Coupling transducers for magnetoinductive waveguides: Minimising reflection over the whole pass band

The characteristic impedance of magnetoinductive waveguides is complex and frequency-dependent, whereas the input impedance of standard RF and microwave devices is real and constant. Transducers capable of coupling magnetoinductive waveguides to other devices are, therefore, required for high-performance magnetoinductive systems. The author designed and experimentally realised a resonant coupling transducer capable of minimising reflections from magnetoinductive waveguides over the whole pass band. For a magnetoinductive cable with the resonant frequency of 95 MHz and the pass band between 73 and 174 MHz, the experimental value of |S11 | was as low as −25 dB at the resonant frequency and about −20 dB over more than 90% of the pass band, the most broadband performance achieved up to date. Yet, the transducer has simple design and comprises only three resonant circuits, which makes it a promising candidate for wide-band applications. © 2011 Elsevier B.V. All rights reserved.