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Active Circulator
In electrical engineering, an active circulator is an active non-reciprocal three-port device that couples a microwave or radio-frequency signal only to an adjacent port in the direction of circulation. Other (external) circuitry connects to the circulator ports via transmission lines. An ideal three-port active circulator has the following scattering matrix: :S = \begin 0 & 0 & 1\\ 1 & 0 & 0 \\ 0 & 1 & 0 \end An active circulator can be constructed using one of several different technologies. One early technology is the use of transistors as the active devices to perform the non-reciprocal function. Varactor circuits are another technology, relying on a time-varying transmission line structure, driven by a separate pump signal. A third technology utilizes spatiotemporally-modulated rings of coupled resonators. Another design approach relies on staggered commutation and integrated circuit techniques. Compared to passive (ferrite) circulators, active circulators have the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Port (circuit Theory)
In electrical circuit theory, a port is a pair of terminals connecting an electrical network or circuit to an external circuit, as a point of entry or exit for electrical energy. A port consists of two nodes (terminals) connected to an outside circuit which meets the ''port condition'' – the currents flowing into the two nodes must be equal and opposite. The use of ports helps to reduce the complexity of circuit analysis. Many common electronic devices and circuit blocks, such as transistors, transformers, electronic filters, and amplifiers, are analyzed in terms of ports. In multiport network analysis, the circuit is regarded as a "black box" connected to the outside world through its ports. The ports are points where input signals are applied or output signals taken. Its behavior is completely specified by a matrix of parameters relating the voltage and current at its ports, so the internal makeup or design of the circuit need not be considered, or even known, in de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scattering Parameters
Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals. The parameters are useful for several branches of electrical engineering, including electronics engineering, electronics, communications system, communication systems design, and especially for microwave engineering. The S-parameters are members of a family of similar parameters, other examples being: Y-parameters and Z-parameters, Two port#Hybrid parameters (h-parameters), H-parameters, #Scattering transfer parameters, T-parameters and ABCD-parameters. They differ from these, in the sense that ''S-parameters'' do not use open or short circuit conditions to characterize a linear electrical network; instead, impedance matching, matched loads are used. These electrical termination, terminations are much easier to use at high signal frequencies than open-circuit and s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Varactor
A varicap diode, varactor diode, variable capacitance diode, variable reactance diode or tuning diode is a type of diode designed to exploit the voltage-dependent capacitance of a reverse-biased p–n junction. Applications Varactors are used as voltage-controlled capacitors. They are commonly used in voltage-controlled oscillators, parametric amplifiers, and frequency multipliers. Voltage-controlled oscillators have many applications such as frequency modulation for FM transmitters and phase-locked loops. Phase-locked loops are used for the frequency synthesizers that tune many radios, television sets, and cellular telephones. The varicap was developed by the Pacific Semiconductor subsidiary of the Ramo Wooldridge Corporation who received a patent for the device in June 1961. The device name was also trademarked as the "Varicap" by TRW Inc., TRW Semiconductors, the successor to Pacific Semiconductors, in October 1967. This helps explain the different names for the device as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resonator
A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies, than at other frequencies. The oscillations in a resonator can be either electromagnetic or mechanical (including acoustic). Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal. Musical instruments use acoustic resonators that produce sound waves of specific tones. Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency. A cavity resonator is one in which waves exist in a hollow space inside the device. In electronics and radio, microwave cavities consisting of hollow metal boxes are used in microwave transmitters, receivers and test equipment to control frequency, in place of the tuned circuits which are used at lowe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circulator
In electrical engineering, a circulator is a passivity (engineering), passive, non-Reciprocity (electrical networks), reciprocal three- or four-port (circuit theory), port device that only allows a microwave or radio frequency, radio-frequency (RF) signal to exit through the port directly after the one it entered. Optical circulators have similar behavior. Ports are where an external waveguide (electromagnetism), waveguide or transmission line, such as a microstrip line or a coaxial cable, connects to the device. For a three-port circulator, a signal applied to port 1 only comes out of port 2; a signal applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of port 1. An ideal three-port circulator thus has the following scattering parameters, scattering matrix: :S = \begin 0 & 0 & 1\\ 1 & 0 & 0 \\ 0 & 1 & 0 \end Theory of operation Microwave circulators rely on the anisotropic and ''non-Reciprocity (electrical networks), reciprocal'' proper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DC Power
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current. The abbreviations ''AC'' and ''DC'' are often used to mean simply ''alternating'' and ''direct'', as when they modify ''current'' or ''voltage''. Direct current may be converted from an alternating current supply by use of a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be converted into alternating current via an inverter. Direct current has many uses, from the charging of batteries to large power suppl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise (electronics)
In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics and central to thermodynamics. Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically, and even then quantum noise would remain inherent. Electronic noise is a common component of noise in signal processing. In communication systems, noise is an error or undesired random disturbance of a useful information signal in a communication channel. The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from interference, for example in the signal-to-noise ratio (SNR), signal-to-interference ratio (SIR) and signal-to-noise plus interference ratio (SNIR) measu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
