

References in the present disclosure to “one embodiment,” “an embodiment,” or any variation thereof, means that a particular element, feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment. The appearances of the phrases “in one embodiment,” “in some embodiments,” and “in other embodiments” in various places in the present disclosure are not necessarily all referring to the same embodiment or the same set of embodiments.

Additionally, use of words such as “the,” “a,” or “an” are employed to describe elements and components of the embodiments herein; this is done merely for grammatical reasons and to conform to idiomatic English. This detailed description should be read to include one or at least one, and the singular also includes the plural unless it is clearly indicated otherwise.

FIG.2is a flowchart of a method10for hybrid RF beamforming comprising, consisting of, or consisting essentially of the following steps. The first step10aentails providing an antenna structure, such as is depicted inFIG.3, which comprises: a driven element, a plurality of parasitic elements, a first plurality of RF switches, a feed system, a second plurality of RF switches, and a controller. Another step10bprovides for selectively attenuating an output of each of the four ports with the controller according to a stored configuration, which is stored in a memory, by changing the four ports' respective phase or attenuation. Another step10cprovides for selectively changing a loading of each parasitic element by activating each parasitic element's corresponding RF switch with the controller according to the stored configuration so as to produce a desired null/beamforming pattern.

FIGS.3and4are respectively perspective-view and bottom-view illustrations of an embodiment of an antenna structure12, which comprises, consists of, or consists essentially of a driven element14, a plurality of parasitic elements16, a first plurality of RF switches18, a feed system20, a second plurality of RF switches22, and a controller24. The plurality of parasitic elements16are arranged around the driven element14and each of the plurality of parasitic elements16is configured to couple/decouple a linearly polarized radiation pattern. The first plurality of RF switches18is electrically connected to the plurality of parasitic elements16. The feed system20comprises four ports26that are 90 degrees out of phase with each other. The four ports26are connected to the driven element14. The second plurality of RF switches22are connected to the four ports26. The controller24is operatively connected to the first and second pluralities of RF switches16and22respectively.

One embodiment of the antenna structure12may comprise multiple driven elements14, such as concentric, circular patch antennas. Each driven element14may have its own feed port26, or a driven element14may have multiple feed ports26, such as is shown inFIGS.3and4. The parasitic elements16may be arrayed around, or in between the feed ports26or driven element(s)14. All of the driven element ports26have means for attenuating their outputs by changing their phase or attenuation. InFIG.4, each feed port26is shown as connected to a phase shifter28. Additionally, all of the parasitic elements16have means (e.g., the RF switches18) for changing their loading and becoming partially, or fully absorbing or reflecting of RF energy.

The radiation pattern of the antenna structure12may be altered due to the loading effect of the driven element14. This is because the phase and attenuation of two adjacent feed ports26can be changed, such that they neutralize/enhance each other. The loading of the parasitic elements16is also able to change the radiation pattern by itself. This is because the parasitic elements16can absorb or reflect the surviving vertical electric field, not annihilated by the ground plane of driven element14. The combined effect of both enhances the radiation performance of the antenna structure12, i.e. enhances the null or beamforming, and aids in the steering, increasing the granularity of the steering. The specific configuration of RF switches18and22that produce the desired null/beamforming and the steering is known beforehand and can be stored in a memory29.

The feed ports26and the parasitic elements16may be activated by the first plurality of RF switches18and loading resistor (R), inductor (L), capacitor (C) circuitry, which can be in lumped form or distributed through transmission lines. Transmission lines or phase shifters may be used to shift the phase of the driven element(s)14. The number of available configuration of null/beamforming is large. If the number of driven elements14is N and the number of parasitic elements16is P, the number of different radiation pattern configurations is N*2{circumflex over ( )}P. The number of parasitic elements16that can be aggregated is arbitrary; however their number must be such that the input impedance of the antenna structure12is not critically affected. The parasitic elements16can be of any desired size/shape. Suitable examples of the parasitic elements16include, but are not limited to, linearly polarized dipoles or monopoles, which tend to be the most effective capturing the linearly polarized electric fields of the antenna structure12. Other shapes may be more effective in the near-field, depending on the specific vertical or horizontal component of the electric field that's most desired to neutralize. The number of parasitic elements16depends on how close they are located to a center of the antenna structure12, and their effect on the input impedance of the antenna structure12.

In the embodiment of the antenna structure12shown inFIG.3andFIG.4, the driven element14surrounds a central pad30and an array of monopole parasitic elements16surrounds the driven element14. The first and second pluralities of RF switches18and22respectively enable lumped or distributed loading of the parasitic elements16. As shown, each feed port26of the feed system20is connected to a corresponding RF switch in the second plurality of RF switches22. The controller24is configured to change the loading of the feed system20via the corresponding RF switches22. The feed ports26can be attenuated in their outputs by the second plurality of RF switches22individually changing the phase or attenuation as well as loading of the individual feed ports26of the feed system20. In this way, the loading effects on the feed ports26in the feed system20can change the radiation pattern of the antenna structure12by changing the loading on the driven element14.

