Ruba Rajan - Academia.edu (original) (raw)

Papers by Ruba Rajan

This latest technology Li-Fi (Light Fidelity) refers to 5G Visible Light Communication systems us... more This latest technology Li-Fi (Light Fidelity) refers to 5G Visible Light Communication systems using light-emitting diodes as a medium to high-speed communication in a similar manner as Wi-Fi.Harald Haas says his invention, which he calls D-LIGHT, can produce data rates faster than 10 megabits per second, which is speedier than your average broadband connection. In the days where internet has become a major demand people are in a search for Wi-Fi hotspots. Li-Fi or New Life of data communication is a better alternative to Wi-Fi in wireless communication. Li-Fi has thousand times greater speed than Wi-Fi and provides security as the visible light is unable to penetrate through the walls, which propose a new era of wireless communication. Such technology has brought not only greener but safer and cheaper future of communication. INTRODUCTION Now a day " s Wi-Fi is widely used in all the public areas like home, cafes, hotels, airports. Due to this radio frequency is getting blocked day by day, at the same time usage of wireless data is increasing exponentially every year. Everyone is interested to use wireless data but the capacity is going down. Wireless radio frequencies are getting higher, a complexities are increasing and RF interferences continue to grow. In order to overcome this problem in future, light –fidelity (Li-Fi) technology came into existence since 2011. Li-Fi is a wireless communication system in which light is used as a carrier signal instead of traditional radio frequency as in Wi-Fi. Li-Fi is a technology that uses light emitting diodes to transmit data wirelessly. Visible light communication (VLC) uses rapid pulses of light to transmit information wirelessly that cannot be detected by human eye. This paper will focus on Li-Fi technology over Wi-Fi technology and challenges for the new VLC technology.

The certificate shall carry the supervisor's signature and shall be followed by the supervisor's ... more The certificate shall carry the supervisor's signature and shall be followed by the supervisor's name, academic designation (not any other responsibilities of administrative nature), 3.10 List of References -The listing of references should be typed 4 spaces below the heading "REFERENCES" in alphabetical order in single spacing leftjustified. The reference material should be listed in the alphabetical order of the first author. The name of the author/authors should be immediately followed by the year and other details.

In this paper, the bandwidth of rectangular Microstrip antenna is enhanced by V-slot loaded recta... more In this paper, the bandwidth of rectangular Microstrip antenna is enhanced by V-slot loaded rectangular microstrip patch antenna. It can be seen that bandwidth of Microstrip antenna is increased up to great extant when v slot loaded and a rectangular cut. In some applications which the increased bandwidth is needed, proposed antenna is one of the alternative solutions.The proposed antenna has single frequency band. The proposed antenna has frequency band (1.338-2.953GHz) in which the fractional bandwidth is 75.27% which is suitable for broad band applications. The gain has been improved up to 4.190dBi, directivity 4dBi and efficiency 99.99%. The proposed loaded V slot Microstrip patch antenna is fed by 50Ω Microstrip feed line .The designed structures and performance of different structures are simulated by using IE3D Zealand simulation software.

One of the common problems faced by visually impaired people is of independent path-based mobilit... more One of the common problems faced by visually impaired people is of independent path-based mobility in an unfamiliar indoor environment. Existing systems do not provide active guidance or are bulky, expensive and hence are not socially apt. In this paper, we present the design of an omnipresent cellphone based active indoor wayfinding system for the visually impaired. Our system provides step-by-step directions to the destination from any location in the building using minimal additional infrastructure. The carefully calibrated audio, vibration instructions and the small wear-able device helps the user to navigate efficiently and unobtrusively. Results from a formative study with five visually impaired individuals informed the design of the system. We then deployed the system in a building and field tested it with ten visually impaired users. The comparison of the quantitative and qualitative results demonstrated that the system is useful and usable, but can still be improved.

Now-a-days, internet has become a major demand people are in search of Wi-Fi hot spots. Li-fi or ... more Now-a-days, internet has become a major demand people are in search of Wi-Fi hot spots. Li-fi or Light Fidelity was invented by Professor Harald Hass of university of Edinburgh. This is the latest technology in present day communication system which makes the use of LEDs, Light Emitting Diodes that helps in the transmission of data much more faster and flexible than the data that can be transmitted through Wi-Fi. It is basically a 5G technology of visible light communication system which utilizes light emitting diodes as a medium of high speed communication in similar manner as Wi-Fi

Blind people are desperately in need of special requirements and services including the public tr... more Blind people are desperately in need of special requirements and services including the public transportation to give them the rights and ability to move smoothly and independently from one place to another. One of the requirements for ease and comfort in enjoying life is the ability to move independently from one place to another using different transportation means such as cars, metro ...etc.

