Design of a Two-layer SIW Power Divider with Slot Aperture Y-Junction for Enhanced Narrowband Isolation

This study presents a 3 dB power divider based on a two-layer Substrate Integrated Waveguide (SIW) structure designed to achieve high isolation and optimal return loss at both output ports while maintaining low insertion loss. The initial configuration uses a conventional Y-junction SIW power divider, which demonstrates limited isolation between output ports. A rectangular slot was incorporated at the Y-junction, significantly enhancing isolation. Although this adjustment introduced some insertion loss, a second substrate layer with a copper patch was added above the slot, effectively minimizing insertion loss and preserving strong isolation without the need for an isolation resistor. The resistor-free design simplifies fabrication and improves reliability by avoiding components that may fail under high power conditions. Due to fabrication constraints, the power divider is optimized for performance at two center frequencies, 12 GHz and 24 GHz, with prototyping focused on 12 GHz. Simulated and measured results at 12 GHz are in close agreement, confirming measured isolation performance with at least 10 dB of isolation over a fractional bandwidth of 9.9%. While this narrowband design may not suit all applications, it offers high precision for systems that require strict frequency isolation, making it especially advantageous for targeted narrowband applications where isolation and reliability are critical.