Total Antenna Efficiency Research Articles

Dual-Band Monopole MIMO Antenna Array for UAV Communication Systems.

This study proposes a compact, low-profile, four-port dual-band monopole multiple-input-multiple-output (MIMO) antenna array for unmanned aerial vehicle (UAV) communication systems. Each monopole antenna of the array features a modified T-shaped radiator configuration and is printed on a Rogers RT5880 substrate with compact dimensions of 134.96 mm × 134.96 mm × 0.8 mm. A four-element square MIMO configuration with sequential 0°, 90°, 180°, and 270° rotations was integrated smoothly into the UAV body. A prototype of the MIMO array was fabricated and experimentally evaluated, with measured results showing a close correlation to simulated results. The proposed dual-band monopole antenna demonstrated one of the widest impedance bandwidths of 46.15% at 2.4 GHz (2.04 to 3.25 GHz) IEEE 802.11b and 31.85% at 5.8 GHz (5.37 to 7.38 GHz) IEEE 802.11a on a thin 0.0064 λo substrate while achieving high transmission efficiency. The isolation of the proposed four-port MIMO design was measured at 23 dB at 2.4 GHz and 19 dB at 5.8 GHz. The MIMO array's total efficiency of each monopole antenna was measured at 96% at 2.4 GHz and 89% at 5.8 GHz. The design has measured diversity parameters such as an ECC below 0.01 and a DG of approximately 10. Based on these results, the proposed design suits the UAV communication system.

W‐band multimode monopulse horn feed for reflector antenna

AbstractThis letter proposes a W‐band multimode monopulse horn (MMH) feed to improve the total efficiency (TE) of the reflector antenna. The feed consists of a MMH and a single‐layer comparator. The MMH utilizes one pyramidal horn and four rectangular waveguides (RWGs) for feeding. The eight electric modes required in the MMH yield excellent sum and difference patterns. The impact of unwanted modes is suppressed using a 90° phase difference approach. The comparator contains four novel 3 dB couplers and E‐plane RWGs, providing low loss and high multiport transmission performance. The MMH feed has been fabricated, tested, and applied to a Cassegrain antenna. The measured maximal TE for the Cassegrain antenna between 90 and 97 GHz is 54.9%. The realized gain of the sum beam is 40.3 dBi at 93.5 GHz. The null depths of difference beams in the azimuth and elevation planes are about −37.7 and −29.1 dB, respectively.

Decoupling Method for Four Closely Spaced Planar Inverted-F Antennas Using Parasitic Elements and Bridge Lines

This study proposed a novel decoupling method for four planar inverted-F antennas (PIFAs) operating at 2.0 GHz (f0). The edge-to-edge and center-to-center spacings of the adjacent PIFAs are extremely small (0.05λ0 and 0.17λ0, respectively), resulting in strong mutual coupling among them. In our previous study, we proposed a structure consisting of parasitic elements (PEs) and a bridge line (BL) for the decoupling of two PIFAs. One attractive feature of the proposed method is that no adjustment of the original structure and size of the PIFAs is necessary. However, as the number of PIFAs increases to four, their decoupling becomes considerably more complicated, and impedance mismatch is also an issue to be considered. Therefore, in this study, PEs and BLs are functionally developed to simultaneously achieve low mutual coupling and improved impedance matching of the four PIFAs. The simulated results showed that loading the proposed PEs and BLs onto the four PIFAs could reduce as well as maintain all mutual coupling for less than -10 dB, and simultaneously improve impedance matching. Therefore, the total antenna efficiency at 2.0 GHz could be significantly improved from 64.2% to 84.8% for PIFA1 and PIFA4, and from 35.9% to 74.2% for PIFA2 and PIFA3. Four PIFAs with PEs and BLs were fabricated and measured to validate the simulation results.

Ultrawideband Dual Circularly Polarized Waveguide Array Antenna for K- and Ka-Bands Satellite Communications

In the letter, a wideband dual circularly polarized (CP) waveguide antenna array is designed for K and Ka dual-band satellite communications. A multi-stage square waveguide structure is exploited into the radiating part to facilitate the excitation of a dual polarization response. A ridge waveguide polarizer is integrated to form the left-hand circular polarization (LHCP) and the right-hand circular polarization (RHCP). For a better arrangement of the feeding network, a transition structure with E-plane waveguides to double-ridge waveguides reduces the cross-sectional area of the feeding network. An 8 x 8 array antenna prototype was designed, fabricated and measured for demonstration purposes. The axial ratio (AR) and impedance bandwidth of the array antenna are more than 45%, according to simulation and measurement results. Input reflection coefficient and isolation lower than -15 dB for the dual CP from 19 to 30 GHz, the total antenna efficiency for the entire operating band exceeded 72%. For both polarizations, the peak gain ranges between 24.6 and 28.8 dBi from 19 to 30 GHz.

