This letter presents a novel wideband circularly polarized antenna design based on tightly coupling effect. The antenna consists of four tightly coupled dipoles, radiating parasitic structures, four tapered baluns, and a broadband feeding network. This design achieves broadband performance and a compact structure by employing tightly spaced dipoles for capacitive bandwidth enhancement, coupling patches for low-frequency extension. Additionally, the implemented parasitic radiating layer significantly improves high-frequency radiation pattern characteristics. The proposed design finally achieves a 10 dB return loss bandwidth of 105.6% (1.84 GHz to 5.96 GHz) and a 3 dB axial ratio bandwidth of 97% (1.89 GHz to 5.45 GHz). The design exhibits a 3 dB gain bandwidth of 76.6% (2.15 GHz to 4.82 GHz) with a peak gain of 11.8 dBic. The overall dimensions of the antenna array are only 0.85${\bm{\lambda}}_L$ x 0.85${\bm{\lambda}}_L$ x 0.12${\bm{\lambda}}_L$ (where lambda(L) represents the wavelength in free space at the lowest operating frequency). Acceptable agreement is observed between simulated and measured results.

This paper presents a novel characteristic modebased self-decoupling filter circularly polarized (CP) antenna array for multi-input multi-output (MIMO) systems. The design uses a double-layer substrate with orthogonal eigenmodes for CP radiation. Opposite induced currents on adjacent patches enable self-decoupling without additional structures. U-shaped slots etched in the patches provide a filtering response. Measured results show an overlapped bandwidth of 3.42~3.52 GHz(S11/S22<-10 dB, axial ratio <3 dB), peak isolation of 40 dB, and a low correlation coefficient of 0.002.

This paper presents a low-complexity, wideband unit cell design suitable for reconfigurable reflectarrays (RRAs). To overcome the challenges of high implementation complexity associated with high-bit quantization, and the performance degradation resulting from one-bit quantization, a 1.5-bit phase quantization approach is proposed. The developed unit cell can operate in multiple modes to realize reflection phase delay, resonance tuning, and true-time delay, controlled by two PIN diodes. By switching the states of these diodes, the unit cell provides four reflection states. Wideband operation is achieved by selecting appropriate states across the frequency range to ensure continuous phase coverage. To validate the proposed concept, a unit cell was designed and simulated. The simulation results demonstrate stable three-phase responses with low reflection amplitude variation under different incidence angles across the 13.4-19.2 GHz frequency band.

To address the degradation in radiation performance caused by external deformations in variable-curvature cylindrical conformal antenna arrays, this letter proposes a real-time beam pattern synthesis method based on a multi-branch neural network. Using a cylindrical flexible array with a curvature radius ranging from 100 mm to 300 mm as an example, a five-branch neural network framework is constructed to enable both low-sidelobe and adaptive null beam synthesis. The average inference times of the two neural networks are 2.42 ms and 2.51 ms, respectively, which ensures real-time performance. The effectiveness of the proposed method is validated through full-wave simulations and experimental measurements.

A quadrature-spoof surface plasmon polariton (SSPP) unit cell (QS-UC) is proposed and theoretically characterized for circularly polarized (CP) wave generation. The proposed QS-UC is composed of a fishbone SSPP waveguide (FSW) and a spine quadrature mode converter (SQMC), which converts the SSPP mode into a quadrature radiating mode. An equivalent circuit is established to derive the cascaded ABCD matrix and the conditions for quadrature CP generation. Scattering parameters and dispersion characteristics are extracted from the established circuit model. The generated CP far-field wave is calculated through the quadrature-mode current distribution on the SQMC. The theoretically calculated results are also compared to the EM-simulated results, with good agreement. Based on the proposed QS-UC, a quadrature SSPP linear array (QS-LA) is developed, fabricated, and measured for the verification of CP generation. Detailed measured results show that the developed QS-LA has a wide impedance bandwidth of 5.28-11 GHz (70.3%). More importantly, the developed QS-LA shows a wide CP bandwidth covering 5.8-10 GHz (53.2%), with CP beams covering (-65 degrees, 16 degrees) for right-hand CP(RHCP) generation at port 1 and symmetrical range of (-16 degrees, 65 degrees) in left-hand CP(LHCP) generation at port two. These excellent performances verify the effectiveness of the proposed QS-UC in CP generation.

