The invention relates generally to radio frequency (RF) signal communication and, more particularly, to dual-fed dual-frequency antenna configurations.
The use of wireless communications has become so widespread as to nearly have become ubiquitous. Various devices, such as cellular phones, smart phones, personal digital assistants (PDAs), tablet devices, notebook computers, Internet of Things (IoT) devices, cameras, drones, etc. (collectively referred to herein as “wireless devices”), utilize wireless communication links for communicating voice, images, data, and/or the like.
The foregoing wireless devices are often adapted for communication in multiple radio frequency (RF) bands. For example, some such wireless devices may be adapted to utilize the communication networks of multiple service providers (e.g., a cellular network of mobile network operator A and a cellular network of mobile network operator B) for establishing wireless communication links, wherein network infrastructure of the different service providers may operate in different RF bands. Additionally or alternatively, some such wireless devices may be adapted for multiple modes (e.g., a cellular network of a mobile network operator and a wireless network of an Internet service provider) of wireless communications, wherein the different communication modes may operate in different RF bands.
Often some form of dual-frequency antenna system is provided in configuring wireless devices for communication in multiple RF bands. For example, a single radiator that is resonant in the different frequency bands (e.g., a broadband antenna) may be coupled (e.g., using a single RF signal interface, port, or “feed”) to the RF front end circuitry of a wireless device for use in communication in multiple RF bands. Such antenna configurations, however, often suffer significant performance loss at either RF operating band due to compromises in the design for broadband or multiband operation. Moreover, further performance loss is often experienced due to the use of various circuit components (e.g., diplexers) used in accommodating the single feed antenna configuration. The general design of a dual-fed dual-frequency antenna is to use two horizontally or vertically arranged radiators, each operating in a single frequency band of the different frequency bands. Since different elements are used for the lower- and higher-frequency parts, large frequency ratios can be achieved easily. However, the total size and weight of such an antenna configuration can be considerable, particularly with respect to mobile wireless devices such as smartphones, PDAs, tablets, etc.
The present invention is directed to systems and methods which provide a hollow dielectric block dual-fed dual-frequency antenna configuration, such as may be utilized for wireless device communication in multiple RF bands, multi-frequency radar applications, etc. Embodiments of a hollow dielectric block dual-fed dual-frequency antenna provide operation with respect to widely separated frequencies (i.e., provide a relatively large frequency ratio), such as to operate at frequencies in both a millimeter-wave band and a microwave band (e.g., operate at frequencies separated by an order of magnitude).
A hollow dielectric block dual-fed dual-frequency antenna of embodiments of the invention may be fabricated from a single hollow dielectric block configured to integrate a dielectric resonator antenna (DRA) and a Fabry-Perot resonator antenna (FPRA). For example, a hollow dielectric block may be configured to serve as the resonator for a microwave DRA and the superstrate for a millimeter-wave FPRA simultaneously. In providing the foregoing integrated DRA and FPRA configuration, the FPRA of a hollow dielectric block dual-fed dual-frequency antenna configuration may use the sidewall of the hollow region instead of spacers (e.g., foam or plastic cylinder) to support the dielectric superstrate of the FPRA, in contrast to a conventional FPRA configuration.
In operation, the hollow dielectric block of a hollow dielectric block dual-fed dual-frequency antenna may be excited by two ports simultaneously at two different frequencies. For example, a DRA of a hollow dielectric block dual-fed dual-frequency antenna may be excited by a vertical excitation strip on its sidewall, whereas a FPRA of the hollow dielectric block dual-fed dual-frequency antenna may be excited by a waveguide below the ground plane.
