In this communication, we introduce a novel design for mitigating the side-lobe level (SLL) of the half-mode substrate integrated waveguide (HMSIW)-based leaky-wave antenna (LWA). Applying a novel ...approach through modification of the side aperture of HMSIW, we achieved an SLL of −13.8 and −11.2 dB in the upper hemisphere and full space, respectively. The key novelty of this communication is the reduction of SLL in full space while the state-of-the-art antennas only mitigated the SLL in the upper hemisphere. Furthermore, tapering the open side aperture in a thin trapezoid shape led to a significant reduction of beam squint. The operating frequency band of the antenna matches the allocated 5G wireless network millimeter-wave bands from 26 to 30 GHz. The measured peak realized gain of the antenna is 10.6 dBi at 28.5 GHz. The length, width, and height of the HMSIW antenna are 70, 15, and 0.5 mm, respectively. The antenna was fabricated on a Rogers RT/Duroid 5880 substrate. Excellent agreement between the measurements and simulated results was observed. The discrepancies between the measured and simulated results were analyzed by a complete and thorough sensitivity analysis that included the effects of the fabrication tolerances, connectors' misalignment, and bending due to the mechanical stress. High gain, low SLL, and compactness are among the advantages of the proposed antenna making it a suitable candidate for the miniaturization of 5G communication systems.
3D printing has enabled materials, geometries and functional properties to be combined in unique ways otherwise unattainable via traditional manufacturing techniques, yet its adoption as a mainstream ...manufacturing platform for functional objects is hindered by the physical challenges in printing multiple materials. Vat polymerization offers a polymer chemistry-based approach to generating smart objects, in which phase separation is used to control the spatial positioning of materials and thus at once, achieve desirable morphological and functional properties of final 3D printed objects. This study demonstrates how the spatial distribution of different material phases can be modulated by controlling the kinetics of gelation, cross-linking density and material diffusivity through the judicious selection of photoresin components. A continuum of morphologies, ranging from functional coatings, gradients and composites are generated, enabling the fabrication of 3D piezoresistive sensors, 5G antennas and antimicrobial objects and thus illustrating a promising way forward in the integration of dissimilar materials in 3D printing of smart or functional parts.
Metamaterials are artificially engineered novel substances (or matter) that exhibit properties not found in nature. One of the earliest examples of a metamaterial structure is the split-ring ...resonator. This article is a current review of metamaterials, what it is, its classification, and its applications towards the field of antennas and radio frequency identification (RFID) devices. There are two major types of metamaterial antennas: leaky-wave antennas, and resonant antennas. Antennas can be made from composite right-left handed metamaterials, or antennas can be loaded with a metamaterial screen such as a shelled electrically small antenna (ESA) fed by coax. Metamaterial resonators can aid in reducing the antenna size, help improve the gain, improve the directivity, improve the return loss, and control the radiation pattern (by loading the antenna with a tunable unit). Recent advances in printing and fabricating technologies have allowed for use of metamaterial antennas in wearable gadgets and textiles; and can be used in conjunction with RFID devices and tags to advance and aid (emergency) equipment used by first responders.
A comprehensive survey of the reconfigurable leaky-wave antennas (LWAs) is made in this paper. Beam-steering and unique radiating features of LWA are highlighted particularly. Therefore, the ...radiation mechanism of different types of LWA, including uniform, quasi-uniform, periodic, and metamaterial LWAs are discussed in detail. The guiding structures for realizing LWAs, namely microstrip, waveguide, substrate integrated waveguide (SIW), and half-mode SIW (HMSIW) are investigated as well. Basic concepts of electronic beam-scanning LWAs are also introduced, and several state-of-the-art reconfigurable LWAs are studied thoroughly. The investigated reconfigurable LWAs are suitable for beam-scanning applications due to their compactness, ease of implementation, reasonably high gain, and relatively wide beam-scanning range, as will be demonstrated through this comprehensive review.
In this paper, a comprehensive review of portable microwave sensors for monitoring moisture content (MC) is presented. MC monitoring is crucial in different industries, particularly food and farming. ...Microwave-based approaches for measuring the MC of the grains and mineral materials are studied. These approaches are categorized into three groups: S-parameters, dielectric constant, and impedance measurements. While these methods are interrelated, they have differences. The investigated methods use different microwave antenna sensors for MC monitoring, such as coaxial probes, horn antennas, loop antennas, microstrip patch antennas, and frequency selective surface (FSS) antenna. State-of-the-art microwave sensors were investigated thoroughly to clarify the current challenges and possible solutions of MC monitoring. A comparison between the investigated sensors was made to determine their advantages and disadvantages. According to the comparison, sensors operating above 10 GHz suffer from cross-interference. Moreover, microstrip patches can monitor a wide MC range as extensive as 60%. At the same time, the FSS sensor has the highest sensitivity with an error as low as 0.023% at X-band. Microstrip patch and FSS antennas can be printed directly on a flexible, low-loss, and lightweight material to monitor the grain MC. The flexibility, compactness, portability, ease of environment-friendly fabrication, and high sensitivity are among the criteria determining the most suitable microwave sensors for industrial and consumer MC monitoring applications.
