Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its phase, as in phase modulation.
In electronics, the figures of merit of an amplifier are numerical measures that characterize its properties and performance. Figures of merit can be given as a list of specifications that include properties such as gain, bandwidth, noise and linearity, among others listed in this article. Figures of merit are important for determining the suitability of a particular amplifier for an intended use.
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.
Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a method of controlling the average power delivered by an electrical signal. The average value of voltage fed to the load is controlled by switching the supply between 0 and 100% at a rate faster than it takes the load to change significantly. The longer the switch is on, the higher the total power supplied to the load. Along with maximum power point tracking (MPPT), it is one of the primary methods of controlling the output of solar panels to that which can be utilized by a battery. PWM is particularly suited for running inertial loads such as motors, which are not as easily affected by this discrete switching. The goal of PWM is to control a load; however, the PWM switching frequency must be selected carefully in order to smoothly do so.
Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the input. The average or peak output signal level is used to dynamically adjust the gain of the amplifiers, enabling the circuit to work satisfactorily with a greater range of input signal levels. It is used in most radio receivers to equalize the average volume (loudness) of different radio stations due to differences in received signal strength, as well as variations in a single station's radio signal due to fading. Without AGC the sound emitted from an AM radio receiver would vary to an extreme extent from a weak to a strong signal; the AGC effectively reduces the volume if the signal is strong and raises it when it is weaker. In a typical receiver the AGC feedback control signal is usually taken from the detector stage and applied to control the gain of the IF or RF amplifier stages.
A class-D amplifier or switching amplifier is an electronic amplifier in which the amplifying devices operate as electronic switches, and not as linear gain devices as in other amplifiers. They operate by rapidly switching back and forth between the supply rails, using pulse-width modulation, pulse-density modulation, or related techniques to produce a pulse train output. This passes through a simple low-pass filter which blocks the high-frequency pulses and provides analog output current and voltage. Because they are always either in fully on or fully off modes, little energy is dissipated in the transistors and efficiency can exceed 90%.
A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency (RF) power amplifier, some of which have output power measured in kilowatts, and are used in amateur radio. Other types of linear amplifier are used in audio and laboratory equipment. Linearity refers to the ability of the amplifier to produce signals that are accurate copies of the input. A linear amplifier responds to different frequency components independently, and tends not to generate harmonic distortion or intermodulation distortion. No amplifier can provide perfect linearity however, because the amplifying devices—transistors or vacuum tubes—follow nonlinear transfer function and rely on circuitry techniques to reduce those effects. There are a number of amplifier classes providing various trade-offs between implementation cost, efficiency, and signal accuracy.
A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in L/C circuits to set the resonance frequency, e.g. to tune a radio, or as a variable reactance, e.g. for impedance matching in antenna tuners.
A radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. Radio waves are electromagnetic waves with frequencies between about 30 Hz and 300 GHz. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. Transmitters are necessary parts of all systems that use radio: radio and television broadcasting, cell phones, wireless networks, radar, two way radios like walkie talkies, radio navigation systems like GPS, remote entry systems, among numerous other uses.
Polar modulation is analogous to quadrature modulation in the same way that polar coordinates are analogous to Cartesian coordinates. Quadrature modulation makes use of Cartesian coordinates, x and y. When considering quadrature modulation, the x axis is called the I (in-phase) axis, and the y axis is called the Q (quadrature) axis. Polar modulation makes use of polar coordinates, r (amplitude) and Θ (phase).
A radio-frequency power amplifier is a type of electronic amplifier that converts a low-power radio-frequency signal into a higher-power signal. Typically, RF power amplifiers are used in the final stage of a radio transmitter, their output driving the antenna. Design goals often include gain, power output, bandwidth, power efficiency, linearity, input and output impedance matching, and heat dissipation.
A valve RF amplifier or tube amplifier (U.S.) is a device for electrically amplifying the power of an electrical radio frequency signal.
Power management integrated circuits are integrated circuits for power management. Although PMIC refers to a wide range of chips, most include several DC/DC converters or their control part. A PMIC is often included in battery-operated devices and embedded devices to decrease the amount of space required.
A baseband processor is a device in a network interface controller that manages all the radio functions ; however, this term is generally not used in reference to Wi-Fi and Bluetooth radios. A baseband processor typically uses its own RAM and firmware. Baseband processors are typically fabricated using CMOS or RF CMOS technology, and are widely used in radio-frequency (RF) and wireless communications.
Exynos, formerly Hummingbird (Korean: 엑시노스), is a series of ARM-based system-on-chips developed by Samsung Electronics' System LSI division and manufactured by Samsung Foundry. It is a continuation of Samsung's earlier S3C, S5L and S5P line of SoCs.
The Samsung Galaxy S5 is an Android-based smartphone unveiled, produced, released and marketed by Samsung Electronics as part of the Samsung Galaxy S series. Unveiled on 24 February 2014 at Mobile World Congress in Barcelona, Spain, it was released on 11 April 2014 in 150 countries as the immediate successor to the Galaxy S4. As with the S4, the S5 is an evolution of the prior year's model, placing a particular emphasis on an improved build with a textured rear cover and IP67 certification for dust and water resistance, a more refined user experience, new security features such as a fingerprint reader and private mode, expanded health-related features including a built-in heart rate monitor, a USB 3.0 port, and an updated camera featuring speedy auto-focus through phase-detection. The video resolution has been upgraded to 2160p (4K) and the frame rate at 1080p has been doubled to 60 for a smooth appearance.
The Samsung Galaxy S5 Mini is an Android smartphone developed by Samsung Electronics. It was announced in May 2014 and released on July 1, 2014. The S5 Mini is a mid-range model of its flagship Galaxy S5 smartphone and a successor to the Galaxy S4 Mini. It competes with the HTC One Mini 2 and the Sony Xperia Z1 Compact. It has a similar design and software features to its high-end counterpart, the Galaxy S5.
The Samsung Galaxy Alpha (SM-G850x) is an Android smartphone produced by Samsung Electronics. Unveiled on 13 August 2014, the device was released in September 2014. A high-end device, the Galaxy Alpha is Samsung's first Android-powered smartphone to incorporate a metallic frame, although the remainder of its physical appearance still resembles previous models such as the Galaxy S5. It also incorporates Samsung's new Exynos 5430 system-on-chip, which is the first mobile system-on-chip to use a 20 nanometer manufacturing process.
The Samsung Galaxy Mega 2 is an Android smartphone/tablet computer hybrid manufactured by Samsung and is the successor to the Samsung Galaxy Mega. It was released in September 2014.
In electronics, power amplifier classes are letter symbols applied to different power amplifier types. The class gives a broad indication of an amplifier's characteristics and performance. The classes are related to the time period that the active amplifier device is passing current, expressed as a fraction of the period of a signal waveform applied to the input. A class A amplifier is conducting through all the period of the signal; Class B only for one-half the input period, class C for much less than half the input period. A Class D amplifier operates its output device in a switching manner; the fraction of the time that the device is conducting is adjusted so a pulse-width modulation output is obtained from the stage.
