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1.
Sensors (Basel) ; 20(3)2020 Feb 04.
Artículo en Inglés | MEDLINE | ID: mdl-32033139

RESUMEN

The permittivity of blood glucose is not a strong function of its concentration in microwave or millimeter-wave frequencies. Measuring glucose concentrations remains a challenge, particularly in the presence of interference caused by the ambient leaky waves. In this paper, however, we demonstrate that a near-linear correlation between the glucose concentration and the blood permittivity was noticeably observed at a whispering gallery mode resonance. METHOD: the proposed sensor was a vacuum suction aspirator partially wounded with a turn of the Goubau line. This arrangement enabled a fixed cylindrical volume of a skin tissue bump or glucose/water solution to be formed and used as a whispering gallery resonator for in-vivo and ex-vivo measurements. RESULTS: in the in-vivo study, a near-linear correlation between the glucose levels and the S21 parameters was noticeably observed at the fundamental whispering gallery resonance (i.e., at 2.18 GHz). In the ex-vivo study, a similar correlation was observed between the concentration of a glucose/water solution and the S21 parameters 56.6 GHz. CONCLUSION: the results of both investigations were consistent not only with the invasive measurements using the Accu-checkTM, but also with the conclusion drawn by some other research groups who have successfully measured blood glucose concentrations at millimeter-wave frequencies.


Asunto(s)
Técnicas Biosensibles , Automonitorización de la Glucosa Sanguínea/instrumentación , Glucemia/análisis , Piel/patología , Algoritmos , Automonitorización de la Glucosa Sanguínea/métodos , Radiación Electromagnética , Voluntarios Sanos , Humanos , Microondas , Reconocimiento de Normas Patrones Automatizadas , Fantasmas de Imagen , Reproducibilidad de los Resultados , Agua/análisis
4.
Mymensingh Med J ; 26(3): 642-649, 2017 07.
Artículo en Inglés | MEDLINE | ID: mdl-28919622

RESUMEN

Post operative complications after pituitary tumour surgery vary according to procedure. There are several surgical procedures being done such as transcranial, transsphenoidal microsurgical and transsphenoidal endoscopic approaches. One of the commonest complications is diabetes insipidus (DI). Our main objective was to find out the incidence of diabetes insipidus in post operative period among patients undergoing surgical intervention for pituitary tumour in our institute. The presence of diabetes insipidus in the postoperative period was established by measuring serum Na+ concentration, hourly urine output and urinary specific gravity to find out the incidence of diabetes insipidus in postoperative period in relation to age, gender, tumour diameter, function of tumour (i.e., either hormone secreting or not) and operative procedure used for surgical resection of pituitary tumor. As it is the most common postoperative complication so, in this study we tried to find out how many of the patients develop diabetes insipidus in postoperative period following surgical resection of pituitary tumour. This cross sectional type of observational study was carried out in the department of Neurosurgery, BSMMU from May 2014 to October 2015 on 33 consecutive patients who underwent surgical intervention for pituitary tumour for the first time. Data was collected by using a data collection sheet. The incidence of diabetes insipidus was found 23.1% of patients in <30 year age group, 38.5% of patients in 31-40 year age group and 38.5% of patients in ≥40 year age group (p=0.764). In case of distribution of patients according to gender 38.5% of male and 61.5% of female developed diabetes insipidus (p=0.073). Regarding tumour size 30.8% and 69.2% of patients developed diabetes insipidus having tumour diameter <30mm and ≥30mm respectively (p=0.590). In case of operative procedure 69.2% of patients developed diabetes insipidus who was operated by transsphenoidal endoscopic approach, 23.1% and 7.7% of patients developed diabetes insipidus who underwent pituitary tumour resection through transsphenoidal microscopic approach and transcranial microscopic approach respectively (p=0.432). 17.6% of patients develop DI having functioning pituitary macroadenoma and 62.5% of patients develop DI having nonfunctioning pituitary macroadenoma. This observational study has been performed to find out the incidence of diabetes insipidus. Incidence of postoperative DI is more at or around the age of 40 years. It is slightly predominant in female. Most of the patients manifest DI in the first 24 hours of surgical intervention. Incidence of DI is low among patients having functioning pituitary macroadenoma.


