3-D twelve-port multi-service diversity antenna for automotive communications

This paper presents a twelve-port ultra-wideband multiple-input-multiple-output (MIMO)/diversity antenna integrated with GSM and Bluetooth bands. The twelve-port antenna is constructed by arranging four elements in the horizontal plane and eight elements in the vertical plane. The antenna element, which is created using a simple rectangular monopole, exhibits a frequency range of 3.1 to 12 GHz. The additional Bluetooth and GSM bands are achieved by introducing stubs into the ground plane. The size of the MIMO antenna is 100 × 100 mm2. The antenna offers polarization diversity, with vertical and horizontal polarization in each plane. The diversity antenna has a bandwidth of 1.7–1.9 GHz, 2.35–2.55 GHz, and 3–12 GHz, the radiation efficiency of 90%, and peak gain of 2.19 dBi. The proposed antenna offers an envelope correlation coefficient of < 0.12, apparent diversity gain of > 9.9 dB, effective diversity gain of > 8.9 dB, mean effective gain of < 1 dB, and channel capacity loss of < 0.35 bits/s/Hz. Also, the MIMO antenna is tested for housing effects in order to determine its suitability for automotive applications.

A meta-parameter tuning model to improve the genetic algorithms design of labeling diversity mappers

Evolutionary algorithms (EAs) have recently been applied to Uncoded Space-Time Labeling Diversity (USTLD) systems to produce labeling diversity mappers. However, the most challenging task is choosing the best parameter setting for the EA to create a more ‘optimal’ mapper design. This paper proposes a ‘meta-Genetic Algorithm (GA)’ used to tune hyperparameters for the Labeling Diversity EA. The algorithm is examined on 16, 32 and 64QAM; 32 and 64PSK; 16, 32 and 64APSK and 16APSK constellations that do not show diagonal symmetry. Furthermore, the meta-GA settings and original GA settings are compared in terms of the number of generations taken to converge to a solution. For QAM constellations, the output using the meta-GA settings matched but did not improve with the original settings. However, the number of generations needed to converge to a solution took 120 times less than the number of generations using the original settings. In the 64PSK constellation, a diversity gain of [Formula: see text][Formula: see text]dB was observed while improving on the actual fitness value from 0.0575 to 0.0661. Similarly, with 32APSK constellation, an improvement in fitness value from 0.1457 to 0.1748 was made while showing diversity gains of [Formula: see text][Formula: see text]dB. 64APSK constellation fitness value improved from 0.0708 to 0.0957, and a [Formula: see text][Formula: see text]dB gain was observed. The most significant improvement was made by the asymmetric 16APSK constellation, with gains of [Formula: see text][Formula: see text]dB and increasing its fitness value three times (0.0981 to 0.3000). A study of the effects of optimizing the GA parameters shows that the number of swaps during crossover [Formula: see text] and the radius [Formula: see text] were the two most important variables to optimize when executing this GA.

Wearable Metamaterial Dual-Polarized High Isolation UWB MIMO Vivaldi Antenna for 5G and Satellite Communications

A low-profile Multiple Input Multiple Output (MIMO) antenna showing dual polarization, low mutual coupling, and acceptable diversity gain is presented by this paper. The antenna introduces the requirements of fifth generation (5G) and the satellite communications. A horizontally (4.8–31 GHz) and vertically polarized (7.6–37 GHz) modified antipodal Vivaldi antennas are simulated, fabricated, and integrated, and then their characteristics are examined. An ultra-wideband (UWB) at working bandwidths of 3.7–3.85 GHz and 5–40 GHz are achieved. Low mutual coupling of less than −22 dB is achieved after loading the antenna with cross-curves, staircase meander line, and integration of the metamaterial elements. The antennas are designed on a denim textile substrate with = 1.4 and h= 0.5 mm. A conductive textile called ShieldIt is utilized as conductor with conductivity of 1.8 × 104. After optimizing the proposed UWB-MIMO antenna’s characteristics, it is increased to four elements positioned at the four corners of a denim textile substrate to be employed as a UWB-MIMO antenna for handset communications, 5G, Ka and Ku band, and satellite communications (X-band). The proposed eight port UWB-MIMO antenna has a maximum gain of 10.7 dBi, 98% radiation efficiency, less than 0.01 ECC, and acceptable diversity gain. Afterwards, the eight-ports antenna performance is examined on a simulated real voxel hand and chest. Then, it is evaluated and compared on physical hand and chest of body. Evidently, the simulated and measured results show good agreement between them. The proposed UWB-MIMO antenna offers a compact and flexible design, which is suitably wearable for 5G and satellite communications applications.

