INTERNATIONAL JOURNAL OF INFORMATION TECHNOLOGY - volume 5 issue 6, Aug-Sep
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Realization of Low RCS and Wide Beam Radiating Element for Ku- Band Electronically Steered Phased Array
Author: Raj Kumar1 , Pramendra Kumar Verma1*, M.V. Kartikeyan 2
Category: Microwave Measurements
Abstract:
The present paper discusses the design, analysis, and development of a low profile, low RCS, diagonally polarized and wide beam radiating element at Ku-Band for Electronically Steered Phased Array Antenna (ESPAA) for airborne applications. Radar Cross Section (RCS) of the antenna has been minimized by proper selection of substrate and eliminating the diffraction and scattering of the incident wave through the antenna. Finite element method (FEM) based full wave ANSYS's HFSS EM Simulation software was used for simulation and optimization of the antenna. The measured half power beam width of the antenna element is 90 degree and RCS better than -30 dBsm over the wide angular coverage of radiating element.
Keywords: Phased Array Antenna, RCS, SATCOM, VSWR
DOI: 10.32452/IJAMT.2019.194197
DOI URL: http://dx.doi.org/10.32452/IJAMT.2019.194197
Full Text:
Missing text in Vol 1 Issue 4 Article No 3
In vitro drug release study
Dissolution studies were conducted for a period of 24 hours using USP dissolution apparatus II at an rpm of 50 and at a temperature of 37± 20C and 900ml dissolution medium of 0.1 N HCl. Cumulative % drug release of micromatrices formulations made of ethyl cellulose after 24 hour time interval was found to be FEC1 had 89.93%, FEC2 had 97.52%, FEC3 had %84.63, FEC4 had 79.48%, FEC5 had 73.18%, and FEC6 had 72.68%. From this data we can know that with increase in concentration of ethyl cellulose there is decrease in drug release. FEC2 formulation had maximum release. FEC6 has the lowest release which had a drug: polymer ratio of 1:6. In vitro drug release of Micromatrices formulations made of Ethyl Cellulose was tabulated in Table No.6 and curves are as shown in Fig. No.10.
Optimized formulations for preparation of rapimelts:
Out of all formulations of Micromatrices with Ethyl Cellulose as controlled release polymer, based on the above results it was found that FEC2 had optimum flow properties, highest drug content of 96.52 ± 0.21%, acceptable moisture content of 0.1%, and cumulative % drug release of 97.52%. Thus FEC2 was selected as the optimized formulation among the Micromatrices with Ethyl Cellulose polymer for the preparation of Zolmitriptan rapimelts.
Characterization of Micromatrices blends:
Bulk density of all formulation blends were in the range of 0.53gm/cc to 0.55gm/cc. Tapped density of all Tablet blends were in the range of 0.54gm/cc to 0.57gm/cc. Carr’s index of all the Tablet blends containing ethyl cellulose micromatrices were between 2.19% and 3.95%, which indicate that the flow properties of all the Tablet blends were excellent. Hausner's ratio of all the Tablet blends containing ethyl cellulose micromatrices were between 1.022 and 1.04, which indicates the flow properties of the Tablet blends of all formulations are excellent. Angle of repose of EF2, EF3 and EF5 were 35.220C, 35.220C, and 35.530C respectively indicates fair flow property which does not require any aid and the other formulations EF1, and EF4 were 33.690C and 34.980C respectively indicates good flow properties. The results were depicted in Table No. 7.
Evaluation of Rapimelts for Thickness, Weight variation, Hardness, friability and drug Content:
Thicknesses of tablets of all the formulations were in the range of 4.93 ± 0.02mm to 5.16 ± 0.08mm. The average weights of all formulations were within the permissible limits. Hardness of the Tablet was between 5kg/cm2 and 6kg/cm2 and was maintained for all the batches in order to minimize the effect of hardness on the drug release because the effect of polymer concentration is the only area of interest. Friability test of all the formulations was found satisfactory showing enough resistance to the mechanical shock and abrasion. The weight loss was found to be in between 0.16% and 0.72% which shows that all the formulations comply with the friability test. Drug content uniformity in all formulations was calculated and the percent of active ingredient ranged from 93.57± 1.15% to 97.72 ± 0.49%. The results of thickness, weight variation, hardness, friability and drug content are shown in Table No.8.
