Egyptian Axe Dipole Research Articles

Low-Profile, Electrically Small, Ultrawideband Antenna Enabled With an Inductive Grid Array Metasurface

A low-profile, electrically small, ultrawideband (UWB) antenna enabled with a grid array metasurface is presented. The design incorporates a driven dipole, an electric near-field resonant parasitic (NFRP) element, and a grid array structure which operates as an inductive metasurface. The NFRP element is an Egyptian axe dipole (EAD) that is excited by the driven dipole. This combination itself is an electrically small NFRP dipole antenna. In contrast to previous versions, its operation in both its first and third resonant modes is established. The presence of the grid, which consists of identical interconnected rectangular loops, then provides a new dipole mode and facilitates the reduction of the frequency ratio of the NFRP dipole’s modes. The resulting overlap of these three resonant modes yields the UWB operation. The electrically small ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ka</i> = 0.92), low-profile ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.003\lambda _{0}$ </tex-math></inline-formula> ) antenna exhibits uniform radiation patterns and stable and high radiation efficiency (RE) performance characteristics. The antenna was optimized, fabricated, and tested. The measured results, in good agreement with their simulated values, demonstrate that the antenna yields an ultrawide, 67.7%, −10 dB impedance bandwidth with stable realized gain (RG) values, ~1.6 dBi, and high RE values, RE >77%, over its entire operational bandwidth.

Electrically small, low‐profile, full‐duplex Huygens dipole filtenna

AbstractAn electrically small, full‐duplex Huygens dipole filtenna (HDF) is realized as a dense array of two HDF elements consisting of Egyptian axe dipole and capacitively‐loaded loop near‐field resonant parasitic (NFRP) elements. The dual‐band HDF elements operate at two very nearby frequency bands and are physically separated by only 0.12 λLB. Benefitting from the HDF element's good out‐of‐band rejection performance characteristics, high isolation levels between the lower‐band (LB) and higher‐band (HB) ports are obtained without any decoupling structure. The measured results, in good agreement with their simulated values, demonstrate that the entire system is electrically small (ka = 0.975) and low‐profile (0.041 λLB). The measured isolation levels at its LB (HB) port is, respectively, over 33.9 (29.2) dB. When the LB (HB) port is excited, its fractional bandwidth, broadside realized gain, front‐to‐back ratio, and overall efficiency values are, respectively, 0.86% (0.77%), 2.1 (2.31) dBi, 8.1 (9.6 ) dB, and 62.1% (62.8%).

Electrically Small, Planar, Frequency-Agile, Beam-Switchable Huygens Dipole Antenna

An electrically small, planar, frequency-agile, beam-switchable Huygens dipole antenna is investigated in this article. The near-field resonant parasitic (NFRP) design incorporates an Egyptian axe dipole (EAD) and a capacitively loaded loop (CLL) that function as the electric and magnetic NFRP elements, respectively. A varactor diode is integrated into each of these NFRP elements to facilitate simultaneous tuning of its operating frequency and switching its main beam direction. By changing the capacitance values of these two varactor diodes, the antenna realizes two independent, antipodal, unidirectional endfire radiating states with similar realized gain (RG) and front-to-back ratio (FTBR) values within virtually the same frequency-agile ranges. The experimental results demonstrate that the developed antenna exhibits a 5% frequency-agile fractional impedance bandwidth in both of its two oppositely directed endfire states. The antenna is electrically small at the highest frequency of this bandwidth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${ka}_{high} &lt; 0.86$ </tex-math></inline-formula> ) and has measured relatively high radiation efficiency (RE >67.7%), peak RG (2.1–3.19 dBi), and FTBR (5.61–13.4 dB) values, together with stable and uniform radiation patterns, over this frequency-agile range.

Polarization-Reconfigurable Yagi-Configured Electrically Small Antenna

An electrically small, high-directivity, Yagi-configured, near-field resonant parasitic (NFRP) antenna with four reconfigurable polarization states is presented. The antenna is composed of two NFRP elements and a customized, electrically controlled, reconfigurable driven element. The elements are stacked vertically in a Yagi configuration. The upper NFRP element acts as the director, and the lower one acts as the reflector. Both elements have a cross-shaped Egyptian axe dipole form. By integrating four p-i-n (PIN) diodes into its coax-fed asymmetric driven element, four polarization states, i.e., two orthogonal linear polarization (LP) and two circular polarization (LHCP and RHCP), are enabled which are controlled with the ON/OFF-states of the PIN diodes. The measured and simulated results of this electrically small (ka = 0.7) sized polarization-reconfigurable system are in good agreement. This simple, Yagi-configured antenna exhibits stable radiation performance in all four of its polarization states. The measured results demonstrate that, in its x (y)-LP state, the peak realized gain, front-to-back ratio, and radiation efficiency values are, respectively, ~3.08 (3.2) dBi, ~11.0 (11.05) dB, and ~77% (73%), and that, in its LHCP (RHCP) state, they are, respectively, ~3.0 (3.1) dBi, ~12.1 (11.18) dB, and ~72% (70%).