Frequency Diversity Gain of a Wideband Radar Signal

Wideband radar has high-range directional resolution, which can effectively reduce the fluctuation of echo and improve the detection probability of a target under the same detection probability requirement. In this paper, a unified wideband radar χ2 distribution target model with more practical significance is innovatively established, on which the probability density function and detection probability function of Swerling 0, Swerling II and Swerling IV targets are analyzed, respectively. A generalized “frequency diversity gain” of wideband radar is proposed and defined based on the contradiction between suppression of fluctuation and accumulation loss, which represents the ratio of Signal-to-Noise Ratio (SNR) gain between broadband signal and reference bandwidth signal under the same condition (when the reference bandwidth is used, the radar target has only one range unit), and the mathematical relation equation of the target detection performance and signal bandwidth (equivalent to the number of distinguishable range elements of the target) is given. A Monte Carlo simulation experiment is designed. Based on the target model established in this paper, the optimal number of target range units corresponding to different detection probability requirements is obtained, which verifies the correctness of the concept proposed in this paper.

On the design and performance analysis of wristband MIMO/diversity antenna for smart wearable communication applications

The design of a silicone rubber-based wristband wearable antenna exploiting pattern diversity is presented in this paper. The wristband diversity antenna consists of four identical antenna elements with an inter-element spacing of 0.68λ0, where λ0 is the lower cut-off wavelength. A modified trapezoidal-shaped radiator with a rectangular ground structure is used to achieve ultra-wide bandwidth. The proposed multiple-input-multiple-output (MIMO)/diversity antenna covers a frequency range of 2.75–12 GHz. The antenna element offers a radiation efficiency of 89.3% and a gain of 3.41 dBi. The size of the wristband diversity antenna is 1.1λ0 × 18.4λ0 × 0.18λ0. The diversity performance characteristics of the prototype antenna are examined, with the envelope correlation coefficient (ECC) < 0.18, apparent diversity gain (ADG) > 9.5, effective diversity gain (EDG) > 9.5, mean effective gain (MEG) < 1 dB, total active reflection coefficient (TARC) < − 10 dB, and channel capacity loss (CCL) < 0.1 bits/s/Hz over the entire operating band. The specific absorption rate (SAR) of the proposed wristband antenna is analyzed to determine its radiation exposure on the human body, and the results show that the values are less than 0.02 W/kg.

Miniaturized MIMO Antenna with Low Inter-radiator Transmittance and Band Rejection Features

In this article, compact a multiple-input and multiple-output (MIMO) system with flag-shaped radiators and a mountain-shaped ground plane is presented. Isolation is enhanced with the help of a decoupling stub placed between radiators, where two bands are stopped with the help of slits etched into the radiators. The overall size of the proposed antenna is 15 mm ×25 mm ×1.6 mm. The reflection coefficients are less than -10 dB between 3–10.9 GHz, except the bands WiMAX (3.2–3.7 GHz) and WLAN (5–6 GHz); similarly, measured and simulated transmission coefficients are less than -20 dB across the entire band of UWB. The envelope correlation coefficient (ECC) is less than 0.02 and the diversity gain is greater than 9.9 dB. The gain, ECC, radiation pattern, multiplexing efficiency, diversity gain and various other parameters are discussed and evaluated in detail.

