A miniaturized high-gain flexible unmanned aerial vehicle (UAV) antenna is presented in this study. The proposed antenna basically comprised of three parts of printed patch in series, etched on dielectric substrate. And, a flexible cable is loaded on the bottom of dielectric substrate. A coplanar waveguide (CPW) with asymmetric ground feeding structure is employed to provide good impedance matching. The surface current can achieve the same phase for the straight-line patch and the flexible cable, through adjusting the dimensions of the meander line patch, which increases radiation gain while maintaining the compact size. As an important merit to be highlighted, the flexible cable can greatly reduce the volume and aerodynamic drag of the antenna. It has a low-profile compact size of 196 × 15 × 0.8 mm3 (excluding flexible cable). The results show that the omnidirectional gain fluctuates within 4.5 ± 0.1 dBi in the desired band (902 MHz–928 MHz), which is high enough for the UAV application. Details of the antenna design and experimental results are presented and discussed.

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This letter proposes a novel compact ceramic cavity bandpass filter with surface silver coating and air coupling apertures. It is constituted of a sextuplemode ceramic cavity as the main resonator, two single-mode cavities to connect the sextuple modes transversely with source and load, and two single cavities to suppress higher harmonics. This proposed filter has the advantages of compact size, wide band, low insertion loss, high selectivity, wide spuriousfree window, as well as coplanar source and load interfaces. There are no blind holes in the filter, which is beneficial for improving the machining accuracy.One prototype filter operating at 3.5 GHz is fabricated and measured. The minimum insertion loss in the passband is 0.65 dB. The inherent spurious mode of the sextuple-mode resonator at around 1.2f C (f C center frequency) is suppressed under −30 dB. The measured and simulated results are in good agreement.

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