A Compact and High Gain X/Ku Band Shared Aperture Antenna Array With Enhanced Inter-Band and Cross-Band Isolation

This paper introduces a dual-band shared-aperture antenna (SAA) designed to operate in both X and Ku-bands. The approach begins with the initial design and optimization of X-band and Ku-band antenna arrays on separate apertures. Subsequently, these arrays are integrated onto a single aperture to create a shared-aperture antenna array. For the X-Band, a single-port $4\times 1$ element array is designed using a series-fed network. This configuration is later upgraded to a four-port $4\times 4$ element array to enhance gain. The inter-element spacing is optimized at 19.1 mm to accommodate Ku-band array elements. The Ku-Band antenna array employs an aperture-coupled feeding technique with a corporate feed network, maintaining a consistent inter-element spacing of 19.1 mm. Both $4\times 4$ element antenna arrays for X and Ku-bands, configured with multi-ports and single-port networks, are fabricated on a single aperture while maintaining an overall size of $114\times 96\times 1.6$ mm3. Performance analysis of both the configurations i.e. Multiport Shared Aperture Antenna (MPSAA) Array and Single Port Shared Aperture Antenna (SPSAA) array is conducted. The achieved gains are 13.1/13.4 dBi for MPSAA and 18.5/19.1 dBi for SPSAA in both respective X/Ku bands, while maintaining a Side Lobe Level (SLL) of −9 dB and −10 dB. In addition, the measured results indicate significant inter-band and cross-band isolation, surpassing 25/35 dB (for X/Ku band) and 35 dB for MPSAA and crossband of >40 dB for SPSAA, respectively. The return loss bandwidth in the case of MPSAA for X/Ku-band is measured at 350/900 MHz, with resonance between 10.0-10.35 GHz and 13.0-13.9 GHz, respectively. The design utilizes Rogers RT/Duroid-5880 with a 0.79 mm thickness as the substrate. Simulation and measured results show good agreement. The compact size, high gain, and exceptional inter-/cross-band isolation make this design suitable for integration into modern communication systems and beamforming applications.