Electrically Small, Single-Substrate Huygens Dipole Rectenna for Ultracompact Wireless Power Transfer Applications

An electrically small, single-substrate Huygens dipole rectenna with exceptional physical and radiation performance characteristics is reported. A highly efficient rectifier circuit is seamlessly integrated with an ultrathin, electrically small, Huygens dipole antenna (HDA) on a single piece of Rogers 5880 substrate. It consists of two metamaterial-inspired near-field resonant parasitic (NFRP) elements, an Egyptian axe dipole (EAD) and a capacitively loaded loop (CLL) that are etched on the top and bottom metallization layers of the substrate, respectively. A printed receiving dipole is amalgamated tightly with the rectifier on the CLL layer. This ultracompact rectenna system has a large electromagnetic wave capture capability and achieves nearly complete conversion of the incident energy into dc power. The HDA prototype has a realized gain of 4.6 dBi and a half power beamwidth (HPBW) greater than 130°. The entire rectenna is electrically small with ka =0.98, is low cost and easy to fabricate, and has a measured 88% ac-to-dc conversion efficiency. The developed rectenna system is the ideal candidate for ultracompact far-field wireless power transfer (WPT) applications.

Wirelessly Powered Light and Temperature Sensors Facilitated by Electrically Small Omnidirectional and Huygens Dipole Antennas.

Wirelessly powered, very compact sensors are highly attractive for many emerging Internet-of-things (IoT) applications; they eliminate the need for on-board short-life and bulky batteries. In this study, two electrically small rectenna-based wirelessly powered light and temperature sensors were developed that operate at 915 MHz in the 902–928-MHz industrial, scientific, and medical (ISM) bands. First, a metamaterial-inspired near-field resonant parasitic (NFRP) Egyptian axe dipole (EAD) antenna was seamlessly integrated with a highly efficient sensor-augmented rectifier without any matching network. It was electrically small and very thin, and its omnidirectional property was ideal for capturing incident AC wireless power from any azimuthal direction and converting it into DC power. Both a photocell as the light sensor and a thermistor as the temperature sensor were demonstrated. The resistive properties of the photocell and thermistor changed the rectifier’s output voltage level; an acoustic alarm was activated once a threshold value was attained. Second, an electrically small, low-profile NFRP Huygens antenna was similarly integrated with the same light- and temperature-sensor-augmented rectifiers. Their unidirectional nature was very suitable for surface-mounted wireless power transfer (WPT) applications (i.e., on-body and on-wall sensors). Measurements of the prototypes of both the light- and temperature-sensor-augmented omni- and unidirectional rectenna systems confirmed their predicted performance characteristics.

Electrically Small Huygens Antenna-Based Fully-Integrated Wireless Power Transfer and Communication System

This paper introduces the first reported electrically small Huygens dual-functional wireless power transfer (WPT) and communication system operating in the 915-MHz ISM band. It is realized by the seamless combination of a Huygens linearly polarized (HLP) antenna and a highly efficient HLP rectenna. The configuration consists of two orthogonally oriented HLP subsystems. Each one intrinsically combines two pairs of metamaterial-inspired near-field resonant parasitic elements, i.e., an Egyptian axe dipole (EAD) and a capacitively loaded loop (CLL). Through the development of a very tightly coupled feed subsystem that includes the WPT mode's rectifier circuit and the communications mode's feedline while preserving their isolation, the independent operation of both functions is facilitated in an electrically small volume (ka <; 0.77). The measured results of its fabricated prototype agree well with their simulated values. The communications mode antenna resonates at 910 MHz and radiates a cardioid-shaped Huygens pattern with the peak gain of 2.7 dBi. The Huygens-based WPT rectenna achieves an 87.2% peak ac-to-dc conversion efficiency at 907 MHz. The dual-functional system is an ideal candidate for many emerging Internetof-Things (IoT) wireless applications that require simultaneous wireless information and power transfer (SWIPT) and wirelessly powered communications (WPC).

