Broadside Modes Research Articles

Dual‐band pattern diversity liquid antenna with passive beam‐steering of the broadside modes

AbstractA dual‐band liquid cylindrical dielectric resonator antenna with pattern diversity at two different frequency bands is proposed using the lower order and higher order modes of the HEM and TM modes namely HEM11δ, HEM12δ+1, HEM31δ+1, HEM13δ, TM01δ, and TM02δ. The proposed antenna is designed to cover the GPS L2 band and the lower Wi‐Fi band at 1.227 and 2.4 GHz frequencies, respectively. The HEM modes which constitute the primary radiating modes achieved around 20.84% and 19.35% impedance bandwidth at lower and higher bands, respectively. In the later stage, beam‐steering is performed, whereby the realised broadside HEM modes at both lower and higher bands were passively steered with simple physical re‐orientation of the antenna structure. For this, the liquid's natural fluidic property of adhering to gravity is taken as an advantage which makes the proposed antenna adaptively steer its radiation pattern always towards the sky, irrespective of the tilt angle of the antenna. This concept of passively steering two modes at two different frequency bands without the use of any mechanical, electrical, or other associated components is presented for the first time.

Low-Profile Millimeter-Wave Metasurface-Based Antenna with Enhanced Bandwidth.

A millimeter-wave broadband metasurface-based antenna with a low profile is proposed. In order to guide the mode excitation, the characteristic mode analysis (CMA) is used for the design and optimization of the proposed antenna. Four sets of coplanar patches with different dimensions on a thin printed circuit board are used to generate four adjacent broadside modes, which are directly fed by a coaxial probe. Then, to expand low-frequency bandwidth, a new resonant mode is introduced by etching slots on the parasite patch. Meanwhile, the extra mode introduced does not significantly change the radiation performance of the original modes. Moreover, dual slots are etched on the mid patch fed by the coaxial probe, which moves the orthogonal modes of the chosen modes out of the operating band to reduce cross-polarization levels. The proposed antenna realized 25.02 % (30-38.58 GHz) impedance bandwidth with dimensions of 1.423×1.423×0.029λ0 3 (λ0 is the wavelength at 34 GHz in free space), and the realized gain in the band is 8.35-11.3 dB.

Dual-Band Dual-Sense High-Gain Circularly Polarized Metasurface Antenna Using Characteristic Mode Analysis

A novel dual-band dual-sense (DBDS) circularly polarized (CP) metasurface (MTS) antenna with high-gain performance is designed. A 2×3 square patch array, as the basic MTS, is investigated at first. We observe that besides the two fundamental modes with desired broadside patterns, the basic MTS also possesses two higher-order modes with high-level sidelobes. The sidelobes are yielded by the reverse currents on the middle patches of the MTS, which can be canceled by modifying the middle patches into poor radiators. Then, two coupled-fed slots are employed to excite two fundamental modes and two higher-order modes of the modified MTS. Moreover, the fields of the four orthogonal broadside modes are adjusted to meet the magnitude and phase requirements of the CP wave. All the mentioned processes are under the guidance of the characteristic mode analysis. Finally, the proposed MTS antenna is fabricated and measured. The measured results agree well with the simulations, showing 3-dB axial ratio (AR) bandwidths of 4.37-4.45 and 6.03-6.24 GHz with CP waves in different handedness. The measured peak gains in the lower and higher bands are 10.22 and 10.72 dBic, respectively.

A Low-Profile Wideband Dual-Resonance Tri-Port MIMO Antenna

A low-profile wideband tri-polarized multi-input multi-output (MIMO) antenna is proposed in this communication. Based on characteristic mode analysis (CMA) of a circular patch, four slots are etched symmetrically on the patch to transform the high-order monopole-like modes into broadside modes with lower resonant frequencies. Four sets of shorting pins are also applied to simultaneously adjust the resonant frequencies of the monopole-like modes and broadside fundamental modes of the patch. The effects of the slots and the shorting pins on these modes are analyzed in detail. Three dual-resonance ports with high isolation are achieved by exciting three pairs of orthogonal modes of the patch. The proposed antenna is wideband with respect to its profile (bandwidth/height = 216), as facilitated by the dual-resonance property of each port. Experimental results show that the proposed antenna features high port isolation (>35 dB) and high gain (>5.58 dB). The proposed low-profile wideband tri-port antenna can be applied in highly integrated MIMO systems.

