Theses and Dissertations
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Item Open Access Design and Analysis of Graphene Based Microstrip Patch Antenna at 7 THz(2021) Pala, Vidhi; Agrawal, Yash; Gupta, SanjeevThe need for high-speed transmission of information has extensively increased in today’s wireless and communication world. For an effective antenna design, material, and peripheral circuit to it are important parameters to attain high speed and effective transmission. It is investigated that conventional copper-based antennas are limited by various non-ideal effects at high-frequency operations. Consequently, this has triggered a lot of researches to investigate new materials that can work efficiently at high frequencies with considerable small latency and high bandwidth. It has been vividly explored that graphene is a prominent alternative to traditional copper material owing to its significantly high physical, chemical, thermal and mechanical properties. The graphene-based antennas possess high potential. However, this has been very marginally explored till date. This has been henceforward excitingly taken up in current work. In the present work, a rectangular inset-fed graphene-based patch antenna at 7 terahertz (THz) frequency has been designed. Further, the performance of graphene-based antenna is examined with different substrate materials like glass, teflon, silicon-dioxide, and quartz. It is analyzed that silicon dioxide and quartz substrates give remarkable return loss and high gain. It is also observed that if the patch is sandwiched between substrate and superstrate, then the performance of the antenna can be further improved in terms of gain and directivity. Mathematical analysis using FDTD (Finite Difference Time Domain) has also been explored for copper based microstrip patch antenna. The FDTD technique has been learnt during the project and result has been observed.Item Open Access Design and Analysis of Active RF Mixer for Wideband Communication System(Dhirubhai Ambani Institute of Information and Communication Technology, 2017) Mangukiya, Chiragkumar; Gupta, Sanjeev"This work presents active RF double-balanced down converter mixer with some modification and new techniques. Gilbert topology provides overall good gain and LO-RF isolation. It has poor noise figure performance. It is a narrow band in terms of Conversion Gain (CG), input matching and Noise Figure (NF). So noise cancelling transconductor is presented which lower noise figure of the first stage. With this technique, noise from input matching network can be eliminated and noise figure from rest of circuit can be minimized. To provide current requirement of the trans-conductor stage and to increase overall gain of mixer circuit current-bleeding circuit is used. This technique is used to make active mixer wideband in terms of parameters i.e. noisefigure, conversion gain, input-reflection coefficient, third order input-intercept point, and isolation. This circuit is implemented using MOSFET 0.18 ?m technology. It achieves conversion gain of 13.0 to 17.3 dB, the noise figure of 4 to 7.5 dB, third order inputintercept point is -3.78 dBm over a frequency range 1 GHz to 3 GHz. LO-RF isolation is good and input-reflection coefficient is also given better result in the entire frequency range. Active Mixer consumes 10.2 mA current from 1.6 V supply."Item Open Access Novel local oscillator circuit for sub-harmonic mixer(Dhirubhai Ambani Institute of Information and Communication Technology, 2005) Kishore, G. Pavan Krishna; Biswas, R. N.; Parikh, Chetan D.Direct Conversion RF transceiver is the enabling technique for the next generation cellular and personal communication devices striving for miniaturization, long life of battery and cost effectiveness. Existing techniques of Direct Conversion suffer from undesired carrier radiation from the receiver. This leads to distortion in the signal received by the users in the close proximity. The proposed transceiver design is an approach to address the discussed issue of carrier radiation. The existing systems use Sub Harmonic mixer to overcome this problem with a sinusoidal Local Oscillator (LO) running at half of the required carrier frequency. The W-CDMA systems which use QPSK modulation need eight phases of the LO, the generation of which consume large power due to the linear circuits used. The proposed design implements the octet phase LO using non-linear circuits. This leads to the significant improvement in terms of power consumption and area. The core work of the thesis involves designing and analysis of new circuit topology that uses CMOS inverter chain for generating the octet-phase trapezoidal LO, to drive the Sub Harmonic mixer. The improvements are possible through the reduced size of transistors used in inverter and its non-linear operation. Thorough analysis of the circuit is performed for both sinusoidal and trapezoidal LO. Competitive results are obtained from the analysis of the design in terms of conversion gain, carrier suppression and Input referred 3rd order Intercept Point (IIP3). The design is modified to make it robust for varying ambient temperatures using a junction diode. A two port model of the Sub Harmonic mixer is derived, which proves a non-sinusoidal LO can be used in place of sinusoidal.