Grating-Lobe Reduction for Uniform Under-Sampled Phased Array Using Dielectric Dome Lens

Under-sampled arrays exhibit low mutual coupling, alleviating heat dissipation challenges associated with active radio frequency (RF) components in integrated front-end designs. This paper presents an effective dielectric dome lens (DDL) for a uniform array with one-wavelength inter-element spacing, enabling beam scanning with reduced grating lobes, making it suitable for millimeter-wave communication systems. The shape of the DDL is optimized using the geometric optics (GO) algorithm, allowing for the reflection of grating lobes while maintaining effective main beam scanning. The DDL is then miniaturized, integrated with absorber sheets to dissipate reflected grating lobes, and equipped with matching layers to improve radiation performance. The subsequent full-wave simulation further optimizes the design, accounting for factors overlooked by the GO algorithm and finalizing the DDL structure for operating with a under-sampled array. Finally, a 3 × 8 under-sampled rectangular patch array working at 28 GHz, integrated with a cylinder DDL, is fabricated and measured to validate the design approach. The experimental results are in agreement with the simulations. With the help of the DDL, the array with one-wavelength inter-element spacing achieves a continuous, symmetrical-to-boresight beam-scanning range of 110°, with a scan loss (SL) within 3 dB. The grating lobe is consistently reduced, maintaining peak side-lobe levels more than 9 dB below the main beam. This scanning performance remains effective over a bandwidth of 2 GHz.