Search

In this paper, a novel end-loaded resonator is investigated and applied to design tunable bandpass fillter (BPF) and bandstop fillter (BSF). The novelty of the resonator lies in that two varactors are added to the two ends of the resonator, and then its resonant frequency can be bi-directionally tuned. As a result, the theoretical frequency tuning range can be significantly extended to approximately double that of the conventional tunable resonator. For demonstration, the proposed resonator is applied to design tunable BPF and BSF. As expected, the tuning ranges are 52.4% and 53.5% for the BSF and BPF, respectively. Good agreements can be observed between the simulated and measured results. [ABSTRACT FROM AUTHOR]

A high-selectivity microstrip wideband bandpass filter with six transmission zeros using transversal signal-interaction concepts is proposed. A fifth-order wide passband with six transmission zeros (0-2f0, f0 is center frequency of the passband) can be realized two transmission paths. The bandwidth and locations of the transmission zeros can be adjusted conveniently by changing the characteristic impedances of open stub and coupling coefficients of the open/shorted coupled lines. A prototype of planar wideband bandpass filter with 3-dB fractional bandwidth 43.3% (2.33-3.63 GHz) is designed and fabricated. The measured and simulated results both indicate good performances of high selectivity and wideband harmonic suppression. [ABSTRACT FROM AUTHOR]

The design of a VHF-band lumped-element ferrite circulator has been introduced. The experiments have indicated that the ferrite circulator has good performances in the room temperature. However, when the ambient temperature has changed, the significant degradations of performances of the ferrite circulator have been observed. A temperature-compensation technique has been adopted to guarantee the good performances of the ferrite circulator, in which one kind of special alloy has been employed and an experimental prototype has been constructed. The measured data have shown that, excellent performances can be obtained in the frequency range 140–180 MHz and over 20 dB isolation has been guaranteed throughout the temperature range of 0°C∼70°C. [ABSTRACT FROM AUTHOR]

The cutoff characteristic equation of the modes in circular waveguide is derived in this paper. The TM01 mode inversion has been investigated. Two kinds of technique of dielectric loading have been discussed. When the dielectric tube is filled in the waveguide next to the waveguide wall, there is no window of TM01 mode inversion observed in the cutoff characteristics. Contrarily, when the dielectric is filled centrally in the circular waveguide, there always exists one "window" within which the TM01 mode can propagate in the waveguide in the sense of single mode. [ABSTRACT FROM AUTHOR]

A new microstrip ultra-wideband (UWB) differential bandpass filter using two broadband planar Marchand baluns is proposed. Based on the transversal signal-interference concept, a passband with adjustable fractional bandwidth from 80 to 124% can be achieved for the differential mode, while the common mode can easily be suppressed in the whole frequency band. Good agreement is observed between simulation and measurement. [ABSTRACT FROM AUTHOR]

A high-selectivity wideband bandpass filter consisting of a ring resonator and stepped impedance resonators is proposed. A wideband bandpass filter with multiple transmission poles and transmission zeros is obtained. For demonstration, a prototype operating at the frequency band of 4.14-9.56 GHz (with a fractional bandwidth of 79.1%) is designed and fabricated. Good agreements between the simulated and the measured results have been observed, indicating a very sharp out-of-band rejection. [ABSTRACT FROM AUTHOR]

A high selectivity dual-wideband bandpass filter using a T-shaped structure based on transversal signal-interaction concepts is proposed. Several transmission zeros close to the two passbands can be achieved due to the superposition of signals for the two transmission paths. A planar dual-wideband bandpass filter prototype for GPS and WLAN bands with 3 dB fractional bandwidths of 28.8 and 22.7% has been designed and fabricated. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the impact of interventional therapy on top of drug therapy on cardiac function and structure in heart failure with reduced ejection fraction (HFrEF) patients complicating with middle aortic syndrome caused by Takayasu arteritis (TA-MAS). Methods: It was a retrospective longitudinal study. The data of patients with TA-MAS and HFrEF, who received interventional therapy on top of drug therapy in Fuwai Hospital from January 2010 to September 2020, were collected and analyzed. Baseline clinical data (including demographic data, basic treatment, etc.) were collected through the electronic medical record system. Changes of indexes such as New York Heart Association (NYHA) classification, N-terminal pro-brain natriuretic peptide (NT-proBNP), left ventricular end diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), left ventricular mass index (LVMI) before and after therapy were analyzed. Results: A total of 10 patients were collected. There were 8 females in this patient cohort, age was (18.4±5.0) years and onset age was (15.3±5.0) years. All 10 patients received standard heart failure medication therapy in addition to hormone and/or immunosuppressive anti-inflammatory therapy, but cardiac function was not improved, so aortic balloon dilatation and/or aortic stenting were performed in these patients. The median follow-up was 3.3(1.3, 5.6) years. On the third day after interventional therapy, the clinical symptoms of the 10 patients were significantly improved, NYHA classfication was restored from preoperative Ⅲ/Ⅳ to Ⅱ at 6 months post intervention( P <0.05). Compared with preoperation, NT-proBNP ( P =0.028), LVEDD ( P= 0.011) and LVMI ( P =0.019) were significantly decreased, LVEF was significantly increased ( P <0.001) at 6 months after operation. Compared with preoperation, NT-proBNP ( P =0.016), LVEDD ( P =0.023) and LVMI ( P =0.043) remained decreased, LVEF remained increased ( P <0.001) at 1 year after operation. Conclusion: Results from short and medium term follow-up show that interventional therapy on top of heart failure drug therpay can effectively improve left cardiac function and attenuate cardiac remodeling in patients with TA-MAS comorbid with HFrEF.

