MINIATURIZED AND WIDEBAND LUMPED LTCC BRANCH-LINE COUPLER FOR DOZENS OF MEGAHERTZ APPLICATIONS

A miniaturized and wideband lumped-element branch-line coupler is proposed in a 10-layer low-temperature co-fired ceramic (LTCC) substrate for dozens of megahertz applications. The proposed topology not only enables a wide fractional bandwidth of 32.3% with a small number of elements but also makes the required capacitance and inductance lower for element size reduction. The further miniature is achieved using vertically interdigital-capacitors with eight fingers and spiral inductors with 9.5 turns. The proposed coupler has the smallest reported size of only 0.005 x 0.004 x 0.0004 lambda g. Measured S-11, S-21, S-31, and S-41 are better than -15, -4.6, -3.9, and -13 dB from 52 to 72 MHz, respectively. And inband phase difference between the coupled and direct ports is within 91 degrees +/- 61 degrees. (C) 2014 Wiley Periodicals, Inc.