Investigation on Rotated Rectangular Slots to Improve the Circular Polarization in Cylindrical Dielectric Resonator Antenna

To achieve wideband circular polarization (CP) characteristics, a new structure with a single feeding technique has been proposed. In the proposed CP structure, to excite the cylindrical dielectric resonator (CDR) four asymmetrical rectangular slots are etched on the ground plane, each rectangular slot is rotated by an angle of ( θ = 30 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> ) with respect to its adjacent slots. The electric fields at each slot are separated by 30° in space with respect to its adjacent slot to create 90° angular separations between the E-field components. Two orthogonal broadside modes ( HE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11δ</sub> ) are excited inside the cylindrical dielectric resonator antenna (CDRA) independently to obtained CP characteristics. To compare the simulated outcomes with the experimental results, fabrication of the proposed antenna prototype has been done. The measured percentage of bandwidth achieved by the proposed radiator for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | and CP is 26.73% and 23.59%, respectively, and the whole usable axial ratio (AR) frequency bands overlap the impedance passband of the presented CP structure. The proposed radiator has achieved the maximum gain and radiation efficiency of 3.4 dB and 95% over the operating frequency range of the designed antenna, respectively. The proposed CP DRA has been configured for the WLAN band application.

A Tripolarized Antenna With Ultrawide Operational Bandwidth

In multiscattering environment, the channel capacity can be enhanced by employing dual-polarized antennas, and more significantly, using tripolarized antennas. Aiming at providing a wide coverage of both existing wireless communication systems and the new 5G sub-6 GHz band, this article presents a compact ultrawideband tripolarized antenna. The proposed design consists of a monopole-equivalent structure for vertically linearly polarized (LP) omnidirectional radiation and two orthogonal stepped dipoles for ±45° LP broadside radiation. Several important design features are proposed and implemented. The dipoles act as parasitic elements for the monopole structure, which broadens the monopole bandwidth and reduces the mutual coupling. Furthermore, the port isolation is improved by inserting two metallic posts between the crossed dipoles and the ground plane. The measured results indicate that the fabricated prototype achieves an overlapped bandwidth of 84.73% (1.68–4.15 GHz) for <−10 dB reflection coefficient and coupling value of <−30 dB among all ports. Tripolarized radiation is verified with pattern measurement, showing peak realized gains of 8.4 and 9.4 dBi in monopole and two broadside modes, respectively.

Microtrip‐line‐slot feed dual‐band dual‐mode element and array antenna based on mushroom structure

One patch antenna with dual-band dual-mode (DMDB) characteristic based on mushroom structure is designed and analysed in this study. The antenna operates at two modes: the bidirectional mode with endfire radiation patterns and the directional mode with broadside radiation patterns. The equivalent circuit, dispersion diagrams, field distributions, reflection coefficients and radiation patterns are given for confirming the working principle. Compared with the former DMDB antennas, array antenna could be designed to realise gain enhancement for both the two modes. Both element and 1 × 2 array antenna prototypes were fabricated for verification. The measured results show that the two modes resonant at about 9.8 and 11.95 GHz, respectively. Comparing with the element, gain enhancement of about 2.8 and 2.1 dB are realised by the array for the endfire and broadside modes, respectively. With pattern diversity and array realisation, this antenna type owns potential application value in wireless communication systems.