Asunto(s)
Adenoma , Diabetes Insípida , Neoplasias Hipofisarias , Adenoma/cirugía , Adulto , Estudios Transversales , Diabetes Insípida/etiología , Femenino , Humanos , Incidencia , Masculino , Neoplasias Hipofisarias/cirugía , Complicaciones Posoperatorias , Estudios Retrospectivos
5.
Mymensingh Med J ; 26(3): 684-688, 2017 07.
Artículo en Inglés | MEDLINE | ID: mdl-28919629

RESUMEN

Acinar cell carcinoma (ACC) of the pancreas is a very rare neoplasm. We report a case of pancreatic acinar cell carcinoma involving the uncinate process of the pancreas. A 45 year old man presented with a painful upper abdominal mass without any jaundice or weight loss. Computed Tomography (CT) and Magnetic Resonance Cholangio-Pancreatography (MRCP) indicated a mass lesion in the uncinate process of the pancreas. He underwent Whipple's procedure (Pancreaticoduodenectomy). Histological slides revealed features of Acinar cell carcinoma (ACC) in the uncinate process of the pancreas and a lymph node.


Asunto(s)
Carcinoma de Células Acinares , Neoplasias Pancreáticas , Carcinoma de Células Acinares/cirugía , Humanos , Ganglios Linfáticos , Masculino , Persona de Mediana Edad , Neoplasias Pancreáticas/cirugía , Pancreaticoduodenectomía , Tomografía Computarizada por Rayos X
6.
Mymensingh Med J ; 25(1): 126-31, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26931261

RESUMEN

A strong association between total serum Immunoglobulin E (IgE) levels, skin test reactivity to aeroallergens, and asthma phenotype was found in previous studies. The current study has been undertaken to observe the total serum IgE level in asthmatic patients compared with normal healthy volunteers (control) of Bangladeshi subjects and to see its prospect in diagnostic aid. This case-control study was carried out in the department of Respiratory Medicine of National Institute of Diseases of the Chest and Hospital (NIDCH), Dhaka during the period from July 2008 to June 2009. Four hundred & eight (408) cases (asthmatics matching age, sex and geographic location) and 478 controls (non-asthmatics matching age, sex and geographic location) were studied. The level of serum IgE was found more in asthma patients than control group which were 345.88 and 224.64 respectively (p<0.001). In both group, serum IgE level was more in male than female. There was wide variation in serum IgE level in both the asthma and control group (4.2 to 3471.0 iu/ml in asthma group and 1.2 to 1045.7 iu/ml in control). Considerable overlap has been observed between the IgE values of control and asthma group. Due to this overlap its diagnostic significance in allergic condition in Bangladeshi population seems to be limited.


Asunto(s)
Asma/diagnóstico , Inmunoglobulina E/sangre , Adolescente , Adulto , Asma/etiología , Asma/inmunología , Bangladesh , Estudios de Casos y Controles , Niño , Femenino , Voluntarios Sanos , Humanos , Masculino , Persona de Mediana Edad , Centros de Atención Terciaria , Adulto Joven
7.
Mymensingh Med J ; 25(1): 18-22, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26931243

RESUMEN

Pregnancy is a great stressful physiological condition in women during their reproductive period. During pregnancy several hemodynamic, biochemical and hematological modifications occur as a part of the physiological adaptation of the body. Changes in blood pressure occur in third trimester of pregnancy, which may be associated with increased maternal and infant mortality and morbidity. This cross-sectional study was carried out in the Department of Physiology, Mymensingh Medical College, Mymensingh, from July 2013 to June 2014. Study subjects were selected by following purposive sampling procedure and the protocol of this study was approved by Institutional Ethics Committee (IEC) of Mymensingh. This study enrolled 100 pregnant women of third trimester of pregnancy and 100 aged matched non-pregnant women from Mymensingh district. Mean systolic blood pressure in study group were 124.8±14.51 mm of Hg and in control group were 106.50±10.67 mm of Hg, which was statistically increased. Diastolic blood pressure in study group was 83.00±13.37 mm of Hg and in control group 71.05±7.12 mm of Hg, which was also statistically significant. The changes in blood pressure in third trimester of pregnancy is the major concern of developing the risk of pre-eclampsia & eclampsia, and increased prevalence of IUGR, pre-maturity and perinatal mortality. This study reveals significant changes of blood pressure during third trimester of pregnancy.