FIG.5is a top, perspective view illustration of an embodiment of a portion of the antenna structure12. In this embodiment, the antenna structure12includes a dielectric member32with a plurality of parasitic member holes34formed there-through. The thickness T of the dielectric member32is chosen according to the desired bandwidth and gain of the antenna structure12. A driven element14is placed on top of the dielectric member32and electrically connected to a ground plane36, upon which the dielectric member32is disposed. In this embodiment, the driven element14is a circular patch antenna that is concentrically arranged with the dielectric member32and the ground plane36; and the parasitic member holes34are evenly and circularly arranged around the driven element14.

FIG.6is a perspective view illustration of the feed system20. In this embodiment, the feed system20comprises four feed ports26a,26b,26c, and26d. The parasitic elements16are arranged to coincide with the number and arrangement of parasitic member holes34. In this embodiment, the parasitic elements16extend orthogonally away from the ground plane36and driven element14. The first plurality of RF switches18connect the parasitic elements16to the ground plane36. The controller24can selectively open or close the RF switched18to selectively ground individual parasitic elements16. In this embodiment, each parasitic element16corresponds to one of the plurality of RF switches18. An RF combiner may be used to combine the four feed ports26into a single port.

FIG.7is a perspective-view illustration of an embodiment of the antenna structure12having multiple driven elements14. Each parasitic element16is received in a corresponding parasitic member hole34formed through the dielectric member32. The dielectric member32is in contact with the ground plane36. The parasitic elements16are arranged concentrically around the central pad30at a separation distance D. The separation distance D is less than λ/4, where λ is the effective design wavelength for the antenna structure12. Because of this separation distance D, no reactive loading is required for this embodiment of the antenna structure12, and so no capacitors and inductors are required for the RF switches18for the parasitic elements16. The controller24is configured to selectively open and close the RF switches18in order to form radiation pattern nulls in a desired direction. Combinations of open and closed RF switches18can generate nulls in particular/desired directions.

FIG.8is an illustration of a radiation pattern that may be generated by the antenna structure12as a result of practicing steps of an embodiment of the hybrid beamforming method10wherein only some of the parasitic elements16are activated. In other words,FIG.8describes the radiation pattern of the antenna12under a specific parasitic loading configuration. As shown inFIG.8, an inclined null40is formed facing the reader while a beam42is formed pointing into the upper left of the page.

FIG.9shows another radiation pattern generated by the same antenna structure12as used to generate the pattern shown inFIG.8but with a given feed port26phase-shifted by 90 degrees. The null40changes shape and it is deeper for a more controlled shape of the radiation pattern. Many other configurations (N*2{circumflex over ( )}P) can be produced, with a single or with multiple nulls, according to the hybrid beamforming method10as desired.

The antenna structure12may be controlled by the controller24, which may be a radio or an intermediate control mechanism that activates the RF switches18and22for the parasitic elements16and the feed ports20respectively. This controller24may use a combination of software and algorithms to control the RF switches18and22to produce the desired null/beamforming according to a predetermined setting stored in the memory29. Because the antenna structure12can be used with all kinds of processing, the electronics supporting the operation of the antenna structure12can be a combination of known antenna-supporting electronics.

Antenna structure12and method10allow for radiation pattern beamforming or null-forming of otherwise non-steerable, single beam antennas in specific directions. Sharp nulls, such as depicted inFIGS.8and9, can be created that effectively make the antenna structure12“deaf” in a chosen noisy direction, thus avoiding interference from unintended users, co-sited radios or other sources of interference. The hybrid architecture of antenna structure10allows for effective parallel processing of multiple signals from different driven elements/ports, while the use of parasitic elements can be employed to adapt, or further refine an already adapted radiation pattern. The antenna structure12may be used in conjunction with a large variety of control algorithms. In addition to being useful for single beamforming processes, the antenna structure12enables hybrid beamforming solutions. For example, standard beamforming algorithms, such as DBF, MBF, LBF, or OBF processing, may be employed in conjunction with the ABF algorithm all on the same embodiment of the antenna structure12. For instance, direction of arrival (DOA) algorithms, widely used in DBF and abundant in the literature, can be used to quickly ascertain the direction in which the antenna structure12should place a beam or a null and the parasitic elements16can be used to further refine the width and the elevation of the null using OBF algorithms.

From the above description of the method10and the antenna structure12, it is manifest that various techniques may be used for implementing the concepts of method10and the antenna structure12without departing from the scope of the claims. The described embodiments are to be considered in all respects as illustrative and not restrictive. The method/apparatus disclosed herein may be practiced in the absence of any element that is not specifically claimed and/or disclosed herein. It should also be understood that method10and the antenna structure12is not limited to the particular embodiments described herein, but is capable of many embodiments without departing from the scope of the claims.