This letter presents a broadband filtering circularly polarized (CP) folded transmitarray antenna (FTA) with a linearly polarized (LP) feed antenna based on metasurface (MS). The whole antenna mainly consists of two MSs located on the top and bottom layers and an LP feed antenna. LP to CP wave (LP-CP) conversion and phase compensation are achieved across the entire X-band with the designed top MS. The top bandpass MS is also used as a spatial filter, utilizing its out-of-band suppression characteristics and high passband edge selectivity. A fabricated prototype was measured, and the results reveal that its maximum gain is 27.8 dBi at 10.2 GHz with an aperture efficiency of 40%. It also achieves a 3-dB gain bandwidth of 24.5% and a 3-dB axial-ratio (AR) bandwidth of 41.1%, which is in good agreement with the simulation results as well. The proposed broadband CPFTA achieves a bandpass filtering response while also retaining the advantages of low profile, high gain, and low cost, which illustrates great application potential in future wireless communication systems.

In this work, a size-reduced wideband coupler is presented and demonstrated, which explores the slow-wave half-mode substrate integrated waveguide (SW-HMSIW) technique on a printed circuit board process. The SW-HMSIW coupler is composed of two SW-HMSIW transmission lines loaded with a polyline network. Along the coupler, energy is coupled by the electric and magnetic field between the two parallel SW-HMSIW lines. Compared with conventional microstrip coupler, the proposed coupler presents lower loss owning to the HWSIW structure performance. In addition, the proposed SW-HMSIW coupler exhibits a smaller size against its SIW and HWSIW counterparts, thanks to slow-wave effects of the loaded polyline. Measured and simulated results are in a good agreement.

This paper presents an E-band substrate integrated waveguide (SIW) dual-polarized antenna system, which consists of an orthomode transducer (OMT) and a dual-polarized horn antenna. On the basis of a two-layer substrate design, the function of OMT is realized by utilizing an SIW section to excite TE10 mode for vertical polarization, a quasi-coaxial stripline (CSP) to excite quasi-TEM mode for horizontal polarization. And also, a slot line transition is placed at the common port of the two structures for impedance matching with the ridge SIW dual-polarized horn antenna. In this way, the dual-polarized horn antenna is designed with an exponential ridge structure simultaneously for better impedance matching and higher efficiency of the antenna. To verify the functionality of the proposed integrated OMT-antenna structure, an experimental prototype is fabricated and measured, and a good agreement is found between its simulated and measured results. Over the frequency range of 83-87 GHz, return loss better than 10dB at all ports and cross-polarization less than -25 dB are obtained. The maximum antenna gain is about 14dBi for horizontal polarization and 15.2 dBi for vertical polarization. It is believed that the proposed OMT-antenna design is suitable for ultra-high capacity millimeter-wave backhaul applications in future wireless communication systems.

This letter presents a bandpass filter (BPF) based on a hybrid structure of quarter-mode substrate integrated waveguide (QMSIW) and coplanar waveguide (CPW). By incorporating two CPW resonators into two QMSIW resonators, the proposed filter obtains a high selectivity as the coupling between two CPW resonators is electric coupling, which helps to generate two transmission zeros. It also achieves compact layout as the embedded CPW resonators do not occupy extra area. In order to verify the design, a BPF with a center frequency of 8.7 GHz is fabricated and measured. The measured results show good agreement with the simulation results.

In this review, the conservation methods for various types of cultural relics enabled by hyperspectral imaging are summarized, and the hyperspectral cameras and techniques utilized in the process from data acquisition to analyzation are introduced. Hyperspectral imaging is characterized by non-contact detection, broadband, and high resolution, which are of great significance to the non-destructive investigation of cultural relics. However, owing to the wide variety of cultural relics, the utilized equipment and methods vary greatly in the investigations of the associated conservation. Previous studies generally select a single type of cultural relic for conservation. That is, seldom study has focused on the application of hyperspectral techniques to generalized conservation methods that are simultaneously suitable for different types of cultural relics. Hence, some widely used hyperspectral cameras and imaging systems are introduced first. Subsequently, according to the previous investigations, the methods used for image acquisition, image correction, and data dimensionality reduction in hyperspectral techniques are described. Thirdly, a summary of methods in cultural relic conservation based on hyperspectral techniques is presented, which involves pigments, grottoes and murals, and painting and calligraphy. Later, some challenges and potential development prospects in hyperspectral-based methods are discussed for future study. Finally, the conclusions are given.

In this letter, substrate-integrated waveguide (SIW) power combiner/divider incorporating absorbing material for isolation is presented. Based on the Riblet coupler theory, the proposed SIW power combiner/divider contains two extra ports to improve isolation between the dividing ports. Its longitudinal axis symmetry illustrates its equal power-dividing property, and ensuring the dividing ports to have good and balanced amplitude and phase properties. By loading the isolated ports with shaped absorbing material, an SIW power combiner/divider prototype is realized. Measured results are in good agreement with simulated ones, and a fractional bandwidth of 36% with over 15-dB isolation is achieved, which is wider than other similar SIW power dividers.