Multiplexer | Demultiplexer | FDM | TDM | PAM | Applications

Multiplexing Principles Multiplexer: Multiplexing is the process of simultaneously transmitting two or more individual signals over a single communication channel, cable, or wireless. In effect, it increases the number of communication channels so that more information can be transmitted. Often in communication, it is necessary or desirable to transmit more than one voice or data … Read more

Digital Codes | Hartley’s Law | ASCII | Asynchronous | Encoding Methods

Digital Codes Digital Codes: Data processed and stored by computers can be numerical (e.g., accounting records, spreadsheets, and stock quotations) or text (e.g., letters, memos, reports, and books). As previously discussed, the signals used to represent computerized data are digital, rather than analog. Even before the advent of computers, digital codes were used to represent … Read more

FSK | PSK | DPSK | QPSK | QAM | Spectral Efficiency | Modem Concepts

Modem Concepts and Methods FSK | PSK | DPSK : Binary signals are switched dc pulses, so how do such signals get transmitted over telephone lines, cable TV, coaxial cables, twisted-pair cables, or wireless links? Binary pulses can be transported over short cables even at very high data rates. The transformers, capacitors, and other ac … Read more

PCM ( Pulse Code Modulation ) | T-Carrier Systems| Duplexing

Pulse-Code Modulation (PCM) PCM : The most popular form of TDM uses pulse-code modulation (PCM) (see Sec. 7-4), in which multiple channels of digital data are transmitted in serial form. Each channel is assigned a time slot in which to transmit one binary word of data. The data streams from the various channels are interleaved … Read more

Receiver and Transceiver | AM | FM | SW Radio | SDR | Wi-Fi

VHF Aircraft Communication Circuit Receiver:- Most modern receivers are in IC form. Virtually all of the circuitry can be incorporated in a single chip. Some external discrete components are still needed but are minimal. These may include coils, bypass, and tuning capacitors, antennas, crystals, filters, and in the case of audio, a power amplifier, and … Read more

IF Amplifiers | RF Input Amplifiers | Squelch Circuits | Controlling Gain

Typical Receiver Circuits IF Amplifiers : This section focuses on RF and IF amplifiers, AGC and AFC circuits, and other special circuits found in receivers. RF Input Amplifiers The most critical part of a communication receiver is the front end, which usually consists of the RF amplifier, mixer, and related tuned circuits and is sometimes … Read more

Noise Level & Types | Conversion Receivers | Signal-to-Noise Ratio (SNR)

Intermediate Frequency and Images The choice of IF is usually a design compromise. The primary objective is to obtain good selectivity. Narrowband selectivity is best obtained at lower frequencies, particularly when conventional LC tuned circuits are used. Even active RC filters can be used when IFs of 500 KHz or less are used. There are … Read more

Signal Reproduction | Super heterodyne | RF Amplifiers | Mixing

Basic Principles of Signal Reproduction Signal Reproduction: A communication receiver must be able to identify and select the desired signal from thousands of others present in the frequency spectrum (selectivity) and to provide sufficient amplification to recover the modulating signal (sensitivity). A receiver with good selectivity will isolate the desired signal in the RF spectrum … Read more

Impedance Matching Networks | T and π | Transformers and Baluns

Impedance Matching Networks Impedance Matching Networks: Matching networks that connect one stage to another are very important parts of any transmitter. In a typical transmitter, the oscillator generates the basic carrier signal, which is then amplified, usually by multiple stages, before it reaches the antenna. Since the idea is to increase the power of the … Read more

Power Amplifier | Linear Amplifier | Switching Power Amplifier

Power Amplifier The three basic types of power amplifier used in transmitters are linear, class C, and switching. Linear amplifiers provide an output signal that is an identical, enlarged replica of the input. Their output is directly proportional to their input, and they therefore faithfully reproduce an input, but at a higher power level. Most … Read more