A differential single-port switched-RC N-path filter with band-pass characteristic is proposed. T... more A differential single-port switched-RC N-path filter with band-pass characteristic is proposed. The switching frequency defines the center frequency, while the RC-time and duty cycle of the clock define the bandwidth. This allows for high-Q highly tunable filters which can for instance be useful for cognitive radio. Using a linear periodically time-variant (LPTV) model, exact expressions for the filter transfer function are derived. The behavior of the circuit including non-idealities such as maximum rejection, spectral aliasing, noise and effects due to mismatch in the paths is modeled and verified via measurements. A simple RLC equivalent circuit is provided, modeling bandwidth, quality factor and insertion loss of the filter. A 4-path architecture is realized in 65 nm CMOS. An off-chip transformer acts as a balun, improves filter-Q and realizes impedance matching. The differential architecture reduces clock-leakage and suppresses selectivity around even harmonics of the clock. The filter has a constant 3 dB bandwidth of 35 MHz and can be tuned from 100 MHz up to 1 GHz. Over the whole band, IIP3 is better than 14 dBm, dBm and the noise figure is 3-5 dB, while the power dissipation increases from 2 mW to 16 mW (only clocking power).

It has been shown that an arrangement of four MOS switches and four baseband lowpass impedances c... more It has been shown that an arrangement of four MOS switches and four baseband lowpass impedances can synthesize on-chip high-Q bandpass filters if the switches are driven by proper clock phases. The technique has been successfully utilized in receivers to replace external SAW filters. This paper analyzes performance of these filters in SAW-less receivers against imperfections such as clock phase-noise, thermal noise of switches, secondorder non-linearity of switches and clock phase error. Such receivers deal with out-of-band blockers by utilizing on-chip high-Q 4-phase bandpass filters.

A tunable Q-enhanced filter with low passband distortion is presented. The Q of the on-chip spira... more A tunable Q-enhanced filter with low passband distortion is presented. The Q of the on-chip spiral inductors that form the filter resonators is enhanced by using a cross-coupled differential pair which is degenerated by a second LC tank. This technique allows for frequency dependent compensation of inductor losses and ensures that the Q-enhanced LC resonators have a frequency behaviour close to the ideal in the passband of the filter. The circuit allows DC voltage control of Q-enhancement. The filter centered at 2.0 GHz with a 130 MHz bandwidth is tunable in frequency by 3%, exhibits a 6.6 dBm 1-dB compression point and a 15 dB noise figure while consuming 17 mW of DC power. The circuit was fabricated in 0.18-m CMOS and the performance was verified experimentally.

phase bandpass filters (BPFs) are analyzed, and variations of the structure are proposed. For val... more phase bandpass filters (BPFs) are analyzed, and variations of the structure are proposed. For values of that are integer multiples of 4, the conventional -phase BPF structure is modified to take 4 complex baseband impedances and frequency-translate their complex impedance response to the local oscillator frequency. Also, it is demonstrated how the -phase BPF can be modified to implement a high quality factor (Q) image-rejection BPF with quadrature RF inputs. In addition, we present high-Q BPFs whose center frequencies are equal to the sum or difference of the RF and IF (intermediate frequency) clocks. Such filters can be useful in heterodyne receiver architectures.

Chebyshev low pass filter presented based on lumped-network and microstrip line structure suitabl... more Chebyshev low pass filter presented based on lumped-network and microstrip line structure suitable for wireless communication purpose. In this paper chebyshev microstrip lowpass filter of order 3 and 1dB pass band ripple is designed on duroid substrate using step-impedance method for 1GHz cut-off frequency using Ansoft Designer and Ansys HFSS.

This paper presents a direct design of Infinite Impulse Response filters (IIR filters) which mini... more This paper presents a direct design of Infinite Impulse Response filters (IIR filters) which minimizes group delay without changing the magnitude response of filters. In this paper Butterworth and Chebyshev1 lowpass filters are designed by using allpass filters. The design specifications are passband and stopband frequencies and passband ripple and stopband attenuation. In this paper MATLAB programming is used for implementation of proposed algorithm. Experimental results show that the proposed method can effectively optimize the group delay of the designed Butterworth and chebyshev1 low pass filters.

— This paper presents a direct design of Infinite Impulse Response filters (IIR filters) which mi... more — This paper presents a direct design of Infinite Impulse Response filters (IIR filters) which minimizes group delay without changing the magnitude response of filters. In this paper Butterworth and Chebyshev1 lowpass filters are designed by using allpass filters. The design specifications are passband and stopband frequencies and passband ripple and stopband attenuation. In this paper MATLAB programming is used for implementation of proposed algorithm. Experimental results show that the proposed method can effectively optimize the group delay of the designed Butterworth and chebyshev1 low pass filters.