The resonant frequencies of the DRA and FPRA of a hollow dielectric block dual-fed dual-frequency antenna of embodiments of the invention can be determined independently. For example, changing the value of one or more design parameters (e.g., a dielectric height, cavity height, etc.) can shift the resonant frequency of the DRA substantially without affecting the resonant frequency of the FPRA. This aspect of a hollow dielectric block dual-fed dual-frequency antenna of embodiments may be utilized in obtaining a desired (e.g., large) frequency ratio with respect to the frequencies of the dual-frequency antenna configuration.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
A hollow dielectric block dual-fed dual-frequency antenna of embodiments of the invention provides a configuration in which a dielectric resonator antenna (DRA) and a Fabry-Perot resonator antenna (FPRA) are integrated into a single antenna element. For example, as illustrated in the schematic diagrams of
As shown in
In providing a dual-fed dual-frequency antenna configuration, hollow dielectric block dual-fed dual-frequency antenna 100 of the illustrated embodiment comprises DRA port 130 and FPRA port 140 providing separate RF signal interfaces for multiple frequencies simultaneously. DRA port 130 may comprise vertical excitation strip 131 disposed upon a sidewall of hollow dielectric block 110, such as may be sized to induce hybrid electric and magnetic (HEM) mode resonation of the DRA at desired millimeter-wave frequencies. For example, the DRA may be excited in its HEM11δ mode by vertical excitation strip 131 of length LS and width WS as shown in
Although a hollow region, such as cavity 111, can widen the bandwidth of a DRA at the cost of increasing its crosspolar field of radiation pattern, cavity 111 of hollow dielectric block dual-fed dual-frequency antenna 100 of embodiments herein is configured for integrating a FPRA mode, in addition to the DRA mode, with respect to hollow dielectric block dual-fed dual-frequency antenna 100. Accordingly, various attributes of dielectric 111 and/or cavity 112 (e.g., heights, widths, diameters, dielectric constants, etc.) of hollow dielectric block 110 are configured for providing an integrated FPRA implementation in combination with the DRA implementation according to embodiments of hollow dielectric block dual-fed dual-frequency antenna 100.
In accordance with the foregoing, to enhance broadside radiation of the FPRA, the heights of cavity 112 (HC) and dielectric 111 (HS) of hollow dielectric block 110 may be given by
where n, m are integers (m is odd), and λg and λ0 are resonant wavelengths in the dielectric and air (or a second dielectric forming cavity 112 having a different dielectric constant than dielectric 111), respectively. From equations (1) and (2), it can be appreciated that increasing m and n will increase the heights of the superstrate (HS) and hollow region (HC), respectively. Because m and n do not affect the resonant frequency of FPRA, they are typically set as m=n=1 in a conventional FPRA design for convenience. However, in configurations of hollow dielectric block dual-fed dual-frequency antenna 100 of embodiments herein, m and n are set (e.g., m≠n and/or m≠1) so as to enhance the gain of the FPRA and to provide a desired resonate frequency with respect to the DRA. For example, the gain of the FPRA can be enhanced by increasing the cross-sectional area of the superstrate, and thus m and n may be set to provide the heights of cavity 112 (HC) and dielectric 111 (HS) facilitating maximized cross-sectional area of hollow dielectric block 110. Moreover, the resonate frequency of the DRA can be selected by the heights of the cavity and dielectric portions of the dielectric resonator.
