The Design of The Logarithmic Detector in The Front-End Board of Sonography Systems

Front-End design is one of the most challenging parts in an ultrasound system (sonography) in which the modulated signals from the body are received with very low amplitude within the frequency range of 2 to12 MHz. Since the main concern is to design small circuits, here, an applicable circuit is proposed with the objective of using the minimum number of electronic devices which absorbs very low noise within its nominal range. The proposed circuit is the logarithmic amplifier detector which is a part of the Front-End board. The conventional logarithmic amplifiers use an inductor to modulate the current to voltage in order to be robust against noise. Here, in addition to proposing an efficient circuit, the inductor is replaced with a small circuit. The simulation results in the OrCAD software demonstrate the proper behavior of the proposed circuit.