Pattern-Reconfigurable, Flexible, Wideband, Directive, Electrically Small Near-Field Resonant Parasitic Antenna

A pattern-reconfigurable, flexible, wideband, directive, electrically small near-field resonant parasitic (NFRP) antenna is presented. The antenna consists of a pair of Egyptian axe dipole NFRP elements, together with a pair of shaped metallic strips that act as the driven element and are fed by a coaxial cable. These NFRP and driven elements are designed to achieve compactness. Two pairs of p-i-n diodes are integrated into the driven element to enable the pattern reconfigurability. The antenna has two switchable directive endfire states, each pointed in direct opposition to the other. Examples of the evolution of the antenna are used to illustrate its operating principles. A prototype of the optimized design operating in a frequency range centered at 1.8 GHz was fabricated and measured. The simulation and experimental results are in good agreement. The antenna exhibits a wide ~13.1% impedance bandwidth and a ~4.42 dBi peak realized gain in both pattern-reconfigurable states while maintaining its electrically small size: $\textit {ka} \sim 0.94$ . The flexibility of this antenna is demonstrated under different bending conditions by mounting it on cylinders with several different radii, and the results confirm that its performance characteristics are maintained under all of them.

Electrically Small, Low-Profile, Huygens Circularly Polarized Antenna

The design, simulation studies, and experimental verification of an electrically small, low-profile, broadside-radiating Huygens circularly polarized (HCP) antenna are reported. To realize its unique circular polarization cardioid-shaped radiation characteristics in a compact structure, two pairs of the metamaterial-inspired near-field resonant parasitic elements, the Egyptian axe dipole (EAD) and the capacitively loaded loop (CLL), are integrated into a crossed-dipole configuration. The EAD (CLL) elements act as the orthogonal electric dipole (magnetic dipole) radiators. Balanced broadside-radiated electric and magnetic field amplitudes with the requisite 90° phase difference between them are realized by exciting these two pairs of electric and magnetic dipoles with a specially designed, unbalanced crossed-dipole structure. The electrically small (ka = 0.73) design operates at 1575 MHz. It is low profile $0.04\lambda _{\mathbf {0}}$ , and its entire volume is only $0.0018\lambda _{\mathbf {0}}^{\mathbf {3}}$ . A prototype of this optimized HCP antenna system was fabricated, assembled, and tested. The measured results are in good agreement with their simulated values. They demonstrate that the prototype HCP antenna resonates at 1584 MHz with a 0.6 dB axial ratio, and produces the predicted Huygens cardioid-shaped radiation patterns. The measured peak realized LHCP gain was 2.7 dBic, and the associated front-to-back ratio was 17.7 dB.

A Study of 28 GHz, Planar, Multilayered, Electrically Small, Broadside Radiating, Huygens Source Antennas

Two 28 GHz, planar, electrically small Huygens source antennas are presented that are broadside radiating and are based on multilayer PCB technology. The designs seamlessly integrate electric Egyptian axe dipole and magnetic capacitively loaded loop near-field resonant parasitic elements with a coax-fed dipole radiator. Both linearly polarized (LP) and circularly polarized (CP) systems are demonstrated. The simulations of the LP system indicate that it is electrically small: ka = 0.961; has peak realized gains and front-to-back ratios (FTBRs) in the range from, respectively, 3.77 to 4.54 dBi and 7.16 to 33.92 dB; and radiation efficiencies higher than 81.14% over its entire 2.14%, −10-dB fractional impedance bandwidth (FBW−10dB). A prototype was fabricated and tested; the measured and simulated results are in good agreement. The CP system exhibits similar properties: ka = 0.942; 1.41% FBW−10dB with a 0.47% 3-dB axial ratio fractional bandwidth; and peak realized gain, FTBR, and radiation efficiency values equal to 2.03 dBi, 26.72 dB, and 73.4%, respectively. To confirm their efficacy for on-body applications, the specific absorption rate values of both the LP and CP Huygens source antennas were evaluated and found to be very low.

