In this letter, a full metal antenna array with frequency switched bidirectional beams and polarization diversity is proposed for mmWave tunnel vehicle to infrastructure (V2I) communications. By exciting the TE011 mode in a shared cavity, a 4×4 slot array inherently generates symmetric forward and backward radiation with a single feed. Horizontal and dual ±45° linear polarizations are achieved by simply adjusting the slot orientations without increasing the feeding complexity. Furthermore, by coupling two degenerate cavity modes, a narrowband frequency switching mechanism continuously evolves both the beam direction and polarization, enabling forward only, bidirectional, and backward only radiation within a narrow frequency band. A prototype is fabricated and measured. Experimental results demonstrate peak realized gains ranging from 12.84 to 14.10 dBi across the three operating states, showing good agreement with the simulations. The proposed antenna array provides a compact and efficient solution for multifunctional beam control in mmWave tunnel V2I communications.
A topology-aware ocean ray-tracing (TAORT) method is proposed for electromagnetic scattering simulation of sea–target scenes. FFT-generated ocean meshes have uniformly distributed vertices on the horizontal plane. By exploiting this topological property, TAORT avoids constructing conventional acceleration structures for sea surfaces and converts the three-dimensional search for sea-surface intersections into a two-dimensional grid traversal. The initial candidate grid is obtained by analytical indexing, and subsequent grids are searched through grid-to-grid traversal on the projected ocean grid, avoiding the recursive bounding-volume hierarchy traversal used in conventional ray tracing process. A hybrid acceleration framework combining TAORT for sea surfaces and bounding volume hierarchies (BVHs) for maritime targets is developed for target–sea coupling scattering simulation. Numerical results show that the proposed method reduces computational cost and memory consumption, especially for electrically large scenes.
In the paper, a wideband co-circularly polarized simultaneous transmit and receive (STAR) antenna system is proposed for self-interference suppression in in-band full-duplex applications. The design employs a dielectric resonator antenna (DRA) array configured for right-hand circular polarization (RHCP) in both transmit (TX) and receive (RX) modes, each driven by a dedicated sequential- ly rotated parallel feeding network. The unit cell consists of a rectangular DR loaded with T-shaped extensions and excited through a cross-shaped slot coupled to two orthogonal U-shaped feeding lines, thereby simultaneously enhancing impedance bandwidth and TX-RX isolation. The two feeding networks incorporate port-swapped wideband 90° couplers to enable equal-amplitude quadrature excitation, thereby achieving wideband RHCP operation. A 4×4 prototype is fabricated and measured, demonstrating identical RHCP radiation over a wide operating band of 7.3–10.8 GHz (38.7%) with TX-RX isolation exceeding 34 dB.
This letter presents a low-profile Metasurface (MTS) antenna featuring wide In-Band Circular Polarization (CP) Coverage and stable gain. The prototype consists of two F4BM220 substrate layers with overall dimensions of 1.16λ₀ × 1.16λ₀ × 0.07λ₀. Optimized MTS elements on the top layer excite a pair of orthogonal resonant modes to realize wideband CP radiation, while a star-shaped aperture-coupled feed on the bottom layer combined with copper metallic probe further improves the in-band CP performance. Measured results show an impedance bandwidth of 29.44% (6.14–8.26 GHz), a 3dB Axial‑Ratio bandwidth of 23.2% (6.51–8.24 GHz), and an In-Band CP Coverage ratio of 78%. Stable gain ranging from 7.7 to 9.1 dBic is achieved across the operating CP band. Therefore, the proposed antenna is an attractive candidate for broadband wireless systems and C‑band satellite communication terminals.
Time-Modulated Arrays (TMAs) enable multibeam radiation from a single RF channel, but flexible harmonic beam control often requires complex modulation structures or optimization. This letter presents a hardware-oriented method for independent harmonic beam scanning by constructing a unified full-aperture time-modulation waveform from independently specified harmonic beam directions and mapping it to finite phase states. The proposed method requires neither subarray partitioning nor iterative optimization, enabling flexible multibeam scanning with a simple phase-only modulation architecture. The effects of waveform quantization on harmonic leakage, radiation performance, and implementation complexity are also investi gated. Simulated and measured results demonstrate independent three, four, and five-beam scanning, validating the effectiveness and hardware feasibility of the proposed method.
