An endfire antenna with sum and difference beams is designed based on phase transforming of a proposed asymmetric spoof surface plasmon polariton (SSPP) structure. The asymmetric arrays of grooves, with different groove depths, periods, and/or duty ratios, serve as transmission structure and transmit electromagnetic (EM) waves in SSPP modes. Due to the distinct phase constants for the EM fields on the two sides of the asymmetric structures, the transformation of phase difference for the EM waves is realized. Superposition in the endfire direction for the in-phase and out-of-phase EM fields forms the endfire radiations with sum and difference beams. A design procedure is proposed where operating frequencies of the endfire antenna are predicted with the dispersion curves of the asymmetric SSPP structures and allocated by phase transformation. A prototype is implemented to validate the proposed design principle. Sum beam operating frequencies of the endfire antenna are at 5.50, 6.60, and 7.09 GHz, while difference beams appear at 6.10 and 6.90 GHz. Good agreement of the results validates the feasibility of the proposed mechanism and design procedure. The proposed endfire antenna with sum and difference beams has broad prospect in direction finding, tracking, and anti-interference applications.

A compact decoupling structure, implemented by the postwall slotline (PWS) based stepped impedance resonator (SIR), is proposed for enhancing the isolation between patch antennas. A pair of SIRs are placed between microstrip antennas to cut off the coupling path, which enhances the decoupling performance greatly at resonance frequency. Meanwhile, designed with a combination of conventional slot line (CSL) and the PWS, the decoupling structure has a compact profile and thus is suitable for miniaturized element space. A two-element patch array is designed and fabricated to verify the decoupling effectiveness of the proposed structure, by providing simulated and measured results. Realized gain of the antenna with proposed structure is about 5.4 dBi. High isolation of 30.4 dB at 5.7 GHz is achieved and the edge-to-edge distance is 0.059 ${{\lambda}_{0}}$ with the decoupling structure. Moreover, with the decrease of element distance, isolation improvement will be significantly enhanced. The compact size and isolation performance show the potential of the structure to be applied in antennas arrays including multi-input-multi-output (MIMO) systems and adaptive arrays.

Objectives Diabetes mellitus has been associated with stroke. However, the association between fasting blood glucose (FBG) and stroke risk in a general population remains not clear. The purpose of our study was to examine the FBG levels on subsequent stroke risk in a community-based cohort in China. Design Prospective cohort study, employing Cox proportional hazard model to analyse the association of FBG levels with stroke risk. Setting A community-based cohort study included adults participating in a baseline survey conducted in 2013 in Changshu, eastern China. Participants 16 113 participants were recruited with a multistage sampling method, excluding participants with severe disability, severe cancer, severe psychiatric disturbance or previous stroke before enrolment. Primary outcome measures Stroke events. Results During a median follow-up of 5.5 years, 417 incident cases of stroke were identified. The adjusted HR for total and ischaemic stroke for participants in the fourth quartile of FBG compared with the first quartile was 1.44 (95% CI 1.07 to 1.94) and 1.57 (95% CI 1.11 to 2.21), respectively. FBG levels of ≥7.0 mmol/L were associated with an increased risk of stroke based on two clinical classifications (American Diabetes Association: 1.68 (1.24 to 2.27); WHO: 1.62 (1.21, 2.13)). In stratified analyses, risk associations existed in women (HR: 1.92, 95% CI 1.22 to 3.01) and postmenopausal women (HR: 1.68, 95% CI 1.06 to 2.68) for the fourth quartile versus the first. More importantly, the meta-analysis observed a positive association between FBG levels and stroke risk (pooled HR: 1.70, 95% CI 1.27 to 2.29; n=7)). Conclusions Higher FBG level was independently associated with an increased risk of stroke in Chinese adults, especially significant in women.

An endfire frequency scanning tapered slot antenna (FSTSA) is proposed and investigated. The proposed FSTSA is a two-conductor structure with a gradient slots array etched only on one of two inner edges in the FSTAS. The asymmetrical inner edges enable the antenna to excite two modes with different phase constants simultaneously along the two inner edges. Due to dispersion characteristics of spoof surface plasmon polaritons (SSPPs), the phase difference between the EM waves along the two conductors changes versus frequencies, which enables the main lobe of the FSTSA to scan through the endfire direction. An analysis model is conceived to provide insights into the design, which accurately predicts main lobe directions and initial values of the proposed antenna. The proposed antenna is fabricated, and the measured results show that the main lobe of the antenna scans from −15° to 14° (endfire direction at 0°) from 6.60 to 7.70 GHz, with the scanning rate of 26.4°/GHz. This antenna could be suitable for radar, plane integrated communication system, and certain other beam-scanning applications.

A circularly polarized (CP) endfire antenna is proposed and designed based on the sequentially rotated corrugated Goubau lines. The open-ended corrugated Goubau lines serve as endfire radiators, and simultaneously realize phase transforming function for phase control. A pair of corrugated Goubau lines could be etched on two edges of a common metal strip, and four corrugated Goubau lines with different corrugations along two perpendicular metal strips provide sequentially rotated radiated fields, establishing the CP radiation. Complexity and space occupation of the feeding structure could be reduced by applying the phase-transforming element radiators, which is significant especially in array design. A prototype antenna is fabricated and measured to verify the design. The measured axial ratio is below 3 dB and the return loss is over 15 dB from 8.9 to 9.5 GHz. Peak gain is 8.6 dBic and the cross-polarization level is around -20 dB at 9 GHz.

A spoof surface plasmon polariton (SSPP) antenna with dual-band endfire gain and small frequency ratio (FR) is presented. It uses asymmetric structure to support two independent surface waves with different nonlinear phase constants. Due to the different phases of the superposed E-field at the terminal of the proposed structure, dual-band endfire gains and endfire radiation null are achieved. The odd-mode and even-mode feedings, providing additional phase differences, are also investigated. Three prototypes, with FRs of 1.06, 1.11 and 1.5, are designed, simulated and measured respectively. All results validate the mechanism and demonstrate that the FR of the proposed antenna can be achieved easily in the range of 1.06 to 1.5 by choosing different unit cells and feeding modes. Moreover, the measured endfire out-of-band gain suppression, over 17 dB, presents a good directional interference inhibition. This small-FR endfire antenna shows a broad prospect for band coverage and directional noise inhibition with very close operating frequencies.