Investigations of a Load-Bearing Composite Electrically Small Egyptian Axe Dipole Antenna

An electrically small, metamaterial-inspired Egyptian axe dipole (EAD) antenna has been investigated for use in structural composite materials. The EAD antenna consists of a differentially fed dipole element integrated with a near-field resonant parasitic EAD element. These elements have been adapted to these materials resulting in a system that is impedance matched and radiates efficiently at 307 MHz. Three cases have been identified and investigated to ascertain the performance of the manufacturing techniques and material properties used to build these electrically small antennas, as well as their performance characteristics. Uniquely, an embroidered conductive thread and a new carbon fiber based, nonwoven mat have been investigated for use as the conducting elements. Both cases are compared with a copper variant of the EAD antenna. All three prototypes were tested. Measurements confirm that both the nonwoven mat and the embroidered versions of the EAD antennas perform similarly with maximum realized gains ranging from 1.72 to 1.90 dBi.

Design and Testing of Simple, Electrically Small, Low-Profile, Huygens Source Antennas With Broadside Radiation Performance

The efficacy of a simple, electrically small, low-profile, Huygens source antenna that radiates in its broadside direction is demonstrated numerically and experimentally. First, two types of electrically small, near-field resonant parasitic (NFRP) antennas are introduced and their individual radiation performance characteristics are discussed. The electric one is based on a modified Egyptian axe dipole NFRP element; the magnetic one is based on a capacitively loaded loop NFRP element. In both cases, the driven element is a simple coax-fed dipole antenna, and there is no ground plane. By organically combining these two elements, Huygens source antennas are obtained. A forward propagating demonstrator version was fabricated and tested. The experimental results are in good agreement with their analytical and simulated values. This low profile, $\sim 0.05\lambda _{0}$ , and electrically small, $ka = 0.645$ , prototype yielded a peak realized gain of 2.03 dBi in the broadside direction with a front-to-back ratio of 16.92 dB. A backward radiating version is also obtained; its simulated current distribution behavior is compared with that of the forward version to illustrate the design principles.

Two‐element Egyptian axe dipole arrays emphasising their wideband and end‐fire radiation performance

Combinations of two metamaterial-inspired electrically small antennas are investigated numerically to achieve high directivity and enhanced bandwidth operation near 300 MHz. Two Egyptian axe dipole (EAD) antennas, one active and one passive, are arranged in an end-fire array configuration. The elements are designed to optimise the out-of-phase current distribution of the parasitic element to achieve enhanced directivity performance characteristics, including a peak gain >4.5 dB, front-to-back ratio >15 dB, and radiation efficiency >74% over a 3.73 MHz frequency range centred at 312.9 MHz when the separation distance between the elements is ~0.04 λ res and the total electrical size of the array is ka = 0.43. By simply increasing the width of both EAD parasitic elements, the array's end-fire characteristics are transformed into a configuration that has more than a six times increase of the impedance bandwidth. A frequency-agile version of the array is obtained by incorporating a varactor between the two EAD parasitic elements. The simulation studies indicate that this frequency-agile, electrically small, end-fire array provides a much wider effective impedance bandwidth with improved end-fire radiation characteristics.

Low Profile, Broadside Radiating, Electrically Small Huygens Source Antennas

It is demonstrated numerically that a metamaterial-inspired, low profile (height approximately λ/80), electrically small (ka = 0.45) Huygens source antenna can be designed to radiate at 300 MHz in its broadside direction with a high radiation efficiency and a large front-to-back ratio. Two electrically small, near-field resonant parasitic (NFRP) antennas are first designed. Both are based on a coax-fed dipole antenna. An electric dipole response is obtained by combining it with a tunable Egyptian axe dipole (EAD) NFRP element. A magnetic dipole response is obtained by spatially loading the driven dipole with tunable, extruded capacitively loaded loop (CLL) NFRP elements. The driven dipole and the EAD and CLL NFRP elements are combined together and retuned to achieve a broadside radiating Huygens source antenna. Two different designs, one with two CLL elements and one with four, are obtained, and their performance characteristics are compared.

Performance Characteristics of Planar and Three-Dimensional Versions of a Frequency-Agile Electrically Small Antenna

Two electrically small antenna designs are analyzed numerically and are then compared. The first is a frequency-agile version of the three-dimensional (3D) Egyptian-axe dipole (EAD) antenna. The second is its two-dimensional (2D) planar counterpart. The frequency-agile performance characteristics of both the two-dimensional and three-dimensional Egyptian-axe dipole designs are studied and compared. Their potential for non-Foster augmentation to achieve large instantaneous fractional bandwidths is detailed.

