A low-noise amplifier (LNA) is an active RF device that will amplify a very low-power signal without degrading its signal-to-noise ratio significantly.
For the design of LNA, the designer needs to choose low-noise components, circuit topologies and operating points of the amplifier design by matching other design goals such as RF power gain and impedance matching.
To learn more about RF communication systems, we recommend you to check the following books.
To understand the RF low noise amplifiers in a better way, we recommend you to check the details of the following components, which are used along with the LAN.
In this RF and Microwave amplifier article, we will cover,
LNAs are the prime component of communication systems building blocks, which primarily deal with weak signals, just above the noise floor and intermodulation distortion. In the design of LNA, attributes like Gain, RF input power, Noise figure, Linearity, and output impedance match need to consider.
Low noise figure and high amplification in the first stage of LNA design is achieved by using high-electron-mobility transistors (HEMTs) or junction field-effect transistors (JFETs). They are driven by a high-current regime and reduce the relative amount of shot noise.
The amount of gain generated in an LNA is often compromised. High gain makes weak signals strong and such high-level signals may exceed the amplifier's dynamic range and cause other types of noise like nonlinear mixing or harmonic distortion etc.
The perfect march impedance between source and input will maximize the power transfer to the device.
Low Noise Amplifiers are used in the front end of the receive chain right after the antenna and filter to amplify the received very low strength signal with minimal degradation and without amplifying the noise in it.
As LNA is used very close to the signal source like an antenna, the signal gain created by the LNA helps to avoid the effect of noise in the subsequent stages of the receiver. LNA enables optimum retrieval of the desired signal by boosting the signals' power and adding as little noise and distortion into the later stages of the receiver system.
When selecting RF low noise Amplifiers for the system design, the designer needs to consider the following features to optimise the receiver chain.
The frequency range of the LNA is the range of frequency over which it operates by meeting all other electrical parameters. In general, low noise amplifiers will have a narrow bandwidth to optimize input and output impedance match and offer very high-level noise figures.
The noise figure indicates the amount of noise added to the signal during amplification. A lower noise figure indicates a higher signal to noise ratio and it leads to a quality output signal to the receiver chain.
Power Compression (P1dB) is the point at which the input signal to the LNA is amplified by a level that is 1 dB below the small-signal gain of the amplifier. Power Compression indicates the gain point beyond which amplifier gain is no longer linearly to the input power.
As the LAN may need to connect to various loads, it is better to have good input and output impedance match to avoid unwanted signal reflection and it may affect the LNA and the quality of the original signal.
The gain of the LNA indicates the ratio of the output to the input power level expressed in decibels (dB). LNA usually will have a higher gain in the range of 30 to 40 dB.
Gain flatness shows the variation in the level of the gain over the entire frequency range of operation. Lower variation, better the performance of the Low noise amplifiers.
Low noise amplifiers are generally available in various package options like a Connectorized module, Surface Mount, or as a die or chip form. For connectorised modules, the designer can choose various RF connector options as per the design requirements.
As LNA, mostly need to fix along with the antenna in a hub or outdoor space, the operating temperature range of low noise amplifiers need to consider for matching the environmental conditions around the antenna.
A low-noise amplifier (LNA) is the most important, active device present in radio and other signal receivers to amplify signals of very low strength from an antenna before passing on to the receiver chain. LNA’s are generally capable of amplifying the barely recognizable signals without adding any noise to the original signal.
Below is the list of top-rated LNA manufacturers, from which you can choose a suitable amplifier for the RF system design.
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