What does noise meter - low noise amplifier mean
Low noise amplifier is a special type of electronic amplifier mainly used for amplifying signals received from antennas in communication systems, in order to facilitate processing by subsequent electronic devices. Due to the fact that signals from antennas are generally very weak, low noise amplifiers are generally located very close to the antenna to reduce the loss of signals passing through the transmission line. This configuration of "active antennas" is widely used in microwave systems such as the Global Positioning System (GPS). This is because coaxial cables have significant losses in the microwave frequency range.
It is precisely because the low noise amplifier is located in the first stage of the entire receiver adjacent to the antenna that its characteristics directly affect the quality of the signal received by the entire receiver. To ensure that the signal received by the antenna can be correctly restored in the final stage of the receiver, a good low noise amplifier needs to generate as low noise and distortion as possible while amplifying the signal. These two parameters are typically characterized by noise coefficient and third-order input cutoff.
Impedance matching and noise matching at the input and output terminals are key to achieving high gain and low noise. Modern low noise amplifiers not only need to achieve impedance matching within a narrow band range, but new applications such as ultra wideband technology also require them to achieve impedance matching and noise matching over a very wide frequency range.
A low noise broadband amplifier has a very low noise figure and a wide frequency range. When the signal is weak, the output of the probe is first amplified by the low noise amplifier and then sent to the receiver. The main function of a low noise amplifier is to amplify the weak signal received by the antenna from the air, reduce noise interference, and provide the system with the necessary information data for demodulation. Increasing the gain of a low noise amplifier is very beneficial for reducing the noise figure of the entire machine. However, if the gain of a low noise amplifier is too high, it will affect the linearity of the entire receiving machine and put forward high requirements.