In an example of the foregoing, hollow dielectric block dual-fed dual-frequency antenna 100 may be configured to operate at frequencies in both a millimeter-wave band and a microwave band, such as to provide an implementation in which the DRA is operable with respect to a microwave frequency band centered at approximately 2.4 GHz and the FPRA is operable with respect to a millimeter-wave frequency band centered at approximately 24 GHz (e.g., the hollow dielectric block dual-fed dual-frequency antenna being operable at frequencies separated by an order of magnitude). In this exemplary embodiment, the dielectric resonator (hollow dielectric block 110 in the illustrated embodiment) may be fabricated from a dielectric bar with a cross-sectional area of 50×50 mm2 and the radius of the dielectric resonator chosen as RS=24 mm. The height of cavity 112 (HC) and the height of dielectric 111 (HS) may be designed using λ0=12.50 mm at frequency f=24 GHz. Using m=n=1 gives HC=6.25 mm and HS=1.19 mm. However, with these heights the resonant frequency of the DRA is much higher than 2.4 GHz, and thus the size of the dielectric resonator (hollow dielectric block 110 in the illustrated embodiment) should be increased in order to decrease the resonant frequency to 2.4 GHz. Setting m=11 (corresponding to HS=12.99 mm), for example, provides a resonant frequency of the DRA close to 2.4 GHz. In this case, the maximum gain of the FPRA is 24.25 GHz (as determined from simulation results), which is the upper frequency of 24-GHz ISM band (24-24.25 GHz). It should be appreciated that this deviation from 24 GHz can be expected because the theory assumes an infinite lateral structure but the structure when implemented is finite. To shift the maximum-gain frequency of the FPRA closer to 24.0 GHz, the values of HC and HS may be shifted to 6.30 mm and 13.10 mm, respectively, which gives λ0=12.60 mm or f=23.80 GHz. This frequency is slightly lower than 24 GHz to compensate for the small (upward) frequency shift in the simulated result.
To demonstrate the dual-frequency operation of a hollow dielectric block dual-fed dual-frequency antenna implemented in accordance with the concepts herein, a hollow dielectric block dual-fed dual-frequency antenna configured for operation in the 2.4-GHz and 24-GHz ISM bands was designed using ANSYS HFSS and its prototype was fabricated. The dimensions of the hollow dielectric block dual-fed dual-frequency antenna of this exemplary implementation are given by LG=100 mm, HG=4 mm, RC=23 mm, RS=24 mm, HC=6.30 mm, HS=13.10 mm, εr=7, ε0=1, n=1, m=11, λ0=12.60 mm, λg=λ0/√{square root over (εr)}=4.76 mm, LS=15.5 mm, and WS=2 mm. Measurements made with respect to operation of the exemplary hollow dielectric block dual-fed dual-frequency antenna were divided into the microwave and millimeter-wave parts for analysis of the dual-frequency operation. For the microwave measurements, the S-parameters were measured with an Agilent E5071C network analyzer, whereas the radiation pattern, realized gain, and the antenna efficiency were measured by a Satimo StarLab system. For the millimeter-wave measurements, the S-parameters were measured using an E8361A network analyzer, and the radiation pattern and realized gain were measured with an NSI measurement system. Since the antenna efficiency cannot be directly measured by the NSI system, the antenna efficiency of the FPRA is calculated from the ratio between its measured realized gain and directivity.
From the forgoing it can be seen that embodiments of a hollow dielectric block dual-fed dual-frequency antenna fabricated from a single hollow dielectric block disposed upon a ground plane according to the concepts herein may provide a dual-frequency antenna having a relatively large frequency ratio with respect to the operating frequency bands. Moreover, a hollow dielectric block dual-fed dual-frequency antenna of embodiments of the invention allows for independently determining the resonant frequencies facilitating the operating frequency bands, such as by changing the value of one or more design parameters of the hollow dielectric block.
It should be appreciated that particular aspects of the exemplary embodiments described above are to aid in the understanding of the concepts herein and various differences may be provided with respect to implementations of hollow dielectric block dual-fed dual-frequency antennas. For example, although embodiments of a hollow dielectric block dual-fed dual-frequency antenna have been described herein with reference to a hollow dielectric block comprised of a dielectric and a cavity disposed therein, it should be appreciated that the concepts of the present invention are applicable to additional or alternative configurations. Accordingly, the cavity portion (e.g., cavity 112) of embodiments of a hollow dielectric block dual-fed dual-frequency antenna may comprise an area of dielectric material having a different dielectric constant than that of the dielectric portion (e.g., dielectric 111) of a hollow dielectric block (e.g., hollow dielectric block 110). As another example, although the ground plane (e.g., ground plane 120 of
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
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