Analysis and Design of Fm Transmitter Essay




This kind of chapter handles the process of obtaining the design technical specs of the cellular Frequency Regulated Transmitter having a frequency of 100MHz in a range of 100m beneath accurate circumstances. From the prevent diagram shown in FIG. 2 . you, various circuit components are chosen and appropriate estimated values have become chosen to match its homes as well as perform duties from the stages. The entire system could be grouped into two major stages

The Q1 stage consisting the oscillator, the music amplifier and the modulator

The Q2 level which is constructed majorly of the RF amplifier and the antenna 3. 2Q1 STAGE

A single transistor is employed as the audio frequency (AF) augmenter. The Colpitt's oscillator is utilized. It consist a receptor which amplifiers the AF and the fish tank circuit to get the generation of the company wave. The model of the oscillator employed is demonstrated in FIG. 3. 1 )


R1 T



R2 C4_


For the transistor to function as a great amplifier it should be biased in the forward lively region. Theraja & Theraja, (2002). i actually. e.

Basic emitter verse must be frontward biased (VBE= 0. 7v)

VCE= zero. 3v

A BC108 transistor with the explained configuration was used. A 9V DC supply was used to power the whole system. Immediate and alternating current flow in this circuit. The direct current is usually brought about by the 9V DC battery even though the alternating current electrical generator is the carbon microphone. Salgat (2007) mentioned that capacitors do not allow direct current through these people. Hence the DC equivalent of FIG. 3. one particular is as demonstrated in FIG 3. two and FIG 3. 3.




FIG 3. a couple of


IB 0. 7vBfIB



FIG three or more. 3

Now for the forward active function,

VBE=0. 7V, choosing Ic = 5. 5mA, Bf =200 Ic = Bf IBIB sama dengan 5. 5mA/200 =0. 0275mA. Applying Kirchhoff's Voltage Rules (KVL) for the collector-emitter loop 9 – VCE – R2(Ic & IB) sama dengan 0 -------- (7)

9 – 3. 5 – 5. 5275R2 = 0

R2 sama dengan 9 – 3. a few = 0. 995KΩ

your five. 5275

≈ 1KΩ

Applying KVL towards the base-emitter trap

9 – R1IB – 0. 7 – R2(IC + IB) = zero --------- (8)

R1 = 9 – zero. 7 – 5. 5275 = 99. 83KΩ

zero. 0275

Value of R1 used in design = 90 KΩ

Part CC in FIG 3. 1 can be described as coupling capacitor.

three or more. 2 . 2FILTERS

In practical application, the carbon microphone (the alternating current era in FIG 3. 1) accepts a large range of frequency. This has to be carefully processed through security to allow only the audio selection (20Hz – 20KHz) to get amplified and transmitted. Theraja & Theraja (2002) stated that by making use of various combinations of resistors, inductors and capacitors, brake lines can be built that have the exact property or rejecting either low or higher frequency or group of consistency. These frequency selective sites are called filters. Filters will be broadly of two types

Lively filters- which use transistors and op-amps along with resistor, inductor and capacitor elements.

Passive filters- which usually consist just series-parallel combos of resistor, inductor and capacitor elements. Theraja & Theraja (2002) further stated that there are 4 types of passive filters- high-pass filter, low-pass filtering, band-pass filtration and band-stop filter. Only the high-pass and low-pass filtering are used in this project function.

High-Pass Filter (HPF)- allows indicators with higher frequency to pass through although rejecting reduced frequencies. The minimum rate of recurrence which that allows to pass through is called cut-off frequency. You will discover RC and RL high-pass filters. Only the RC substantial pass filtration is used through this project function.

Low-Pass Filter (LPF)- allows only low regularity to pass through although attenuates (to a higher or lesser extent) all bigger frequencies. The cut off...


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