In this paper, the concept of high-gain multifunctional antenna based on folded reflectarray antenna (FRA) and polarization-sensitive frequency selective surface (FSS) is proposed. Antenna with multiple functions can be realized by using a polarization-sensitive FSS as the subreflector of FRA instead of the traditional polarizing grid. To validate this concept, a high-gain filtering antenna designed at Ka band is presented as a design example. Good filtering performance of the antenna has been achieved due to the frequency selective characteristics of FSS. Besides, the relationship between the focal-length-to-diameter (F/D) ratio of FRA and the size of FSS element has also been discussed.

The design and implementation of a wideband circularly polarized folded reflectarray antenna (CPFRA) with a linearly polarized (LP) feed antenna is presented in this letter. The subreflector of the proposed CPFRA is in the form of a polarization-sensitive frequency selective surface (FSS) based on the antenna-filter-antenna (AFA) technology other than the traditional polarizing grid. The AFA FSS is designed to convert the LP incident wave into circularly polarized (CP) wave within its passband and reflect the orthogonal LP incident wave over a wide frequency band. Futhermore, the sequential rotation technique is applied in the design of main reflectarray and subreflector to greatly enhance the axial ratio (AR) bandwidth of the CPFRA. An antenna prototype has been fabricated and measured at X -band. Good agreement between the measured and simulated results has been achieved by the wideband CPFRA. The measured results show that the maximum antenna gain reaches up to 28.2 dBic at 10.2 GHz with its aperture efficiency of 43.3%. The 3 dB gain frequency band is from 9.1 to 10.6 GHz and the 3 dB AR frequency band from 8.7 to 11.2 GHz, respectively.

The design and implementation of a single-layer vialess polarization rotation reflective surface (PRRS) with high frequency selectivity is presented in this paper. The periodic element of the proposed PRRS is mainly made up of a dual-mode rectangular ring resonator backed with the metallic ground. Second-order bandpass frequency response can be observed by the proposed PRRS with the linearly-polarized incidence converted into the cross-polarization reflected wave. Meanwhile, sharp roll-off passband edge of the proposed PRRS has been achieved with a cross-polarization reflection null, which can be flexibly located at the lower or upper stopband and conveniently controlled in the PRRS design. Two PRRS prototypes have been designed with the center frequency of 30GHz to verify the proposed design. Good agreement between the simulation and measurement has been achieved. In addition, the proposed PRRS has the advantages of easy fabrication and low cost, since no via hole fabrication is needed and only one layer of the substrate material is required in the whole PRRS design.

This paper presents the design and implementation of a bandwidth-enhanced circularly polarized reflectarray antenna (CPRA), which is realized with the novel ultralow-profile subwavelength Pancharatnam–Berry (PB) metasurface based on the triple-mode rectangular ring resonator. The PB metasurface exhibits a third-order quasi-elliptic bandpass frequency response under circularly polarized incidence while maintaining the ultralow profile of 0.04λ0. Stable frequency response of the PB meta-atom can be observed with the oblique incidence up to 30° in a wide frequency range. To validate the CPRA design method, a Ku-band offset-fed CPRA prototype with a left-hand circularly polarized (LHCP) feed antenna has been designed, fabricated, and measured. The measured CPRA performance aligns well with simulations, demonstrating that the measured 1dB gain bandwidth and 3dB axial-ratio (AR) bandwidth are 8.8% and 10.1%. Meanwhile, the maximum antenna gain of the CPRA reach up to 25.0dBic at 15GHz with the corresponding aperture efficiency of 51.3%.

This paper presents the principle, design and implementation of N th-order polarization rotation reflective surface (PRRS) with high frequency selectivity based on the transversal coupling topology. The transversal coupling topology allows all the radiative resonators of PRRS couple to the free space simultaneously. All the resonators are simultaneously excited by the linearly polarized (LP) incidence and re-radiate the LP reflection wave with 90-degree polarization rotation. As the results, the overall frequency response of the PRRS is the superposition of the counterparts of all the resonators. For an N th-order PRRS, up to N -1 cross-polarization reflection zeros can be achieved using N resonances in the transversal coupling topology. These N resonances can be realized by either single-mode or multi-mode resonators. Two second-order PRRS designs have been presented to verify the operating principle of PRRS and show the advantages of this design method. Then the design guideline of the transversal PRRS has been drawn. Furthermore, three X -band transversal PRRS prototypes exhibiting the third-order, fourth-order and fifth-order quasi-elliptic bandpass frequency response have been presented. The cross-polarization reflection zeros can be found at both the lower and upper stopband of PRRS, leading to the high roll-off frequency response. To minimize the size of PRRS unit cell, the dual-mode and triple-mode rectangular ring resonators have been utilized in the three PRRS designs. Good agreement between the simulation and measurement has been obtained by these PRRS prototypes, validating this proposed PRRS design method based on the transversal coupling topology.

Weak atmospheric signals received by radar wind profilers (RWPs) often overlap with the clutter, making it difficult to identify pure atmospheric spectra. A solution with great potential is to develop RWPs with adaptive dynamic identification capabilities. We therefore propose a multi-feature dynamic weighting (MFDW) method and specifically define a score function that includes spectral statistical features and their weights. This score function first calculates multiple spectral features and constructs a prediction function that maps the features to prediction values. Then, the weights are determined by Gaussian curve fitting and contributed to the predicted score calculation to extract pure atmospheric spectra. After that, the multi-parameter cost function (MPCF) method is first improved by Doppler window settings, and then utilized to estimate accurate spectral moments and profiles. MFDW method is validated using RWP data from different regions and frequencies, and the extracted profiles are compared with GPS radiosonde (GPS RS) data. Research results confirm that dynamic weighting is adaptable to various overlap cases. Furthermore, Doppler wind profile estimation with this proposed method has a good match with GPS RS data. Both the detection accuracy and the running time excel many currently adopted methods. In brief, the chief contributions in this paper lies in our innovative MFDW method and feature- and weights-involved score function.