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 × 0.004 × 0.0004 λg. 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° ± 1°. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2001–2005, 2014