wideband high-gain low-profile end-fire linearly polarized (LP) / circularly polarized (CP) antennas for 5G millimeter-wave applications are presented in this letter. The basic structure of the antennas include a stripline fed horn as the feeder and multiple magnetic diploe directors (MDDs) printed on a single layer substrate. The stripline fed horn exhibits a wide bandwidth and stable end-fire radiation, and magnetic dipole directors help further improvement the end-fire gain. A linearly polarized (LP) antenna based on a LP feeder and vertically polarized (VP) MDDs (supporting VP resonance) working at the 5G mmWave band is firstly designed. Then, on this basis, a circularly polarized (CP) antenna based on a CP feeder and dual-polarized MDDs (supporting two orthogonal polarized resonances) working at the same band is designed. The two proposed antennas with the low profile of 0.14 $\lambda_{0}$ are fabricated and measured, both of which show good impedance matching, high gain, and low cross-polarization within the 5G mmWave band.

This letter presents a miniaturized dual-wideband millimeter-wave (mm-wave) antenna in package with filtering function. The proposed antenna mainly consists of four radiation patches and metallized vias. By introducing a pair of shorting pins underneath each radiation patch, the proposed antenna realizes dual-band operation in different modes. The upper band operates in the magnetoelectric dipole mode, while the lower band radiates through a new magnetic dipole. Besides, a radiation null is generated in-between the two operating bands to suppress signals. Furthermore, another pair of shorting pins is loaded on both sides of the probe, which generates two radiation nulls in the upper stopband. The dimensions of antenna are only 0.28 λ_l × 0.28 λ_l × 0.075 λ_l at 24 GHz. To verify the proposed approach, a prototype of 1×4 array is fabricated using a high density interconnection (HDI) process. The measured −10 dB bandwidth of the array covers 24−30 GHz and 37−43.5 GHz with an average gain of 8 dBi and 9.1 dBi, respectively. Besides, three radiation nulls are formed, suppressing the out-of-band gain by more than 13dB. The proposed antenna with such superior performance demonstrates great potential for millimeter-wave applications.

Hyperspectral anomaly detection (HAD) has always been a hot topic in hyperspectral image (HSI) processing. The Reed-Xiaoli (RX) detector is one of the most widely used methods for HAD. However, most improved versions of RX are usually only improved from the view of reducing the contamination of anomaly pixels on the background modeling. Considering the rich spatial information of HSI and the influence of anomaly pixels on background modeling, we propose an ensemble and random RX with multiple features (ERRX MFs) anomaly detector. First, the spectral, Gabor, extended morphological profile (EMP), and extended multiattribute profile (EMAP) four features are extracted. Then, random subsampling is used on RX to obtain multiple detection results for each feature. Finally, the detection results of these four features are further fused to the final detection result by ensemble learning. Experimental results on four real hyperspectral datasets validate that our proposed method can achieve more satisfactory results compared with other state-of-the-art methods.

A compact ultra-wideband circularly polarized crossed-dipole antenna with post fence and parasitic elements is proposed in this paper. The proposed antenna consists of two dipoles with unequal semi-ellipses, four symmetrical rectangular patches, and a post fence structure. Two vacant-quarter rings are utilized to provide the 90° phase difference for feeding the cross-arranged dipoles. Wide axial ratio bandwidth (ARBW) is achieved by employing a metal pillar-back cavity through the introduction of five cavity modes, while also compacting the overall antenna structure. Four sequential rotating patches are positioned along the substrate edges to improve the axial ratio at higher frequencies. The proposed antenna exhibits an impedance bandwidth (IBW) from 0.87 to 3.17 GHz and an axial ratio bandwidth (ARBW) from 0.98 to 2.99 GHz. This indicates that the overlapped IBW and ARBW reaches 101.3%. Moreover, the overall dimensions of the proposed antenna are 0.52×0.83×0.17•L3 corresponding to the lowest operating frequency, showing that it has great potential in wireless communications.

A planar conical beam array antenna with low profile, high gain, and low side lobe level (SLL) is proposed in this letter. The array is composed of three concentric annular planar inverted-F antenna (APIFA) elements, each of which is excited by uniform distributed feeding points with the same excitation amplitude and phase and thus obtain an axisymmetric conical beam. Shorting pins and cambered slots are employed on the APIFA element to realize impedance matching for a given number of feeding points. Synthesis of conical beam for the array can be flexibly realized by adjusting the excitation amplitudes and phases of the elements. A prototype with a low profile of 0.11 λ ₀ is designed, fabricated, and measured. Measured results show that the prototype achieves 11.2% (4.71 ∼ 5.27 GHz) -10-dB impedance bandwidth. Within the impedance bandwidth, a stable gain of 11.3 to 12.7 dBi, a stable beam-pointing angle (BPA) of about 15°, and a low SLL of less than -12.5dB is obtained, indicating good conical beam performance.

In this letter, an ultrawideband low-profile circularly polarized (CP) antenna with asymmetric cross-dipoles, parasitic patches, and artificial magnetic conductor (AMC) is proposed. A vacant-quarter ring connects orthogonal dipole arms to introduce the required 90° phase difference for generating CP radiation. To reduce the profile of the antenna, an AMC reflector is positioned beneath the radiator. The AMC reflector consists of hybrid metallic patterns printed on a substrate, where two different types of unit cells are arranged in the center and around the periphery separately to expand the in-phase reflection bandwidth. Additionally, metallic strips are added around the edge of the ground to improve the axial ratio and radiation pattern at lower frequencies. Measured results indicate that the impedance bandwidth and the axial ratio bandwidth of the antenna are 1.51 GHz to 5.13 GHz (109%) and 1.54 GHz to 3.57 GHz (79.5%), respectively. The antenna gains maintain 6.3 dBic to 8.3 dBic within the whole operating bandwidth. Furthermore, the antenna features a low profile of 0.13λ_L corresponding to the lowest operating frequency.