An Ultrawideband Unidirectional Bowtie Antenna with Enhanced Radiation

An improved ultrawideband (UWB) Bowtie Antenna (BA) with low profile is presented in this paper. The basic geometry of the proposed antenna is combined by a novel acorn-shaped bent Bowtie patch and a hollowed stepped back cavity. The hybrid utilization of loop circuits and loading techniques that including resistive and capacitive loading can improve the radiation efficiency of the BA while expanding the low-frequency bandwidth. Additionally, a novel technique of cavity groove is proposed to design the reflector. The optimized cavity tightly coupling with the radiation part overcomes the shortcomings of conventional cavity-backed BAs. The simulated −10dB impedance bandwidth of the proposed antenna is over 100MHz-1000MHz while the experimental bandwidth is 250MHz-850MHz. This BA of folded type obtains a high realized gain of 5dB at 850MHz. Field tests for practical ground penetrating radar (GPR) application have been carried out and the results demonstrate the advanced performance.