A compact dual-mode interlocked UWB MIMO antenna for reconfigurable wireless systems

Abstract This paper presents the design and experimental validation of an interlocked frequency-switchable multiple-input multiple-output (MIMO) antenna. The proposed reconfigurable antenna is based on an ultra-wideband (UWB) radiator consisting of a circular patch integrated with a four-armed floral slot resonator and extended slotted stubs. The main radiator achieves a reflection coefficient bandwidth from 3 to 10.6 GHz, thereby covering the entire UWB frequency range. To enable a high-performance narrowband mode centered at 3.5 GHz, a compact low-pass filter (LPF) using a butterfly-shaped resonator with a 4 GHz cut-off frequency is integrated adjacent to the radiator. A feed selection network with PIN diodes allows seamless switching between UWB and narrowband operations. The antenna element, with an electrical size of 0.24 λ 0 × 0.16 λ 0 ( λ 0 = 100 mm at 3 GHz), is extended into a 4 × 4 MIMO antenna using an interlocked layout to achieve frequency reconfiguration and pattern diversity. A fabricated prototype shows good agreement with simulations with a gain above 4.2 dBi, radiation efficiency over 85%, and diversity metrics such as envelope correlation coefficient, diversity gain, and channel capacity loss are well within acceptable limits. The dual-mode operation between UWB and 3.5 GHz makes the antenna desirable for next-generation wireless networks, 5G sub-6 GHz communications, IoT and short-range high-speed data links.