Analog & Digital Communication

Definition: A multiplexing technique by which multiple data signals can be transmitted over a common communication channel in different time slots is known as Time Division Multiplexing (TDM). It allows the division of the overall time domain into various fixed length time slots. A single frame is said to be transmitted when it’s all signal components gets transmitted over the channel. Theory of TDM As we know, multiplexing allows the transmission of several signals over a common channel. … [Read more...] about Time Division Multiplexing (TDM)

Definition: A digital modulation technique that transmits data by varying the phase of the carrier wave in accordance with the digital modulating signal, is called Phase Shift Keying (PSK). The easiest form of PSK is BPSK i.e., binary phase shift keying. However, PSK can be extended to 4 level and 8 level PSK that totally depends on the need of the system. Principle of BPSK BPSK technique is the simplest among all the PSK techniques. In this, each signalling element is represented by a … [Read more...] about Phase Shift Keying – PSK

Definition: A digital modulation technique that allows data transmission by changing the frequency of the carrier wave according to the digital modulating signal is known as frequency shift keying (FSK). It is the most straightforward and efficient digital signal transmission scheme. Theory of Frequency Shift Keying The simplest form of FSK is Binary frequency shift keying (BFSK). Here, the frequency of the carrier wave changed between discrete binary values of the modulating signal. Thus, … [Read more...] about Frequency Shift Keying – FSK

Definition: A digital modulation technique in which the amplitude of the carrier wave is altered according to the modulating signal (bitstream) is known as Amplitude Shift Keying (ASK). It is the easiest and straightforward digital modulation scheme. ASK is sometimes known as On-Off keying because the carrier wave swings between 0 and 1 according to the low and high level of input signal respectively. Theory of Amplitude Shift Keying In ASK, frequency and phase of the carrier wave is kept … [Read more...] about Amplitude Shift Keying – ASK

Definition: Vestigial Sideband (VSB) modulation is a modulation technique which allows transmission of one sideband in addition with a part or vestige of the other. It is basically a compromise between DSB-SC and SSB modulation. VSB technique was introduced to overcome the drawbacks of SSB modulation. As SSB modulation requires accurate frequency response of the filter to transmit only one sideband completely. Thus by using VSB modulation one can simplify the design of the filter to a … [Read more...] about Vestigial Sideband (VSB) Modulation

Definition: Single sideband modulation (SSB) is an amplitude modulation scheme in which only a single sideband is transmitted through the channel. It is also known as SSB-SC which is an acronym for Single Sideband Suppressed Carrier as it allows suppression of one sideband and carrier completely. As we know, DSB-SC modulation technique generates an output wave having twice the bandwidth as that of the original modulating signal. So, in order to avoid doubling factor of bandwidth in such … [Read more...] about Single Sideband (SSB) Modulation

Definition: DSB-SC is an amplitude modulated wave transmission scheme in which only sidebands are transmitted and the carrier is not transmitted as it gets suppressed. DSB-SC is an acronym for Double Sideband Suppressed Carrier. The carrier does not contain any information and its transmission results in loss of power. Thus only sidebands are transmitted that contains information. This results in saving of power used in transmission. This saved power can be inserted into the 2 sidebands. … [Read more...] about Double Sideband Suppressed Carrier (DSB-SC) Modulation

Definition: Frequency Mixer is a non-linear device. It generates a number of frequencies on the application of two different frequencies at the input of the mixer. It is the core process in RF technology and design. Here, the input frequency gets converted into different frequency components so as to process the signals more effectively. It is clearly shown below that out of the two provided frequencies one is the input signal while the other is the local oscillator signal. Let’s … [Read more...] about Frequency Mixer

Definition: Vocoder is an audio processor that is used to transmit speech or voice signal in the form of digital data. The vocoder is used as short form for voice coder. Vocoders are basically used for digital coding of speech and voice simulation. The bitrate for available narrowband vocoders is from 1.2 to 64 kbps. Vocoder operates on the principle of formants. Formants are basically the meaningful components of a speech that is generated due to the human voice. Whenever a speech signal … [Read more...] about Vocoder

Definition: Frequency division multiplexing is a multiplexing technique in which multiple separate information signals can be transmitted over a single communication channel by occupying different frequency slots within common channel bandwidth. FDM technique is basically used for muxing of analog signals. Look at the figure given below to understand how multiple signals can be transmitted over a common channel. In Frequency division multiplexing simultaneous transmission of the … [Read more...] about Frequency Division Multiplexing (FDM)