Search Results (50)

In this letter, a circularly polarized (CP) 4 × 4 array antenna generating a fan-beam radiation pattern is presented, along with its application as the primary pattern of an offset reflector antenna. A sequentially rotated feed network is incorporated into the proposed antenna, enabling a wide axial ratio (AR) bandwidth of 1.9 GHz centered at 8.2 GHz. The proposed array antenna generates about 27.5° and 14.5° of half-power beamwidth (HPBW) in $\varphi =0°$ and $\varphi =90°$ planes, respectively. The fabricated antenna shows good agreement with the simulated results in terms of impedance bandwidth, gain, and radiation characteristics. Furthermore, the offset reflector antenna fed by the proposed CP array is evaluated, resulting in a gain enhancement of approximately 17 dB and a fan-beam radiation characteristic with half-power beamwidths of 3.95° and 2.15°, with an axial ratio bandwidth of 1 GHz. Full article

To mitigate acoustic beam drift, which degrades the signal-to-noise ratio (SNR) and limits the measurement range in ultrasonic gas flowmeters (USFMs), we present a miniaturized transit-time USFM that integrates a single piezoelectric micromachined ultrasonic transducer (PMUT) with a non-axisymmetric conical cavity. This design increases acoustic transmission gain and produces anisotropic directivity across orthogonal radiation planes, thereby broadening acoustic coverage along the flow direction and reducing beam steering. With an optimized cavity angle combination of (50°, 70°), the system achieves a 7.4 dB transmission gain and a half-power beamwidth (HPBW) of 29.1°. Experimental validation demonstrates a sound pressure attenuation of only 0.72 dB at 18.74 m/s. Within the 0.06–12 m³/h flow range, the USFM exhibits indication errors of ±2% (<1 m³/h) and ±1.5% (≥1 m³/h), with repeatability below 0.5%. The performance meets the Class 1.5 accuracy standard specified in CJ/T 477-2015, offering an innovative solution for wide-range miniaturized gas flow measurement. Full article

To address the diverse requirements of satellite communication applications involving medium-/low-rate reliable links and high-rate high-capacity services, an integrated S/Ka dual-band dual-reflector antenna is proposed as an effective solution. Owing to the stringent spatial constraints of satellite platforms, the longer operating wavelengths in the S-band lead to oversized feed horns in the integrated antenna design, which induces severe secondary aperture blockage, thus degrading aperture efficiency and impeding practical mechanical layout implementation. To alleviate this critical drawback, the proposed antenna achieves multi-band aperture reuse by deploying an array with four miniaturized S-band radiating elements around a broadband Ka-band feed horn. A frequency-selective surface (FSS)-based sub-reflector is further designed to effectively enhance the effective aperture size for the S-band operation, while ensuring unobstructed electromagnetic propagation in the Ka-band, thus enabling simultaneous dual-band high-gain radiation. After comprehensive electromagnetic simulation and parametric optimization for the antenna feed and the FSS sub-reflector, experimental measurements verify that the S-band left-hand and right-hand circularly polarized (LHCP/RHCP) channels achieve more than 20.2 dBic gains with more than 6° half-power beamwidths (HPBWs), and the Ka-band channel yields gains exceeding 41.2 dBic, with HPBWs greater than 0.8°. Full article

This paper presents a compact wide bandwidth, wide beamwidth circularly polarized (CP) antenna for satellite communication (SatCom) mobile terminals. The radiator is based on a cavity-backed crossed dipole, while a commercial quadrature power-divider/phase-shifter IC replaces conventional quarter-wavelength phase-delay lines to suppress dispersion-induced phase errors and maintain stable CP performance over a broad frequency range. To broaden the beam, a tightly coupled arc-shaped parasitic strip encircles the tapered semicircular arms, and the cavity cross-section is reduced to enhance lateral radiation. In addition, the cavity sidewalls are electrically connected to the parasitic element to increase the effective electrical length, downshift the operating frequency, and enable miniaturization. A prototype was fabricated and measured. The measured impedance bandwidth (IMBW, |S11| < −10 dB) is 1.76–3.08 GHz, fully covered by the AR < 3 dB bandwidth. The peak gain remains above 2 dBic over 1.7–3.1 GHz, while the half-power beamwidth (HPBW) stays around 114–142° and the 3 dB axial-ratio beamwidth (ARBW, AR < 3 dB) is around 114–144° across the entire operating band. These results indicate that the proposed antenna is a promising candidate for integrated multi-band SatCom terminals requiring wide bandwidth operation and wide-angle coverage. Full article