Contactless Method to Estimate Antenna Efficiency in a Reverberation Chamber

Measuring the efficiency of electrically small antennas and integrated antennas is challenging, since for electrically small antennas, the probe may significantly affect the results and for integrated antennas, establishing a connection with the integrated antenna is in many cases not possible. Therefore, a contactless method to estimate the efficiency of electrically small antennas and integrated antennas is necessary. This paper proposes a novel method to estimate antenna efficiency contactlessly using a reverberation chamber: the contactless efficiency method. In the contactless efficiency method, we combine the two-antenna method with the contactless characterization method, to estimate the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameters contactlessly. To validate the results, the contactless efficiency method measurements are compared to the measurements of the widely-used two-antenna method and for both methods an uncertainty analysis is performed. Results show a good agreement in the 95% confidence interval between the contactless efficiency method and the existing connectorized method for both the total antenna efficiency and the radiation antenna efficiency. The uncertainty of the contactless efficiency method with a 95% confidence level is below 6% for the whole 0.55 GHz to 1.05 GHz frequency band.

Axial ratio beamwidth enhancement of a low-profile circularly polarized antenna using defected ground structures

AbstractThis article explores the possibilities of incorporating a defected ground structure (DGS) for widening the 3 dB axial ratio beamwidth (ARBW) of a simple low-profile planar circularly polarized (CP) antenna. Two pairs of DGSs are etched symmetrically along the diagonals of the ground plane to overcome the limited 3 dB ARBW performance of a crossed-slotted circular-shaped planar CP antenna. Here, one pair of DGSs is orthogonal to another pair of DGSs. The distance between the pairs of DGSs plays a key role in enhancing the 3 dB ARBW by 40.62%. A gap of 0.18λ0 is considered between the DGSs to maintain the symmetrical electric field distribution in the substrate. It also helps to reduce orthogonal current components and provides uniformly distributed patch surface currents. These phenomena collectively help the proposed CP antenna to exhibit right-handed circular polarization radiation with the 3 dB ARBW of 186° and 188° in the E-plane and H-plane, respectively. The measured results yield impedance bandwidth (S11 ≤ −10 dB) of 2.6% (2.283–2.342 GHz), CP bandwidth of 0.9% (2.294–2.315 GHz), gain higher than 4.8 dBic, and total antenna efficiency more than 64% across the entire CP band.

Bandwidth Maintenance and Decoupling for Two Planar Inverted-F Antennas Using Bridge Line

In this paper, a simple method is proposed that allows two planar inverted-F antennas (PIFAs) maintain their bandwidth while simultaneously reducing the mutual coupling between them. By creating a slit on each PIFA patch and then connecting the two PIFAs by a bridge line (BL), the bandwidth can be maintained and the mutual coupling between them can be simultaneously reduced to less than －10 dB. Therefore, total antenna efficiency can be significantly improved over a wide band. The proposed model is fabricated and measured, and the simulation results are validated by the measurement results.

Wideband MIMO Antennas for 5G Mobile Terminals

An approach of using the concept of CM (common mode) and DM (differential mode) to design two wideband antennas in a pair has been proposed. The two antennas in the antenna pair have wide bandwidth and high isolation, though they share the same radiator and total electric length of the antenna pair is just a half wavelength. A rigorous analysis has been presented to explain and illustrate the operating principle of the wideband antenna pair. An antenna design example operating in 5G New Radio (NR) N1, N2, N3, N7, N38 and N41 bands with frequency ranging from 1.71-2.69 GHz has been examined to demonstrate the effectiveness of the proposed approach. The simulated results, including S-parameters, antenna total efficiency and ECC (envelope correlation coefficient), are in good agreement with measured ones.

