low noise amplifier
A.S. Petrov, L.A. Parkachev, A.S. Smirnovov
New cascaded multi-sectional cable tract schematic was proposed. The whole scheme breaks into n cascades, which are, in turn, divided into m separate sections. Besides, minimization of the noise figure in each section is achieved by installation LNA at inputs of the cable separate pieces, the gain factors of which exceed losses in cable pieces by 15-20 dB.
As soon as the output power in the m- sectional scheme constructed in this way will exceed some maximum allowable limit determined by designer, the additional piece of cable that provides excess power dissipation and makes summary gain figure of the cascade equal to 0 dB, should be set on the cascade output. For this reason, the last section of each cascade will have bigger length than the first sections. When necessary, n such cascades are included in the scheme.
If it is not allowed to install in this system amplifiers with gain figure values mentioned above, it is still possible to achieve noticeable reduction of the total noise figure if accept the excess of gain over losses in each cascade achieve by 12 dB.
At equal values of summary gain factor the proposed cascaded multi-sectional scheme is characterized by lower noise figure and grater length compared with conventional multi-sectional cable tract.