A novel method for designing a quasiconformal antenna with wideband and wide-angle low-scattering properties based on unit equivalent reactance regulation (UERR) and arrangement optimization is proposed. By establishing the ideal equivalent reactance boundary (IERB) for scattering cancellation, a pair of antenna units with similar radiation performance and stable wideband scattering cancellation over 5.48-11.91 GHz is designed based on UERR. In addition, a spatial scattering field optimization algorithm (SSFOA) is introduced to optimize the unit arrangement, effectively homogenizing the scattered energy distribution. Both the simulated and measured results validate that the proposed quasiconformal array achieves a wideband monostatic RCS reduction (RCSR) of 5-12 GHz, with an average reduction exceeding 9 dB, while maintaining an operational radiation bandwidth of 10-11.75 GHz and wide-angle beam coverage of +/- 60 degrees in the quasi-conformal plane. Compared with existing designs, the proposed array significantly improves both the monostatic RCSR bandwidth and bistatic scattering performance.

A closely arranged self-decoupled antenna pair with dual-ports filtering properties for fifth-generation (5G) mobile terminal is proposed in this communication. The antenna pair can achieve coupling suppression in multifrequency bands. To address coupling at the operating band, a high-isolation antenna pair is designed by exciting two orthogonal modes of the loop antenna. To reduce coupling in adjacent frequency band, the two ports of the antenna pair are designed with filtering properties. First, based on the cross-coupling mechanism, electromagnetic coupling branches are introduced to generate out-of-phase radiation paths in adjacent frequency bands, resulting in radiation nulls for port 1. Next, the nonradiative mode and lumped elements are designed to obtain the radiation nulls of port 2. Due to the shared-radiator and partial structure reutilization, the dual-ports filtering antenna pair exhibits a compact configuration. Based on the proposed filtering antenna pair, an 8x8 multiple-input-multiple-output (MIMO) array is developed, which operates in the 3.3-3.8 GHz, with isolation better than 16.9 dB and an envelope correlation coefficient (ECC) lower than 0.05. In addition, the MIMO array features the advantages of zero ground clearance and full-port filtering properties.

This paper presents a frequency-reconfigurable microstrip conformal antenna designed by adjusting the resonant dimensions of the radiating structure. By loading a metallic patch between two PIN diode switches, the radiating slot can be switched between an I-shape and an L-shape, enabling frequency reconfigurability. This specific configuration of the loaded patch and diodes also facilitates the integration of DC bias circuits. The antenna operates in two distinct states with center frequencies of 2.45 GHz and 2.05 GHz. The fractional bandwidths for these states are 17.9% and 14.6%, respectively, with a radiation efficiency exceeding 95% across both operating bands.

This randomized controlled trial evaluates an innovative interdisciplinary teaching model co-led by radiologists and vascular surgeons within China's standardized residency training program. Forty trainees were randomized into two groups: one receiving collaborative teaching, which included joint lectures, radiologist-attended ward rounds, and interdisciplinary case conferences; and the other undergoing traditional vascular single-discipline training. The experimental group exhibited superior performance in CT interpretation accuracy (92.0% vs. 71.0%, P < 0.01), diagnostic accuracy (87.0% vs. 67.0%, P < 0.01), treatment plan rationality (mean 4.40 ± 0.75 vs. 3.65 ± 0.88, P < 0.01), and communication skills (median 43.00 vs. 33.00, P < 0.0001). These findings validate that structured interdisciplinary collaboration effectively bridges the gap between radiology and clinical practice, suggesting a paradigm shift in vascular surgical education.

As an indispensable supplement to the terrestrial Internet of Vehicles (IoV), satellites provide a promising alternative for broad IoV coverage. To improve the broadband connection in satellite IoV service, this paper presents a novel broadband 2-bit circularly polarized (CP) reflectarray (RA). By analyzing the phasing characteristic of dual-loop unit cell, a -180 degrees phase difference is achieved through a novel method of arranging resonances of the single loop and dual-loop. Owing to the wider phasing bandwidth of the dual-loop unit cell, -90 degrees and -270 degrees phase delays are obtained by changing the parameters of the dual-loop unit cell. The phase bandwidth of 70.5 degrees <=|phi|<= 109.5 degrees is first-time introduced to characterize the AR bandwidth for the developed 2-bit unit cells. Therefore, compared to the traditional method focusing solely on the scaled size for reflective phase response, broadband AR and gain performances are obtained. Finally, as a performance demonstration, a planar RA composed of the developed 2-bit unit cells was fabricated and measured. Measured results confirm that broad 3dB gain bandwidth of 32% and 3dB AR bandwidth of 53% are achieved with high gain radiation, which show a good candidate for low-cost broadband and wide area coverage for satellite IoV service.

