A Cross-Joint Vivaldi Antenna Pair for Dual-Pol and Broadband Testing Capabilities

The non-standalone 5G antenna wireless communication standard and devices operating under Wi-Fi 5, 6, and 6E operate at the 3 GHz frequency bands and above. With the increasing demand for these devices and technologies, it is crucial to test them rapidly and economically for commercial usage. This paper presents a dual-polarized Vivaldi antenna for the over-the-air (OTA) measurement of wireless communication devices used in the 3–7 GHz band. The dual-polarization performance is realized by vertically intersecting two planar Vivaldi antennas and soldering them at the back end. A three-step 1/4 wavelength balun is applied to the input for the wideband impedance matching of the antenna, which is attached to a Teflon holder for easy mounting. It has excellent performance and is designed to be manufactured at low cost. The fabricated antenna was tested in an anechoic chamber and showed S11 less than -10 dB from 2.63–7.15 GH, and a realized gain of more than 5 dBi from 3 GHz and above. A measured half-power beam width of more than 60° was realized with symmetric E/H-plane. Much of the required symmetry was achieved with the designed Teflon holder. The antenna has a measured cross-polarization discrimination of better than 15 dB across the entire operating bandwidth.

Chipless RFID Label with Identification and Touch-Sensing Capabilities

This article presents a 14-bit chipless RFID label which, in addition to classical identification feature, can be used as decimal numeric keypad, allowing the deployment of secure access control applications. A low-cost single layer label comprising 10 RF loop scatterers is used to code information in the frequency domain. In addition, each resonator is associated to a digit in the decimal number system, and the difference in the spectrum caused by the touch event is exploited for the detection of each key pressing. The shape of the resonators has been carefully selected to be both highly resonant and to show high sensitivity to the presence or absence of the human finger. The concept is validated by measurements in an office environment using an FCC compliant low-cost chipless reader and microstrip vivaldi antennas. Simple detection algorithms are proposed for both identification and touch sensing in real environment.

A Novel Approach on Microwave Hyperthermia

Microwave hyperthermia (MH) requires the selective focusing of microwave energy on the targeted region while minimally affecting the healthy tissue. Emerging from the simple nature of the linear antenna arrays, this work demonstrates focusing maps as an application guide for MH focusing by adjusting the antenna phase values. The focusing of the heating potential (HP) on different density breast models is performed via the proposed method using Vivaldi antennas. The effect of the tumor conductivity on the focusing is discussed. As a straightforward approach and utilizing the Vivaldi antennas, the system can be further combined with MH monitoring application.

Microwave Breast Imaging Using Compressed Sensing Approach of Iteratively Corrected Delay Multiply and Sum Beamforming

Microwave imaging (MI) is a consistent health monitoring technique that can play a vital role in diagnosing anomalies in the breast. The reliability of biomedical imaging diagnosis is substantially dependent on the imaging algorithm. Widely used delay and sum (DAS)-based diagnosis algorithms suffer from some significant drawbacks. The delay multiply and sum (DMAS) is an improved method and has benefits over DAS in terms of greater contrast and better resolution. However, the main drawback of DMAS is its excessive computational complexity. This paper presents a compressed sensing (CS) approach of iteratively corrected DMAS (CS-ICDMAS) beamforming that reduces the channel calculation and computation time while maintaining image quality. The array setup for acquiring data comprised 16 Vivaldi antennas with a bandwidth of 2.70–11.20 GHz. The power of all the channels was calculated and low power channels were eliminated based on the compression factor. The algorithm involves data-independent techniques that eliminate multiple reflections. This can generate results similar to the uncompressed variants in a significantly lower time which is essential for real-time applications. This paper also investigates the experimental data that prove the enhanced performance of the algorithm.

