Analysis and Design of Fm Transmitter
CHAPTER THREE
ANALYSIS AND DESIGN
3.1 INTRODUCTION
This chapter deals with the process of obtaining the design specifications of the wireless Frequency Modulated Transmitter with a frequency of 100MHz in a range of 100m under accurate conditions.
From the block diagram shown in FIG. 2.1, various circuit components are now chosen and appropriate approximate values are now chosen to match its properties as well as perform duties of the stages.
The entire system could be grouped into two major stages The Q1 stage consisting the oscillator, the audio amplifier and the modulator The Q2 stage which is made up majorly of the RF amplifier and the antenna
3.2 Q1 STAGE
One transistor is used as the audio frequency (AF) amplifier.
The Colpitt’s oscillator is used. It consist a transistor which amplifiers the AF and the tank circuit for the generation of the carrier wave.
The model of the oscillator used is shown in FIG. 3.1. + R1 L C3 CC C1 R2 C4 _ FIG 3.1: CIRCUIT REPRESENTATION OF THE COLPITTS OSCILLATOR WITH AF INPUT.
3.2.1 DESIGN SPECIFICATION FOR THE COLPITTS OSCILLATOR
For a transistor to function as an amplifier it must be biased in the forward active region. Theraja & Theraja, (2002). i.e. Base emitter junction must be forward biased (VBE= 0.7v) VCE= 0.3v
A BC108 transistor with the stated configuration was used. A 9V DC supply was used to power the entire system.
Direct and alternating current flow in this circuit. The direct current is brought about by the 9V DC battery while the alternating current generator is the carbon microphone.
Salgat (2007) stated that capacitors do not allow direct current through them. Hence the DC equivalent of FIG. 3.1 is as shown in FIG 3.2 and FIG 3.3. R1 Q1 R2
FIG 3.2 Ic IB 0.7v BfIB R1
9V R2
FIG 3.3
Now for the forward active mode,
VBE=0.7V, choosing Ic = 5.5mA, Bf =200 Ic =
ANALYSIS AND DESIGN
3.1 INTRODUCTION
This chapter deals with the process of obtaining the design specifications of the wireless Frequency Modulated Transmitter with a frequency of 100MHz in a range of 100m under accurate conditions.
From the block diagram shown in FIG. 2.1, various circuit components are now chosen and appropriate approximate values are now chosen to match its properties as well as perform duties of the stages.
The entire system could be grouped into two major stages The Q1 stage consisting the oscillator, the audio amplifier and the modulator The Q2 stage which is made up majorly of the RF amplifier and the antenna
3.2 Q1 STAGE
One transistor is used as the audio frequency (AF) amplifier.
The Colpitt’s oscillator is used. It consist a transistor which amplifiers the AF and the tank circuit for the generation of the carrier wave.
The model of the oscillator used is shown in FIG. 3.1. + R1 L C3 CC C1 R2 C4 _ FIG 3.1: CIRCUIT REPRESENTATION OF THE COLPITTS OSCILLATOR WITH AF INPUT.
3.2.1 DESIGN SPECIFICATION FOR THE COLPITTS OSCILLATOR
For a transistor to function as an amplifier it must be biased in the forward active region. Theraja & Theraja, (2002). i.e. Base emitter junction must be forward biased (VBE= 0.7v) VCE= 0.3v
A BC108 transistor with the stated configuration was used. A 9V DC supply was used to power the entire system.
Direct and alternating current flow in this circuit. The direct current is brought about by the 9V DC battery while the alternating current generator is the carbon microphone.
Salgat (2007) stated that capacitors do not allow direct current through them. Hence the DC equivalent of FIG. 3.1 is as shown in FIG 3.2 and FIG 3.3. R1 Q1 R2
FIG 3.2 Ic IB 0.7v BfIB R1
9V R2
FIG 3.3
Now for the forward active mode,
VBE=0.7V, choosing Ic = 5.5mA, Bf =200 Ic =