In this paper, a physics-informed deep neural network (PIDNN)-based approach with phase-only weighting is proposed for the synthesis of a cosecant-squared radiation pattern time-modulated linear array (TMLA). A deep neural network is trained using a physics-informed loss function to minimize deviation between the desired shaped beampattern and the actual one, thus eliminating the need for timeconsuming optimization techniques, such as evolutionary optimization algorithms. The sidelobe level (SLL) of the fundamental signal and the maximum sideband levels (SBLs) of the harmonic signals are simultaneously reduced by controlling both the phase and periodic switching time sequence of each element of the TMLA. The simulation results reveal that the proposed method achieved the desired patterns along with very low SLL and SBLs for 30- and 40-element TMLAs. For the 30-element TMLA, an SLL of −39.54 dB and a maximum SBL of −42.27 dB was achieved. For the 40-element TMLA, the obtained SLL and maximum SBL were −29.28 dB and −32.02 dB, respectively. Moreover, PIDNN demands considerably less computation time than evolutionary optimization algorithms—for a 30-element TMLA, the genetic algorithm took 47.13 minutes to complete the optimization process while PIDNN took only 2.87 minutes.

The immense threat posed by ballistic missiles has prompted many nations to develop ballistic missile defense systems. To operate these defense systems effectively, it is essential to quickly identify the missile type in flight and prioritize responses accordingly. Given that ballistic missiles follow a consistent elliptical trajectory, it is reasonable to employ inverse synthetic aperture radar (ISAR) for missile identification. However, due to minimal external differences between various types of ballistic missiles, conventional ISAR methods have limitations in distinguishing between them. This paper proposes a method that converts scattered wave data collected at different observation angles into range profiles to directly estimate scattering centers. The position data of these scattering centers are transformed into the frequency domain to generate ISAR images. Additionally, by merging traditional ISAR images with those incorporating scattering center positions, this method demonstrates the possibility of achieving enhanced ISAR image visibility.

In this study, an orbital-angular-momentum (OAM)-generating folded transmitarray antenna is proposed. The antenna is fed by dual probe ports that are excited to generate right-handed and left-handed circularly polarized (CP) vortex waves in the lower and higher frequency bands, respectively. This is principally conducted based on the linear polarization-to-circular polarization conversion of vortex waves, which primarily depends on phase and amplitude control of a transmitarray (TA) and a reflectarray (RA). The linearly polarized (LP) vortex waves are generated from the RA, while the conversion of LP-to-CP vortex waves with OAM mode l = -1 is achieved when the electromagnetic waves pass through the TA. The measured operating bandwidth (|<i>S</i><sub>11</sub>| < -10 dB and AR < 3 dB) of the proposed antenna was observed to be 9.1–9.3 GHz (4.4%) and 11.1–11.5 GHz (6.1%) for the lower and upper bands, respectively. The measured antenna peak gain reached up to 12.1 dBi and 15.3 dBi for the lower and upper bands, respectively. The antenna dimensions were maintained at 7.85λ<sub>0</sub> × 7.85λ<sub>0</sub> × 1.41λ<sub>0</sub>, where λ<sub>0</sub> represents the wavelength in free space at the center frequency of the lower band, while the profile-to-focal-length ratio was approximately 1/5.4, indicating a large decrease in profile.

In this study, a compact quad-band antenna inspired by metamaterials is proposed for WLAN, biomedical ISM (2.4 GHz and 5.8 GHz), and aeronautical and radio navigation applications. Specifically, a multiband metamaterial-inspired antenna with a hexagonal split-ring resonator is designed for multiband wearable applications. The proposed antenna is composed of a hexagonal split-ring resonator (SRR) and a complementary SRR, which generate four operating bands and two notch bands—one at 2.59 GHz to eliminate mobile terrestrial services and the other at 4.55 GHz to eliminate fixed mobile services. Furthermore, the wearable application is verified using a four-layer phantom model at different positions from the antenna, with the proposed antenna achieving a specific absorption rate lower than 0.4998 W/kg. Overall, the antenna is considered suitable for wearable applications owing to its broadcasting capabilities in the 2.4 GHz and 5.8 GHz biomedical bands, WLAN, and for radio-location applications, with notch bands at 2.59 GHz and 4.56 GHz helping reject the mobile communication spectrum.

In this paper, the clutter rejection threshold corresponding to the maximum Doppler frequency of mainlobe clutter in high pulse repetition frequency airborne radar with frequency modulation (FM) ranging is proposed. The clutter spreading due to range-Doppler coupling in FM ranging radar is analyzed, and based on that, four clutter rejection thresholds corresponding to the maximum sidelobe/mainlobe clutter frequencies without/with FM ranging are presented. In particular, the clutter rejection threshold for achieving mainlobe clutter-free condition with FM ranging is derived by analyzing the mainlobe clutter boundaries for various beam steering angles. The detection capability corresponding to each of the four thresholds is analyzed, and it is shown that the detection capability can be improve by applying the clutter rejection threshold proposed in this work.

