The armstrong oscillator is used to produce a sine-wave output of constant amplitude and of fairly constant frequency within the rf range. The armstrong oscillator uses transformer coupling to feed back a portion of the amplifier output to the amplifier input Armstrong is also called tuned based oscillator.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRACT
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE PROJECT
- AIM OF THE PROJECT
- OBJECTIVE OF THE PROJECT
- SIGNIFICANCE OF THE PROJECTS
- ADVANTAGES OF THE PROJECT
- PROBLEM OF THE PROJECT
- APPLICATION OF THE PROJECT
- SCOPE OF THE PROJECT
CHAPTER TWO
LITERATURE REVIEW
- DIFFERENT TYPES OF OSCILLATORS CIRCUITS
- DEFINITION OF OSCILLATOR
- HISTORICAL BACKGROUND OF OSCILLATOR
CHAPTER THREE
METHODOLOGY
- SYSTEM BLOCK DIAGRAM
- DESCRIPTION OF THE SYSTEM BLOCK DIAGRAM
- SYSTEM CIRCUIT DIAGRAM
- COMPONENT DESCRIPTION
- OPERATION OF THE SYSTEM
- CONDITION FOR OSCILLATION
CHAPTER FOUR
- CONSTRUCTION PROCEDURE AND TESTING ANALYSIS
- ASSEMBLING OF SECTIONS
- TESTING OF SYSTEM OPERATION
- CONSRUCTION OF THE CASING
- ECONOMIC OF THE PROJECT
- PROJECT VIABILITY
CHAPTER FIVE
- CONCLUSION
- RECOMMENDATION
- REFERENCES
1.0 INTRODUCTION
Oscillator converts the DC signal to AC signal. There are many types of oscillators; out of that the LC oscillator works on the principle of positive feedback. The Armstrong oscillator[1] is an electronic oscillator circuit which uses an inductor and capacitor to generate an oscillation. It is the earliest oscillator circuit, invented by US engineer Edwin Armstrong in 1912 and independently by Austrian engineer Alexander Meissner in 1913, and was used in the first vacuum tube radio transmitters. It is sometimes called a tickler oscillator because its distinguishing feature is that the feedback signal needed to produce oscillations is magnetically coupled into the tank inductor in the input circuit by a "tickler coil" (L2, right) in the output circuit.
Armstrong oscillator is a basic feedback LC circuit. In the proposed circuit, we are introducing the tank circuit between the base and ground. The tuned circuit is actually made of an inductor and a capacitor in parallel. In the proposed circuit, transformer and capacitor is used. The transistor starts its operation when the power is supplied to the base of the transistor. The collector current which flows through the secondary coil of the transformer induces a voltage in the primary coil of the transformer. The capacitor stores the charges produced by mutual induction. The capacitor starts discharging and the tank circuit functions.
When the capacitor is totally discharged the primary coil now induces voltage by self-induction and this results in storage of charges in the capacitor which in turn charges the tank circuit to produce oscillations. The part of the oscillation is now fed to the base of the transistor which is amplified. The oscillations sustain longer when the feedback is high. The oscillations become distorted when the feedback is too high and they die out very soon if the feedback is too low. The oscillations are sustained because of positive feedback. Thus the Armstrong (tuned base) oscillator is successful in producing the required output.
1.1 AIM OF THE PROJECT
The main of this work is to write on a device that produces a sinusoidal wave output of constant amplitude and of fairly constant frequency within the given RF range. It uses an LC tuned circuit to establish the frequency of oscillation.
1.2 OBJECTIVES OF THE PROJECT
After studying the material in this chapter, the student involved would be able to:
- State the function of the oscillator.
- Describe positive feedback, how it is produced, and how it maintains oscillations after an oscillator is triggered.
- List the three requirements for proper oscillator operation.
- Describe the operating characteristics of the Armstrong LC oscillators.
- Describe the operation and perform the complete frequency analysis of a Armstrong LC oscillators.
- Describe the operation of the Armstrong LC oscillators.
The armstrong oscillator is used to produce a sine-wave output of constant amplitude and of fairly constant frequency within the rf range. The armstrong oscillator uses transformer coupling to feed back a portion of the amplifier output to the amplifier input Armstrong is also called tuned based oscillator.
1.4 ADVANTAGES OF THE PROJECT
- The main advantage is that, the construction of Armstrong-type tube oscillators using a tuning capacitor where one side is earthed. It produces a stable frequency and stably amplified output waveform.
The main problem of this circuit is that the resulting electromagnetic vibrations may contain interfering harmonics very light, which are undesirable in most cases.
1.6 APPLICATIONS OF ARMSTRONG OSCILLATOR
- It is used to generate the sinusoidal output signals with a very high frequency.
- It is generally used as a local oscillator in receivers.
- It is used in the radio and mobile communications.
- Used as a source in signal generators and as a radio-frequency oscillator in the medium- and high-frequency range.
An Armstrong oscillator is actually an LC feedback oscillator which uses capacitors and inductors in its feedback network. The Armstrong oscillator circuit can be built from a transistor, an operational amplifier, a tube, or some other active (amplifying) devices. The identifying characteristics of the Armstrong oscillator
- It uses an LC tuned circuit to establish the frequency of oscillation.
- Feedback is accomplished by mutual inductive coupling between the tickler coil and the LC tuned circuit.
- Its frequency is fairly stable, and the output amplitude is relatively constant.
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