A compact dual-band high-front-to-back-ratio microstrip antenna using four-petal slot geometry for C/X-band applications

A high–front-to-back-ratio (FBR) dual-band microstrip antenna employing a compact four-petal slot geometry and tapered offset feed mechanism is presented in this work. The antenna is fabricated on a Rogers RO4003 substrate with a thickness of 1.52 mm and a dielectric constant of 3.55. The proposed structure exhibits two well-defined resonances at 6.8 GHz and 9.6–9.8 GHz, validated through both full-wave simulations and prototype measurements. The measured reflection coefficient achieves return-loss values of −21.8 dB at 6.8 GHz and −18.7 dB at 9.8 GHz, closely matching simulated values. The realized peak gain measured across the dual bands is 6.1 dBi at 6.8 GHz and 6.3 dBi at 9.8 GHz, while simulations indicate corresponding gains of 6.4 dBi and 6.7 dBi, respectively. A key achievement of the proposed design is its high FBR of 15–18 dB, which outperforms several existing dual-band printed antennas that typically exhibit FBR below 12 dB. The radiating mechanism is further analyzed using an equivalent series-RLC circuit comprising two series-RLC branches in parallel with a small series inductive reactance, accurately emulating the dual-resonant behaviour. The floral petal-shaped slot and tapered feed synergistically establish two independent current paths, enabling dual-band operation without stacked layers or parasitic elements. The antenna maintains stable broadside radiation patterns with low cross-polarization and suppressed rear lobes across both frequency bands. Due to its compact size, moderate gain, and superior FBR, the proposed antenna is well-suited for C-band and X-band radar modules, point-to-point wireless systems, and applications requiring enhanced isolation and focused directional radiation. The combination of structural simplicity, analytical insight, and validated high-FBR behaviour makes this design an attractive candidate for next-generation wireless front-end architectures.