Design Of Full-band Digital Television Transmitting Antenna Based On Bowtie Structure

In the crucial period of improving the digital television(DTV)coverage network and completing the transition from analog to digital,DTV transmission system should cover a wider range,occupy less space resources and carry more channels.Antenna is an important part of DTV transmitter,and the DTV transmitting antenna with low voltage standing wave ratio(VSWR)and high gain,which covers the whole frequency band(470MHz-862MHz)can improve the quality of TV programs,increase the reliability of the system,and reduce the operating cost effectively.Therefore,it is of great significance to study the full-band digital transmitting antenna.The research topic of this paper comes from the project of "development of passive components in DTV transmission system" of Liaoning Putian Digital Co.,Ltd.and design full-band DTV transmission antennas.The main work of this paper is as follows:(1)A multi-mode dual-layer bowtie antenna element is proposed.The dual-layer trapezoid unit of the board structure is adopted,and the two layers are supported by adjustable insulated screws.By adding a parasitic bowtie dipole and introducing a new resonance mode,the impedance bandwidth of the antenna element is widened.The impedance flatness is further optimized and the gain is increased by using two,antenna elements as sub-array elements.(2)A horizontally polarized DTV transmitting antenna array based on the dual-layer bowtie structure is designed and implemented.The antenna elements of the two sub arrays are arranged in a flush manner,and the T-type broadband matching network is used for equal power division feeding to form a 1×4 antenna array.Then,a broadband stepped complex impedance matching network is proposed.to realize the full-band matching of the antenna array.The test results are consistent well with the simulation results.The relative bandwidth is 62.4%(455MHz-865MHz)for the VSWR less than 1.15,and the relative bandwidth is 58.9%when the VSWR is less than 1.13 in the full band(470MHz-862MHz).The gain is stable with the range of 11.6dBi-12.6dBi in the full band.All of them meet the requirements of the DTV transmitting antenna.(3)A vertical polarization digital TV transmitting antenna array based on dual-layer bowtie structure is designed.The two sub-array elements are arranged in a common axis manner,and then through the T-type broadband matching network,a 2×2 array antenna is formed.Two stepped complex impedance converters and the balun structures are introduced to make the antenna array match well in the whole frequency band.The simulation results show that the VSWR is less than 1.10,the gain is greater than 11.6dBi,and the maximum gain is 13.3dBi,which meets the requirements of the DTV transmitting antenna.Finally,the multi-plane and multi-layer combination modes of vertical polarization antenna array are analyzed.According to the simulation results and engineering requirements,the antenna is arranged reasonably,and the zero point of field strength of the vertical plane is filled.