Planar Antenna Elements Research Articles

Millimeter micro‐coaxial beam steering array for high‐speed satellite communications

AbstractWide‐band low‐loss passive beam steering array presents to be essential part of the RF front‐ends for high‐speed detection during deep space exploration missions. In this letter, the copper‐based additive manufacturing technology is proposed for the implementation of low‐profile (~0.1λ) antenna design. Adopting the micro‐coaxial line as the basic design unit enables wide bandwidth design. In addition, the broadband designs of Butler matrix, planar antenna element, and transmission transitions are proposed, respectively. The miniaturization of the metallic patch antenna is realized using a double slotted design, ensuring an array space of ~0.5λ, which beneficial for the low‐lobe beam steering. Experimental results show that the antenna array with an overall size of 39 × 29 × 0.5 mm presents four beams located at ±14° and ±43°, respectively. The bandwidth of return loss better than −10 dB ranges from 65 to 71 GHz. The measured result matches well with the simulated ones, which makes its potential operation for satellite applications.

A dual‐band tightly arranged multiple‐input multiple‐output antenna pair for 5G mobile terminals

AbstractThis paper presents a dual‐band multiple‐input multiple‐output (MIMO) antenna pair for 5G cell phones. The antenna pair consists of two planar concave antenna elements that are tightly arranged on a vertical substrate. By adding capacitors to form a resonant network, an additional operating mode is excited, resulting in dual‐band performance. The resonant frequency of the additional mode can be adjusted independently by changing the capacitance value. Moreover, a neutralization line is used to improve the isolation of the high band without affecting the low band. The antenna pair occupies a small area of 13.2 × 6.3 mm2 and operates at both 3.5 and 4.85 GHz bands. The isolations are better than 17 dB at the 3.5 GHz band and better than 19 dB at the 4.85 GHz band. The proposed dual‐band antenna pair might be a good choice for 5G terminals.

Ka-band flat panel circularly polarized antenna array for LEO satellite communication systems

In this paper, a high gain circularly-polarized antenna array with a flat panel structure for low Earth orbit (LEO) satellite communication systems is proposed. This new CP structure can efficiently achieve high directivity and can easily be integrated with beamforming ICs (BFIC) when designing an antenna module, resulting in a good candidate for Ka-band satellite communications. Furthermore, the proposed FPAA can easily be extended to a larger scale array from a base unit in a 2 × 2 sub-array structure. Each sub-array is configured by four high-gain planar segmented antenna (PSA) elements with a sequentially rotating arrangement, where a single 4-channel BFIC can drive CP radiation. Unlike previously reported PSA elements that have limited CP performance, the proposed PSA-CP configuration adopts additional conductors and ground-via structures to further improve the CP gain, axial-ratio (AR), and cross-polarization (XPD) characteristics. To verify the performance of the proposed PSA-CP, a 2 × 2 left-hand circular polarization (LHCP) sub-array was fabricated at 28 GHz and tested with a BFIC. The measured 10-dB impedance and 3-dB AR bandwidths of the proposed 2 × 2 array were 13.92% and 12.5%, respectively. In addition, the measured peak gain was 15.2 dBic at 28.5 GHz with an XPD level of less than 15 dB.

Phased Array With Pattern Shaping and Scan Loss Reduction for Millimeter Waves

In this work, we investigate antenna architectures to implement dual-mode operation in phased array designs. Planar slot antenna elements are used in array configuration, in combination with artificial dielectrics layers (ADLs) located in the close proximity of the array, to achieve pattern shaping. The artificial dielectric superstrate supports the propagation of leaky waves that can be optimized to enhance the gain in a specific angular region or to enlarge the array field of view. By controlling the amplitude and phase of the antenna elements, the radiation patterns can be combined to realize either wide or narrow beams. This concept present advantages for both millimeter-wave (mm-wave) communication and radar applications. A design of a four-element array fabricated in standard printed circuit board (PCB) technology validates the feasibility of the dual-mode operation. The measured results also show good agreement with simulations.