In this letter, a multifunctional broadband array with integration of radiation and scattering reconfiguration is proposed. First, the switching method of the array radiation and scattering field is analyzed theoretically. It follows that the radiation and scattering functions share the same array structure with low structure mode scattering field, and the switchable impedance feed network design for the antenna mode scattering reconfiguration. With the different p-i-n diode switching and using the approximate open and short impedance of the feed network, the antenna enables reconfiguration between radiation and 1-bit reconfigurable scattering states. As a result, the array maximizes the use of received energy to achieve a large dynamic range monostatic radar cross section (RCS) reconfiguration, and achieves the multifunctional of radiation and scattering within the broadband. Simulation results show that the antenna RCS reconfiguration bandwidth is 4.65 GHz to 6.35 GHz with the 10 dB reconfigurable value, the maximum reconfigurable value is 26.5 dB, and radiation performance is maintained in 5.25 GHz to 6.4 GHz. It is adapted to the demand for multifunction and scattering modulation in Internet of Things (IoT) applications. The measured results show good agreement with the simulated results.

This paper proposes a novel method for enhancing the half-power beamwidth (HPBW) of an end-fire circularly polarized (CP) terminal antenna, whereby the end-fire CP antenna is designed for 6 G satellite communication. First, the CP property is realized by allocating the resonances of both In-phase mode (IM) and out-of-phase mode (OM) based on the theory of characteristic mode (TCM). The HPBW of OM and IM is enhanced by layering the radiator, which introduces interlayer currents for OM and substrate thickness for IM. Besides, by using the stepped ground edge to regulate field distribution in the radiator, the HPBW is further broadened. The proposed wide HPBW CP antenna is manufactured and measured to validate the novel design concept. The measured results show that -6 dB impedance bandwidth is 2.45 similar to 2.56 GHz, and 3 dB axial ratio (AR) bandwidth is 2.48 similar to 2.50 GHz. The measured HPBW in the xoy and yoz planes are 76 degrees and 94 degrees, respectively. The high normalized comprehensive coefficient (NCC), considering AR bandwidth, Gain, HPBW, and antenna size, proves that the proposed antenna is especially suitable for 6 G terminal satellite communication.

This article presents a novel ultrawideband wide-angle scanning dual-polarized conformal array antenna using the modular concave-down dipole (CDD). The CDD reduces the complexity of the traditional tightly coupled dipole arrays (TCDAs) while maintaining the ultrawideband performance. The shunt capacitance generated by the concave-down structure reduces the active input impedance, which eliminates the need for a complex impedance-matching network and enables direct feeding through a coaxial cable. The mechanisms of generating loop-mode resonance and common-mode resonance in the dual-polarized CDD array are analyzed. A modified tapered coaxial cable loaded with a low-loss ferrite block is proposed to suppress these resonances and achieve wideband operation of the antenna. The profile of the antenna is 0.067 lambda(low) ( lambda(low) is the wavelength at the lowest operating frequency). Leveraging the inherent discontinuity between CDD elements and the compact feed structure, the array is designed in a modular form. Applying the modular approach, a 9x9 dual-polarized CDD array is developed and it is conformally mounted on a cylindrical surface with a radius of 80 mm ( 0.24 lambda(low) ). The proposed antenna is capable of beam scanning of +/- 90 degrees in the conformal plane and +/- 60 degrees in the nonconformal plane within the frequency band of 0.9-5.0 GHz (5.6:1). Besides promising radiation performance, the proposed design uses the modular approach and provides a flexible solution for different platforms including curved platforms.

In this paper we propose a miniaturized large-angle beam scanning phased array antenna using liquid crystal. We innovatively combine the liquid crystal electrically tunable structure with the wide-beam antenna element structure and design an integrated multi-layer antenna structure which realizes large-angle beam scanning within the working bandwidth. The problems of low beam control accuracy and narrow scanning angle of traditional array antenna are effectively addressed. The overall dimensions of the prototype are 74 & times;60 & times;4 mm. Based on the test results of the prototype the gain has reached 20.2 dBi at 27 GHz and the scanning angle was greater than +/- 60 degrees.