Wireless power transfer with transmit diversity

Background: Wireless power transfer is important for energizing and recharging the Internet-of-Things (IoT) cordlessly. Harnessing energy effectively from radio waves has become a crucial task. It is known that diversities at the transmitting antenna and waves (i.e. simultaneous continuous waves with center frequencies separated apart) can enhance the radio frequency (RF) to direct current (DC) energy conversion. What remains unknown is the extent of which the wave diversity enhances the conversion gain. This study attempts to examine the RF-to-DC conversion gain of applying wave diversity. This paper investigates the effects of wave diversity on the energy conversion efficiency, and contributes the analytical expression that relate the conversion efficiency to the diversity count, i.e. the number of simultaneously transmitted sinewaves. Methods: We adopted a theoretical approach to the problem. First, we derived and presented a theoretical model that incorporated different forms of transmit diversity, i.e. antenna and wave diversities. This model then connected a RF-to-DC energy conversion model resulting from polynomial fitting on circuit simulation results. With the availability of these two models, we determined the theoretical energy conversion gain of simultaneously transmitting multiple sinewaves. Results: The results showed that transmitting multiple sinewaves simultaneously yields diversity gain and higher energy conversion efficiency. Most importantly, the gain and conversion efficiency can now be theoretically quantified. For example, at certain RF power measured at the receiver circuit, the diversity gain of transmitting four sinewaves is 2.6 (as compared to transmitting single sinewave). In fact, both the diversity gain and conversion efficiency increased with the number of simultaneously transmitted sinewaves. In another example, the conversion efficiency of transmitting four sinewaves is 0.1 as compared to 0.075 of two sinewaves. Conclusions: In summary, this paper presents a novel analytical expression for wave diversity in the context of wireless power transfer.

SMIMO Radar: MIMO Radar with Subarray Elements of Phased-Array Antenna

Unlike Phased-MIMO Radar (PMIMO) which employs overlapping equal subarrays (OES) only on the transmit (Tx), Subarray-MIMO (SMIMO) radar utilizes the combination of subarrays, both in the transmit (Tx) and receive (Rx). SMIMO radar is MIMO radar with subarray elements acting as Phased-Array (PA). It simultaneously combines the primary advantages of PA and the MIMO radar; they are high directional gain and high diversity gain, respectively. High directional gain is beneficial to improve the range target, while high diversity gain is beneficial to improve the number of target detection. The use of the subarray methods in the Tx-Rx array could be configured such as in verlapping subarray (OS), non-overlapping subarray (NOS), equal subarray (ES), unequal subarray (US), and/or the combination of all configurations. Various configurations in Tr-Rx would determine the performance of radar, such as the number of virtual arrays, the maximum number of target detections, the detection accuracies, and the angular resolutions along with its effectivity compared to PA, MIMO, and Phased-MIMO radar. Numerical results and simulation showed that SMIMO provided higher flexibility than other radars by configuring Tx-Rx to easily adapt to various changes of target conditions and their surroundings.

Miniaturized CPW-fed UWB-MIMO antennas with decoupling stub and enhanced isolation

In this paper, a coplanar waveguide-fed ultra-wideband-multiple-input and multiple-output (UWB-MIMO) antenna with a novel stub for isolation has been presented. The dimensions of the proposed antenna are 18 × 22 × 1.6 mm3. The proposed antenna is design on an FR4 substrate and simulated in CST studio. The |S11| of the presented MIMO antenna is less than −10 dB between 2.8 and 13 GHz with an impedance bandwidth of 10.2 GHz. The envelope correlation coefficient (ECC) is less than 0.007 and diversity gain (DG) is greater than 9.97 dB. The proposed UWB-MIMO antenna is analyzed in terms of isolation, reflection coefficient, current distribution, ECC, DG, peak gain, multiplexing efficiency, and radiation pattern.