Project Proposal Name:
Making necessary circuits that are required for frequency modulation and connecting them.
Objective:
Generating modulating signal by audio generator circuit and completing the modulation process using
varactor modulator circuit.
Process:
Firstly, a modulating or message signal will be generated by using audio generating circuit which is
basically the digital form of any analog signal e.g., human voice. To make the audio generator circuit that
will form modulating signal, the required components are:
➢ Oscillator circuit:
e.g., Function generator IC (XR2206 or ICL8038)
➢ Resistors
➢ Capacitors
➢ Power supply
➢ Amplitude control (Potentiometers)
➢ Amplifier circuit:
e.g., Audio amplifier ICs (LM386)
➢ Speaker or Audio jack
➢ Control Interface (Switches and Buttons)
➢ Breadboard
➢ Connecting wires
Figure 1:Audio generator circuit diagram
After generating the modulating signal, it will be used as input to the varactor modulator circuit.
Frequency Modulation (FM) is a modulation technique is used to encode information or message signal
on a carrier wave by varying its instantaneous frequency in proportion to the amplitude of the modulating
signal. In FM, the frequency of the carrier wave changes in accordance with the changes in the amplitude
of the modulating signal, while the amplitude and phase remain constant. Varactor modulator circuit will
be used here for frequency modulation process and the necessary components required to make this
circuit are:
➢ Resistors
➢ Capacitors
➢ Inductor
➢ Varactor diode
e.g., BB204 or MV2109
➢ DC biasing component (Potentiometer)
➢ Power Supply
➢ Oscillator Circuit
➢ e.g., Function generator IC (XR2206 or ICL8038)
➢ Connecting wires and Switches
➢ Amplifier circuit:
e.g., Audio amplifier ICs (LM386)
Figure 2: Varactor modulator circuit diagram
Conclusion:
When the modulation process is done, the output can be connected to an oscilloscope to observe the
modulated signal and hence the frequency modulation process is done.