A Low-Profile Wideband Tripolarized Antenna

As a combination of three orthogonal dipoles, the tripolarized antenna has been demonstrated to significantly improve signal quality in scattering environment. In this communication, we propose a low-profile tripolarized antenna with wideband characteristics. The tristate includes 0° and 90° linear polarizations (LP) with the main beam at broadside and a vertically LP with omnidirectional pattern in the azimuth plane. The design consists of a monopolar patch and two orthogonal dipoles. The wideband performance for the monopolar patch is obtained from two nearly overlapped radiating modes controlled by an array of shorting wires. For the two orthogonal dipoles, the antenna profile is reduced with the effect of parasitic patches. One of the key design features is to utilize the shorting wire in the monopolar patch to feed the dipoles, allowing a simple design and avoiding any feeding network. The concept is experimentally verified with a prototype exhibiting an overlapped bandwidth of 14% with a low profile of 0.09λ, where λ is the free-space wavelength at the lowest operating frequency. The measured peak gain in two broadside modes and in monopolar mode are 10 and 7.5 dBi, respectively. Measured isolation between any port is better than 31 dB in the whole frequency range.

Design of a Low-Profile Tripolarized Antenna With Wide Bandwidth

In this paper, a low-profile tripolarized antenna with the wideband operation is presented. It includes a monopolar patch element for vertically linear polarization (LP) omnidirectional radiation in the horizontal plane and two orthogonal dipoles for ${x}$ - and ${y}$ -direction LP broadside radiations. In order to achieve the wideband, nevertheless keeping the low-profile, the monopolar patch antenna is coupled with an annular ring, while the two orthogonal dipoles are incorporated with a metasurface. Optimized design with a profile of $0.09\lambda _{\min}$ ( $\lambda _{\min}$ is the free space wavelength referring to the lowest operational frequency) has been fabricated and measured. The measurements result in an overlapped bandwidth of 24.45% (2.19–2.80 GHz) for reflection coefficient < −10 dB and coupling coefficients of < −30 dB among the three ports. In addition, the antenna yields measured peak gains of 8.4 and 9.5 dBi in monopolar mode and two broadside modes, respectively.

Wideband Multimode Monostatic Spiral Antenna STAR Subsystem

A wideband, multimode, and monostatic simultaneous transmit and receive (STAR) antenna subsystem is proposed. The configuration is composed of a single four-arm spiral and two analog circuit layers designed to maximize isolation between the transmitting (TX) and receiving (RX) channels. The first layer consists of two Butler matrix beamformer networks (BFNs); one for each TX and RX. The second layer integrates four, ideally phase-matched, circulators between the spiral arms and the BFNs. Theoretically, this configuration achieves infinite isolation irrespective of circulator’s quality. However, the BFN imbalances and the dissimilarities between the four circulators degrade the overall isolation. The operational principles are discussed under the ideal conditions and in the presence of circuit imperfections. For a four-arm spiral, the utilized BFN provides orthogonal modes 1, −1, 2, and 3, allowing STAR capability with multimode and diverse radiation patterns. The subsystem isolation and far-field performances are characterized experimentally and computationally for different modes of operation. A simple approach to achieve a dual-polarized STAR operation over narrower bandwidth with the proposed subsystem is also discussed. The multimode subsystem is demonstrated over 4:1 bandwidth with high isolation, VSWR < 2, consistent patterns, axial ratio < 3 dB over a wide field of view for the broadside modes (1, −1) and < 4.2 dB for other conical modes (2, 3).

Cavity model analysis of 30°–60°–90° triangular microstrip antenna

Modal analysis of probe fed 30°–60°–90° triangular microstrip antenna (TMA) is presented using cavity model for TMz mode. Probe excitation is modeled here in three simple ways. A comparative study among these three types of feed modeling is given in a systematic way, hitherto unreported. Input impedance, quality factor, radiation patterns, efficiency, gain are discussed for first five modes. Closed form expressions for calculating the far-field radiation patterns are given here for the first time. New broadside modes are identified and excited successfully, hitherto unreported. Theoretical results are in good agreement with measured data and/or data obtained using 3D EM simulator. It is found that all first five modes show a peak in broadside direction. The results should be useful for practical design of 30°–60°–90° TMA.

