Faculty Publications
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Item Design of square patch antenna with a notch on FR4 substrate(2007) Bhardwaj, D.; Sancheti, S.; Bhatnagar, D.The simulation and experimental results of square patch antennas having a notch and designed on FR4 substrate are reported in this paper. The notch angle is varied and different radiation properties of antennas are tested. It is found that on reducing the notch angle θ from 180° to 164°, the patch resonates at a single frequency. However on reducing notch angle further, the patch starts resonating at two different frequencies. The f2, f 1 ratio almost linearly increases on decreasing the notch angle. The 10dB impedance bandwidth (VSWR 2:1) of antenna increases up to notch angle 151° but thereafter that antenna behaves simply as a dual frequency antenna with narrow bandwidth at each resonance frequency.Item Analysis of Raised Cosine Filtering in communication systems(2007) Sharma, O.P.; Janyani, V.; Sancheti, S.In this era of wireless communication systems Inter Symbol Interference (ISI) is a major issue. In this paper the inter symbol interference rejection capability of a Raised Cosine Filter (RCF) is analyzed. Simulation is done for analyzing the importance of Rolloff factor and its selection in a raised cosine filter for evaluating the desired response. Communication toolbox in CAD Tool MATLAB is being employed for the simulation.Item Design of square patch antenna with a notch on FR4 substrate(2008) Bhardwaj, D.; Bhatnagar, D.; Sancheti, S.; Soni, B.Simulation and measured results of a square patch antenna with a notch to search their possible application on modern communication systems including WiMax systems are presented. The antennas are designed on an FR4 substrate and the notch angle is varied under different conditions. It is found that on varying the notch angle from 180° to 164°, antennas resonate at a single frequency but on reducing the notch angle further, antennas start resonating at two frequencies with improved bandwidth. The optimum performance of an antenna is obtained when the notch angle is set to 151°. Different radiation parameters of the antennas under varying conditions are analysed and their possible applications in modern communication systems are investigated. © 2008 The Institution of Engineering and Technology.Item Multipath fading characteristics of millimeter wave radio propagation in urban microcellular environment(2008) Joshi, S.; Sancheti, S.The frequency region 28-38 GHz has potential applications in fixed-wireless broadband services on account of availability of large spectrum and adequate device support to ease spectrum congestion problems, particularly in urban centers. This paper envisages development of a multiray propagation model to investigate multipath fading prevailing in millimeter wave radio propagation in a micro cellular environment. The model is simulated and measurements are carried out to estimate fast fading, propagation loss, and delay spread along micro cellular streets of variable width. The results depicted in the paper yields quantitative trends, with specific use in planning radio cells for fixed- wireless broadband services in urban microcellular environment. © 2008 IEEE.Item Foliage loss measurements of tropical trees at 35 GHz(2008) Joshi, S.; Sancheti, S.The presence of foliage in the propagation channel can lead to severe signal attenuation, and thus the effects of vegetation in the propagation environment need to be considered in any prediction model. In the present work, a measurement study is undertaken to quantify the attenuation caused due to tree canopies, at 35 GHz. The trees prevailing in typical Indian deserts, having variation in the leaf size and leaf density along the tree canopy are included in the study and in each case, attenuation characteristics are reported. The results presented in the paper may be of vital importance for radio cell planning operating at millimeter wave frequency. © 2008 IEEE.Item Square patch microstrip antenna with single notch having an air gap(2008) Bhardwaj, D.; Komal; Bhatnagar, D.; Sancheti, S.The paper presents a modified rectangular patch microstrip antenna having a triangular notch in one of its straight arm and designed on dielectric material under the presence of variable air gap. The measured performances of this antenna without air gap are compared with those obtained through simulation results of this antenna under the presence of variable air gap. It is observed that the performance of antenna improves significantly. © 2008 IEEE.Item Radiation performance of an elliptical patch antenna with a circular for modern communication systems(2008) Bhardwaj, D.; Bhardwaj, V.; Bhatnagar, K.D.; Sancheti, S.The paper presents the radiation performance of an elliptical (a=15mm, b=10.5mm) patch antenna having circular slot (R=4.8mm) designed on glass epoxy FR4 substrate and its performance is compared with a simple elliptical patch antenna without slot. The simulation results for this antenna are obtained with available IE3D simulation software by varying semi major axis (a) and semi minor axis (b). The elliptical patch antenna with circular slot of specific radius not only resonates at two different frequencies but also presents a relatively wide bandwidth, higher directivity and enhancement of gain. By designing antenna on low permittivity substrate, a much higher bandwidth may be achieved. ©2008 IEEE.Item Design and development of SiGe HBT based high gain amplifier for GPS application(2008) Soni, B.; Ramasubramanian, R.; Sancheti, S.A two stage high gain small signal amplifier for GPS based receiver application is designed and realised using SiGe Hetrojunction Bipolar transistor (HBT). The measured gain and noise figure is 33.5 dB and 2.9dB respectively at Vce of 2 V, and total current of 10mA. The circuit is fabricated on microstrip configuration using RT duroid substrate of dielectric constant 10.5 and height 50 mils. This circuit is being used in satellite based GPS receiver. © 2008 IEEE.Item Broad band parasitically coupled concentric semi circular elliptically ring antenna surrounding an elliptical patch with air gap(2009) Bhardwaj, D.; Sharma, K.; Bhatnagar, D.; Sancheti, S.The paper presents the performance of a parasitically coupled semi circular elliptical ring antenna surrounding elliptical patch geometry having air gap between conducting patch and ground plane. With proposed modifications in the conventional circular patch geometry, the bandwidth of modified antenna with an air gap is around seven times higher than that of a simple circular patch antenna. The gain, directivity and efficiency of modified circular patch antenna with air gap is also improved to some extent but still these are less than desired values. The E and H plane radiation patterns presented by antenna in the frequency range where broadband performance is obtained are identical in shape and nature. Direction of maximum intensity retained by antenna at both frequencies is normal to patch geometry. ©2009 IEEE.Item Radiations from double notched square patch antenna on FR4 substrate(2008) Bhardwaj, D.; Bhatnagar, D.; Sancheti, S.; Soni, B.This paper presents the radiation performance of a square patch antenna having two triangular notches on opposite edges designed on glass epoxy FR4 substrate and its performance is compared with a simple square patch antenna without any notch. The simulated results for this antenna are obtained by varying notch angle and compared with the measured results. The results indicate that square patch antenna with both notch angles equal to 168o resonates not only at two different frequencies but also offers a much higher bandwidth in comparison to a normal square patch (without notches). Both these resonance frequencies lie in the median band (3.25 to 3.85 GHz) allotted by IEEE 802.16 working group for WiMAX systems. The performance of antenna is optimized considering different conditions to obtain an antenna with dual band and high bandwidth performance. The radiation patterns, gain and radiation efficiency of antenna are also determined. © 2008 SBMO/SBMag.