Multilayer Dielectric Periodic Antenna Structure in a Cascade View

The spectral response of the periodic antenna structure placed in a dielectric homogeneous medium depends on the antenna geometry, the parameters of the medium, the angle of incidence, polarization, and the geometry of the excitation field. Increasing the number of antenna structure parameters can be achieved by introducing a multilayer dielectric medium with a certain number of metallized periodic surfaces located on flat boundaries between the dielectric layers. There are two complementary approaches to the analysis of such structures. In the first, the composite antenna system is analysed by constructing supermodes of the entire structure. In the second, the system is considered as a cascade assembly of flat discrete elements, i.e., the boundaries between two dielectrics, periodic metallized planes, and dielectric layers. The latter approach leads to the definition of the scattering, transmission, or impedance matrix of the entire structure by cascading the corresponding matrices associated with the individual discrete elements of the antenna structure. It is particularly useful in modelling dielectric multilayer antenna walls, where the stored data on one planar antenna element can be used many times in the analysis of various antenna systems with modified parameters of other discrete structure elements. Microstrip antennas combine field and peripheral problems and require the use of analytical methods of a high degree of complexity. Therefore, at present, there are no standard methods that can be used in engineering practice. This work is a step towards filling these gaps.

Compact Multiband Reconfigurable MIMO Antenna for Sub- 6GHz 5G Mobile Terminal

In this paper, the design of a multiband multiple-input multiple-output (MIMO) antenna with compound reconfiguration capability in the 5G sub-6 GHz band is presented. Frequency and radiation pattern reconfiguration are enabled on the antenna consisting of two planar inverted-F antenna (PIFA) elements using PIN diodes and DC biasing circuits. This results in reconfigurability in multiple bands, ranging from 0.8 GHz to 6 GHz for GSM, UMTS, LTE and 5G-NR bands. At the same time, reflection coefficients of less than -6 dB and high isolation of at least -10 dB between ports ensures satisfactory MIMO diversity performance. Within the operating bands, total efficiencies of between 46.2% and 74.5% is achieved, with less than 0.3 of envelope correlation coefficient. This enables a channel capacity of 9.86 to 10.5 bit/s/Hz. Simulated antenna performance parameters agreed well with measurements, and potentially enables reliable and consistent data throughput for 5G mobile terminals.

Design of a Low-Profile and Low Scattering Wideband Planar Phased Antenna Array

This communication presents a low-profile and low scattering wideband planar phased antenna array with enhanced coupling (PAA-EC). The proposed chessboard-like PAA-EC consists of two different types of low-profile planar antenna elements that have similar radiation performance in the X-band. In addition, the two types of antenna elements have a 180°±37° reflection phase difference over the X-band, which guarantees the cancellation of scattering fields for low scattering purpose. On the other hand, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times 8$ </tex-math></inline-formula> reference PAA-EC and a low scattering PAA-EC are developed and fabricated to validate the radiation performance and scattering characteristics. The simulated and measured results show that the proposed low-profile planar PAA-EC operates in the 8–12 GHz band with ±45° scanning range. It also achieves at least 9 dB scattering cross section (SCS) reduction in the 8–15.2 GHz band as compared with the reference PAA-EC.

Mutual Coupling Reduction between Finite Spaced Planar Antenna Elements Using Modified Ground Structure

In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrate-integrated pin wall. The use of the modified ground structure causes a more than 28 dB (measured value) mutual coupling reduction. The modified ground structure has been optimized and validated with a finite spaced planar 2 × 1 antenna array operating at 4.16 GHz, intended for unmanned aerial vehicle radar altimeter applications. The patch antennas built with the MGS exhibit high gain (greater than 6 dBi throughout the operational band), along with inter-element coupling as low as −65 dB. Mutual coupling reduction at lower contours is beneficial for altimeter applications.

