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Antenna Elements, Arrays, and Systems for Through-the-Wall Radar Imaging
Published in Moeness G. Amin, Through-the-Wall Radar Imaging, 2017
A UWB antenna must cover multiple-octave bandwidths in order to transmit pulses that are approximately a few hundred picoseconds in duration with minimal distortion. Vivaldi antennas [43–45], in particular, are excellent candidates for various UWB applications, especially TWRI [46]. The Vivaldi antenna is a useful configuration due to its simplicity, wide bandwidth, and end-fire radiation pattern with low side-lobe levels and high gain at microwave frequencies. Moreover, the antenna has an almost constant gain with frequency, given that at different frequencies different parts of the Vivaldi antenna radiate. This keeps the size of the radiating part constant in wavelength and theoretically provides a constant beamwidth over its operating frequency range.
Homogeneous Metamaterials: Super Crystals
Published in Tie Jun Cui, Wen Xuan Tang, Xin Mi Yang, Zhong Lei Mei, Wei Xiang Jiang, Metamaterials, 2017
Tie Jun Cui, Wen Xuan Tang, Xin Mi Yang, Zhong Lei Mei, Wei Xiang Jiang
A high-directivity Vivaldi antenna was developed in Reference 67, by combining the features of AZIM and traditional Vivaldi antenna together. Vivaldi antenna is a type of planar microstrip antenna with exponentially tapered slot. It works in a broad frequency band but suffers from low directivity since it radiates cylindrical-like waves. According to the principle introduced in Section 4.4.2, when proper AZIM is incorporated in the exit area of the tapered slot, the resulting modified Vivaldi antenna will generate plane-like waves instead of cylindrical-like waves. Hence, a significant enhancement of directivity can be obtained with AZIM loading.
Design and Developments of UWB Antennas
Published in Chinmoy Saha, Jawad Y. Siddiqui, Yahia M.M. Antar, Multifunctional Ultrawideband Antennas, 2019
Chinmoy Saha, Jawad Y. Siddiqui, Yahia M.M. Antar
The Vivaldi antenna has a modestly wide beamwidth which is approximately the same in both the E- and H-planes, that is, the antenna can produce a symmetrical pattern though it has a planar structure. The gain of the antenna is proportional to its length as is the case with most traveling wave antennas. The aperture size of the antenna in wavelengths increases with frequency, so the gain also increases with frequency.
Wideband Vivaldi Antenna for Reduced Radar Cross Section in Stealth Applications
Published in IETE Journal of Research, 2022
The radar technology development has vital role in various fields such as geology, aviation, medicine, and civil engineering. Military applications require the design of targets that exhibits low RCS values so that the devices/equipment is untraceable and undetectable by the enemy radar signals. For such stealth applications, high radiation performance in terms of gain, side-lobe level, size and thickness should also be considered along with the RCS measurements. For radar and stealth applications, Vivaldi antenna is the preferred option because it has high gain, wide bandwidth, directional radiation pattern, and low profile. Directional ultra-wide band antenna is used in various fields such as biomedical detection, radar communication, and pulse communication. Although the performance of high-profile antennas such as circular polarized dielectric resonator antenna, horn antenna, and omni directional square patch antennas are impressive, due to the complexity of the numerical solver model, the stealth design is complicated [1].
Improved radiation characteristics of compact antipodal Vivaldi antenna with the hybrid technique for UWB applications
Published in Electromagnetics, 2021
Vivaldi antenna (one type of tapered slot antenna) is well-known for its broadband, moderate gain, planar structure, and end-fire radiation. These characteristics allow it to be considered an excellent candidate for UWB application. Even so, there are still some challenging problems on the conventional Vivaldi antenna with UWB including low gain at both ends of the bandwidth, instable radiation pattern, and main beam tilt, restrict its application.
A compact antipodal vivaldi antenna for modern surveillance systems
Published in International Journal of Electronics Letters, 2023
Harikrishna Paik, Kambham Premchand
Over the past few decades, the world has experienced significant developments in modern radar systems and electronic navigation techniques for surveillance, and tracking of aircraft, warships, and enemy missiles (Sonnenberg, 2013). As known, radio frequency signals are transmitted to the targeted object, and the echoes returned from the target are analysed to determine complete information about the target. For this, ultra-wideband and high gain antennas operating at relatively high frequencies are employed to achieve the desired range resolution, shape, and size of the target (Mao et al., 2009). Among several antennas, the Vivaldi antennas and their variants are most often used due to their ultra-wideband performance and directional and stable radiation characteristics (Abdulmjeed et al., 2021; K. Zhang et al., 2022). These antennas have gained significant popularity in applications such as military, cellular and mobile communication (Zhu et al., 2018), satellite communication systems (Hanbay & Aydemir, 2019), and medical imaging (Lu et al., 2019). The primary limitation of a conventional Vivaldi antenna is its flat flare, which increases the sidelobe level (SLL) and degrades the antenna’s directivity. The antipodal Vivaldi antenna (AVA), one of the three varieties of the Vivaldi antenna, is a wideband antenna, which provides high gain, and stable radiation patterns. This antenna has been widely used due to its simple geometry, lesser design complexity, and lightweight in comparison to the balanced AVA (BAVA) (Natarajan et al., 2015; Ravichandran et al., 2019). However, several challenges concerning AVA characteristics, including cross-polarisation, SLL, front-to-back ratio, and limitations on operating at lower frequencies have drawn attention among the researchers. In recent years, several approaches have been employed to improve the overall performance of the conventional AVA, such as using metamaterials (Li et al., 2017), corrugated structures at the flare edges (Thaiwirot et al., 2022) and dielectric lenses (Moosazadeh & Kharkovsky, 2015). These techniques result in a large-dimensional antenna, making the design more complex. Additionally, the tapered slot edge antenna (Fei et al., 2011), elliptically shaped strip conductors (Y. Zhang et al., 2016), rectangular slot edge, and structural modifications (Oliveira et al., 2015) have also been used to reduce the SLL and improve antenna directivity. Typically, the edge slots on the radiating flares decrease the surface current, which reduces the SLL and increases the antenna directivity. Although balanced antipodal Vivaldi antennas have been used to minimise cross-polarisation, no significant reduction in SLL has yet been achieved. Therefore, instead of using a balanced type Vivaldi antenna, an antipodal Vivaldi antenna is preferred to achieve high directivity, stable radiation patterns, and low SLL. Additionally, the antipodal Vivaldi antenna offers the advantage of reduced design complexity and lower manufacturing cost.