Binary Phase Shift Keying BPSK Modulation Demodulation Computer Science Essay

Binary Phase Shift Keying BPSK Modulation Demodulation Computer Science Essay This experiment is based on the Binary Phase Shift Keying (BPSK) modulation/demodulation technique. The aim of the experiment is to gain familiarity with the components of a simple data transmission system, gain experience using an experimental communication system and studying its performance under the influence of white noise and also, to compare experimental results with theoretical deductions. Bandpass modulation, of which BPSK is a type, is a process whereby, a sinusoid usually called a carrier wave, is modulated or have its characteristics changed by a digital pulse baseband signal in other to enable wireless based transmission. In BPSK modulation, the phase of the carrier waveform is shifted to either 0Â ° or 180Â ° by the modulating data signal. To effectively model the transmission channel, the AWGN generator is used which adds the effect of noise to the signal at the receiver in other to properly characterise what obtains in real systems. SNR measurements are taken after the noise is added before the receiver and results of each stage of the experiment are presented. 2.0 RESULTS AND DISCUSSION The results obtained from the experiment and brief discussions are now presented. 2.1 The frequency of the waveform was measured to be 1.493kHz 2.2 The amplitude of the waveform was measured to be 3.608V 2.3 C:Documents and SettingsAGEBNIGADesktopLAB RESULTSPart 2.bmp Fig. 1: Square Waveform from NE555 timer circuit. The timer circuit produces a sequence of ones and zeros which together with the resistors and capacitor, produces a square waveform. It can be observed that the square top and bottom are not perfectly straight but with ripples, this is due to the resonance effect presented by the capacitor. Also, the rising pattern of the top is due to the voltage rise time in the capacitor. 2.4 The frequency of the message sequence is measured to be 374Hz 2.5 C:Documents and SettingsAGEBNIGALocal SettingsTemporary Internet FilesContent.WordPart 4 5.bmp Fig. 2: M essage sequence at the output of the frequency divider. The SN74LS74 integrated circuit implements a second order frequency divider, 2n (n=2). Hence the frequency of the timer circuit is divided by four. Hence, this is also evident in the frequency of the message sequence in 2.4 above. 2.6 The cut-off frequency of the 2nd order Butterworth low pass filter is given by; The cut-off frequency is the frequency at which the magnitude of the transfer function drops to 0.7071 of its maximum value which represents the point at which the power in the circuit is 3dB less than the maximum value. 2.7 The frequency of the sinusoid at the output of the filter was measured to be 1.328kHz. 2.8 C:Documents and SettingsAGEBNIGALocal SettingsTemporary Internet FilesContent.Wordpart 8.jpg Fig. 3: Output of the first and second Butterworth LPF. A B A – Output of first filter; B – Output of second filter The Butterworth lowpass filter is used to generate the sinusoidal carrier required for the baseband signal. The Butterworth filter has a gentle roll-off, has no ripple in the pass or stop band hence, it has a monotonic response. To maximise the smoothness of the sinusoid, we use two of such filters in series.

Written response; What is the purpose of Mama's retelling of familiar Essay

Written response; What is the purpose of Mama's retelling of familiar stories, specially the cuentos, during afternoon coffes - Essay Example Cofer shares the significance of Mama to her in these words, â€Å"I saw her as my liberator and my model. Her stories were parables from which to glean the Truth† (Cofer 69). The characters in Mama’s stories might be fake, but they were knit into stories that depicted the realities of life. The girls were in the age of adolescence and thus, in a state of transition from childhood to adulthood. They needed an interesting way of being informed of the challenges lying ahead in their lives, and Mama’s cuentos exactly addressed that concern. Cofer shares how she would reflect upon Mama’s stories together with Sara to draw conclusions from them in these words, â€Å"Sara and I discussed everything we heard the women say, trying to fit it all together like a puzzle that, once assembled, would reveal life’s mysteries to us† (Cofer 70). Mama’s house was a very suitable place for the cuentos to be narrated in as there was no intrusion of any sort from men in there; â€Å"Then Mama’s house belonged only to us women†¦and the women telling their lives in cuentos are forever woven into the fabric of my imagination, braided like my hair that day I felt my grandmother’s hands teaching me about strength, her voice convincing me of the power of storytelling† (Cofer 70). The stories Mama narrated depicted, in one way or another, realities of the lives of her own daughters. Storytelling not only provided Mama with a unique and interesting way of developing a strong connection and understanding with the young grand-daughters, but also of raising them into well-educated, civilized, and decent girls who would not trust the love of men until they signed the contract of marriage with them. Mama’s stories had lessons hidden in them. Giving those stories deep thoughts would lead Cofer to the realization that a woman loses to nothing and nobody but her own self by letting herself fall into love; â€Å"We understood that neither the name nor any of the facts were

Legalizing marijuana Research Paper Example | Topics and Well Written Essays - 2250 words

Legalizing marijuana - Research Paper Example A number of possible arguments for its legalization are also refuted in support of the actual and feared social, health and economic effects. The more immediate social effect of legalization marijuana production and use would be the higher chances for more crimes which could really have its related health and economic effects. If sins are the enemies of heaven, crimes are the enemies of a just and peaceful society. Thus legalizing the marijuana would have the effect of increasing the number of drug-related crimes. It is argued by those who favour legalization of the marijuana argues that the use and production domestically were not addressed by long practice of prohibiting the same. It is claimed by some supporters that despite the use of criminal penalties to prevent the use of hemp or marijuana for three quarters of a century, there still existed millions of users, which to them should be considered an evidence of such failure of prohibiting its free use and production (â€Å"420 Campaign – Top Ten Reasons Marijuana Should Be Legal†). Said claim essentially rested on the premise that people will not fear what is beneficial even in the eyes of threat of imprisonment. The validity of the above claims by the supporter of legalization become doubtful when the fallacy of the claim is exposes. The continued number of users via illegal means cannot be evidence of its failure since choosing to violate existing laws is still part of human. The fact that the substance is being used by a number people despite its being prohibited does not mean that prohibiting the same has become less effective. On the other hand, claims of success for such prohibition can be supported with crimes continued to be drug-related. It could therefore be countered that had there been no prohibition on the use and production of marijuana the greater would have been the number of crimes and therefore social effects would have been