Asunto(s)
Presión Sanguínea , Tercer Trimestre del Embarazo , Adolescente , Adulto , Bangladesh , Estudios Transversales , Femenino , Humanos , Embarazo , Adulto Joven
8.
Mymensingh Med J ; 25(1): 27-30, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26931245

RESUMEN

Zinc plays a vital role in the immune status. Its deficiency affects host defense by reducing the number of circulating T cells and phagocytosis activity of other cells which ultimately impair cell mediated immunity. The cell-mediated immunity plays a major role in the causation of pulmonary tuberculosis. The present study was carried out to estimate serum zinc level in newly detected multidrug resistant tuberculosis (MDR-TB) in adult population. In this study total fifty (50) MDR-TB patients were enrolled conveniently from the in-patients departments of National Institute of Diseases of the Chest Hospital (NIDCH), Bangladesh. Serum zinc was estimated by atomic absorption spectrophotometry method from early morning fasting blood sample. Serum zinc level was assessed according to normal cut-off value 70-120 µgm/dl and 76% studied population were found lower than this value. The mean±SD serum zinc level was observed 60.40±8.91 µgm/dl. No associations were found between serum zinc level with age (p=0.11) and with sex (p=0.085) of the study population respectively. The low level of serum zinc in MDR-TB patients suggested impaired immune status of our study population.


Asunto(s)
Tuberculosis Resistente a Múltiples Medicamentos/sangre , Tuberculosis Pulmonar/sangre , Zinc/sangre , Adolescente , Adulto , Anciano , Bangladesh , Femenino , Humanos , Masculino , Persona de Mediana Edad , Adulto Joven
9.
Mymensingh Med J ; 25(1): 31-8, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26931246

RESUMEN

This case control study was done to ascertain the association between exposures to biomass cooking fuel smoke and pulmonary tuberculosis. Cases were all newly diagnosed pulmonary tuberculosis patients, randomly collected from the Hospital (DOTS centers) Registry from January 2012 to June 2012 from two Upazillas of Sirajganj district, Bangladesh. A home visitation program was done subsequently. Healthy controls were recruited from the neighbourhood of each case through a predefined procedure. Total 276 new pulmonary tuberculosis cases and 276 neighbourhood controls were enrolled. A semi-structured questionnaire containing demographic information, smoking habits, cooking place, kitchen condition, use of biomass fuel for cooking was used for interview. Crude (unadjusted) odd ratios and their corresponding 95% confidence limits for independent variables were determined by binary logistic regression. All significant variables were entered into a multivariate conditional logistic regression model and a final fitted model was determined by backward elimination methods. In univariate analysis, member of a nuclear family {Unadjusted odd ratio (Unadj. OR) 1.570, 95% CI 1.008-2.44)}, having non-formal education (Unadj. OR 2.739, 95% CI 1.219, 6.153) or primary (Unadj. OR 3.407, 95% CI 1.492, 7.782) to secondary level (Unadj. OR 2.392, 95% CI 1.032, 5.544) education, using cow dung (Unadj. OR 3.961, 95% CI 1.267, 12.376) and biomass fuel i.e. plant origin (Unadj. OR 3.382, 95% CI 1.087, 10.518) for cooking, past smoker (Unadj. OR 2.504, 95% CI 1.061, 5.910), using open oven (Unadj. OR 3.109, 95% CI 0.995, 9.716), having small kitchen area (Unadj. OR 0.99, 95% CI 0.989, 0.999) all were significantly associated with tuberculosis. When all significant variables were entered into a multivariate conditional logistic regression model nuclear family {Adjusted odd ratio (Adj OR) 1.808, 95% CI 1.127, 2.9)}, primary level education (Adj OR 2.86, 95% CI 1.23, 6.647) and non formal education (Adj OR 2.312, 95% CI 1.013, 5.276), biomass fuel (plant origin, Adj OR 3.497, 95% CI 1.059, 11.55), and cow dung (Adj OR 4.368, 95% CI 1.319, 14.464)) used in cooking and irregular smoker (who stop smoking at least 6 month back) (Adj OR 2.806, 95% CI 1.141, 6.901) were significantly associated with tuberculosis cases. From this study significant association have been found between exposure to combustion of biomass cooking fuel and tuberculosis.