Cross Polarized 2x2 LTE MIMO System for Automotive Shark Fin Application

In this research we propose two orthogonally placed FR4 printed planar monopole antenna elements for use in the automobile roof top shark fin antenna for LTE MIMO applications. The discussed MIMO antenna system is designed to cover the worldwide LTE frequency band from 698MHz to 2700MHz. The goal of this research is to achieve satisfactory MIMO performance across the whole band while staying within physical constraints of the shark fin style antenna. The target reflection coefficient (S11) of each element is -6dB. Because of physical constraints of the automotive shark fin design antenna MIMO decorrelation is achieved by cross polarization and small distance separation. Correlation better than -12dB is targeted and achieved in higher bands, while in lower frequency bands antennas would not benefit from MIMO performance. Numerical simulation of the MIMO antenna system is performed using FEKO in order to verify the design parameters. Simulation findings are confirmed by manufacturing antennas and testing in the lab.

Planar Sectoral Antenna for IR-UWB Localization With Minimal Range Estimation Biasing

A planar sectoral antenna is presented, optimized for highly precise impulse-radio ultrawideband (IR-UWB) indoor localization with minimal range estimation biasing. By judiciously combining two planar inverted-F antenna elements into one footprint, a large half-power beamwidth (HPBW) is obtained in the [3.2448-4.7424] GHz band, thereby covering channels 1-4 of the IEEE 802.15.4a-2011 standard. Through system-level optimization, the system fidelity factor (SFF) is maximized for a minimal value of at least 90$\text{\%}$ within its entire HPBW, while minimizing the orientation-specific range estimation biasing down to 10 mm. To validate the antenna performance, measurements have been performed in both the frequency and time domain, showing a HPBW larger than 120$^\circ$ in the complete frequency band of operation and an SFF larger than 90$\text{\%}$ and range biasing lower than 4 mm within the antenna's HPBW.

A broadband multiple-input multiple-output loop antenna array for 5G cellular communications

In this study, we propose a multiple-input/multiple-output (MIMO) antenna array for fifth-generation (5G) mobile-phone applications. Its configuration is composed of eight planar loop antenna elements located at different edges of the mobile-phone mainboard with 75 × 150 × 0.8 mm3 FR-4 dielectric. In order to easily integrate with phone circuits, the ground-plane and antenna resonators have been etched on the same side of the substrate. By addling modified arrow-shaped strips among the adjacent loop antennas, the operation bandwidth and isolation level of the closely spaced radiators have been improved. The presented MIMO antenna is designed to cover the spectrum of commercial sub 6 GHz 5G network with the bandwidth of 3.2–4 GHz. Due to the compact size and placements of the loop radiators, the presented MIMO antenna array occupies a small part of the board. In addition, the proposed array provides not only full radiation coverage covering different sides of the PCB but also the diversity function to support both vertical and horizontal polarization. The MIMO performance and radiation behavior of the proposed antenna design in the presence of the user-hand/user-head phantoms are also discussed. Moreover, a new and compact phased array millimeter-wave (MM-Wave) antenna with broad bandwidth and end-fire radiation is introduced to be easily integrated into the smartphone antenna system.

A Symmetrically Stacked Planar Antenna Concept Exhibiting Quasi-Isotropic Radiation Coverage

This letter presents a symmetrically stacked planar antenna (SSPA) featuring switchable quasi-omnidirectional and omnidirectional radiation patterns to accomplish a quasi-isotropic radiation coverage. The proposed antenna consists of two identical planar patch antenna elements. By separately controlling the phase of the two excitation ports, the comprised antenna collectively emulates either an electric dipole mode or a magnetic dipole mode. Collectively, these two complementary dipoles enable a full spherical coverage with a simulated far-field gain variation lower than 6.8 dB. In actual usage scenarios, the proposed antenna can encapsulate various RF circuits and components between the two antennas due to the ground planes functioning as electromagnetic shielding structures. Studies confirm that quasi-isotropic characteristics are preserved for highly integrated user scenarios.