This paper underscores the paramount significance of through-wall communications by providing a comprehensive exploration of pivotal aspects like wall characterization, relevant technologies, ...versatile applications, and future prospects. Through-wall communication has the potential of being adopted in diverse fields, from indoor wireless communications, ground penetrating radar, through-wall radar imaging, to even power transmission. To augment the efficiency and reliability of signal detection, a whole variety of tools, such as antenna elements, frequency-selective structures, metasurfaces, and lenses, are exploited. By surveying the landscape of relevant technologies and applications in the existing literature, this paper serves as a beacon for researchers and engineers alike. Furthermore, it extends an invitation for pioneering exploration in this field, advocating the examination of tunable and adaptive systems, as well as the untapped potential of 3D printing in reshaping the future of through-wall communications.
A new reconfigurable slotted antenna is presented in this manuscript. The proposed antenna is realized on a half-mode substrate integrated waveguide (HMSIW). The beam-steering is achieved using ...embedded varactor diodes in circular cells. Sweeping the bias voltage causes variations of the phase constant, which leads to the fixed frequency beam-scanning. Each reconfigurable cell includes a circular slot at the top plate and varactor switch, DC block, and RF block at the backside of the structure. The operating frequency is chosen as 28.5 GHz in the support of the upcoming 5G mm-wave communications systems. The proposed antenna beam scans 29° of space by switching among different states at 28.5 GHz. The length, width, and height of the antenna are 67 mm, 48 mm, and 0.32 mm, respectively. The proposed antenna's main novelties are compactness and electronic beam-scanning capability using a single switch per cell. The measured peak realized gain and sidelobe level (SLL) at 28.5 GHz are 8.2 ± 0.6 dBi and 5 dB, respectively. While the impedance bandwidth of the proposed antenna is 1.5 GHz. A good agreement between measured and simulated results is observed. The discrepancies are investigated through a sensitivity analysis. Fixed frequency beam-scanning capability, compactness, simplicity of the assembly, backward radiation, and slight gain variation of the proposed antenna make it a suitable candidate for blind-spot monitoring and 5G vehicle to everything (V2X) communications.
A novel method for confining the undesired radiation of the feed transition of a low‐profile leaky‐wave antenna (LWA) is demonstrated in this paper. The proposed design method uses novel tapered CPW ...transitions resulting in variation of the parasitic capacitance and electrical length of the feed. This leads to the reduction of the side‐lobe level (SLL), which is dictated by the feed and the slotted sections of the antenna. The undesired radiation from the feed becomes crucial in the low‐profile antenna in which the surface‐mounted connector along feed transition is the only practical feeding mechanism. The key novelty of the proposed approach is the reduction of SLL by exclusively modifying the feed structure rather than the slotted radiation section. To validate the proposed approach, a modified compact feeding mechanism for LWA is designed. The antenna is realized based on the substrate integrated waveguide (SIW). The antenna's length, width, and height are 110 mm, 31 mm, and 0.5 mm, respectively. The operating frequency band was chosen as 26 to 30 GHz, covering an allocated 5G band. The measured peak realized gain and SLL are 6.1 dBi and − 11.4 dB, respectively. An improvement of 5.7 dB in SLL compared to the conventional LWA was observed. The simple fabrication process and efficiency of the proposed method make it a viable approach for reducing the SLL of the low‐profile antennas. Compactness, low SLL, and proper gain of the reported antenna make it a suitable candidate for 5G vehicle to everything (V2X) communications and mm‐wave navigation systems.
This brief demonstrates the performance of the first active bandpass filter to implement an active inductor in gallium nitride (GaN) technology. Fabrication of the filter and inductor was done using ...a 0.5 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> pHEMT GaN process with the system implemented on one 2 mm by 2 mm die. The tuning range of the active filter was measured to be 749 MHz at a centre frequency of 3.39 GHz with separate amplitude and quality factor tuning. An amplitude range for S 21 was measured to be from −12.2 dB to 13.7 dB within the operating frequency range. Taking advantage of the active inductor's negative impedance the filter was able to produce a quality factor of 138. On-chip, the active inductor occupies an area of 350 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> by 175 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> compared to approximately 350 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> by 350 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> for their passive counterparts of similar inductance (a 50% decrease in size). The filter was designed for LTE/WLAN applications to demonstrate the capabilities of the active inductor.
An approach for improving the gain of the leaky-wave antenna (LWA) is presented in this paper. Embedding cavities in the structure leads to gain improvement. To validate the proposed method, it was ...implemented on a half-mode substrate integrated waveguide (HMSIW) LWA. The proposed HMSIW LWA was realized on a low temperature co-fired ceramic (LTCC) structure to achieve a compact structure. The key novelty of the proposed antenna is the gain improvement by using embedded cavities without increasing the antenna size. Applying the novel design method results in a measured peak realized gain of 7.6 dBi. Tapering the aperture leads to about 6 dB reduction of sidelobe level (SLL) in the upper hemisphere as well. The impedance matching frequency bandwidth of the antenna ranges from 28.3 to 29 GHz that falls within the 5G mm-wave frequency bands. The length, width, and thickness of the antenna are 40 mm, 16 mm, and 1 mm, respectively. The compactness, medium gain, and low loss of the proposed antenna make it a suitable candidate for 5G wireless devices. A good agreement between the measured and simulated results is observed.
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