Asunto(s)
Contaminantes Atmosféricos/efectos adversos , Contaminación del Aire Interior/efectos adversos , Culinaria/métodos , Humo/efectos adversos , Tuberculosis Pulmonar/epidemiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Bangladesh/epidemiología , Biomasa , Estudios de Casos y Controles , Culinaria/instrumentación , Femenino , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Tuberculosis Pulmonar/inducido químicamente , Adulto Joven
10.
Mymensingh Med J ; 25(1): 109-18, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26931259

RESUMEN

Diabetes mellitus (DM) is defined as a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. This study was undertaken to explore the basic defect in type 2 diabetes patients in Bangladesh. This was an observational study with case control design, was conducted in the Biomedical Research Group, Research Division, Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine Metabolic Disorders (BIRDEM), Dhaka, Bangladesh, during the period of July 2008 to June 2009. A total of 153 subjects were included in study of which 63 belonged to type 2 diabetes mellitus group and 90 were healthy controls. Fasting and 2 hours postprandial blood glucose, serum insulin, HOMA%B, HOMA%S, QuickI, Glucose /insulin ratio, TG were measured and age, BMI, WHR were recorded. Waist-hip ratio (WHR), was significantly higher in T2DM as compared to control subjects [WHR, mean±SD, 0.94±0.12 vs. 0.88±0.06, p<0.001]; Glucose and insulin ratio of T2DM was significantly higher as compared to control subject [Glu: Ins, Median (range) of 0.54 (0.17-2.33) vs. 0.37(0.06-1.52)]. Insulin secretion (HOMA%B) was significantly lower in diabetic as compared to control subjects [HOMA%B, median (range), 71(4.90-391) vs. 180(59-634) p<0.001]; The quantitative insulin sensitivity check Index (QUICKI) of diabetic subjects were significantly higher as compared to control [QUICKI median (range) 39.90(4.80-138.10) vs. 0.55(0.36-0.85), <0.001]. Triglyceride (TG) and cholesterol (Chol) were significantly higher [(mg/dl), (mean±SD), TG (142±80.14) vs. (142±80.14); Chol (189±50.76) vs. (172±45), p=0.029] in T2DM as compared to control subjects. Those with diabetes showed significant association with insulin secretory defect (HOMA%B, p=0.006) and insulin resistance as assessed by GINR (p<0.001) and QuickI (p<0.001) but not by HOMA%S (p=0.127). The present data suggest that both insulin secretory defect and insulin sensitivity are present in T2 diabetic subjects of Bangladesh.


Asunto(s)
Diabetes Mellitus Tipo 2/epidemiología , Diabetes Mellitus Tipo 2/metabolismo , Hiperglucemia/epidemiología , Resistencia a la Insulina , Insulina/metabolismo , Adulto , Bangladesh , Glucemia/metabolismo , Estudios de Casos y Controles , Colesterol/sangre , Diabetes Mellitus Tipo 2/sangre , Femenino , Humanos , Hiperglucemia/etiología , Insulina/sangre , Secreción de Insulina , Masculino , Persona de Mediana Edad , Triglicéridos/sangre
11.
Mymensingh Med J ; 25(2): 211-4, 2016 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-27277349

RESUMEN

In the present study serum glucose were estimated in pregnant women during the first trimester of pregnancy and third trimester of pregnancy to observe the frequency of hyperglycemia during pregnancy and to assess the incidence of gestational diabetes mellitus. This study was a cross sectional study, carried out in the Department of Physiology of Mymensingh Medical College, Mymensingh from July 2014 to June 2015. For this purpose, total 300 women with age ranged from 18 to 35 years were selected and divided into 100 healthy non pregnant women as control group and 200 normal pregnant women as study group. Study group was further divided into 100 pregnant women in first trimester of pregnancy and 100 pregnant women in third trimester of pregnancy. Diagnosed case of type I and type II diabetes, hypothyroidism, cushing's syndrome, polycystic ovary, antipsychotic drug users, regular steroid users were excluded from this study. Serum glucose was evaluated by the glucose-oxidase principle by GOD-PAP method in women with 1st trimester of pregnancy, 3rd trimester of pregnancy and in non pregnant women. Statistical analysis of data was done by unpaired student's t test. The results showed that the serum glucose levels increased significantly in third trimester and the value is not significant in first trimester. The increasing frequency of serum glucose level in third trimester may predispose the women to hyperglycemia of pregnancy or gestational diabetes mellitus.


