Antenna Feed Research Articles

Studying a Method for Applying Phase Shift Using a Three‐Channel Phase Shifter at a Central Frequency of 10 GHz: Design, Simulation and Construction

ABSTRACTFeeding phased array antennas are crucial components of this type of antenna system. To change the angle of the beam in phased array antennas, the antenna arrays need to have a phase difference. A method for applying phase shifts in the power divider is presented, which can be integrated into a single antenna feed system structure. Using Substrate Integrated Waveguide (SIW) technology, which has been widely used in the manufacturing of microwave devices recently, makes it possible to design and manufacture all elements such as antennas, power dividers, filters, and phase shifters on a single substrate. This approach reduces manufacturing costs, size, and weight of microwave circuits; more importantly, it eliminates the losses associated with non‐coplanar connections and circuits. A three‐port phase shifter is proposed, illustrating how to control the phase difference between output ports. After designing, simulating, and optimizing the relevant parameters at a frequency of 10 GHz, the phase shifter was manufactured and measured on the Rogers RO4003 substrate. The measurement results matched well with the simulation results, and all findings are presented.

Hybrid phase-correction metasurfaces for accurate near-field manipulation

Although metasurface has attracted significant attention in recent years due to its ability to manipulate electromagnetic waves, discrepancies are often observed when comparing the designed and realized near-field performances. Among various contributing factors, one important issue is related to the fact that the elements arranged on a metasurface are typically designed under the assumption of normal incident excitation, whereas in practice they are actually excited at various oblique incidence angles depending on the element's relative position to the feed antenna. This introduces amplitude and phase errors in the reflection or transmission coefficients of the elements within the metasurface, thereby affecting its overall performance. In this paper, a hybrid phase-correction method is proposed to compensate for the effect of oblique incidence on metasurfaces. The actual oblique incidence angles are decomposed into elevation and azimuth directions: In the elevation direction, the element characteristics under oblique incidence replace those under normal incidence, while in the azimuth direction, element rotation is introduced to compensate for the local effects. Near-field focusing and holographic metasurfaces are designed to verify the proposed hybrid phase-correction method. Full-wave electromagnetic simulations show that the proposed metasurface has the advantage in sidelobe levels without significant costs in terms of the amount of element-level computations. Finally, the near-field focusing metasurfaces are fabricated, and the measured results further demonstrate the potential of the proposed design for accurate near-field manipulation.

An ultrawideband monopulse feed with slant polarization for tracking radar systems

An ultrawideband slant-polarized monopulse feed is designed and fabricated for microwave applications. The proposed configuration features four end-launched diagonal horns allowing for the production of sum and difference channels in two principal planes. The key advantage of this proposed monopulse antenna over traditional monopulse feeds is its ability to combine the benefits of ultrawideband performance with slant polarization while maintaining acceptable side lobe level. The design is validated by fabricating a prototype of the proposed feed antenna. Measurement results are in a reasonable agreement with the simulations. The measured ratio bandwidth is 2.5:1 from 8 to 18 GHz with a peak gain of 17.92 dBi. The null depth in the difference patterns is approximately − 32 dB. Given these characteristics, the proposed monopulse feed is a suitable choice for use in commercial tracking radar systems that require wide bandwidth and slant polarization, such as those found in satellite-based applications.

Joint Optimization of Antenna System Matching and Specific Absorption Rate Focusing in Microwave Hyperthermia Cancer Treatment

Objective: Microwave hyperthermia is a clinically proven cancer treatment used in combination with conventional therapies to enhance the overall treatment outcome. It consists in selectively increasing the temperature of tumor cells to 40–44 °C by means of electromagnetic fields that are externally generated and coupled to the patient body via antenna applicators. The primary goal is to shape the power deposition (specific absorption rate, SAR) with focusing on the tumor region, and minimizing the risk of hotspots in the surrounding healthy tissues. Methods: For non-superficial tumors, phased-array antennas are used to focus the energy on the tumor. Finding patient-specific optimal antenna feeding coefficients represents an essential step to ensure an effective and safe administration of the heating. In this article, we present a way to optimize the array power transfer effectiveness (impedance matching) that does not deteriorate the spatial power deposition performance. A global optimization approach is adopted, using a cost function properly tailored to incorporate the active reflection coefficients of the array and the Hotspot-to-Target SAR Quotient (HTQ)—the latter being the standard in hyperthermia applications. Results: The effectiveness of the technique is demonstrated in a scenario relevant to the treatment of tumors in the neck region. The results show that our method significantly improves antenna matching without compromising the HTQ, achieving values within the recommended limits. The performance of the proposed approach is also experimentally tested with full heating in a corresponding phantom. Conclusions: This study introduces an optimization approach that enhances phased-array antenna performance for hyperthermia treatments without affecting spatial power deposition.