Evaluation of rapimelts for In vitro disintegration time, Wetting time, Dispersion time, Uniformity of Dispersion and Water absorption ratio (%)
The In vitro disintegration values of all formulations in Phosphate Buffer PH 6.8 were in between 28.5sec and 50sec that is not more than 60sec which is the acceptable limit of an orally disintegrating Tablet. The values of EF4 and EF5 were 28.5 ± 0.70sec and 31 ± 1.41sec which were less than other formulations. The values are as follows: EF1 had 31 ± 1.41sec, EF2 had 40.1 ± 1.41sec, and EF3 had 38.5 ± 0.70sec. This difference may be because of the presence of combination of superdisintegrants in EF4 and EF5.
Wetting time of all the formulations were in the acceptable limit. They were in the range of 35.5sec to 45.97sec.
Dispersion times of all the formulations were in the acceptable limit. They were in the range of 31.98 ± 1.41sec to 48.5 ± 2.12sec. All the formulations passed through #22 no. sieve without any precipitate remaining and thus all of them were uniform. Water absorption ratios (%) of all the formulations were in the acceptable limit. They were in the range of 50.23 to 61.81. Drug content in the Tablets were observed for all the formulations. The results were shown in Table No.9.
In vitro dissolution studies
Dissolution studies were conducted for a period of 24 hours using USP dissolution apparatus II at an rpm of 50 and at a temperature of 37± 20C and 900ml dissolution medium of 0.1 N HCl. Cumulative % Drug release of rapimelts having ethyl cellulose micromatrices after 24 hour time interval was found to be EF1 had 80.99%, EF2 had 82.55%, EF3 had 85.71%, EF4 had 98.21%, and EF5 had 91.23%. From this data we can know that. EF4 and, EF5 formulations had maximum release. The dissolution data is shown in Table No.10 and the dissolution profiles were shown in Fig. No.11.
Dissolution Kinetics:
EF1 and EF2 formulations fit into Higuchi model as they have highest R2 values of 0.93823 and 0.9382 respectively. EF3 (0.9429) follows first order as its R2 value is highest in first order. EF4 (0.9518) and EF5 (0.9535) follows Peppas model. The n values of all the formulations are below 0.5 and thus the drug release mechanism follows Fickian diffusion. The first order for some of the formulations may be due to the action of other excipients used in Tableting. The release kinetics was shown in Table No.11 and the graphs were shown in Fig. No.12.
The Rapimelts containing Zolmitriptan micromatrices were successfully prepared by Mass Extrusion method and direct compression method. Micromatrices were prepared by mass extrusion method with drug: polymer ratios of ethyl cellulose (FEC). All the evaluation parameters of micromatrices were within the limits. The optimized formulation FEC2 showed the drug content of 96.52 ± 0.2, the cumulative % drug release of 97.52±0.041. Zolmitriptan rapimelts were prepared and evaluated for different parameters. All the evaluation parameters of all the formulations were within the official limits. The optimized formulations EF4 showed the highest drug content of 97.72 ± 0.49, the cumulative percentage drug release of 98.21±0.08. Their formulation includes the combination of superdisintegrants sodium starch glycolate (2%) and crosspovidone (2%). The release kinetics showed that the best fit of EF4 followed Krosmeyer Peppas and Higuchi model respectively. Out of the formulations EF4 is selected as the best since the drug release followed Krosmeyer Peppas model which is best suited for matrix type sustained release dosage form where the drug release is by Fickian diffusion.
Acknowledgment: The authors are thankful to Shri C. Srinivasa Baba, Shri G. Brahmaiah and Shri M.M. Kondaiah Management of Gokula Krishna College of Pharmacy, Sullurpet, SPSR Nellore Dist, A.P, India for availing the laboratory facilities during the course of research studies.
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