Broadside Radiating, Low-Profile, Electrically Small, Huygens Dipole Filtenna

An electrically small, low-profile, Huygens dipole filtenna is presented that operates near 1.28 GHz. The design incorporates a pair of magnetic and electric near-field resonant parasitic (NFRP) elements and a driven element. Two pairs of interdigitated capacitor structures are integrated into the magnetic NFRP element to produce two deep radiation nulls at both the lower and upper frequency edges of the passband, respectively. The two nulls can be independently controlled to achieve good out-of-band suppression levels. A prototype was fabricated and tested. The measured results, in good agreement with their simulated values, demonstrate that the Huygens dipole filtenna is electrically small (ka = 0.943) and low-profile (0.0385 λ0), together with enhanced out-of-band rejection performance characteristics. Its fractional bandwidth, broadside realized gain, front-to-back ratio, and overall efficiency values are, respectively, 1.16%, 2.33 dBi, 8.45 dB, and 63.1%.