The terahertz (THz) band offers ultra-wide bandwidth for next-generation high-speed wireless communication systems. However, achieving compact, high-gain, and beam-symmetric THz antennas remains challenging due to fabrication and propagation constraints. This paper presents a simulation-based design and optimization of a stacked substrate-integrated waveguide (SIW) pyramidal horn antenna achieving equal half-power beamwidths (HPBWs) in both E- and H-planes. The design employs vertically stacked SIW layers coupled through optimized slot apertures to ensure dominant TE₁₀ mode propagation with minimal reflection. Using full-wave electromagnetic simulations, the effects of layer number, dielectric loading, amplitude tapering, and phase distribution are systematically analyzed. The optimized five-layer configuration exhibits 10 dBi gain, 41° HPBW, and sidelobe levels around −3.2 dB at 210 GHz. This framework aims to develop high-performance, beam-symmetric THz SIW antennas compatible with standard LTCC/PCB technologies. Full article

Reflectarray antenna design traditionally depends on computationally intensive full-wave simulations and experimental measurements, which significantly increase design time and cost. To address these limitations, we propose PhaseNet, an end-to-end deep learning framework that leverages phase maps and radiation angles as inputs to predict reflectarray antenna gain values. PhaseNet integrates spatial features extracted by a convolutional neural network (CNN) backbone with an angle-embedding module, and employs a regression head to enable efficient forward prediction. After training, the model achieves near-real-time inference with a single forward pass, facilitating rapid exploration of high-dimensional design spaces and providing immediate design feedback. In addition, we introduce two novel evaluation metrics, Half-Power Beamwidth (HPBW) and Main-Lobe Root Mean Square Error (RMSE), which allow for a multidimensional evaluation of prediction performance across the full radiation pattern and within the critical main-lobe region. These metrics provide refined criteria for reflectarray antenna design optimization beyond conventional error measures. In particular, PhaseNet achieved the best performance compared to existing models on these newly proposed evaluation metrics, recording up to 0.45 lower HPBW RMSE than existing methods, thereby validating both the relevance of the metrics and the effectiveness of the model. To further enhance practicality, we present a rapid generation of diverse bit-encoded datasets, substantially reducing the time and cost associated with data acquisition. Overall, the proposed framework effectively reduces prediction errors in reflectarray antenna design. Full article

The misuse of drone technology poses significant risks to public and personal safety, emphasizing the need for accurate and efficient aerial target detection to prevent detection failures due to randomly distributed airborne targets and mitigate interference from undesired directions. Unlike conventional beam-synthesis techniques that often require either a large number of array elements or iterative numerical optimization, the proposed method analytically derives the excitation distribution by solving a newly formulated weighted-constraint problem, thereby fully accounting for mutual coupling between elements and ensuring both computational efficiency and design accuracy. In this communication, a 10 × 4 planar microstrip antenna array with a wide flat-top beam and low sidelobe is designed based on the extended method of maximum power transmission efficiency. The optimized distribution of excitations for the antenna array, which achieves a shaped beam with uniform gain over the desired angular range while suppressing sidelobe levels (SLLs) outside the shaped region, is derived by analytically solving a newly formulated weighted constraint problem. To reduce the number of antenna elements and enhance radiation characteristics, the inter-element spacings in the E-plane and H-plane are set to 0.55 λ₀ and 0.75 λ₀, where λ₀ is the free-space wavelength at 3.5 GHz. Measurement results indicate that the flat-top beam in the E-plane has a wide half-power beamwidth (HPBW) of 51.2° and a low SLL of −30.1 dB, while the beam in the H-plane has a narrow HPBW of 20.1° and a low SLL of −30.5 dB, thereby demonstrating its capability in aerial target detection and airborne tracking applications. Full article

This paper proposes wideband circularly polarized (CP) 1-D connected array antennas with slant slot feeders and gradient artificial dielectric layers (ADLs). The slant slot feeder introduces an identical electric field (E-field) along the x- and y-directions. Three slabs consisting of multiple ADLs are stacked above the slot feeder. Due to the different boundary conditions of a 1-D connected array in the $zx$- and $zy$-planes, the guided wave in the slabs exhibits different multipath lengths along the x- and y-directions, leading to a 90° phase difference between the $E_x$ and $E_y$ components. Moreover, the cascaded slabs are designed with gradient effective permittivities for a gradual impedance transition from the guided mode to the radiating mode, allowing for wideband matching and CP performance. To validate the proposed design approach, an 8 × 1 array was fabricated and measured. The antenna shows a 1.96:1 (10.1–20 GHz) impedance bandwidth (VSWR < 2) and a 1.46:1 (12–17.5 GHz) 3 dB axial ratio bandwidth in measurement. The array exhibits an average right-hand CP boresight gain of 12.39 dBic. Moreover, we produced a frequency-invariant beam pattern with an average half-power beamwidth (HPBW) of 24.77° and a standard deviation below 3.63° over 12–18 GHz for the target pattern, with a HPBW of 26°, demonstrating wideband electronic warfare performance using the proposed array. Full article