Additively Manufactured Three-Dimensional Microstrip Balun for Wearable Applications

We present a three-dimensional, additively manufactured microstrip balun design for the balanced feeding of wearable antennas. Extensive research has been performed regarding wearable antennas, but the balun design is often ignored. The balun may be omitted, a commercial off-the-shelf balun may be used, or a bulky microstrip balun may be implemented; however, these options are either incorrect or add a significant size to the antenna that is not acceptable for wearable applications. We propose a three-dimensional, conformal microstrip balun enabled by additive manufacturing (AM) technology, and demonstrate its performance using the wearable High-Contrast Low-Loss Antenna (HCLA) as an example. First, the electromagnetic properties of potential substrate materials are characterized from 0.5 to 3 GHz. Exponential tapered baluns are designed, simulated, and tested in a back-to-back configuration to verify the measured material properties for the substrates. Then, the baluns are integrated with the HCLA using a conformal configuration. The measurement results from 0.5 to 3 GHz on the phantoms agree with the simulation for both the reflection coefficient and transmission loss. Importantly, the proposed balun allows the antenna to be used in wearable applications, where balun size would have previously hindered its implementation. The flexibility of the proposed design also allows for the integration with other antennas aside from the HCLA.

A Miniaturized Loaded Open-Boundary Quad-Ridge Horn with a Stable Phase Center for Interferometric Direction-Finding Systems.

In order to achieve high accuracy in interferometric direction-finding systems, antennas with a stable phase center in the working bandwidth are required. This article proposes a miniaturized loaded open-boundary quad-ridge horn (LOQRH) antenna with dimensions of 40 mm × 40 mm × 49 mm. First, to stabilize the phase center of the antenna, the design builds on the foundation of a quad-ridge horn antenna, where measures such as optimizing the ridge structure and introducing resistive loading were implemented to achieve size reduction. Second, electrically small-sized antennas are more susceptible to the effects of common-mode currents (CMCs), which can reduce the symmetry of the radiation pattern and the stability of the phase center. To avoid the generation of common-mode currents during operation, a self-balanced feed structure was introduced into the proposed antenna design. This structure establishes a balanced circuit and routes the feedline at the voltage null point, effectively suppressing the common-mode current. As a result, the miniaturization of the LOQRH antenna was achieved while ensuring the suppression of the common-mode current, thereby maintaining the stability of the antenna's electromagnetic performance. The measured results show that the miniaturized antenna has a small phase center change of less than 20.3 mm within 2-18 GHz, while the simulated phase center fluctuation is only 14.6 mm. In addition, when taking 18.5 mm in front of the antenna's feed point as the phase center, the phase fluctuation is less than 22.5° within the required beam width. Along with the desired stable phase center, the miniaturized design makes the proposed antenna suitable for interferometric direction-finding systems.

Ultra-wideband and high isolation using defected ground structure modified bowtie antenna array for through wall imaging applications

The design and analysis of an ultra-wideband with high isolation characteristics, utilizing a modified bowtie antenna and coplanar waveguide feeding technique is presented in this paper. Grooves are added to the ground plane's entire structure to reduce the capacitive coupling between the patch and the ground plane. The grooves in the ground plane enhance the impedance matching and radiation efficiency across the ultrawideband frequency range. Also, defected ground structures (DGS) are used to improve isolation between the two antennas. It is novel and different in that it uses defective ground structures (DGS) to provide high isolation (−<50dB) with a high gain of 6.5 dBi and a large impedance bandwidth (155%). Compared to other documented methods, the antenna's design step is very simple, the overall size is small, larger bandwidth (13.5 GHz) and achieves high isolation due to DGS.

Analysis and Improvement of Feed HPM Breakdown

Abstract Antenna feed, as a crucial component of High Power Microwave (HPM) systems, plays a vital role in facilitating the transmission of microwave from vacuum environment to atmospheric space. However, the feed HPM breakdown has become as a frequent fault phenomenon evidently affecting the HPM system stability and output. In this paper, the abnormal waveform during a feed of a HPM simulator test has been studied, it was found that there was severe electric field distortion around the dielectric window fixing screw in the simulation of the feed, much lager than the breakdown threshold. To address this issue, the nylon material screws were employed as replacements for metal screws. In addition, the novel flute in the surface of the dielectric window is designed. The single-shot and repeated tests demonstrated that the improvement were effective, as the fault phenomenon was completely eradicated.

