28-02-2011, 04:30 PM
presented by:
T.U.M Swarna kumari
J.V Ravi Teja
G.Suresh Kumar
N.Sudheer Babu
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A mini project on SIMPLE FM-TRANSMITTER
ABSTRACT:
The aim of the project is to develop a simple FM-Transmitter to be used specialized applications such as in radio broadcasting and telecommunications etc.
Frequency modulation has several advantages over the system of amplitude modulation (AM) used in the alternate form of radio broadcasting. The most important of these advantages is that an FM system has greater freedom from interference and static.
commercial FM radio stations are assigned frequencies between 88 and 108 MHz and will be the intended frequency range of transmission.
WHAT IS MODULATION?
Modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with respect to a modulating signal
Here the three key parameters of a periodic waveform are its amplitude ("volume"), its phase ("timing") and its frequency ("pitch"), all of which can be modified in accordance with a low frequency signal to obtain the modulated signal. Typically a high-frequency sinusoid waveform is used as carrier signal
TYPES OF MODULATION:
Amplitude modulation
a type of modulation where amplitude of a information signal vary while frequency and phase kept constant.
Frequency modulation
a type of modulation where frequency of information signal vary while amplitude and phase kept constant.
Phase modulation
a type of modulation where phase of information signal vary while amplitude and frequency kept constant.
WHY FM?
o Frequency modulation is a type of modulation where the frequency of the carrier is varied in accordance with the modulating signal. The amplitude of the carrier remains constant.
o The information-bearing signal (the modulating signal) changes the instantaneous frequency of the carrier. Since the amplitude is kept constant, FM modulation is a low-noise process and provides a high quality modulation technique which is used for music and speech in hi-fidelity broadcasts
o For FM: the carrier’s frequency is proportional to the baseband’s amplitude, the carrier increases frequency proportional to the positive magnitude of the baseband and decreases frequency proportional to the negative magnitude of the baseband.
ADVANTAGES FREQUENCY MODULATION
• Frequency modulation have some advantages over amplitude modulation, FM is not sensitive to the amplitude noise, and have high efficient use of transmitted power
• Lesser distortion. Frequency modulated wave is less susceptible to intereferences from buildings, traffic etc which provides improved signal to noise ratio (about 25dB) w.r.t. to man made interference.
• Waves at higher frequencies can carry more data than the waves at low frequency.
• Smaller geographical interference between neighboring stations.
• Less radiated power.
• Well defined service areas for given transmitter power
FM-TRANSMITTER:
Transmitter which generates frequency modulated signal is known as FM-Transmitter
APPLICATIONS:
• Non-commercial broadcasting from 88 – 90 MHz (WFM)
• Commercial broadcasting from 90 – 108 MHz (WFM)
• Television audio
• Public Service communications
• Radio Service Communications
• Point-to-point microwave links used by telecommunications companies