This paper presents a compact 24 GHz radar with a 4-transmit (4Tx) and 4-receive (4Rx) CMOS radar IC, integrated with a 4 × 4 Tx array and four 1 × 4 receive Rx array antennas, optimized for enhancing small drone detection. By employing the hybrid beamforming technique based on analog beamforming on the transmit side and independent four-channel digital reception, the proposed radar achieves high spatial resolution and robust target tracking. The proposed radar features an elevation scan range of ±45° with an azimuth fan-beam half-power beamwidth (HPBW) of 80° for a comprehensive detection field. Tests with a small drone measuring 20.3 × 15.9 × 7 cm³, positioned at various elevation angles of up to 45° and azimuth angles of up to ±60° at a distance of 4 m from the radar, verified its detection capability and highlighted the radar’s effectiveness in tracking small aerial targets. This architecture emphasizes the advantages of analog beamforming on Tx and multi-channel Rx, addressing the increasing demands for precise drone detection and monitoring in both civilian and defense domains. Full article

The design of a vane-type magnetron with a resonant frequency in the megahertz range is presented in this article. The initial dimensions are determined based on magnetron empirical formulas. CST Studio Suite was used to simulate a series of magnetron behaviors, including eigenmode analysis and particle-in-cell (PIC) simulations. The relationship between volume and frequency results in a significantly large magnetron size for MHz frequencies. Considering manufacturing convenience and cost factors, the magnetron was simplified from its initial design, and the operating frequencies were compared, revealing a difference of about 40 MHz. The simulated frequency was 193 MHz, and the magnetron field patterns were simulated using CST. In the simulation, a horn antenna-like structure was employed to reduce the magnetron’s half-power beamwidth (HPBW), narrowing it from 101 to 50°. The result of this study can be used for beam focusing. Full article

This article presents the design of a novel, compact, 4 × 2 planar-array antenna that provides quad-beam radiation in the broadside direction, and it enhances coverage and serviceability for millimeter-wave applications. The antenna utilizes a corporate (parallel) feed network to deliver equal power and phase to all elements. Non-uniform element spacing in the two orthogonal planes, exceeding 0.5${\lambda }_1$ (${\lambda }_1$ being the wavelength at 30 GHz), results in a quad-beam radiation pattern. Two beams are formed in the xz-plane and two in the yz-plane, oriented at angles of $\theta =\pm 54°$. However, this spacing leads to null radiation at the center and splits the radiation energy, reducing the overall gain. The measured half-power beamwidth (HPBW) is 30° in the xz-plane and 35° in the yz-plane, with X-polarization levels of −20.5 dB and −26 dB, respectively. The antenna achieves a bandwidth of 28.5–31.1 GHz and a peak gain of 10.6 dBi. Furthermore, increasing the aperture size enhances the gain and narrows the beamwidth by replicating the structure and tuning the feed network. These features make the proposed antenna suitable for 5G wireless communication systems. Full article

Millimeter-wave (mm-Wave) phased array systems need to meet the transmitter (Tx) equivalent isotropic radiated power (EIRP) requirement, and that depends mainly on the design of two key sub-components: (1) the antenna array and (2) the Tx power amplifier (PA) in the front-end-modules (FEMs). Simulations using an electromagnetic (EM) solver carried out in Cadence AWR with AXIEM suggest that for two uniform square patch antenna arrays at 24 GHz, the 4 element array has ~6 dB lower antenna gain and twice the half power beam width (HPBW) compared to the 16 element array. We also present measurements and post-layout parasitic-extracted (PEX) EM simulation data taken on two broadband mm-Wave PAs designed in our lab that cover the key portions of the fifth-generation (5G) FR2-band (i.e., 24.25–52.6 GHz) that lies between the super-high-frequency (SHF, i.e., 3–30 GHz) band and the extremely-high-frequency (EHF, i.e., 30–300 GHz) band: one designed in a 22 nm fully depleted silicon on insulator (FD-SOI) CMOS process, and the other in an advanced 40 nm Gallium Nitride (GaN) high-electron-mobility transistor (HEMT) process. The FD-SOI PA achieves saturated output power (P_OUT,SAT) of ~14 dBm and peak power-added efficiency (PAE) of ~20% with ~14 dB of gain and 3 dB bandwidth (BW) from ~19.1 to 46.5 GHz in measurement, while the GaN PA achieves measured P_OUT,SAT of ~24 dBm and peak PAE of ~20% with ~20 dB gain and 3 dB BW from ~19.9 to 35.2 GHz. The PAs’ measured data are in good agreement with the PEX EM simulated data, and 3rd Watt-level GaN PA design data are also presented, but with simulated PEX EM data only. Assuming each antenna element will be driven by one FEM and each phased array targets the same 65 dBm EIRP, millimeter wave (mm-Wave) antenna arrays using the Watt-level GaN PAs and FEMs are expected to achieve roughly 2× wider HPBW with 4× reduction in the array size compared with the arrays using Si FEMs, which shall alleviate the thorny mm-Wave line-of-sight (LOS)-blocking problems significantly. Full article