Permanent magnet synchronous motors (PMSMs) have been extensively adopted in a range of industrial applications, particularly in the electric vehicle industry, due to their high power and torque density, high efficiency, reliability, and excellent dynamic performance. Between the types of PMSMs, a surface-mounted PMSM (SPMSM) is characterized by identical <i>d</i>- and <i>q</i>-inductances, due to which it only generates magnetic torque. However, SPMSMs also exhibit higher flux density, since the air gap in these motors is smaller and the permanent magnets are located very close to the stator teeth. In contrast, an interior PMSM (IPMSMs) features different <i>d</i>-axis and <i>q</i>-axis inductance components, due to which it can create not only magnetic torque but also reluctance torque. In this paper, two processes are conducted to examine these motors. First, an analytical technique is proposed to design the required parameters for an SPMSM and an IPMSM, where the dimensions of the latter are defined using the fractional-slot concentrated winding configuration, and those of the former are designed based on the approach of keeping the rotor volume, permanent magnet volume, pole–slot combination, and power supply unchanged. Subsequently, a finite element method is presented for computing, simulating, and comparing the electromagnetic parameters of both proposed motors, including their back electromotive force, torque ripple, efficiency, and power factor. Finally, the proposed methods are validated using a 7.5 kW practical motor.

This letter discusses antenna sensitivity enhancement in an LTE/GPS communication module for vehicle-to-everything applications by addressing onboard noise suppression. The performance of antennas in smart vehicles is increasingly complex due to the concentration of electronic devices within small structures, which impacts signal reception. Onboard noise generated by other unknown electronic components on the PCB can couple through the resonance structure of the other antenna, significantly degrading performance. The proposed solution includes an equivalent noise circuit and two double-branch planar inverted-F antennas targeting the B1 and B5 LTE bands and the L1 and L5 GPS bands. The noise circuit can couple with the GPS antenna’s feed loop and requires a noise suppression method to prevent sensitivity degradation. The analysis shows that this approach can increase total isotropic sensitivity from -81.79 dB to -94.61 dB, representing a significant enhancement in antenna sensitivity performance.

In this paper, a dual-band circularly polarized (CP) shared-aperture microstrip patch antenna with a high frequency ratio of 4.1 is presented for S-/X-band satellite communications. The unit cell of the designed antenna is composed of a single perforated S-band trimmed patch and four X-band trimmed patches configured in a 2 × 2 array. The S- and X-band patches are interlaced, thus sharing their apertures within the same layer, which enhances isolation between the two bands and prevents the degradation of CP characteristics. The antenna was designed and optimized for the S-band frequency range of 1.9–2.05 GHz and the X-band frequency range of 7.8–9 GHz. To verify feasibility, the performance of the proposed antenna was measured in a full anechoic chamber. The measured results showed good agreement with the simulated results. The -10 dB impedance bandwidths of the S- and X-band antennas were 7.8% and 13.5%, respectively, while their measured 3-dB axial ratio bandwidths were 2% and 3.9%, respectively. Furthermore, the unit cell antenna achieved left-handed circularly polarized peak gains of 5.7 dBic at 2.02 GHz and 11.6 dBic at 8.28 GHz.

This paper presents a wideband and high-gain 4 × 4 substrate integrated waveguide (SIW) cavity-backed patch array with a simplified feeding network for operation in the millimeter-wave (mmW) band. Furthermore, to improve gain and suppress the sidelobe level, a stepped waveguide horn is vertically integrated with each SIW cavity-backed patch. The proposed 4 × 4 array comprises eight series of 2 × 1 subarrays and a simplified 4-way power distribution network. In addition, two types of series-parallel 4 × 1 subarrays are examined to achieve a low sidelobe level. For verification, the proposed 4 × 4 antenna array was fabricated and measured, with the results showing good agreement with the simulations. The fabricated array prototype realized a -10 dB impedance bandwidth of 14.7% in the 24–27.8 GHz frequency band, with a peak gain of 22.05 dBi. Overall, based on its advantages—wide band, high gain, low cost, and compact feeding network—the proposed array can be considered a potential candidate for use in mmW wireless applications.

An analytical model is developed for coaxial coils with a hollow iron core and a magnetic shield. The problem is solved by an enhanced version of truncated region eigenfunction expansion (TREE). The eigenvalues and eigenfunctions of the complicated mixed regions are solved by the one-dimensional finite element method (FEM). The results are validated by comparisons with measurements and FEM simulation. Additional results reveal that this configuration enables a significant portion of iron core material to be saved while maintaining a high level of magnetic coupling between the coils.