In this letter, a wideband filtering dielectric resonator antenna (DRA) based on the HEM _11δ mode is proposed with high roll-off rate and flat gain response in the whole passband. The proposed filtering DRA is excited by a simple feed structure composed of a driven ring, a parasitic ring and a driven arc. Each of them can excite the HEM _11δ mode at different resonant frequencies, thus enlarging the impedance bandwidth of the proposed filtering DRA. Since the three resonant frequencies belong to the same mode, stable radiation pattern can be achieved simultaneously. In addition, two radiation nulls are generated near the lower and upper edges of the passband by the feed structure, making the proposed DRA obtain high frequency selectivity. All the three resonant frequencies and two radiation nulls are independently adjustable. A prototype has been fabricated and measured for demonstration, and the measured results are coincided with the simulated ones.

In this communication, a wide stopband filtering dense dielectric patch (DDP) antenna (DDPA) with metal vias and metal strips is proposed. The feeding structure consists of a short-circuited microstrip line and a separated slot. Based on this feeding structure, the TE ₁₁ and TE ₁₂ modes of DDP are successfully excited. The electric field region of the TE ₁₁ mode is much smaller than the physical region of DDP. The electric field region of the TE ₁₂ mode is basically the same as the physical region of DDP. The resonant frequency of TE ₁₁ mode is close to the resonant frequency of the TE ₁₂ mode and the passband is formed. Two semi-circular DDPs are etched, and two semi-circular metal strips are introduced to generate the low-frequency radiation null. Then ten metal vias are loaded inside the DDP to further change the resonant frequencies of TE ₁₁ and TE ₁₂ modes. The ten metal vias also adjust the H-plane radiation pattern of TE ₁₂ mode and improve the impedance matching of the proposed filtering DDPA. The measured results are basically consistent with the simulated ones. The relative impedance bandwidth is 4.2% (3.08-3.21 GHz). The low-frequency stopband range is 0.1-3.05 GHz, and the high-frequency stopband range is 3.38-7.0 GHz. The filtering DDPA has good sideband selectivity and wide stopband.

A blockage of the middle cerebral artery (MCA) on the cortical branch will seriously affect the blood supply of the cerebral cortex. Real-time monitoring of MCA hemodynamic parameters is critical for therapy and rehabilitation. Optical coherence tomography (OCT) is a powerful imaging modality that can produce not only structural images but also functional information on the tissue. We use OCT to detect hemodynamic changes after MCA branch occlusion. We injected a selected dose of endothelin-1 (ET-1) at a depth of 1 mm near the MCA and let the blood vessels follow a process first of occlusion and then of slow reperfusion as realistically as possible to simulate local cerebral ischemia. During this period, we used optical microangiography and Doppler OCT to obtain multiple hemodynamic MCA parameters. The change trend of these parameters from before to after ET-1 injection clearly reflects the dynamic regularity of the MCA. These results show the mechanism of the cerebral ischemia-reperfusion process after a transient middle cerebral artery occlusion and confirm that OCT can be used to monitor hemodynamic parameters.

In this letter, a high-gain filtering dense dielectric patch (DDP) antenna (DDPA) based on high-order modes is proposed. The feed structure is composed of four slots and a U-shaped microstrip line. The TE ₁₂ , TE _12+δ and TE ₁₃ modes of DDP are successfully excited. Based on three high-order modes, the designed filtering DDPA achieves high-gain. Radiation nulls (Null 1 and Null 2) are generated by etching a parallel four-slot structure on the ground and the non-radiative mode. By etching the rectangular grooves on the DDP, using the inverted L-shaped defect structure and attaching the C-shaped stub to the microstrip line, better impedance matching and stopband suppression levels are obtained. In order to confirm the design, the proposed filtering DDPA is fabricated and measured, and the prototype's profile is only 0.069λ ₀ . Measured results indicate that the bandwidth of relative impedance is 13.2% (4.6-5.25 GHz). The measured average realized gain and peak gain are 8.66 dBi and 9.85 dBi, respectively. The filtering DDPA has high-gain, wide passband, and good edge selectivity.

In this letter, a high-gain filtering dense dielectric patch (DDP) antenna (DDPA) with metal cylinders is proposed, which consists of DDP and double-layered printed circuit boards (PCBs). The TE ₁₂ mode and TE _1+δ2 mode of DDP are excited by using a slot feed structure, and form a passband. The proposed filtering DDPA itself has a radiation null at the edge of high-frequency passband. Four metal cylinders inside the upper PCB and DDP introduce another radiation null at the edge of low-frequency passband. When the structure of DDP changes from square to rectangle, multiple high-order harmonics are suppressed or shifted towards high frequency. The high-frequency stopband is widened. By diminishing the upper PCB from large square to small rectangle, the impedance matching and filtering response are improved. A prototype is fabricated and measured for demonstration. The measured results are basically consistent with the simulated ones. The designed filtering DDPA has merits of high realized gain and wide harmonic suppression.