Modulation and Demodulation

Generation of DSBSC Signal using Balanced and Ring Modulator: DSBSC signal can be obtained by simply multiplying the modulating signal with the carrier signal. By simple multiplication of Vc sin ωct and Vm sin ωmt, we have the lower and upper sidebands without carrier as shown below: It means that a DSBSC signal is obtained by simply multiplying […]

Square Law Diode Modulator – Circuit Diagram and its V-I Characteristics: Basic circuit of a square law diode modulator is shown in Fig. 22.30. It utilizes the nonlinear region of voltage-current dynamic characteristic of a P-N diode. This square law diode modulator method is suited at low voltage levels because of the fact that current-voltage

Emitter Modulation – Circuit Diagram and its Operation: The circuit for emitter modulation is shown in Fig. 22.29. It is essentially a CE amplifier. The carrier signal from a crystal oscillator is coupled to the base of amplifier through capacitor Cin. The modulating signal is applied to the emitter circuit. The capacitors Cin and CC are

Base Modulation Circuit Working Principle: The circuit for base modulation is shown in Fig. 22.28. The carrier signal from a crystal oscillator is coupled to the base terminal of the amplifier through transformer T1. The modulating signal is applied across resistor R1 through capacitor C1. The capacitor C1 allows only audio frequency ac signal to

Collector Modulation Circuit – Working, Advantages and Disadvantages: This is very popular method for AM generation. The circuit diagram for collector modulation is shown in Fig. 22.26. Here, the transistor Q1 makes an RF class C amplifier. The carrier signal is applied to the base of Q1. VCC makes collector supply used for biasing purpose.

Block Diagram of AM Transmitter: Block Diagram of AM Transmitter is shown in Fig. 22.25. Sound waves produced by speech or music strike the diaphragm of a microphone that converts them into a tiny varying current. The audio frequency output of the microphone is amplified by a low level audio amplifier and, finally, by a

Vestigial Sideband Modulation System (VSB): A Vestigial Sideband Modulation System (VSB) is actually a compromise between DSBSC and SSB modulation systems. In other words, it can be said that it is an optimum choice in which the advantages of DSBSC and SSB modulation systems have been exploited. As a matter of fact, the generation of

Types of Amplitude Modulation (AM): As we know already that, one carrier and two sidebands are produced in AM generation. However, it is not essential that all these signals are transmitted to enable the receiver to reconstruct the original signal. One may attenuate or altogether remove the carrier or any of the sidebands without affecting

Signal Definition and Classification of Signals: A signal is a single valued function of one or more variables that conveys some information. Signals are represented mathematically as the functions of one or more independent variables. A signal may be a function of time, temperature, position, pressure, distance etc. In electrical sense, the signal can be