Possibility of ultra fine isolator for portable phone

There exists a trade-off relationship between miniaturization of an isolator for portable phones and its specific bandwidth. In this paper, we introduce a new way to increase bandwidth over 13%, in spite of a reduction in garnet dimensions by one tenth, by the addition of LC impedance matching circuits. In the preliminary experiments, we obtained a 4 mm square isolator with 4.1% bandwidth at 836 MHz using LTCC technology.