A Ku-Band Compact Offset Cylindrical Reflector Antenna with High Gain for Low-Earth Orbit Sensing Applications.

The rise of CubeSats has unlocked opportunities for cutting-edge space missions with reduced costs and accelerated development timelines. CubeSats necessitate a high-gain antenna that can fit within a tightly confined space. This paper is primarily concerned with designing a compact Ku-band offset cylindrical reflector antenna for a CubeSat-based Earth Observation mission, with the goal of monitoring Arctic snow and sea ice. The development of a Ku-band offset cylindrical reflector, with a compact aperture of 110 × 149 mm2 (6.3λ × 8.5λ), is described alongside a patch array feed consisting of 2 × 8 elements. The patch array feed is designed using a lightweight Rogers substrate and is utilized to test the reflector. Adopting an offset configuration helped prevent gain loss due to feed blockage. Analyzing the reflector antenna, including the feed, thorough simulations and measurements indicates that achieving a gain of 25 dBi and an aperture efficiency of 52% at 17.2 GHz is attainable. The reflector's cylindrical shape and compact size facilitate the design of a simple mechanism for reflector deployment, enabling the antenna to be stored within 1U. The array feed and reflector antenna have been fabricated and tested, demonstrating good consistency between the simulation and measurement outcomes.

The Causal Nexus Between Different Feed Networks and Defected Ground Structures in Multi-Port MIMO Antennas.

Multiple input multiple output (MIMO) antennas have recently received attention for improving wireless communication data rates in rich scattering environments. Despite this, the challenge of isolation persists prominently in compact MIMO-based electronics. Various techniques have recently emerged to address the isolation issues, among which the defected ground structure (DGS) stands out as a cost-effective solution. Additionally, selecting the appropriate feed mechanism is crucial for enhancing the key performance indicators of MIMO antennas. However, there has been minimal focus on how different feed methods impact the operation of MIMO antennas integrated with DGS. This paper begins with a comprehensive review of diverse antenna design, feeding strategies, and DGS architectures. Subsequently, the causal relationships between various feed networks and DGSs has been established through modeling, simulation, fabrication, and measurement of MIMO antennas operating within the sub-6 GHz spectrum. Particularly, dual elements of MIMO antennas grounded by a slotted complementary split ring resonator (SCSRR)-based DGS were excited using four standard feed methods: coaxial probe, microstrip line, proximity coupled, and aperture coupled feed. The influence of each feed network on the performance of MIMO antennas integrated with SCSRR-based DGSs has been thoroughly investigated and compared, leading to guidelines for feed network selection. The coaxial probe feed network provided improved isolation performance, ranging from 16.5 dB to 46 dB in experiments.The aperture and proximity-coupled feed network provided improvements in bandwidth of 38.7% and 15.6%, respectively. Furthermore, reasonable values for envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and mean effective gain (MEG) have been ascertained.

A 3D-printing metasurface-augmented half-circle Maxwell fisheye lens for millimetre-wave analogue beamforming

Abstract This article presents a 2D metasurface-augmented half-circle Maxwell fisheye lens (HMFL) designed to move its focal axis to a targeted direction with a maximum elevation angle of 45 degrees, suitable for switches and power division networks in the millimetre wave (mmWave) band. This metasurface-augmented beamformer enables consistent analogue performance across a bandwidth of 22 - 32 GHz. The proposed beamformer features a reflective metasurface consisting of 2x40 Phoenix unit cells and is integrated with a 10-dielectric zone HMFL in the diameter segment opposite the antenna source. A horn antenna feed is used for excitation in normal and oblique incidences of -15 and -30 degrees. The designed lens prototype was fabricated with 3D-printing technology and printed metasurfaces for several particular cases of focal displacement. The measurements of the proposed HMFL beamformer are presented, demonstrating a close correlation between simulated and experimental results.

Notes on Modified Planar Kelvin–Stuart Models: Simulations, Applications, Probabilistic Control on the Perturbations

In this paper, we propose a new modified planar Kelvin–Stuart model. We demonstrate some modules for investigating the dynamics of the proposed model. This will be included as an integral part of a planned, much more general Web-based application for scientific computing. Investigations in light of Melnikov’s approach are considered. Some simulations and applications are also presented. The proposed new modifications of planar Kelvin–Stuart models contain many free parameters (the coefficients gi,i=1,2,…,N), which makes them attractive for use in engineering applications such as the antenna feeder technique (a possible generating and simulating of antenna factors) and the theory of approximations (a possible good approximation of a given electrical stage). The probabilistic control of the perturbations is discussed.

