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Friis Formulas For Noise
Friis formula or Friis's formula (sometimes Friis' formula), named after Danish-American electrical engineer Harald T. Friis, is either of two formulas used in telecommunications engineering to calculate the signal-to-noise ratio of a multistage amplifier. One relates to noise factor while the other relates to noise temperature. The Friis formula for noise factor Friis's formula is used to calculate the total noise factor of a cascade of stages, each with its own noise factor and power gain (assuming that the impedances are matched at each stage). The total noise factor can then be used to calculate the total noise figure. The total noise factor is given as where F_i and G_i are the noise factor and available power gain, respectively, of the ''i''-th stage, and ''n'' is the number of stages. Both magnitudes are expressed as ratios, not in decibels. Consequences An important consequence of this formula is that the overall noise figure of a radio receiver is primarily establ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harald T
Harald or Haraldr is the Old Norse form of the given name Harold. It may refer to: Medieval Kings of Denmark * Harald Bluetooth (935–985/986) Kings of Norway * Harald Fairhair (c. 850–c. 933) * Harald Greycloak (died 970) * Harald Hardrada (1015–1066) * Harald Gille (reigned 1130–1136) Grand Dukes of Kiev * Mstislav the Great (1076–1132), known as Harald in Norse sagas King of Mann and the Isles * Haraldr Óláfsson (died 1248) Earls of Orkney * Harald Haakonsson (died 1131) * Harald Maddadsson (–1206) * Harald Eiriksson Others * Hagrold (fl. 944–954), also known as Harald, Scandinavian chieftain in Normandy * Harald Grenske (10th century), petty king in Vestfold in Norway * Harald Klak (–), king in Jutland * Harald Wartooth, legendary king of Sweden, Denmark and Norway * Harald the Younger, 9th-century Viking leader Modern name Royalty * Harald V of Norway (born 1937), present King of Norway * Prince Harald of Denmark (1876–1949) Arts and entertainment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunications Engineering
Telecommunications Engineering is a subfield of electrical engineering which seeks to design and devise systems of communication at a distance. The work ranges from basic circuit design to strategic mass developments. A telecommunication engineer is responsible for designing and overseeing the installation of telecommunications equipment and facilities, such as complex electronic switching systems, and other plain old telephone service facilities, optical fiber cabling, IP networks, and microwave transmission systems. Telecommunications engineering also overlaps with broadcast engineering. Telecommunication is a diverse field of engineering connected to electronic, civil and systems engineering. Ultimately, telecom engineers are responsible for providing high-speed data transmission services. They use a variety of equipment and transport media to design the telecom network infrastructure; the most common media used by wired telecommunications today are twisted pair, coaxial cabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal-to-noise Ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. SNR, bandwidth, and channel capacity of a communication channel are connected by the Shannon–Hartley theorem. Definition Signal-to-noise ratio is defined as the ratio of the power of a signal (meaningful input) to the power of background noise (meaningless or unwanted input): : \mathrm = \frac, where is average power. Both signal and noise power must be measured at the same or equivalent points in a system, and within the same system bandwidth. Depending on whether the signal is a constant () or a random variable (), the signal-to-noise ratio for random noise becomes: : \mathrm = \frac where E refers to the expected value, i.e. in this case ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the voltage or current (power, voltage or current amplifier). 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 greater amplitude signal at its output. The ratio of output to input voltage, current, or power is termed gain (voltage, current, or power gain). An amplifier, by definition has gain greater than unity (if the gain is less than unity, the device is an attenuator). An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Factor
Noise figure (NF) and noise factor (''F'') are figures of merit that indicate degradation of the signal-to-noise ratio (SNR) that is caused by components in a signal chain. These figures of merit are used to evaluate the performance of an amplifier or a radio receiver, with lower values indicating better performance. The noise factor is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard noise temperature ''T''0 (usually 290 K). The noise factor is thus the ratio of actual output noise to that which would remain if the device itself did not introduce noise, or the ratio of input SNR to output SNR. The noise ''factor'' and noise ''figure'' are related, with the former being a unitless ratio and the latter being the same ratio but expressed in units of decibels (dB). General The noise figure is the difference in decibels (dB) between the noise output of the actual receiver to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Temperature
