This letter presents a two‐port circularly polarized pattern diversity microstrip patch antenna. The antenna is designed on a single layer with a low profile (0.021λ0, where λ0 is the free‐space wavelength at the central frequency). The broadside pattern and conical pattern of the antenna can be obtained by respectively exciting the fundamental mode of the inner circular patch and the high‐order mode of the entire circular patch. With four pairs of silts on the patch, the antenna achieves circular polarization for both broadside and conical patterns. A prototype of it is fabricated and measured. The measured overlapped bandwidth of 10‐dB return‐loss and 3‐dB axial ratio for both modes are 1.3% (1.569‐1.580 GHz) and 0.6% (1.565‐1.575 GHz), respectively. Moreover, the measured peak gain values are 6.4 and 3.7 dBi for broadside and conical modes, respectively. The satisfactory isolation (|S21| < −22 dB) is also achieved between the two feeding ports in the common impedance matching bands.
Objectives:To estimate the benefits of non-invasive ventilation (NIV) used immediately after planned postextubation in patients with chronic respiratory disorders.Methods:Cochrane Library, PubMed, the Chinese BioMedical Literature Database of clinical trials (CBD) and Embase were searched for pertinent studies by 2 trained investigators. Pooled odds ratios and 95% confidence intervals (CIs) were calculated by employing both fixed-effects and random-effects models.Results:Eight studies enrolling 736 patients were included in the meta-analysis. Compared with general oxygen therapy, NIV used immediately after planned extubation in patients with chronic respiratory disease reduced the reintubation rate (p=0.02), ventilator-associated pneumonia (VAP) incidence rate (p=0.000), and ICU mortality (p=0.002) and increased the level of PO2 (p=0.03).Conclusion:Non-invasive ventilation used immediately after planned extubation seems to be advantageous for decreasing the reintubation rate, VAP incidence, and ICU death rate in patients with chronic respiratory disease.
A novel wideband filtering dumbbell-shaped slot antenna with improved frequency selectivity for both band-edges is proposed in this paper. The filtering slot antenna is composed of a dumbbell-shaped slot, two parasitic patches, eight slot-stubs and a feeding line with a pair of step impedance resonator (SIR) stubs. An additional resonance is generated to increase the bandwidth and a gain null is produced at the upper band-edge to improve the frequency selectivity by loading parasitic patches in the dumbbell-shaped slot. Eight slot-stubs adjacent to the dumbbell-shaped slot are etched to enhance the impedance matching. In addition, the bandwidth is further broadened and two gain nulls are realized at both band-edges by adding a pair of SIR stubs. Moreover, the gain nulls can be adjusted individually by the length of parasitic patches or SIR stubs. As a result, the gain curve of the proposed filtering slot antenna has good flatness and the frequency selectivity for both band-edges is significantly improved. A prototype has been manufactured and measured to verify the validity of the design. The measured impedance bandwidth of |S11|<-10 dB is 62.5% (2.2 GHz-4.2 GHz). High suppression levels of 26 dB and 30 dB can be achieved in the lower and upper stopbands, respectively. INDEX TERMS Filtering slot antenna, wideband, gain nulls, frequency selectivity.
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