Open AccessAutomatic resonant frequency matching of power amplifier by transformer loop sampling
Author(s) -
Lee Han Lim,
Jang HyeongSeok,
Park DongHoon,
Lee MoonQue,
Yu Jong Won
Publication year - 2015
Publication title -
electronics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.375
H-Index - 146
ISSN - 1350-911X
DOI - 10.1049/el.2014.3168
Subject(s) - amplifier , transformer , electronic engineering , transducer , linear variable differential transformer , engineering , ultrasonic sensor , electrical engineering , rf power amplifier , voltage , rlc circuit , acoustics , distribution transformer , capacitor , physics , cmos
A new automatic resonant frequency matching technique based on voltage detection by sampling the output transformer loop of the radio‐frequency power amplifier (PA) in ultrasonic medical applications is proposed. The proposed automatic resonant frequency matching circuitry is composed of a single‐loop coil added to a PA output transformer, voltage divider, diode detector and micro‐controller unit for frequency adjustment. Using the proposed circuitry, the resonant frequency shift due to output load variations can be effectively tracked and compensated to provide optimised power transfer to a nonlinear load. For verification, a prototype ultrasonic medical application using a piezoelectric transducer is implemented and examined with silicone oil to check the resonance.