Asunto(s)
Glucemia/análisis , Diabetes Gestacional/metabolismo , Primer Trimestre del Embarazo/sangre , Tercer Trimestre del Embarazo/sangre , Adolescente , Adulto , Bangladesh , Estudios Transversales , Femenino , Humanos , Embarazo , Adulto Joven
12.
Mymensingh Med J ; 24(3): 464-6, 2015 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-26329940

RESUMEN

Various hormones can cause marked changes in pregnant woman's appearance. Decreased level of serum albumin occurs in third trimester of pregnancy, which may be associated with increased maternal and infant mortality and morbidity. So, this study was carried out to evaluate and assess the level of serum albumin in third trimester of pregnancy. This cross-sectional study was carried out in the Department of Physiology Mymensingh Medical College, Mymensingh. This study enrolled 100 pregnant women of third trimester of pregnancy and 100 aged matched non-pregnant women from Mymensingh district. In this study serum albumin level in study group were 33.41 ± 4.62gm/l and in control group were 37.09 ± 4.21 gm/l, which was statistically decreased. The lower level of serum albumin in third trimester of pregnancy is the major concern of development of physiological edema during pregnancy and may be associated with pre-eclampsia.


Asunto(s)
Tercer Trimestre del Embarazo/sangre , Embarazo/fisiología , Albúmina Sérica/metabolismo , Adulto , Estudios de Casos y Controles , Estudios Transversales , Femenino , Humanos , Preeclampsia/sangre
13.
Mymensingh Med J ; 24(4): 710-6, 2015 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-26620008

RESUMEN

It is suggested in different studies that gender has a great impact on the distribution of risk factors of stroke. This study aims at determining the gender differences in risk factors of acute ischemic stroke among male and female patients. Data extracted for this study were taken from a case control study which was carried out in the departments of Neurology and Medicine of Dhaka Medical College Hospital (DMCH) and Shaheed Suhrawardy Medical College Hospital (ShSMCH) Dhaka from July 2009 to June 2011. We collected data of 125 patients with ischemic stroke and 129 healthy controls from the primary source. All secondary data were divided on the basis of gender. Among all male respondents 70 stroke patients were considered as case and 72 healthy respondents were considered as control and in female group 55 were stroke patients (case) and 57 were healthy control. Risk factors of stroke for male and female were evaluated separately. After multivariate analysis ever smoking (both present and ex smoker) (adj. OR 3.799, 95% CI 1.416, 10.19), diabetes mellitus (adj. OR 5.687, 95% CI 1.99, 16.26), hypertension (adj. OR 18.53, 95% CI 6.43, 53.4) and total cholesterol (adj. OR 1.017, 95% CI 1.01, 1.03) were found significant predictors for stroke in male whereas diabetes mellitus (adj. OR 6.989, 95% CI 1.54, 31.64), hypertension (adj. OR 17.85, 95% CI 5.1, 62.38), serum low density lipoprotein (LDL) (adj. OR 1.04, 95% CI 1.013, 1.07) and serum triglyceride (TG) (adj. OR 1.012, 95% CI 1.004, 1.02) were found significant in female. Besides taking the controlling measure for hypertension and diabetes mellitus, life style modification is an important factor to prevent stroke in both sexes.


Asunto(s)
Isquemia Encefálica/etiología , Accidente Cerebrovascular/etiología , Anciano , Bangladesh , Estudios de Casos y Controles , Colesterol/sangre , Complicaciones de la Diabetes/etiología , Femenino , Humanos , Hipertensión/complicaciones , Masculino , Persona de Mediana Edad , Factores de Riesgo , Caracteres Sexuales
14.
Bangladesh Med Res Counc Bull ; 41(1): 13-8, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-27089629