Design of Compact Antenna Array for MIMO Implementation Using Characteristic Mode Analysis for 5G NR and Wi-Fi 6 Applications

In this paper, we present a compact antenna for 5G new radio (NR) and Wi-Fi 6 applications. Using characteristic mode analysis (CMA), two orthogonal modes have been separated and then a gapcoupled shaped feed-line has been used to excite the radiator. An open stub is added to achieve the wide operating bandwidth of the antenna. The size of a single antenna element and the 1×2 array-unit (AU) are 20×21.5 mm2 and 40×21.5 mm2, respectively. The operating and fractional bandwidths (FBW) of the AU are 5.18-7.71GHz and 39.25%, respectively. The proposed AU is used to develop a number of radiating element-independent multiple-input-multiple-output (MIMO) antennas comprising of 2AUs, 4AUs, and 8AUs with identical electrical characteristics and good isolation (I).18.8 dB. All the AUs have realized gain 3.0 dBi, and the total antenna efficiency 70% making it suitable for the single-user MIMO (SU-MIMO) and multiple users MIMO (MU-MIMO) needed for Wi-Fi 6 applications. To show the application of these antennas, the deployment scenario of a 16AUs MIMO antenna on a large size ground plane which mimics the smart TV panel and router chassis, etc., is also presented. These AUs may find potential applications in radiator-number independent MIMO systems.

Capacity-Oriented Envelope Correlation Coefficient for Multiple Antennas of Mobile Devices

In this article, a capacity-oriented envelope correlation coefficient (ECC) that incorporates a preferred channel model for assessing a multiple antenna system of a multiple-input-multiple-output (MIMO) mobile device is proposed. Originated from the rudimentary law of ergodic channel capacity, the ECC for multiple antennas (ECC-M) is proven to holistically reflect the impact of radiation patterns and total efficiencies of multiple antennas on channel capacity. The closed-form ECC-M expressions for Rayleigh fading channel model and ray-based spatial channel model are studied, leading to an easy-to-use ECC-M expression that approximately incorporates a realistic channel model. The correlation of the proposed ECC-M to the channel capacity is demonstrated through the Monte Carlo (MC) simulation of three four-element MIMO antenna testbeds in two channel models, showing that the antenna total efficiency and a realistic channel model involved in the ECC-M play an important role in assessing the performance of multiple antennas. It is justified that the difference in channel capacities of two multiple antenna systems is highly relevant to their ECC-Ms at high signal-to-noise ratios (SNRs). The proposed ECC-M is also experimentally validated through over-the-air (OTA) throughput measurement, revealing that the ECC-M can effectively assess the OTA performance of multiple antenna systems for MIMO terminal devices.

Leveraging frequency agility of an MIMO antenna cluster with a transmitter IC

AbstractThis paper presents the prototype demonstration where an integrated transmitter circuit drives a mobile handset terminal antenna in order to provide frequency tunability and multiple input multiple output (MIMO) operation across the 0.5–4.5 GHz frequency range. The transmitter implementation incorporates on-chip weighted signal generation, i.e. amplitude and phase scaling to provide sufficient MIMO performance in the low band (700–960 MHz) and in the high band (1.5–4.5 GHz). In the transmitter, two antenna elements are used for MIMO operation in the low band and another two in the high band. The transmitter integrated circuit (IC) is fabricated in a 28 nm bulk CMOS technology with an active on-chip area of 0.2 mm$^2$. A custom antenna measurement procedure is proposed here in order to support and verify active antenna measurements with transmitter IC. A measurement procedure for the transmitter system comprising the transmitter IC and four antenna clusters is developed and discussed in comparison with traditional passive antenna measurements. The measurement results demonstrate that the transmitter IC driving the antenna clusters provides total antenna efficiency of $-6.5$ dB to $-1.5$ dB, and envelope correlation coefficient below 0.4 across the designated frequency bands. The results indicate that the implemented transmitter IC successfully tunes frequency response of the antenna clusters, and enhances the MIMO operation of such mobile antennas.

Ultra-Wideband Millimeter-Wave Planar Array Antenna With an Upside-Down Structure of Printed Ridge Gap Waveguide for Stable Performance and High Antenna Efficiency

In this letter, a wideband millimeter-wave (mmWave) planar array antenna with a printed ridge gap waveguide (PRGW) feeding network is presented. A planar bowtie antenna fed by the PRGW is employed as the array radiation element which combines the bowtie with an upside-down electromagnetic bandgap part by using lamination. Thus, with this new upside-down structure, the proposed array antenna achieves a stable, wideband, and high-antenna-efficiency performance. A prototype of 8 ×8 array is fabricated and measured. The measured results show that the proposed array has an impedance matching bandwidth (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB) of 50.3% from 18.6 to 31.1 GHz. The maximum measured gain is 22.1 dBi at 29 GHz, and the total antenna efficiency is above 60% with a bandwidth of 45% from 18.8 to 29.8 GHz.

