Design Of HF And VHF/UHF Shipboard Antennas

As the key device in sending and receiving radio waves,antenna plays an important role in communication system,at the meantime it is also the technical bottleneck in this field.As it is known,shortwave communication can achieve the long-distance signal transmission.The longer the wavelength,the larger the antenna may be,and it can be the main barrier to the miniaturization of communication system.However developing in some fields,such as Seafaring and Military Industry,a kind of antennas with small size and broad working-band,especially in HF and VHF/UHF bands,are desperately needed in order to improve the quality of long distance communication.In this paper,two kinds of wide-band Shipborne antennas have been designed and fabricated,one is a cage-like conical VHF/UHF antenna with center-fed structure fitting the working frequency from 108 MHz to 400 MHz,the other is a pair of HF twin-whip antennas working in 3~30MHz's band.Details are as follows:1.Based on the study of dipole antenna,this paper has designed a cage-like conical VHF/UHF antenna inspired by the peer-to-peer design structure,and solved three chalenging technical problems related to the design indexes.The technical problems are as follows: First,in order to improve the communication quality in HF band,there is a need to optimize the radiation pattern cracking phenomenon and to control horizontal average gain which can not be less than 1d Bi and horizontal minimum-gain which must be bigger than-1d Bi at the same time.Second,meeting the need of a broad working-band,the VSWR is not alowed to exceed the limit of 2 in 90% of the bandwidth(108~400MHz).Third,minimizing the interference,the imbalance problem between antenna and coaxial line must be solved.In order to obtain the relationship between structure size and technical indicators,simulation based on HFSS as well as lots of antenna optimization debugging had performed.Practical test indicates that,the VSWR is less than or equal 2 in 90% of the bandwidth,the rip-panel of E plane pattern can be well restrained,and antenna pattern out-of-roundness(POR)is not more than 3d B.2.In the design of HF twin-whip antennas,the same design pattern is used.The working frequency is 3~30MHz,VSWR is less than 3 and the out-of-roundness(POR)is not morethan 2d B.There are two major problems in the HF antennas' design process.One is to meet the reduced structure size requirement.The other is to achieve the design and debugging of loading scheme and matching network,conquering the bandwidth shortagecaused by undersize of antenna.After analyzing the antennas' performance parameters and applications,the final design is proposed.This antenna group contains 2 monopole twin-whip antennas with different sizes,which several y cover with bandwidth rangeing 3~9MHz and 9~30MHz.With the use of HFSS,the Dimensions of the antennas are simulated and optimized,as well as the reduced VSWR which is the result of adjusting the matching-net.Finally,a gain comparison test and a short wave radio communication test have been done to verify the direction and communication effect of the sample antennas.