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A low-noise amplifier (LNA) is an electronic component that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio (SNR). Any electronic 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.
The RF amplifier may not be needed and is often omitted (or switched off) for frequencies below 30 MHz, where the signal-to-noise ratio is defined by atmospheric and human-made noise. A local oscillator (LO) which generates a radio frequency signal at an offset from the incoming signal, which is mixed with the incoming signal.
The low-noise quality of an LNB is expressed as the noise figure (or sometimes noise temperature). This is the signal-to-noise ratio at the input divided by the signal-to-noise ratio at the output. It is typically expressed as a decibels (dB) value. The ideal LNB, effectively a perfect amplifier, would have a noise figure of 0 dB and would not ...
If used correctly, the Leeson equation gives a useful prediction of oscillator performance in this range. If a value for f c is included, the equation also shows a curve fit for the flicker noise. The f c for an amplifier depends on the actual configuration used, because radio-frequency and low-frequency negative feedback can have an effect on f c.
The RF signal from the antenna may have one stage of amplification to improve the receiver's noise figure, although at lower frequencies this is typically omitted. The RF signal enters a mixer , along with the output of the local oscillator , in order to produce a so-called intermediate frequency (IF) signal.
The noise power at the output of the amplifier chain consists of four parts: The amplified noise of the source ( N i ⋅ G 1 G 2 G 3 {\displaystyle N_{i}\cdot G_{1}G_{2}G_{3}} ) The output referred noise of the first amplifier N a 1 {\displaystyle N_{a1}} amplified by the second and third amplifier ( N a 1 ⋅ G 2 G 3 {\displaystyle N_{a1}\cdot ...
An RF chain is a cascade of electronic components and sub-units which may include amplifiers, filters, mixers, attenuators and detectors. [1] It can take many forms, for example, as a wide-band receiver-detector for electronic warfare (EW) applications, as a tunable narrow-band receiver for communications purposes, as a repeater in signal distribution systems, or as an amplifier and up ...
Parametric amplifiers are used in applications requiring extremely low noise. A parametric oscillator is a driven harmonic oscillator in which the oscillations are driven by varying some parameters of the system at some frequencies, typically different from the natural frequency of the oscillator.