Design and analysis of high isolated super compact 2 × 2 MIMO antenna for WLAN application

In this article, a DGS structure is applied to enhance the inter-port isolation of super compact 2 × 2 MIMO antenna. Each element of MIMO antenna configuration is designed using a planar inverted-F antenna (PIFA) having dimensions 7 × 7 × 0.8 mm3 and elevated at 2.8 mm from the ground plane of dimensions 100 × 50 × 0.8 mm3 (comparable to the size of mobile handsets). The proposed antenna operates from 5.2 to 6 GHz resonating at 5.65 GHz which is suitable for WLAN applications. The proposed design with and without the isolation enhancement technique is resonating at 5.65 GHz. Therefore, the proposed DGS structure is acting as a perfect isolator without affecting the reflection coefficient of the MIMO antenna configuration. It provides high isolation enhancement from 12 to 25 dB at the resonance frequency. All the diversity parameters of the MIMO configuration are calculated and found within the desirable limits. Thus, it is found that the proposed antenna is well suited for modern wireless applications (WLAN). The radiation performances such as 2D and 3D patterns, total antenna efficiency, and peak realized gain are calculated and analyzed. Finally, a prototype is fabricated and validated experimentally.

SIW Cavity-Backed Antenna Array Based on Double Slots for mmWave Communications

This paper presents a cavity-backed antenna array in substrate integrated waveguide (SIW) technology in the millimeter-wave frequency band. The proposed antenna design uses double slots as radiating elements instead of conventional single slots. The double slots allow better control in the design of the operating frequency bands of the cavity-backed antenna. The performance of the cavity-backed antennas with single and double slots is compared to assess the enhanced behavior of the double slots. As a proof of concept, a 2 × 2 array of cavity-backed antennas is designed, manufactured, and measured. Each cavity-backed antenna contains 2 × 2 double slots; thus, a 4 × 4 antenna array is considered. The experimental operating frequency band of the proposed antenna array ranges from 35.4 to 37 GHz. There is a good agreement between the simulated and measured results. The measured gain is around 17 dBi in the whole operating frequency band with a 75% total antenna efficiency.

Wideband tightly‐coupled dual‐line polarized P‐band antenna array with low‐profile lightweight metal structure

In this article, an all-metal structure antenna array is proposed. The novel hollow-out structures are designed to achieve low profile and lightweight. The top structure of the element is also tightly coupled, once again lowering the antenna array profile. The overall size of the array is 1354.0 × 1354.0 mm2, the spacing between elements is 323.0 mm. The optimized array-structure profile is only 0.12 λ0 (λ0 corresponds to the wavelength of 0.4 GHz). In addition, an excellent dual-line polarization radiation is achieved by using a cross-staggered arrangement. Both polarizations of the array have a cross-polarization-level of smaller than −30 dB. In order to verify the feasibility of the scheme, prototype processing and testing are carried out, and the test results are consistent with the simulation results. The frequency band covers the P-band (0.4-0.7 GHz). The active voltage standing wave ratios (VSWRs) are less than 2.0. In addition, the antenna array has favorable radiation characteristics. The measured realized gain varies from 14.7 to 19.6 dBi over the work band. The total antenna efficiency is higher than 83%. It can be applied to phased arrays for the satellite system and other broadband lightweight metal antennas.

Wideband Integrated Quad-Element MIMO Antennas Based on Complementary Antenna Pairs for 5G Smartphones

In this article, a wideband and highly-integrated quad-element multiple-input multiple-output (MIMO) antenna is proposed for the first time, to adapt to the size-limited environment in fifth-generation (5G) smartphones. First, the wideband decoupling between two extremely closely-spaced open-slot antennas with face-to-face and back-to-back configurations are investigated. Then, based on the complementary antenna pairs, wideband integrated quad-element MIMO antennas are implemented by the ingenious combination of these antenna pairs. For validation, an 8 ×8 MIMO system, constituted by two sets of integrated quad-antenna configurations, is simulated, fabricated, and measured. Both the simulated and measured results show that the 8×8 MIMO system can provide isolation of better than 10 dB between any two ports and a total antenna efficiency of 52.8%-70.8%/40.5%-75.0% across 3.3-5.0 GHz. Compared with the existing integrated quad-antenna design schemes, the proposed solution can expand the bandwidth from less than 200 to 1700 MHz, covering the entire 5G N77, N78, and N79 bands. In addition to the integrated quad-antenna design, further extension to integrated multiantenna configurations is also discussed by the flexible combination of complementary antenna pairs, which paves the way for future higher-order MIMO system in smartphones.

