The low-noise amplifier (LNA) is a special type of electronic amplifier or amplifier used in communication systems to amplify very weak signals captured by an antenna. An electronic amplifier is a device for increasing the power and/or Amplitude of a signal. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into It is often located very close to the antenna. If the LNA is located close to the antenna, then losses in the feedline become less critical. The Feed line in a Radio Transmission, Reception or Transceiver system is the physical cabling that carries the RF signal to and/or This "active antenna" arrangement is frequently used in microwave systems like GPS, because coaxial cable feedline is very lossy at microwave frequencies. Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth Coaxial cable is a cable consisting of an inner conductor surrounded by a tubular insulating layer typically made from a flexible material with a high Dielectric constant, all
It is a key component, which is placed at the front-end of a radio receiver circuit. This article is about a radio receiver for other uses see Radio (disambiguation. Per Friis' formula, the overall noise figure of the receiver front-end is dominated by the first few stages. In Telecommunication, noise figure ( NF) is a measure of degradation of the signal to noise ratio ( SNR) caused by components in the RF signal chain
Using an LNA, the noise of all the subsequent stages is reduced by the gain of the LNA and the noise of the LNA is injected directly into the received signal. Thus, it is necessary for an LNA to boost the desired signal power while adding as little noise and distortion as possible so that the retrieval of this signal is possible in the later stages in the system.
For low noise the amplifier needs to have a high amplification in its first stage. Therefore JFETs and HEMT are used and distributed amplifiers could be used. The junction gate field-effect transistor ( JFET or JUGFET) is the simplest type of Field effect transistor. Distributed amplifiers are a very resourceful example of distributed Circuit design that incorporate Transmission line theory into traditional amplifier design They are driven in a high current regime, which is not energy efficient, but reduces the relative amount of shot noise. Shot noise is a type of Electronic noise that occurs when the finite number of particles that carry energy such as Electrons in an electronic circuit or Photons Input and output matching circuits for narrow band circuits enhance the gain (see gain-bandwidth product) and do not use resistors, as these will add noise. The gain bandwidth product (GBW or GB for an amplifier is the product of the open loop gain (constant for a given Amplifier) and its 3 dB bandwidth Biasing is done by large resistors, because energy efficiency is not needed, and a large resistor prevents leakage of the weak signal out of the signal path or noise into the signal path.
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