Compact Dual-Band Antenna Module for Glonass/GPS GNSS Receivers

A compact dual-band navigation antenna module, consisting of a planar patch antenna element and a two-channel low-noise amplifier with input protection elements, is proposed. The two-channel scheme for constructing the low-noise amplifier is implemented with the use of two duplex filters, which are calculated by the method of oriented graphs. The patch antenna element is realized in a topology that allows it to be excited at the fundamental resonant mode TM10 both in the lower (L2) and upper (L1) frequency bands, which ensures the identity of the radiation pattern shapes in both frequency bands. The design of the antenna module, the equivalent circuit, the VSWR against frequency, the gain against frequency, the radiation patterns at the central frequencies of the L1 and L2 ranges of the antenna element, the gain and noise figure of the low-noise amplifier against frequency, and the radiation pattern of the entire module are presented.

A compact wideband circularly polarized quadrifilar antenna with PIFA elements for UHF RFID readers

AbstractIn this paper, a compact circularly polarized quadrifilar antenna with planar inverted-F antenna (PIFA) elements is presented. The proposed antenna consists of four PIFA elements and a Wilkinson divider-based feed network fabricated on FR-4 substrate (ɛr = 4.4, loss tangent = 0.02, thickness = 1.6 mm). The total size of the antenna is 120 × 120 × 13.2 mm3. Impedance matching with a reflection coefficient &lt;−15 dB and an axial ratio (AR) &lt;3 dB are achieved over the global ultra-high frequency (UHF) radio frequency identification (RFID) frequency band and beyond. The realized gain ranges from 2.25 to 3.75 dBic within the frequency band of interest from 860 to 960 MHz with a directional radiation pattern. The proposed antenna is compact, low-cost and extremely wideband in terms of matching and AR compared to state-of-the-art UHF RFID reader antennas.

Electrically Conformal Antenna Array With Planar Multipole Structure for 2-D Wide Angle Beam Steering

Electrically conformal antenna arrays (ECAA) for 2-dimensional (2-D) beamforming configured by wide beamwidth multipole radiation elements are proposed. Unlike the conventional conformal antenna array with physically curved shape, the proposed arrays are planar structures with wide-angle beam steering. The wide range of beam steering with a low gain variation allows the planar array structure to achieve the electrically conformal phased array patterns. In order to verify the ECAA concept, two different types of ECAA in a 1 × 8 configuration using planar multipole antenna elements were fabricated at 5.8 GHz and compared to the conventional patch array. Each multipole element had half-power-beamwidth (HPBW) wider than 110° at both E- and H-planes with the maximum HPBW of 175°. The first type of ECAA showed a measured peak gain of 10.8 dBi with a measured half power steering angle of 155° while maintaining a side lobe level (SLL) less than -10 dB. Further, the second ECAA showed a measured peak gain of 12.8 dBi with a measured half power steering angle of 144° while keeping the SLL less than -10 dB. These scan angles of the first and second types were extended about 66.7% and 54.8%, respectively from the conventional patch array with the same size. Lastly, two types of 8 × 8 array modules for 2-D beam steering were verified at 5.8 GHz and the first type showed a maximum peak gain of 21.0 dBi. Further, the 2-D half power steering angles in E- and H-planes of the second type were about 145° and 137°, respectively.

All-Around Beam Switched Antenna With Dual Polarization for Drone Communications

This communication presents a drone-to-drone adaptive beam switched antenna with 360° beam coverage and dual polarizations. The proposed antenna maintains the all-around beam coverage with high directivity based on 16 concentric planar Yagi-Uda dipole array. The high gain dipole array beams are configured by eight vertical polarization elements and eight horizontal polarization elements with directors and reflectors. Depending on various communication environments, a single beam, multiple beams with identical polarization, or multiple beams with different polarizations can be adaptively controlled for highly reliable drone-to-drone communication. To ensure the compactness in the antenna array, 16 concentric planar antenna elements are arranged in an orthogonally crossed manner with optimized vertical and horizontal transition matching circuits. Each Yagi-Uda dipole element for vertical or horizontal polarization showed a measured peak gain of 6.35 and 6.40 dBi at 5.5 GHz, respectively. The proposed antenna was integrated with sub-6 GHz transceiver and microcontroller unit (MCU) to verify the switched beam performance with dual polarization. Also, the Tx and Rx operation at random beam conditions was tested by using two proposed antennas and showed an excellent performance from 5 to 6 GHz.