INTERCONNECTION OF VIVALDI ANTENNAS IN THE MIMO ANTENNA ARRAY

Рассматривается MIMO антенная решетка, сформированная из двух антенн Вивальди, которые должны обеспечить работу в частотном диапазоне, выделенном для сетей пятого поколения - 24,25-24,65 ГГц. Для определения основных параметров антенны применялось моделирование, на основе которого были установлены основные характеристики MIMO антенной решетки: коэффициент корреляции огибающей, коэффициент усиления при разнесенном режиме, эффективность сложения. По результатам было определено, что при расстоянии между антеннами в 6,13 мм достигаются максимально возможные характеристики MIMO антенной решетки, а для стабильного функционирования достаточным является расстояние в 2,45 мм. В статье приводятся размеры исследуемой антенны, графики обратных потерь (S - параметров), диаграммы направленности, коэффициентов корреляции огибающих, коэффициента усиления при разнесенном режиме, эффективности сложения при различных расстояниях между антенными элементами. Обеспечение стабильности работы MIMO антенной решетки является важной задачей, так как все современные системы связи используют эту технологию для реализации многоканальной передачи, а следовательно, для повышения скорости передачи информации. Для определения геометрических характеристик и выполнения моделирования применялось специализированное программное обеспечение The article discusses a MIMO antenna array formed of two Vivaldi antennas, which should provide operation in the frequency range allocated for fifth generation networks - 24.25-24.65 GHz. To determine the main parameters of the antenna, we applied modeling, on the basis of which we determined the main characteristics of the MIMO antenna array: the envelope correlation coefficient, the diversity gain, the multiplexing efficiency. According to the results, we determined that with a distance between antennas of 6.13 mm, the maximum possible characteristics of a MIMO antenna array are achieved, and a distance of 2.45 mm is sufficient for stable operation. The article gives the dimensions of the antenna under study, graphs of return loss (S11 - parameters), radiation patterns, envelope correlation coefficient, diversity gain, multiplexing efficiency at different distances between the antenna elements. Ensuring the stability of the MIMO antenna array is an important task since all modern communication systems use this technology to implement multichannel transmission, and, consequently, to increase the information transfer rate. We used specialized software to determine geometric characteristics and perform modeling

Miniaturized Antipodal Vivaldi Antenna with Improved Bandwidth Using Exponential Strip Arms

In this paper, a miniaturized ultra-wideband antipodal tapered slot antenna with exponential strip arms is presented. Two exponential arms with designed equations are optimized to reduce the lower edge cut-off frequency of the impedance bandwidth from 1480 MHz to 720 MHz, resulting in antenna miniaturization by 51%. This approach also improves antenna bandwidth without compromising the radiation characteristics. The dimension of the proposed antenna structure including the feeding line and transition is 158 × 125 × 1 mm3. The results show that a peak gain more than 1 dBi is achieved all over the impedance bandwidth (0.72–17 GHz), which is an improvement to what have been reported for antipodal tapered slot and Vivaldi antennas with similar size.

Ultra-Wideband MIMO Array for Penetrating Lunar Regolith Structures on the Chang’e-5 Lander

The Chang’e-5 lunar exploration mission of China is equipped with a Lunar Regolith Penetrating Radar (LRPR) for measuring the thickness and structures of the lunar regolith in the landing area. Since the LRPR is stationary, an ultra-wideband multiple-input multiple-output (MIMO) array is designed as a replacement for conventional mobile subsurface probing systems. The MIMO array, with 12 antenna elements and a switch matrix, operates in the frequency band from 1.0 to 4.75 GHz. In this work, the design and layout of the antenna elements were optimized with respect to the lander. To this end, the antenna elements were designed as miniaturized Vivaldi antennas with quarter elliptical slots (i.e., quarter elliptical slotted antenna, or QESA). QESAs are significantly small while being able to mitigate the impact of the lander on antenna electrical performances. QESAs also have a wide operating bandwidth, flat gain, and excellent time domain characteristics. In addition, a high-temperature resistant ultra-light radome with high transmissivity is designed to protect the external antenna array. After calibration, the MIMO array is used to detect targets embedded in volcanic ash. The detection depth reaches 2.5 m, and the detection effect is good.