Design of a High-Power Nanosecond Electromagnetic Pulse Radiation System for Verifying Spaceborne Detectors

The Spaceborne Global Lightning Location Network (SGLLN) serves the purpose of identifying transient lightning events occurring beneath the ionosphere, playing a significant role in detecting and warning of disaster weather events. To ensure the effective functioning of the wideband electromagnetic pulse detector, which is a crucial component of the SGLLN, it must be tested and verified with specific signals. However, the inherent randomness and unpredictability of lightning occurrences pose challenges to this requirement. Consequently, a high-power electromagnetic pulse radiation system with a 20 m aperture reflector is designed. This system is capable of emitting nanosecond electromagnetic pulse signals under pre-set spatial and temporal conditions, providing a controlled environment for assessing the detection capabilities of SGLLN. In the design phase, an exponentially TEM feed antenna has been designed firstly based on the principle of high-gain radiation. The feed antenna adopts a pulser-integrated design to mitigate insulation risks, and it is equipped with an asymmetric protective loading to reduce reflected energy by 85.7%. Moreover, an innovative assessment method for gain loss, based on the principle of Love’s equivalence, is proposed to quantify the impact of feed antenna on the radiation field. During the experimental phase, a specialized E-field sensor is used in the far-field experiment at a distance of 400 m. The measurements indicate that at this distance, the signal has a peak field strength of 2.2 kV/m, a rise time of 1.9 ns, and a pulse half-width of 2.5 ns. Additionally, the beamwidth in the time domain is less than 10°. At an altitude of 500 km, the spaceborne detector records a signal with a peak field strength of approximately 10 mV/m. Particularly, this signal transformed into a nonlinear frequency-modulated signal in the microsecond range across its frequency spectrum, which is consistent with the law of radio wave propagation in the ionosphere. This study offers a stable and robust radiation source for verifying spaceborne detectors and establishes an empirical foundation for investigating the impact of the ionosphere on signal propagation characteristics.

W‐band inline waveguide‐to‐coupled microstrip line transition using a compact differential antenna

AbstractHere, a transition technique for converting signals from rectangular waveguide to coupled microstrip lines (CML) is presented, which provides a solution for differential antenna array feeding of automotive radar. The key to the proposed transition structure is to connect the coupling patches together with a short‐bridge structure, thus forming a quasi‐loop structure. Through the short bridge, the radiation efficiency of the antenna is greatly enhanced, and the mode conversion from TE10 of rectangle waveguide to differential mode of coupled microstrip line is realized effectively under the extremely compact size. Finally, the designed transition structure is manufactured and measured. The experimental results show that the back‐to‐back insertion loss is lower than 0.65 dB and the return loss is higher than 16.8 dB in the W‐band (75–110 GHz), which is the best performance and the simplest design among the relevant transition transitions reported so far.

A Dual-polarized Reflectarray Antenna for High-speed Ka-band Satellite Communications

A small-sized reflectarray antenna array with compact production specifications is designed and fabricated for high-speed Ka-band communication systems. In the design phase, firstly, the reflection characteristics of unit cells used in the reflective surface are obtained by the full wave computational analysis tool, CST Microwave Studio. Secondly, an aperture efficiency analysis is carried out to determine the physical size of the reflectarray and the distances between the feeding antenna and the individual unit cells. Then, the entire reflectarray antenna is analyzed by array theory to obtain geometrical dimensions to be used in the fabrication phase. These results are verified by CST Microwave Studio and similar fabrication guidelines are obtained for both TE and TM polarizations. In the fabrication phase, the carefully tailored design parameters of the unit cells are used to build the antenna and measure important parameters such as radiation patterns, gain, cross polarization levels and S11 parameters, which agree with the results obtained in the design phase. The proposed reflectarray antenna makes it possible to support dual-polarized multi-beams in the range 18-20 GHz with stable gain behavior, which makes it possible to use it in high speed 5G satellite communication systems.

