Wide-gap evolved hybrid CPW–GCPW loaded dual symmetric ground shielding patches for compactness, wideband and low cross-polarisation

This paper presents a coplanar waveguide (CPW) loaded with dual symmetric bottom ground patches on a 1.6 mm-thick FR4 substrate. The proposed CPW reflects as an evolved hybrid CPW–GCPW that integrates the characteristics of conventional CPW and grounded CPW (GCPW), offering better physical isolation (larger CPW slot gap width, W ), low cross-polarisation, and wide impedance bandwidth, without sacrificing 50 Ω impedance matching when embedded in an antenna system. From the CPW arrangement, an analytical impedance model is formulated using a conformal mapping technique, facilitating precise input impedance control and permitting an expansion in the CPW slot width to 0.6 mm. The proposed CPW + dual bottom ground patches design has an impedance sensitivity that is twice as low as the conventional CPW with respect to fluctuations in W , with a change of only 19.5 Ω /mm for each 1 mm increment, while maintaining a similar 2-port network bandwidth capacity. When paired with a monopole patch antenna, it experimentally demonstrates a wide impedance bandwidth from 2.85 to 6.60 GHz, along with an average cross-polarisation level below −14 dB. This antenna design is particularly well-suited for developing 5G New Radio (NR) applications due to its compactness (0.34 λ × 0 . 28 λ × 0 . 015 λ ), wide bandwidth (79.4%), low cross-polarisation levels, realised gain of 4.5 dBi@3.3 GHz, and efficiency exceeding 75%.