Study and analysis of the impact of noise on the receiver sensitivity in the digital optical communication system

The effect of thermal noise and shot noise on the receiver sensitivity in a digital optical communication system will be studied and analyzed. Also, the positive and negative effects of Parameters on the receiver sensitivity will be highlighted. The programming tools (MATLAB) is used to study the relationship between the receiver sensitivity and bit rate. It showed that the shot-noise-limited receiver sensitivity is much better than the thermal -noise-limited receiver sensitivity with best 30dB. The study also provided an explanation for the preference of optical detector (APD) compared to that in (PIN) optical detector from sensitivity side due to its internal gain, this can be achieved when the thermal noise is dominant. However, the preference of optical detector(PIN) will be better in case of shot noise is dominant. Analyzed results show that there is a significant improvement in the shot-noiselimited receiver sensitivity for high quantum efficiency and high wavelength. However, the sensitivity is deteriorated to get a lower error rate. The thermal -noise-limited receiver sensitivity showed an improving by increasing the responsivity and the load resistance. However, it decreases by increasing the number of noise and the error rate.

AWGN and Rayleigh Fading effects on BER Compression for Multimedia Application for OFDM system with Different Modulation Techniques

This research offers an analyzing study for BER in OFDM system through Module designed by matlab, the performance was tested with different modulation techniques as PBSK, 8PBSK…. The measurement was taken at multi AWGN levels for different modulation techniques besides BER testing in Rayleigh fading channel and without Rayleigh fading All results illustrated in suitable tables and curve.

Data Acquisition System Design Using a Microcontroller and Digital Elliptic Filters that are able to Remove Noise from EEG signals

Since Electroencephalogram (EEG) signals have very small magnitude, it's very hard to capture these signals without having noise (produced by surrounding artifacts) affect the real EEG signals, so it is necessary to use Filters to remove noise. This work proposes a design of an electronic circuit using a microcontroller, an instrumentation amplifier and an operational amplifier able to capture EEG signals, convert the captured signals from analog state to digital one and send the converted signal (digital signal) to a group of three digital filters. This paper gives a design of three digital elliptic filters ready to be used in real time filtering of EEG signals (which preliminary represents the condition of the brain) making the software part which complements the hardware part in the EEG signals capturing system. Finally we are going to show the way of using the designed electronic circuit with the three designed digital filters, demonstrate and discuss the results of this work. We have used Eagle 6.6 software to design and draw the circuit, CodeVision AVR 3.12 software to write the program downloaded on the microcontroller, Mathworks MATLAB 2014a software to design the three digital filters and Mathworks MATLAB 2014a Simulink tool to make the appropriate experiments and get the results.

Analytical and experimental study of the effect of noise background on the radioactivity measurement

In this experimental work, the instruments used (detector, calibrating sources) has been calibrating, the calibration line of the detector deduced and it has been finding that the equation of calibration line takes the form: The resolution power R has been studying as function of the distance between the activity source and detector; the results obtained show that R decrease by increase the energy of the lines spectrum, this mean that the detector resolution power become bigger. It has been measured the LC، LD and MDA using two different methods of background radiation value, trapezium method and classical method, for two different distances between radioactivity source and detector: (9,3cm) and (10cm). The results show: 1- There is similar comportment of the LC، LD and MDA in function energy and the distance between radioactivity source and detector. 2- The trapezium method gives better results from the classical method to the radiation background, and this leads to lesser MDA value, this means that the sensibility is bigger to measure this quantity. 3- The relative error using MDA is (5%) for large values, and (10%) for small values

Delineation of breast lesions in ultrasound images using Level-set method

Breast cancer is the second leading cause of death of women in the world. The early detection gives a better chance to cure it. Physicians diagnose breast tumors by analyzing the characteristics of the lesion in ultrasound images. Shape data, provided by a tumor contour, is important to physicians in making diagnostic decisions. However, due to the increasing use of technology in medicine, a computer aided detection systems (CAD) have been built to help the expert. This research focuses on using a level-set method as an effective lesion segmentation method for breast ultrasound images. By applying non-local means filter on image, the unwanted speckle noise will be removed and the image's important details will be preserved. Then the initial contours are sketched using the GUI in order to apply level-set method which delineates the contour of the lesion in breast ultrasound image. The proposed method was found to determine the breast tumor contours that are very similar to manual-sketched contours (about 96%).

Low noise transimpedance amplifier design

The aim of this research is to study a simplified approach for the design of low-noise bipolar transimpedance preamplifiers for optical receivers. Analytical solutions for optimum biasing and minimum equivalent input-noise current were derived. The study was achieved by doing comparison between the designed circuits. The equivalent input noise current was calculated by entering the parameters in Matlab program and using Multisim as a simulation tool to detect a pulse signal of 30ns width.

Strong correlation between the ratio of collected charge and the electronic noise in CdTe detectors

Noise and transport characteristics of CdTe gamma - and X-ray detectors have been carried out to determine the 1/f noise sources and their correlation with charge carriers mobility. The noise spectral density was measured by standard set-up. The noise of low ohmic samples has 1/f noise spectral density which increases with the square of voltage. The high ohmic samples show 1/f type noise in low frequency range. This flicker noise leads to degradation in the homogeneity of the contact. The excess of noise changes as 1/fa , 1 a 2 at 10Hz, and it is due to the multitrapping of the CdTe. Thiscontributes to the loss in charge collection efficiency.