In electronics, noise temperature is one way of expressing the level of available noise power introduced by a component or source. (This is to be distinguished from Temperature Noise in Thermodynamics or Principal Interferrometric Analysis Over Cross-Type Interference Between different noise types) The power spectral density of the noise is expressed in terms of the temperature (in kelvins) that would produce that level of Johnson–Nyquist noise, thus: :\frac = k_\text T where: * P_\text is the noise power (in W, watts) * B is the total bandwidth (Hz, hertz) over which that noise power is measured * k_\text is the Boltzmann constant (, joules per kelvin) * T is the noise temperature (K, kelvin) Thus the noise temperature is proportional to the power spectral density of the noise, P_\text/ B. That is the power that would be absorbed from the component or source by a matched load. Noise temperature is generally a function of frequency, unlike that of an ideal resistor which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gain (electronics)
In electronics, gain is a measure of the ability of a two-port electrical network, circuit (often an amplifier) to increase the Electric power, power or amplitude of a Signal (electrical engineering), signal from the input to the output port by adding energy converted from some power supply to the signal. It is usually defined as the mean ratio of the Signalling (telecommunication), signal amplitude or power at the output port (circuit theory), port to the amplitude or power at the input port. It is often expressed using the logarithmic decibel (dB) units ("dB gain"). A gain greater than one (greater than zero dB), that is amplification, is the defining property of an active component or circuit, while a passive circuit will have a gain of less than one. The term ''gain'' alone is ambiguous, and can refer to the ratio of output to input voltage (''voltage gain''), Electric current, current (''current gain'') or electric power (''power gain''). In the field of audio and general ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Figure
Noise figure (NF) and noise factor (''F'') are figures of merit that indicate degradation of the signal-to-noise ratio (SNR) that is caused by components in a signal chain. These figures of merit are used to evaluate the performance of an amplifier or a radio receiver, with lower values indicating better performance. The noise factor is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard noise temperature ''T''0 (usually 290 K). The noise factor is thus the ratio of actual output noise to that which would remain if the device itself did not introduce noise, or the ratio of input SNR to output SNR. The noise ''factor'' and noise ''figure'' are related, with the former being a unitless ratio and the latter being the same ratio but expressed in units of decibels (dB). General The noise figure is the difference in decibels (dB) between the noise output of the actual receiver to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Gain
The power gain of an electrical network is the ratio of an output power to an input power. Unlike other signal gains, such as voltage and current gain, "power gain" may be ambiguous as the meaning of terms "input power" and "output power" is not always clear. Three important power gains are operating power gain, transducer power gain and available power gain. Note that all these definitions of power gains employ the use of average (as opposed to instantaneous) power quantities and therefore the term "average" is often suppressed, which can be confusing at occasions. Operating power gain The operating power gain of a two-port network, GP, is defined as: :G_P = \frac where *Pload is the maximum time averaged power delivered to the load, where the maximization is over the load impedance, i.e., we desire the load impedance which maximizes the time averaged power delivered to the load. *Pinput is the time averaged power entering the network. If the time averaged input power depends on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Receiver
In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves (electromagnetic waves of radio frequency) and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation. Radio receivers are essential components of all systems that use radio. The information produced by the receiver may be in the form of sound, video (television), or digital data. A radio receiver may be a separate piece of electronic equipment, or an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low-noise Amplifier
A low-noise amplifier (LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio. An amplifier will increase the power of both the signal and the noise present at its input, but the amplifier will also introduce some additional noise. LNAs are designed to minimize that additional noise. Designers can minimize additional noise by choosing low-noise components, operating points, and circuit topologies. Minimizing additional noise must balance with other design goals such as power gain and impedance matching. LNAs are found in radio communications systems, medical instruments and electronic test equipment. A typical LNA may supply a power gain of 100 (20 decibels (dB)) while decreasing the signal-to-noise ratio by less than a factor of two (a 3 dB noise figure (NF)). Although LNAs are primarily concerned with weak signals that are just above the noise floor, they must also consider the presence of larg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