Design of a Feed Array Antenna to Obtain a Uniform Near-Field Distribution on a Virtual Surface Placed within a Specified Wavelength

This paper proposes a novel feed array antenna to achieve a uniform electric field distribution in the near-field region for feeding a large-aperture antenna. The feed antenna has a 4 × 4 rectangular array configuration to obtain uniform near-field distribution on a virtual target surface. Each element of the array consists of a Vivaldi radiator and parasitic rings, and these two components have different radiating modes. In particular, the near-field pattern of the parasitic rings can be varied by adjusting their radii. Thus, the required near-field distribution on the virtual target surface can be achieved by optimizing the radii of the parasitic rings. To further enhance the uniformity of the electric field, the input phase of each Vivaldi radiator is adjusted by applying different transmission line lengths to the Vivaldi radiators depending on their positions in the array. To verify the feasibility of the proposed antenna, the electric field distributions are measured in an electromagnetic anechoic chamber. The results demonstrate that the proposed feed array antenna can achieve uniform near-field distribution with an average of 1.7 dB and a deviation of 6.8 dB on the virtual target surface placed within half a wavelength from the antenna aperture.

Shrinking a gradient-index-lens antenna system with a spaceplate

The miniaturization of optical systems is an ongoing challenge across the electromagnetic spectrum. While the thickness of optical elements themselves can be reduced using advances in metamaterials, it is the voids between these elements—which are necessary parts of an optical system—that occupy most of the volume. Recently, a novel optical element coined a “spaceplate” has been proposed, which replaces a region of free space with a thinner optical element that emulates the free-space optical response function—thus having the potential to substantially shrink the volume of optical systems. While there have been a few proof-of-principle demonstrations of spaceplates, they have not yet been deployed in a real-world optical system. In this work, we use a bespoke-designed spaceplate to reduce the length of a gradient-index- (GRIN) lens microwave antenna. Our antenna is designed to operate at 23.5 GHz and the incorporation of a nonlocal metamaterial spaceplate enables the distance between the antenna feed and the GRIN lens to be reduced by almost a factor of 2. We find that the radiation patterns from a conventional and space-squeezed antenna are very similar, with a very low cross-polarization, and only a minor increase in the side-lobe levels when introducing the spaceplate. Our work represents a demonstration of a spaceplate integrated into a real-world optical system operating in microwave spectral region, highlighting the potential for this concept to reduce the physical size of systems in applications including imaging, spectroscopy, radar, and communications. Published by the American Physical Society 2024

WITHDRAWN: A Novel Wideband Circular Polarized Filtering Antenna based on Left Hand Metamaterial

Across a broad frequency range, this reconfigurable antenna can be used for 5G, multi-function radars and automobile applications. To obtain ultra-wideband (UWB), the monopole antenna patch is suitably etched, and a stub is inserted to the feed line. In the meantime, an electromagnetic band gap (EBG) and rectangle slots are added in the partial ground to expand its operational bandwidth, which ranges from 2.7GHz to 23GHz. Size shrinkage rises to 65% when step feed is used in conjunction with partial grinding. Loading left-hand metamaterial (LHM) behind the monopole patch and etching slots at the corners of the rectangular patch results in circular polarization and an increase in gain. By placing a filter across the feedline, the recommended antenna's frequency and bandwidth can be adjusted as needed, enabling bandwidth reconfiguration. The via loaded in the patch extends the axial ratio (AR) bandwidth from 5GHz to 21GHz.The recommended antenna's step feed has a vertical slit that improves impedance matching over a wide operating spectrum.

Streamlined Millimeter-Wave and Subterahertz Spherical Far-Field Measurement System Supporting Various Antenna Types and Feed Interfaces: Use cases of antenna measurement system

Streamlined Millimeter-Wave and Subterahertz Spherical Far-Field Measurement System Supporting Various Antenna Types and Feed Interfaces: Use cases of antenna measurement system

Instrument Design and In-Flight Performance of an Airborne Terahertz Ice Cloud Imager

The Airborne Terahertz Ice Cloud Imager (ATICI) is an airborne demonstration prototype of an ice cloud imager (ICI), which will be launched on the next generation of Fengyun satellites and plays an important role in heavy precipitation detection, typhoon, and medium-to-short-term meteorological/ocean forecasting. At present, it has 13 frequency channels covering 183–664 GHz, which are sensitive to scattering by cloud ice. This paper provides an overview of ATICI and proposes a receiving front-end design scheme using a planar mirror and a quasi-optical feed network which improves the main beam efficiency of each frequency band, with measured values better than 95.5%. It can detect factors such as ice particle size, ice water path, and ice water content in clouds by rotating the circular scanning of the antenna feed system. A high-sensitivity receiver system has been developed and tested for verification. The flight verification results show that the quasi-optical feed network subsystem works well and performs stably under vibration and temperature changes. The system sensitivity is better than 1.5 K, and the domestically produced high-frequency receiver has stable performance, which can meet the conditions of satellite applications. The ATICI performs well and meets expectations, verifying the feasibility of the Fengyun-5 ICI payload.