A High-Directivity, Wideband, Efficient, Electrically Small Antenna System

A high-directivity, wideband, efficient, near-field resonant parasitic, electrically small antenna system is presented. By introducing two different near-field resonant parasitic (NFRP) Egyptian axe dipole elements oriented in parallel in the near field of a traditional small dipole antenna, two nearby fundamental resonance modes are produced. Both are much lower in frequency than the fundamental mode of the driven dipole. The corresponding frequency bands of both resonators are optimized to be overlapping in order to create a wide operating bandwidth. The resulting antenna has linear polarization radiation characteristics broadside to the stack of planes containing the radiating elements. The currents on the NFRP elements dominate the radiation process and are designed to be out-of-phase to achieve a high directivity endfire effect perpendicular to the element stack. A prototype of the antenna is fabricated and tested to demonstrate the effectiveness of this design. The measured results show that this low-profile ( total height = 0.092 λL, where λL indicates the free-space wavelength corresponding to the lower bound of the operating frequency band) and electrically small ( ka = 0.679) antenna provides broadside realized gains in the range of 2.62 ±0.99 dB with ~ 10% fractional bandwidth. The performance characteristics of a yet smaller version ( ka = 0.494) are also explored numerically.

Compact, two‐element array with high broadside directivity

A combination of two high directivity, electrically small, slot-modified conducting disc-augmented Egyptian axe dipole (EAD) antennas is investigated to achieve interesting broadside radiation properties, including a high broadside directivity and front-to-back ratio. Their array arrangement is guided by a simple two-element dipole model. The parasitic conducting disc associated with each EAD antenna is modified only slightly from their original single-element dimensions to preserve nearly complete matching to their sources, to accommodate the coupling between the two elements and to maximise the array pattern characteristics. Parameter studies lead to a final design, whose simulation results demonstrate that the two-element array has outstanding performance characteristics, including a 9.98 dB broadside directivity, an 88.19% radiation efficiency, a 20.03 dB front-to-back-ratio, a - 22.42 dB mutual coupling level, more than a 30 dB level of polarisation purity, and good impedance matching to their respective 50 Ω sources, despite each antenna being electrically small, that is, ka <; 1, and the distance between the centre of each element being only slightly larger than a half wavelength.

Augmenting a Modified Egyptian Axe Dipole Antenna With Non-Foster Elements to Enlarge Its Directivity Bandwidth

Non-Foster elements are introduced to augment an Egyptian axe dipole (EAD) antenna-based system in order to expand its directivity bandwidth. The frequency-agile properties of the original antenna system are investigated near 300 MHz by linearly and discretely changing the values of its internal reactive element. The curve-fit reactance versus frequency curve is established. It is reproduced approximately by augmenting the antenna system with two non-Foster elements implemented internally in one of its near-field parasitic elements and with negative impedance convertor (NIC) designs. It is demonstrated that the resulting electrically small antenna system is capable of achieving excellent unidirectional radiation performance, including a broadside directivity in the range from 5.78 to 6.24 dB with more than a 20 dB front-to-back ratio (FTBR) over a 13% instantaneous fractional bandwidth. The corresponding half-power beamwidths in the E- and H-planes, respectively, are 78° and 138°; the radiation efficiency exceeds 65%.

Efficient, High Directivity, Large Front-to-Back-Ratio, Electrically Small, Near-Field-Resonant-Parasitic Antenna

Enhancements of the directivity and front-to-back ratio (FTBR) of a metamaterial-inspired electrically small, linearly polarized, coaxially-fed Egyptian axe dipole antenna are considered. They are accomplished with a particular augmentation of the original near-field-resonant-parasitic (NFRP) antenna with an additional NFRP element, a small disc conductor modified with two meanderline-shaped slots. The entire system is evaluated numerically with two independent computational electromagnetics simulators. The optimized results demonstrate an electrically small antenna (i.e., ka 20 dB, and maintains large half-power beamwidths, while having a radiation efficiency over 80% with nearly complete matching to a 50 Ω source.

High-Directivity, Electrically Small, Low-Profile Near-Field Resonant Parasitic Antennas

A combination of metastructures is used to achieve high directivity, electrically small, low-profile, linear (LP) and circularly polarized (CP) near-field resonant parasitic (NFRP) antennas. A conformal metamaterial-inspired Egyptian axe dipole antenna is introduced, and its performance characteristics are presented. The electrically small, low-profile LP and CP high-directivity systems are achieved by amalgamating this NFRP antenna with an electromagnetic band-gap (EBG) structure, which acts as an artificial magnetic conductor (AMC) ground plane. As with all of the nonconformal metamaterial-inspired antennas, the designs of the driven and parasitic elements of these low-profile antennas are tailored to achieve nearly complete matching of the entire system to a 50- source without any matching network and to yield high radiation efficiencies.