Objective: To analyze the clinical features and summarize the experience on the diagnosis and treatment of aortic stenosis caused by Takayasu arteritis in pediatric patients. Methods: This study was a retrospective study. Five pediatric patients diagnosed as aortic stenosis caused by Takayasu arteritis in Fuwai Hospital of Chinese Academy of Medical Sciences from January 2016 to August 2018 were included. The clinical features, methods of examination, treatment and outcome were analyzed. Results: There were 2 male and 3 female patients in this cohort. The age of onset ranged from 10 to 13 years. The main clinical symptoms were as follows: intermittent claudication and hypertension (5 patients), heart failure (3 patients). Three patients with heart failure were misdiagnosed with dilated cardiomyopathy in other hospitals. Except 1 patient died due to disease aggravation before operation, the other 4 patients received interventional therapy for severe heart failure or refractory hypertension on the basis of hormone anti-inflammatory treatment, including 2 patients treated with aortic balloon dilatation and 2 patients treated with aortic balloon dilatation and stent implantation. In post-operational follow-up, clinical symptoms and laboratory examination values of the 4 patients treated with interventional therapy were significantly improved. Conclusions: The clinical symptoms of pediatric patients with aortic stenosis caused by Takayasu arteritis mainly present with intermittent claudication, hypertension and heart failure. Aortic intervention strategy should be applied for pediatric patients with severe heart failure or refractory hypertension as early as possible.

Objective: To evaluate the effect of stenting for proximal atherosclerotic extracranial vertebral artery stenosis. Methods: A total of 204 proximal atherosclerotic extracranial vertebral artery stenosis patients underwent stent implantation at Fuwai Hospital were enrolled consecutively between August 2007 and June 2014 prospectively. Medical records were collected and the clinical results were obtained through outpatient and telephone follow up. Results: (1) The patients were (64.1±7.9) years old, and 179 were male (87.7%). (2) Stent implantation was performed on 210 proximal atherosclerotic extracranial vertebral artery stenosis lesions with 210 stents (156 on the left, 54 on the right), and 6 patients received both sides stent implantations. Technical success rate was 100%(210/210). The stenosis of the lesions was decreased from (85.1±6.4) % to (6.5±3.2) % after the stent implantation ( P <0.01). (3) Three (1.5%) patients experienced transient ischemic attack during the procedure, and two (1.0%) patients suffered from minor posterior circulation ischemic strokes on the 2nd and 10th day after the procedure, respectively. (4)The median follow-up was 1.5 (0.8-2.5) years. Three(1.5%) patients died (two non-vacular deaths, and the other one due to sudden cardiac death). Three (1.5%) patients developed stroke (one case ipsilateral posterior circulation stroke, and two cases unrelated area stroke). Four (2.0%) patients experienced transient ischemic attack. One patient suffered nonfatal myocardial infraction. In-stent restenosis occurred in thirty nine (19.4%) patients, of which fourteen (35.9%) patients were totally occluded and four (10.3%) patients with symptomatic restenosis. Kaplan-Meier survival curve showed that the primary patency rate of the vertebral artery were 85.6%, 78.6%, 72.2% and 64.4% at 1, 2, 3 and 5 years, respectively. Conclusions: Stenting for proximal atherosclerotic extracranial vertebral artery stenosis is safe and feasible, with a good middle to long-term patency rate. However, further trials are required to validate the effective results found in this patients cohort.