EE203: ELECTRONICS I. PROJECT REPORT: AM Transmitter

Transcription

1 King Fahd University of Petroleum and Minerals Electrical Engineering Department EE203: ELECTRONICS I Fall 2006 Semester 061 PROJECT REPORT: AM Transmitter Prepared For: Dr. Mohammad A. Alsunaidi Done By: Ahmad Qutb Al-Deen ID: Saleh Naser Al-Mutawa ID: Section: 5 Tuesday 16 /1 /2007

2 Introduction: The intended project to be done for this course is an AM Transmitter. This project's is brought from the internet, literally from: ( web cite. The expected cost of this project is nearly 40 SR. Objective: The aim of this project is to select or design, study by simulation or theory, build, test and document a small electronic circuit. This project is an opportunity to apply on it all the knowledge and experience gained through lectures and lab experiments, and it could be a useful real-life electronic circuit. And due to constraints of time, our project was not that complex design. It was simple to understand and only commonly available circuit components without any ICs or non- discrete components are involved. Overview: AM is a method of broadcasting during the first two thirds of the 20th century and remains widely used into the 21st. The Central Intelligence Agency World FactBook lists approximately 16,265 AM stations worldwide. AM radio began with the first, experimental broadcast in 1906 by Reginald Fessenden, and was used for small-scale voice and music broadcasts up until World War I. The great increase in the use of AM radio came the following decade. The first licensed commercial radio services began on AM in the 1920s. XWA of Montreal, Quebec (later CFCF) was the first commercial broadcaster in the world, with regular broadcasts commencing on May 20, The first licensed American radio station was started by Frank Conrad, KDKA in Pittsburgh, Pennsylvania. Radio programming boomed during the "Golden Age of Radio" (1920s 1950s). Dramas, comedy and all other forms of entertainment were produced, as well as broadcasts of news and music. AM radio technology is simpler than either FM radio or DAB. An AM receiver detects amplitude variations in the radio waves at a particular frequency. It then amplifies changes in the signal voltage to drive a loudspeaker or earphones. The earliest crystal radio receivers used a crystal diode detector with no amplification.

3 The Schematic: As you can see the schematic of the project is in Figure 1: Design Description: Figure 1: The Schematic of the project The circuit is divided in to two parts: 1- The amplifier: a Bipolar Junction Transistor (BJT) Common Emitter amplifier is used to amplify the sound signal. The input sound signal is provided through the base, and the output is received from the collector. The amplified signal is input through the oscillator. This part is built around transistor Q2. 2- The oscillator: which provide the carrier signal, which is the responsible of caring the sound through the air to be received in any nearby receiver. And this part includes Q1, inductor and a variable capacitor. The variable capacitor is used to change the frequency of the carrier signal. Both inductor and capacitor are mainly used to make the oscillation. Because of small problem faced in making the project, the variable capacitor is replaced by constant capacitors. The approximated frequency is about 25.25MHz. Problem Faced: Never will you see circuit design and its implementation with out error or problem faced. And in this project we had agreed with these words as we saw some problems. The major problem is the frequency, when having a deep look to the frequency it is clear that the

4 frequency is high. The expected range of frequencies is between 500 khz and 1600 KHz. The most important difficulty that faced is having some components. Furthermore, finding these components with the right values is another problem. Finding an inductor with inductance 200μH is out of accessibility in the time of implementing this project, and this is not an ordinary inductor, there is a core has to be inside the coil of wires. After finding the intended inductor, a proper capacitance should be there also. The Circuit's Pictures: Left: the circuit components. Right: the signal received by an oscilloscope. Conclusion: An above view to the circuit. It was a good time to do job like this great project especially with this course that relate to some of interesting things for us as two Computer Engineering Student (COE). And we

5 really interest in the hardware component rather than Software. Also, we get the idea of how did this AM Transmitter works. And how dose it could be implemented. Other things are about how we analyze and test the work and the circuit to find the error and the solution until finally it can be seen working. If these analyses and descriptions are not enough, more descriptions and contact information could be found in this website. ( There is a wider range for creativity for those who like it. And this project could be an example, but not a good example.