Closed Form Expressions to Find Radiation Patterns of Rectangular Dielectric Resonator Antennas for Various Modes

A theoretical investigation on radiation patterns of rectangular dielectric resonator antenna (RDRA) is presented. A simple model using magnetic walls (perfect and/or imperfect) and equivalence principle are utilized to predict the radiation patterns for TEmnp <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sup> modes. Approximate solution for the eigenfunction is derived. Closed form expressions of radiation patterns are given. New broadside modes are also identified, hitherto unreported. Radiation Q-factor, gain and bandwidth are also described. Results are compared with measured data or data obtained using 3D EM simulator.

A 4-Port Diversity Antenna With High Isolation for Mobile Communications

A novel wideband four-port diversity antenna that is capable of exciting four different radiation patterns is presented. The antenna consists of four magnetoelectric dipoles arranged in a ring configuration above a ground plane and a vertical electric monopole at the center of the ground plane. A matching network is used to combine the signals from the four magnetoelectric dipoles to produce two orthogonal broadside modes and one conical mode with horizontal polarization. The electric monopole is used to generate a conical beam with vertical polarization in electric feed. The performance of the antenna is studied computationally. A prototype operated at around 2.4 GHz was constructed and tested. Experimentally, the antenna exhibits about 22.2% overlapped bandwidth of the four ports. The two orthogonal broadside modes have about 11 dBi average gain. Whereas for the two orthogonal conical modes, an average gain of 6 dBi is achieved. The measured radiation patterns of the four degenerate modes are stable within the operating band. The measured isolations between different ports are generally less than -26 dB within the overlapped bandwidth. The measured radiating efficiencies of the four modes are all over 80% within the operating band.

Design of a Wide-Band L-Probe Patch Antenna for Pattern Reconfiguration or Diversity Applications

By supporting an L-probe coupled circular patch antenna with four metallic posts at appropriate locations, it is demonstrated that the conical and the broadside modes which are excited separately by two different sets of L-shaped probes, can be operated at the same frequency range. For a tested antenna operated at 1.85 GHz, the bandwidth (SWR<2) achieved is 24%, and the isolation between the two input ports is 28 dB. The gains of the conical and broadside modes are 4 and 8.5 dBi, respectively. With suitable switching feed networks, the antenna can be reconfigurable in radiation pattern. The antenna can also be used as a pattern diversity antenna for modern mobile communications.

Comparison of the characteristics of three broadside modes of the rectangular patch antenna

A detailed comparison of three broadside modes (TM10, TM01, TM03) of the rectangular microstrip patch antenna with regard to directivity, gain and band width is presented. Their dependences on the aspect ratio are delineated. Results are also given showing the variation of the input resistances at resonance as a function of frequency.

Laboratory and field studies of the application of electromagnetic prospecting for groundwater on Marajó Island, Brazil

On Marajó Island, Pará, Brazil, many cattle die due to lack of potable water, since a majority of the shallow groundwater is brackish. Two types of fresh‐water aquifers were delineated using resistivity methods: (1) a deep aquifer at about 100 m depth and (2) shallow buried‐stream channels filled with sand and gravel (ρ = 40 Ω ⋅ m) and embedded in clay and sand beds with brackish water (ρ = 0.8 Ω ⋅ m — 5 Ω ⋅ m). For the demarcation of the shallow buried‐stream channel aquifers, inductive electromagnetic moving source‐receiver methods were tested to replace the cumbersome galvanic resistivity methods. In order to verify the applicability of EM survey techniques for groundwater exploration in hydrogeologic conditions typical of Marajó Island, analog model studies were carried out. The groundwater‐bearing channels buried in the clays or in the sediments with brackish water represent geoelectrically a less conducting body in a more conducting environment. The buried‐channel “Guajará Mirim” on Marajó Island was chosen for test studies. A 500 times reduced model of this channel was constructed using two aluminium sheets of varying thicknesses to simulate host sediments and the sediments in the buried channel. EM profiles were measured in the laboratory across the channel model using horizontal‐coplanar vertical‐coplanar, and vertical‐coaxial coil systems in the broadside and inline modes of operation. Excellent EM model responses were obtained with all six coil configurations. Finally, EM profiles in the field were carried out using horizontal‐coplanar, vertical‐coplanar, and vertical‐coaxial coils in an inline mode of operation. Field and laboratory results are in very good qualitative agreement.