Modulation Techniques in Function Generator

Waves can be modulated with their carrier wave to ensure that they have long-range transmission. It is important to note that modern Function Generator can provide this feature of modulation .Let us see the types of modulation

AM (Amplitude Modulation)

This is the most common type of modulation performed. In the given figure, we have tried to show the setup for performing amplitude modulation and see the waveform generated after amplitude modulation. Observe that in this modulation, the amplitude of the wave is varied in proportion to that of the message signal, which is being transmitted. Function Generator allows us to choose the source of modulation from some other channel without extra circuitry.

FM (Frequency Modulation)

This method comes into mind when we talk about broadcasting because frequency modulation helps in broadcasting multiple frequencies together .It is widely used for video broadcasting, medical monitoring systems, radar and more. Look at the figure below which shows the 1 kHz sine wave that was frequency modulated using sine wave of 10 Hz.

PM (Phase Modulation)

This modulation helps to change the phase of original wave by modulating it with the phase of carrier wave. We can see phase modulation being performed in Wi-Fi, GSM, and satellite broadcasting transmissions. It can performed using different techniques mainly PSK (Phase-shift keying), BPSK (Binary phase-shift keying), QPSK (Quadrature phase-shift keying) and more. Look at a sample phase modulation given below with deviation of 180⁰

The Function Generator is used for generating different types of waveforms, let us see some of them.

• Sine wave: Sine wave is a significant periodic wave which is a common choice for input signal is communication systems. It is denoted by y=sin(x) and can be used for generating other waveforms. It is a smooth wave that oscillates from 0 to 1 and then from maximum value of 1 to a minimum value of -1 until it begins to repeat itself. It can be generated using an RC network and It is mainly used as current and voltage signal for various generators.

• Square wave: Square Wave is a a non-sinusoidal waveform which is periodic and whose amplitude oscillates from maximum to minimum with a constant frequency. There are instantaneous transitions rather than gradual transition. This makes square wave suitable choice for digital data transmission. This wave has a duty cycle of 50% due to which its second harmonic is absent.

• Triangle wave: In a triangular waveform ,signal moves up and down i.e. linearly varies with time. This output is usually generated by an operational amplifier when it works as an integrator. This is a fundamental kind of waveform generated by Function Generator and can be used to generate square pulse as well. The main use of such waveform comes in testing of amplifiers since triangular waveform shows any kind of distortion which other waveforms fail to show. Due to rich harmonics of this kind of pulse, it is used widely in musical instruments. It is used in sound synthesis as it has comparatively less harsh harmonics than other signals which makes it sound good. They are also used in sweep circuits and for testing purposes.

• Sawtooth wave: Sawtooth wave can be categorized as some kind of triangular wave in which the rising edges are very sharp as compared to the falling edges which are gradual. The name comes from the shape of the waveform which appears to be a sawtooth. We can generate this waveform by the same method followed for triangular pulse, the only thing to keep in mind is that difference in falling and rising times should be maintained and this can be done by controlling the rate of charge for each element. Similar to triangular wave, sawtooth wave is also used for sound generation. It helps to create sounds with subtractive analog music synthesizers. It is also used in electroencephalogram (EEG) because alpha oscillations of this wave are easier to remove than sine wave.

• Pulse wave: Pulse waveform is a special kind of waveform used for dealing with digital data. It is a non-sinusoidal waveform that resembles square wave .The only difference is that it has an offset duty cycle which means that the space ratio is 1:1 . Digital data which consists of bits of 0s and 1s is transmitted through these waves. One most wide-spread application of pulse wave is for analyzation of cardiac output during any major surgery or fluid transport. It is widely used in epidemiological and physiological studies to study the stiffness of arteries and calculate any possible risk.

In the field of electronics engineering, scientists and researchers often require signals that can be fed as an input to various devices which can later test their devices on these signals. Devices like modulators, filters, and analog-to-digital convertors require some input signals and other signals for testing. You will wonder what researchers do to get these signals. The answer to this is Function Generator. These are the devices that can generate different types of signals each representing different functions. These can be trigonometric signals, square functions, or any other necessary function. In this article we will see what is a function generator, we will also see the block diagram of a function generator and understand its working through it.