A novel design and implementation of ultrawideband dual-polarized cylindrical conformal phased array is presented with high isolation. Compared to the single-polarized counterpart, the elimination of common-mode resonance (CMR) becomes increasingly tricky in dual polarization due to the challenges in the complexity of the structure and conformal requirements. In this letter, a method of utilizing shorting lines is proposed to eliminate the CMR effect. It is also theoretically derived that the CMR can be removed, so that ultrawideband dual-polarized radiation is realized with high isolation. Initially, an ultrawideband dual-polarized planar infinite array is designed, in which shorting line loading is used to remove the CMR to ensure high polarization isolation within the ultrawideband operation. Subsequently, an 8 x 8 conformal array is developed, which is mounted along a cylindrical surface with 200 mm curvature radius. Finally, due to the straightforward construction of the conformal array, an 8 x 8 conformal array prototype is fabricated and assembled. The measured results show it achieves an operating bandwidth of 3.7:1, with VSWR < 3.0, polarization isolation > 15.1 dB, antenna efficiency >74.0%, and +/- 60 degrees/+/- 45 degrees E-/H-plane scanning with gain variation < 3.0 dB.

The advancement of satellite communication into millimeter-wave bands presents a challenge for gallium arsenidebased power amplifiers in achieving high output power and high power-added efficiency on compact chips. This paper presents a millimeter-wave power amplifier designed based on a $\mathbf{0. 1 5}-\boldsymbol{\mu} \mathbf{m}$ gate-length GaAs pHEMT process. Operating in the $\mathbf{3 0 - 4 0 ~ G H z}$ frequency band, the three-stage PA employs 1, 2, and 4 transistors in its respective stages, utilizing power combining techniques to enhance the output power and power-added efficiency (PAE). Simulation results demonstrate a small-signal gain of $22 \pm 2 \mathrm{~dB}$, input and output return losses better than -10 dB across the band, a saturated output power of greater than 30 dBm, and a PAE exceeding 35%. The chip occupies a compact area of only 2.2 mm $\times \mathbf{1. 5 ~ m m}$.

An ultra-wideband horizontally polarized (HP) omnidirectional array antenna, characterized by superior out-of-roundness, is proposed in this letter. The array antenna comprises 16 radiating elements with a hybrid wide-angle impedance matching layer, a feed network, and a paraboloidal metal reflector. Specifically, three-order dipoles (TODs) are embraced as the radiating elements to obtain ultra-wideband characteristics by adjusting the arm-length ratio of each order appropriately. Meanwhile, a compact feed network is designed in the center of the ring formed by radiating elements, ensuring uniform feeding for each element. Despite maintaining equal amplitude and phase in the feed, the array manifests out-of-roundness deterioration in the reference horizontal plane. To address this concern, a double-layer metal plate is introduced to form a paraboloidal reflector with the reference ground. This structure eliminates the ripples of the radiation pattern, thereby effectively enhancing the out-of-roundness. A prototype is fabricated and measured. The proposed antenna achieves a 4.0:1 operating bandwidth and exhibits excellent omnidirectional pattern characteristics, with out-of-roundness in the horizontal plane less than 1 dB throughout the full operating bandwidth.

This letter presents a wideband differential filtering phase shifter with a four-way configuration. By employing a stepped-impedance main transmission line loaded with short-circuited and open-circuited stubs, multiple resonant modes can be generated within the passband to form a flat phase curve over a broad bandwidth, thereby achieving low phase shift errors. Furthermore, an additional open-circuited stub is incorporated at the input port to enhance frequency selectivity. The proposed design demonstrates low phase error performance throughout the operational bandwidth. Experimental results indicate that the phase shifter operates from 1.21 to 2.99 GHz (84.8%), achieving multiple differential phase shifts of 30 degrees, 60 degrees, and 90 degrees with a maximum phase error of 3.5 degrees.

In this paper, a wideband dual-polarization large-curvature elliptic cylindrical conformal phased array is proposed. The relationship between the common-mode resonance frequency and the radius of curvature of the conformal array is analyzed. The common-mode resonance is suppressed by the large-curvature elliptic cylindrical conformal design, which eliminates the need for an additional resonance suppression structure. Ultimately, the proposed elliptic cylindrical conformal array has a minimum radius of curvature of 11 mm and a scanning performance of +/- 45 degrees in the frequency band from 5.1 to 16 GHz (3.1:1).