A compact multi‐band multi‐input multi‐output antenna for 4G/5G and IoT devices using theory of characteristic modes

A compact four element multi-band multi-input multi-output (MIMO) antenna system for 4G/5G and IoT applications is presented in this paper. The proposed antenna is developed using the theory of characteristic modes helping in systematic design of MIMO antenna system. It consists of four L-shaped planar inverted-F antenna (PIFA) elements each operating at 3.5, 12.5, and 17 GHz bands with the bandwidth of 359 MHz, 1 GHz, and more than 3.7 GHz, respectively. The proposed antenna system is suitable for both 4G/5G and internet of things devices as it shows the satisfactory MIMO system performance. Good isolation characteristics are observed by implementing complimentary Metamaterial structure on the ground plane resulting in isolation level lower than −21 dB between the antenna elements. The proposed antenna is fabricated and experimental results are also presented and discussed.

4-Port 2-Element MIMO Antenna for 5G Portable Applications

In this paper, a compact, low-profile four-port, two-element antenna for the 5G Internet of Things (IoT) and handheld applications with height $h=3.0$ mm is presented. The antenna structure contains two planar inverted-F antenna (PIFA) elements having the same shapes. Each antenna element has two feeding plates placed at the right angle to each other to make them cross-polarized for the exploitation of polarization diversity, whereas spatial diversity is employed by positioning two antennas diagonally on opposite sides of the antenna structure. For reducing mutual coupling, the etching of rectangular slots on each side of the ground plane beneath the top plate of each element has been done to stop the flow of current between two ports of the same antenna element. Maximum isolation achieved among ports is less than −25 dB, and envelope correlation coefficient is below 0.009 in bands of interest. The minimum frequency range covered by the four ports of this antenna is from around 2.7 to 3.6 GHz for $S_{11} dB, thus covering expected future 5G band (3300–3600 MHz), and may be used for small portable and handheld the IoT and cellular applications as a diversity/MIMO antenna.

Mutual coupling reduction with a novel fractal electromagnetic bandgap structure

This work shows the effect of a novel fractal-based electromagnetic bandgap (FEBG) structure between dual planar inverted-F antenna (PIFA) elements. The FEBG structure without any shorting pins builds on a well-known fractal structure called Sierpinski carpet, where two iterations have been applied as a uniplanar EBG between dual PIFAs elements to increase the isolation. The proposed antenna can operate at ~2.65GHz for wireless long-term evolution application with compact design dimensions. The simulations are carried out with Ansoft HFSS ver. 17.0. The second iterative order FEBG band-gap characteristic is verified using more computationally efficient analysis. An investigation on coupling reduction showed more than 27 and 40dB in E -plane and H -plane, respectively, between the dual antenna elements is achieved for an antenna spacing less than half wavelength. The proposed antennas with and without second iterative order FEBG are fabricated and measured. The measurement results are in good agreement with the simulated results. Moreover, the envelope correlation of antenna elements with the proposed FEBG is quite smaller than that of antenna elements without FEBG, which gives the proposed system an excellent diverse performance and suitable for the use in low-frequency narrow-band multiple-input, multiple-output applications.

Low-Profile EndFire Leaky-Wave Antenna With Air Media

A low-profile endfire leaky-wave antenna is proposed in this paper. The proposed low profile antenna utilizes microstrip line to excite planar inverted-L antenna (PILA) elements. Air media is utilized in the proposed array to realize the endfire property. By using air media, the proposed leaky-wave array maintains phase constant slightly larger than the wavenumber in free space and achieves endfire radiation. PILA elements are periodically spaced to radiate and the spacing period is designed as $\lambda _{0}$ /4 ( $\lambda _{0}$ is the wavelength in free space) to achieve a relatively wide impedance bandwidth. A prototype of the proposed endfire antenna is fabricated and tested. The measured results are consistent with full-wave simulation results. The length of the whole leaky-wave array is about $6\lambda _{0}$ , and the measured gain in the endfire direction is 11.5 dBi at 5.1 GHz.