A High-Gain Filtering Quasi-Yagi Antenna Based on Compressed Third-Order Mode Dipole

A high-gain filtering quasi-Yagi antenna based on compressed third-order mode dipole is presented in this paper. The meander line structure is employed on the dipole to realize the compressed dipole. The current distributions on the meander structure are equal amplitude and out-of-phase to cancel the far-field radiation to realize sidelobes suppression. An in-parallel grounded branch consisting of a bandstop filter and a grounded resistor is used to achieve filtering characteristics with four radiation nulls. The reflection coefficients of the bandstop filter are nearly complementary to that of the antenna to generate the radiation nulls. Moreover, directors are set in front of the dipole symmetrically to achieve a stable gain of the passband. To validate the feasibility of proposed antenna, a prototype is fabricated and measured. Good endfire characteristics are obtained with a bandwidth of 2.58 GHz to 2.82 GHz (8.8%), a peak gain of 9 dBi, sidelobe level (SLL) less than -19 dB, and out-of-band suppression larger than 14 dB. The measured results are in good agreement with the simulation.