RESUMEN

Obstructive sleep apnea hypopnea syndrome (OSAHS) is the occurrence of repetitive episodes of complete or partial upper airway obstruction during sleep in association with loud snoring and daytime sleepiness and is a risk factor for hypertension, cardiovascular and cerebrovascular diseases and more. The present study was performed to assess the prevalence as well as the clinical and anthropometric predictors of OSAHS in an urban community of middle aged Bangladeshi population. The study was a cross-sectional, community-based prevalence study which was performed in an urban community in Dhanmondi Thana Pourashava of Dhaka city from July 2007 to June 2008. About 2500 citizens, aged 30-60 years were included in the study. In stage one of the study, they were informed about the polysomnography (PSG) study (stage two of the study) and 2250 of them gave consent. Subjects were then divided into habitual (495) and non-habitual snorers (1755). Among 2250 subjects, the prevalence of obstructive sleep apnea hypopnea (OSAH) in habitual snorers was 48.33% (239/495), and that in non-habitual snorers was 1.66% (29/1755). So, the overall prevalence of OSAH in the screened population was 11.91%, and that of OSAHS was 3.29%. Likewise, the prevalence of OSAH and OSAHS in men were 17.37% and 4.49%, respectively and 6.25% and 2.14% in women. Multivariate analysis revealed that male gender, age, obesity (defined by a high body mass index), waist/hip ratio were significant risk factors for OSAHS. These findings can help us in identifying the prevalence of OSAHS in the community and further planning in the management of obesity and cardiovascular diseases.


Asunto(s)
Apnea Obstructiva del Sueño/epidemiología , Adulto , Antropometría , Bangladesh/epidemiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Polisomnografía , Prevalencia , Factores de Riesgo
15.
ScientificWorldJournal ; 2014: 604375, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24895656

RESUMEN

A novel probe-fed compact inverted S-shaped multifrequency patch antenna is designed. By employing two rectangular slots that change the conventional rectangular patch into an inverted S-shaped patch, the antenna is able to operate in triple frequency in the X-band. The performance criteria of the proposed design have been experimentally verified by fabricating a printed prototype. The measured results show that the -10 dB impedance bandwidth of the proposed antenna at lower band is 5.02% (8.69-9.14 GHz), at middle band is 9.13% (10.47-11.48 GHz), and at upper band is 3.79% (11.53-11.98 GHz). Two elliptical slots are introduced in the ground plane to increase the peak gain. The antenna is excited by a simple probe feeding mechanism. The overall antenna dimension is 0.52λ × 0.60λ × 0.046λ at a lower resonance frequency of 9.08 GHz. The antenna configuration and parametric investigation are conducted with the help of the high frequency structural simulator, and a good agreement is achieved between the simulated and measured data. The stable gain, omnidirectional radiation pattern, and consistent radiation efficiency in the achieved operating band make the proposed antenna a suitable candidate for X-band applications.


Asunto(s)
Tecnología Inalámbrica/instrumentación , Diseño de Equipo
16.
ScientificWorldJournal ; 2014: 673846, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24987742

RESUMEN

This paper introduces a new configuration of compact, triangular- and diamond-slotted, microstrip-fed, low-profile antenna for C/X band applications on polytetrafluoroethylene glass microfiber reinforced material substrate. The antenna is composed of a rectangular-shaped patch containing eight triangles and two diamond-shaped slots and an elliptical-slotted ground plane. The rectangular-shaped patch is obtained by cutting two diamond slots in the middle of the rectangular patch, six triangular slots on the left and right side of the patch, and two triangular slots on the up and down side of the patch. The slotted radiating patch, the elliptical-slotted ground plane, and the microstrip feed enable the matching bandwidth to be widened. A prototype of the optimized antenna was fabricated on polytetrafluoroethylene glass microfiber reinforced material substrate using LPKF prototyping machine and investigated to validate the proposed design. The simulated results are compared with the measured data, and good agreement is achieved. The proposed antenna offers fractional bandwidths of 13.69% (7.78-8.91 GHz) and 10.35% (9.16-10.19 GHz) where S11 < -10 dB at center frequencies of 8.25 GHz and 9.95 GHz, respectively, and relatively stable gain, good radiation efficiency, and omnidirectional radiation patterns in the matching band.


