Ultra-Wideband Low-Profile Planar LPDA Antenna with Gain-Anomaly Suppression and Stable High Gain for Remote Sensing

An ultra-wideband, low-profile planar log-periodic dipole array (PLPDA) antenna with suppressed anomalies and stable high gain is proposed for remote sensing applications. The antenna comprises six planar dipoles with triangular-shaped top loads, stubs, and buried non-fed conformal parasitic Yagi elements. A broadband transition balun merged with striplines forms a balanced back-side feeding network directly integrated into the antenna. The synergistic combination of the LPDA, conformal parasitic Yagi elements, and the integrated balanced feeding network within a stacked planar structure enables continuous operation across the S-, C-, and X-bands while suppressing anomalous resonances and eliminating gain anomalies. Measured results demonstrate an operating band of 2.3-13 GHz (|S11| < -10 dB), corresponding to a 140% fractional bandwidth. The antenna maintains a stable realized gain of 6.8 ± 0.8 dBi across the entire band, with no gain anomalies. The compact footprint of 45 mm × 70 mm achieves improved bandwidth-to-compactness and gain-flatness trade-offs, quantified by Nd/FBW = 0.042 (Nd is the number of dipoles) and ΔG/FBW ≈ 0.011 (ΔG is the gain variation). In comparison, a traditional 19-dipole PLPDA requires a 155% larger footprint to obtain comparable bandwidth while exhibiting multiple gain anomalies. These results confirm that the proposed PLPDA achieves an ultra-wideband operating band with suppressed anomalies and stable high gain in a compact profile by reducing the number of dipoles, making it suitable for multiband satellite-based remote sensing systems.