Dual Band and Dual Diversity Four-Element MIMO Dipole for 5G Handsets.

The increasing popularity of using wireless devices to handle routine tasks has increased the demand for incorporating multiple-input-multiple-output (MIMO) technology to utilize limited bandwidth efficiently. The presence of comparatively large space at the base station (BS) makes it straightforward to exploit the MIMO technology’s useful properties. From a mobile handset point of view, and limited space at the mobile handset, complex procedures are required to increase the number of active antenna elements. In this paper, to address such type of issues, a four-element MIMO dual band, dual diversity, dipole antenna has been proposed for 5G-enabled handsets. The proposed antenna design relies on space diversity as well as pattern diversity to provide an acceptable MIMO performance. The proposed dipole antenna simultaneously operates at 3.6 and 4.7 sub-6 GHz bands. The usefulness of the proposed MIMO dipole antenna has been verified by comparing the simulated and measured results using a fabricated version of the proposed antenna. A specific absorption rate (SAR) analysis has been carried out using CST Voxel (a heterogeneous biological human head) model, which shows maximum SAR value for 10 g of head tissue is well below the permitted value of 2.0 W/kg. The total efficiency of each antenna element in this structure is −2.88, −3.12, −1.92 and −2.45 dB at 3.6 GHz, while at 4.7 GHz are −1.61, −2.19, −1.72 and −1.18 dB respectively. The isolation, envelope correlation coefficient (ECC) between the adjacent ports and the loss in capacity is below the standard margin, making the structure appropriate for MIMO applications. The effect of handgrip and the housing box on the total antenna efficiency is analyzed, and only 5% variation is observed, which results from careful placement of antenna elements.

Анализ эффективности многопортовой печатной антенны

The article considers the patch antenna with several ports to excite a circular polarization. The effect of excitation ports number on the total efficiency of antenna was investigated. Taking into account the mutual coupling of the antenna ports, the total active reflection coefficient was estimated. A comparison of the calculated characteristics and the data obtained by CAD-modeling was carried out. It was shown that the total efficiency of the multiport patch antenna is independent from the number of excitation ports

10 Element Sub-6-GHz Multi-Band Double-T Based MIMO Antenna System for 5G Smartphones

A 10 element multiple input multi output (MIMO)/Diversity antenna system is considered to work in Sub-6 GHz frequency range. The proposed design can work in long term evolution (LTE) band 42(3.4-3.6 GHz), LTE band 43(3.6-3.8 GHz) and LTE band 46(5.15-5.925 GHz). The proposed design consists of 10 identical and highly isolated T-shaped slot antennas fed with T-shaped lines. All three bands have the return loss values (<-6 dB) and total antenna efficiency (>83%) in free space. The peak value of envelope correlation coefficient is 0.06 and the calculated value of ergodic channel capacity is found to be greater than 41bps/Hz in all the bands.The effect of hand grip as well as the presence of battery and LCD screen is investigated. Simulated results are validated via fabrication and measurement of the proposed design.

Frequency Reconfigurable Filtering Dielectric Resonator Antenna With Harmonics Suppression

A filtering dielectric resonator (DR) antenna (DRA) that does not require any filtering circuits is investigated. It deploys a rectangular DR and three slots fabricated in the ground plane. The antenna is excited in the fundamental TE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1δ1</sub> DRA mode and two slot modes. By making use of these three modes, two tunable radiation nulls near the edges of the passband can be obtained, giving filtering effects without the need for any filtering circuits. In this article, the design, with minor modifications of the slots, is extended to a frequency-reconfigurable filtering DRA by using varactors. Its stopband can be extended to the third harmonic. By varying the voltages of the varactors, the antenna has continuous frequency agility of 27.7% (2.15-2.84 GHz), with almost the same harmonics suppression level. The antenna has a gain of ~5.0 dBi and a rejection level of over 16.1 dB across the stopband. Its total antenna efficiency in the passband is ~81%, whereas it is generally lower than the average value of 1.8% in the stopband (up to 7.0 GHz). Compared with the reported frequency-reconfigurable filtering antennas, our design has better frequency agility, more stable filtering response, and weaker radiation in the stopband.