RADIO PHYSICS AND RADIO ASTRONOMY

Subject and Purpose. Methods for determining and ensuring the stability of radio frequency (RF) amplifiers have been progressing quite actively over the past decades. However, most of them are not convenient for practical use. Combining analytical and graphical techniques widely accepted at the moment requires a highly skillful user and licensed software. Also, a bad point is the lack of clear algorithms for increasing the out-of-band high-frequency stability of amplifiers, sending us to the procedure of successive approximations when an optimal solution for an individual scheme is sought. The present work seeks for a simple method that effectively increases the out-of-band high-frequency stability of RF amplifiers and improves the reliability of signal amplification systems, especially those complex structures that incorporate low-frequency radio telescopes.

Methods and Methodology. The parameters of the RF amplifiers and passive circuits are obtained by computer modeling upon the S-parameters given by the manufacturer. The amplifier stability is determined by the K-factor for stability.

Results. A simple universal method has been developed to improve the out-of-band high-frequency stability of RF amplifiers. In this method, a stabilization R_stabL_stab circuit is connected to the amplifier in series with the load. An original procedure has been designed to calculate the stabilization circuit. Also, a metric has been proposed that evaluates the practical margins of the out-of-band high-frequency stability of RF amplifiers and makes it possible to compare them one to another. Finally, the proposed method offers freedom from the licensed software.

Conclusions. The proposed method significantly increases the high-frequency stability of RF amplifiers beyond the operating frequency range and simplifies the technological requirements for the design. The employment of RF amplifiers is more available almost without compromising their performance in the operating frequency range. The method is simple and easy to apply.

Keywords: S-parameters; RF amplifier; Darlington scheme; K-factor for stability

Manuscript submitted  23.05.2023

Radio phys. radio astron. 2023, 28(4): 318-328

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