UNIVERSIDAD AUTONOMA DEL
ESTADO DE MEXICO
UAEMEX
FACULTAD DE INGENIERIA
Comunicación 1
Práctica: Emisor de FM
Maestra: Stephanie Cruz Martínez
Integrantes:
Castillo Nieto Martín Alejandro
Cano Serrano Oscar Yael
Olivares Ochoa Adrián
Introduction
The frequency modulator (FM) is a device used in telecommunications and
transmission systems to modify the frequency of a carrier signal based on the
information or message signal that is to be transmitted. Unlike other
modulation types, such as amplitude modulation (AM), in frequency
modulation, the variation of the carrier signal occurs not in its amplitude, but
in its frequency.
The basic principle of a frequency modulator is to alter the frequency of the
carrier signal in proportion to the input signal, which can be an audio, video,
or any other form of information. This results in an output signal whose
frequency changes over time according to the variations in the message
signal.
Frequency modulation offers several advantages, such as greater resistance
to noise and interference compared to other modulation methods like
amplitude modulation. This makes FM particularly useful in applications such
as FM radio, television, satellite communications, and mobile communication
systems.
In this process, the modulation index and the carrier frequency are key
parameters that determine the range and quality of the transmitted signal.
Frequency modulation also allows for greater spectral efficiency, as it enables
clearer and more reliable transmission of signals, making it ideal for
environments with high interference or noise.
This type of modulation is essential in a wide range of modern technologies
and is widely studied in telecommunications and broadcasting engineering.
Theoretical Framework
GENERATION OF THE FM SIGNAL
Frequency modulation systems are grouped into two classes: 1) Direct FM, where
the carrier is modulated at the point where it is generated, in the master oscillator;
2) Indirect FM, where the master oscillator does not modulate, but modulation is
applied in a subsequent stage.
FREQUENCY MODULATION
Frequency modulation is a case of modulation where both the transmission signals
and data signals are analog, and it is a type of exponential modulation. In this case,
the modulated signal will keep its amplitude fixed, and the parameter of the carrier
signal that will vary is the frequency. This frequency variation occurs according to
the changes in the amplitude of the modulating signal, as shown in Illustration 1. In
other words, frequency modulation (FM) is the process of encoding information,
which can be either digital or analog, into a carrier wave by varying its instantaneous
frequency according to the input signal.
A block diagram of an FM transmitter will provide a better understanding of
how the circuit works, as well as its different stages, as shown in Illustration
2.
Development
• 10 nano capacitor
• 2n2222 transistor
• 4.7 k ohm resistors
• 10 picofarad capacitor
• 270 ohm resistors
• Variable inductors
Simulación del circuito
Como se observa las 3
señales que están
implícitas en una
modulación de
Frecuencia (FM)
En amarillo es la señal
portadora
En azul es la señal
Moduladora
Mientras que la rosa
es la señal modulada
Estas señales generan una señal FM, siguiendo el diseño y simulación procedimos
con la imagen de la simulación
Grafica señal modulada
Conclusion
This work presents the analysis and implementation of a
Frequency Modulated (FM) transmitter circuit, which consists of
three stages: the first stage is the coupling of the signal to be
transmitted, the second stage corresponds to an amplification
stage of the coupled signal; this stage is formed by two 2N2222A
transistors with voltage divider biasing. The third stage of the
circuit can be considered as the modulation stage, formed by an
LC oscillator.
The information transmitted is an audio sine wave signal. A
detailed analysis is provided, both in DC and AC, for each stage,
along with the equations used. The implemented circuit is also
shown, as well as a comparison between the simulation results
and the real implementation.
