Broadband 1-to-N Circuit Combiner for mm-wave Applications

Abstract

Packaging mm-wave and THz circuits, poses many challenges due to the sensitivity of the circuits to any mismatch at the input or output. Traditional interfaces for combining circuits produce significant losses, and standing waves. This paper presents a unique approach to combing circuits at high frequency that results in reflection cancellation, and significant isolation between the circuits. The novel ‘iπ-wave’ approach relies on introducing a set of resistors and 180/N delay lines; where N is the number of circuits to be combined. The approach enables combing 1-to-N circuits with low loss due to its use of low impedance transmission lines, and provides a relative bandwidth of 50 – 200%. The concept is studied theoretically using simulations, and demonstrated experimentally with a 1-to-4 divider. The concept is demonstrated with a 5 – 45 GHz combiner circuit on low loss Alumina substrate featuring high isolation, low loss, and excellent reflection cancellation. The concept can be implemented in hybrid circuits, or MMICs.