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A compact dual-band circularly polarized (CP) shared-aperture antenna is proposed for satellite communication. The antenna enables simultaneous dual-band functionality and CP radiation with right-handed CP in the Ku band and left-handed CP (LHCP) in the Ka band. The shared-aperture is implemented by integrating two independent subapertures, which function through frequency-multiplexed, resulting in a minimized profile (0.04 $ {\lambda _0} $ λ 0 ) and reduced complexity, making it an ideal choice for array applications. To enhance inter-frequency isolation, a circular arrangement of metal vias is incorporated. The measured results indicate that the antenna effectively encompasses a 3 dB axial ratio (AR) bandwidth of 15.6–16.5 GHz in Ku and 26.5–27.5 GHz in Ka bands. Additionally, it exhibits a broader 10 dB impedance bandwidth (IBW) and superior port isolation bandwidth exceeding 30 dB. [ABSTRACT FROM AUTHOR]

In inverse synthetic aperture radar (ISAR) systems, image quality often suffers from the non-uniform rotation of non-cooperative targets. Rotational motion compensation (RMC) is necessary to perform refocused ISAR imaging via estimated rotational motion parameters. However, estimation errors tend to accumulate with the estimated processes, deteriorating the image quality. A novel RMC algorithm is proposed in this study to mitigate the impact of cumulative errors. The proposed method uses an iterative approach based on a novel criterion, i.e., the minimum residual norm of the signal phases, to estimate different rotational parameters independently to avoid the issue caused by cumulative errors. First, a refined inverse function combined with interpolation is proposed to perform the RMC procedure. Then, the rotation parameters are estimated using an iterative procedure designed to minimize the residual norm of the compensated signal phases. Finally, with the estimated parameters, RMC is performed on signals in all range bins, and focused images are obtained using the Fourier transform. Furthermore, this study utilizes simulated and real data to validate and evaluate the performance of the proposed algorithm. The experimental results demonstrate that the proposed algorithm shows dominance in the aspects of estimation accuracy, entropy values, and focusing characteristics. [ABSTRACT FROM AUTHOR]

A wideband polarization-reconfigurable microstrip antenna based on a mode-fusion mechanism is proposed. This simple antenna structure consists of a rectangular radiation patch and a ground, both with crossed slots. The slots crossing the ground are connected by eight PIN diodes and four capacitors such that two orthogonal linear-polarization radiation modes can be realized. The radiation patch is slotted such that a transformed TM 20 mode is excited, realizing broadside radiation that the traditional TM 20 mode is unable to. With fusion of the fundamental TM 10 mode and the transformed- TM 20 (T- TM 20 ) mode, a wide bandwidth of 30.1% is achieved in two reconfigurable polarizations. The measured results agree well with the simulation results. The total efficiency of the proposed antenna is more than 80.0% over the bandwidth. [ABSTRACT FROM AUTHOR]

A beamwidth (BW) and beam direction (BD) reconfigurable antenna based on multi‐mode parasitic coupling is proposed. Two pairs of metal strips connected by only two positive‐intrinsic‐negative diodes are added as parasitic structures over the driven element, a circular microstrip patch, constituting a simple antenna design. By controlling the diode switching state, four pattern reconfigurable modes can be realised. Two beam‐pointing deflection modes in the E‐plane are realised based on the Yagi–Uda principle. Besides, the BW reconfigurability is achieved due to a joint effect of the Yagi principle and beam‐stacking principle. All the reconfigurable modes share a 10% impedance bandwidth from 5.8 to 6.3 GHz. Simulation and measurement results show that the BW can be switched between 67° and 120° in an omni‐directional plane, and the BD can be switched between 0° and ±30° in the E‐plane. [ABSTRACT FROM AUTHOR]

In the increasingly complex electromagnetic environment, main lobe jamming significantly degrades the performance of a wideband radar system. To mitigate this issue, this paper developed a wideband main lobe jamming suppression algorithm based on a distributed array radar. Firstly, this algorithm utilizes eigen-projection matrix processing in the main array to cancel out the main lobe jamming for main lobe maintenance, and then suppresses side lobe jamming through null constraint beamforming. Subsequently, the large aperture of the full array is leveraged to form a narrow beam directed toward the main lobe interference. Finally, joint beamforming using the minimum mean square error criterion is employed. In scenarios where both main lobe jamming and side lobe jamming exist, this algorithm can adaptively cancel main lobe wideband jamming, suppress side lobe wideband jamming, and effectively control the significant loss of the desired wideband signals caused by main lobe jamming within a smaller angular range. Simulation results validate the effectiveness of the algorithm. [ABSTRACT FROM AUTHOR]

A compact ultra‐wide‐beam crossed‐dipole antenna for K‐band phased arrays is proposed. The superior wide beamwidth is achieved by loading four vertical parasitic structures around the dipole patches. A quasi‐coaxial feeding structure is proposed as the antenna size is limited in K‐band, and it cannot be coaxially fed by the conventional feeding method. This structure is constructed by using PCB through‐plated vias, achieving a compact design. The antenna has a compact size of 0.37λ × 0.37λ × 0.35λ (λ is the free space wavelength). The simulated and measured results show that a half‐power beamwidth of more than 140° (from −71° to 72°) and an axial ratio beamwidth of 100° (from −51° to 49°) can be realized. [ABSTRACT FROM AUTHOR]