Dual Open-Stopband Suppression in a Slotline-Based Dual-Band Leaky-Wave Antenna

We propose a novel method for dual open-stopband (OSB) suppression in a slotline-based dual-band leaky-wave antenna (LWA) through a stub-loaded configuration. Firstly, a stub modeled as a series impedance is introduced in the right half-period. By optimizing its position relative to the input, the Bloch impedance near the -1st spatial harmonic (SH) broadside frequency is tuned to achieve impedance matching conditions, thereby suppressing the OSB in the lower band. Similarly, placing an identical stub in the left half-period and adjusting its position suppresses the OSB associated with the -2nd SH. Finally, loading both stubs at their pre-optimized positions achieves simultaneous dual-OSB suppression in the dual-band LWA. A prototype was fabricated and measured, showing good agreement with simulations. The measured results demonstrate for the -1st SH a scanning range of -61° to +69° (6.8–11.6 GHz) with a peak gain of 9.6 dBi, corresponding to a scanning rate of 2.49°/%, while the -2nd SH exhibits a scanning range of -68° to +43° (12.8 19.2 GHz) with a peak gain of 12.4 dBi and a scanning rate of 2.78°/%. Compared to the reference design, the proposed antenna exhibits measured performance enhancements, including 3.3 dB gain with 23.3% higher efficiency near 8.8 GHz and 1.6 dB gain with 10.6% higher efficiency near 16.2 GHz, along with more stable radiation performance across both operating bands. The proposed technique offers an effective and compact solution for dual-band LWAs in 5G frequency-division duplex systems.