This paper presents a comprehensive survey of state-of-the-art UAV–based antennas and propagation measurements. Unmanned aerial vehicles (UAVs) have emerged as powerful tools for in situ electromagnetic field assessments due to their flexibility, cost-effectiveness, and ability to operate in challenging environments. This paper highlights various UAV applications, from testing large–scale antenna arrays, such as those used in the square kilometer array (SKA), to evaluating channel models for 5G/6G networks. Additionally, the review discusses technical challenges, such as positioning accuracy and antenna alignment, and it provides insights into the latest advancements in portable measurement systems and antenna designs tailored for UAV use. During the UAV–based antenna measurements, key contributors to the relatively small inaccuracies of around 0.5 to 1 dB are identified. In addition to factors such as GPS positioning errors and UAV vibrations, ground reflections can significantly contribute to inaccuracies, leading to variations in the measured radiation patterns of the antenna. By minimizing ground reflections during UAV–based antenna measurements, errors in key measured antenna parameters, such as HPBW, realized gain, and the front-to-back ratio, can be effectively mitigated. To understand the source of propagation losses in a UAV to ground link, simulations were conducted in CST. These simulations identified scattering effects caused by surrounding buildings. Additionally, by simulating a UAV with a horn antenna, potential sources of electromagnetic coupling between the antenna and the UAV body were detected. The survey concludes by identifying key areas for future research and emphasizing the potential of UAVs to revolutionize antenna and propagation measurement practices to avoid the inaccuracies of the antenna parameters measured by the UAV. Full article

In this paper, an artificial neural network (ANN) has been proposed to estimate the required values of the adjustable parameters of a Semi-Coprime array with staggered steering (SCASS), which was proposed recently. By adjusting the amount of staggering and the sidelobe attenuation (SLA) factor of Chebyshev weights, SCASS can promise a quite small half-power beamwidth (HPBW) and a high peak-to-side-lobe ratio (PLSR), even when the beam is steered away from broadside direction. However, HPBW and PSLR cannot be improved simultaneously. There is always a trade-off between the two performance metrics. Therefore, in this paper, a mechanism has been introduced to minimize HPBW for a desired PSLR. The proposed ANN takes the array of architectural parameters, the required steering angle, and the desired performance metric, i.e., PSLR, as input and suggests the values of the adjustable parameters, which can promise the minimum HPBW for the desired PSLR and steering angle. To train the ANN, we have developed a dataset in Matlab by calculating HPBW and PSLR from the beampattern generated for a large number of combinations of all the variable parameters. It has been shown in this work that the trained ANN can suggest the optimum values of the adjustable parameters that promise the minimum HPBW for the given steering angle, PSLR, and array architectural parameters. The trained ANN can suggest the required adjustable parameters for the desired performance with mean absolute error within just 0.83%. Full article

Angle estimation for low-altitude targets above the sea surface is a challenging problem due to multipath interference from surface reflection signals, and various approaches have been proposed. This paper proposes a matrix pencil method with multiple apertures. The matrix pencil method effectively responds to dynamic scenarios because it performs better when using a single snapshot than other methods. Also, employing multiple apertures is more economical than using one large aperture. Therefore, we propose a computationally efficient approach using this method and structures. The proposed two-stage MP method incrementally improves the resolution in two stages: in stage 1, we extract the denoised signals at each aperture level, and in stage 2, we further improve the resolution with those signals. In comparison with the angular resolution defined by the half-power beamwidth (HPBW) of a uniform linear array (ULA) antenna with an equivalent number of arrays, the proposed method demonstrated a superior resolution of less than 0.087 of the HPBW at a high signal-to-noise ratio (SNR) of 40 dB, and less than 0.31 of it even at a relatively low SNR of 15 dB, based on 90% of the resolving probability. For the multipath problem, the proposed scheme has the advantage of not requiring prior geometric information, and its performance is demonstrated through simulations to be better than the adaptive beamforming method and the composite monopulse method. Full article