Asunto(s)
Diseño de Equipo , Modelos Teóricos , Tecnología Inalámbrica/instrumentación
17.
ScientificWorldJournal ; 2014: 131374, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24895643

RESUMEN

Analysis of the resonance response improvement of a planar C-band (4-8 GHz) antenna is proposed using parasitic element method. This parasitic element based method is validated for change in the active and parasitic antenna elements. A novel dual-band antenna for C-band application covering 5.7 GHz and 7.6 GHz is designed and fabricated. The antenna is composed of circular parasitic element with unequal microstrip lines at both sides and a rectangular partial ground plane. A fractional bandwidth of 13.5% has been achieved from 5.5 GHz to 6.3 GHz (WLAN band) for the lower band. The upper band covers from 7.1 GHz to 8 GHz with a fractional bandwidth of 12%. A gain of 6.4 dBi is achieved at the lower frequency and 4 dBi is achieved at the upper frequency. The VSWR of the antenna is less than 2 at the resonance frequency.


Asunto(s)
Tecnología Inalámbrica/instrumentación , Diseño de Equipo
18.
ScientificWorldJournal ; 2014: 528489, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24971379

RESUMEN

A band-removal property employing microwave frequencies using complementary split ring resonators (CSRRs) is applied to design a compact UWB antenna wishing for the rejection of some frequency band, which is meanwhile exercised by the existing wireless applications. The reported antenna comprises optimization of a circular radiating patch, in which slotted complementary SRRs are implanted. It is printed on low dielectric FR4 substrate material fed by a partial ground plane and a microstrip line. Validated results exhibit that the reported antenna shows a wide bandwidth covering from 3.45 to more than 12 GHz, with a compact dimension of 22 × 26 mm(2), and VSWR < 2, observing band elimination of 5.5 GHz WLAN band.


Asunto(s)
Modelos Teóricos , Tecnología Inalámbrica
19.
ScientificWorldJournal ; 2014: 831435, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24977230

RESUMEN

A radio frequency (RF) resonator using glass-reinforced epoxy material for C and X band is proposed in this paper. Microstrip line technology for RF over glass-reinforced epoxy material is analyzed. Coupling mechanism over RF material and parasitic coupling performance is explained utilizing even and odd mode impedance with relevant equivalent circuit. Babinet's principle is deployed to explicate the circular slot ground plane of the proposed resonator. The resonator is designed over four materials from different backgrounds which are glass-reinforced epoxy, polyester, gallium arsenide (GaAs), and rogers RO 4350B. Parametric studies and optimization algorithm are applied over the geometry of the microstrip resonator to achieve dual band response for C and X band. Resonator behaviors for different materials are concluded and compared for the same structure. The final design is fabricated over glass-reinforced epoxy material. The fabricated resonator shows a maximum directivity of 5.65 dBi and 6.62 dBi at 5.84 GHz and 8.16 GHz, respectively. The lowest resonance response is less than -20 dB for C band and -34 dB for X band. The resonator is prototyped using LPKF (S63) drilling machine to study the material behavior.


Asunto(s)
Electrónica/instrumentación , Resinas Epoxi/química , Vidrio/química , Sistemas Microelectromecánicos/instrumentación , Modelos Teóricos , Telecomunicaciones/instrumentación , Simulación por Computador , Diseño Asistido por Computadora , Diseño de Equipo , Análisis de Falla de Equipo , Ensayo de Materiales , Microondas , Ondas de Radio
20.
ScientificWorldJournal ; 2014: 345190, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24982943

RESUMEN

Circularly polarized (CP) dual frequency cross-shaped slotted patch antenna on 1.575 mm thick glass microfiber reinforced polytetrafluoroethylene (PTFE) composite material substrate is designed and fabricated for satellite applications. Asymmetric cross-shaped slots are embedded in the middle of the square patch for CP radiation and four hexagonal slots are etched on the four sides of the square patch for desired dual frequency. Different substrate materials have been analysed to achieve the desired operating band. The experimental results show that the impedance bandwidth is approximately 30 MHz (2.16 GHz to 2.19 GHz) for lower band and 40 MHz (3.29 GHz to 3.33 GHz) for higher band with an average peak gain of 6.59 dBiC and 5.52 dBiC, respectively. Several optimizations are performed to obtain the values of the antenna physical parameters. Moreover, the proposed antenna possesses compactness, light weight, simplicity, low cost, and circularly polarized. It is an attractive candidate for dual band satellite antennas where lower band can be used for uplink and upper band can be used for downlink.


Asunto(s)
Diseño de Equipo/métodos , Politetrafluoroetileno/química , Tecnología Inalámbrica/instrumentación , Modelos Teóricos
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