| Vehicle communication antennas are mostly VHF/UHF omnidirectional antennas with long whip covering multiple frequency bands.If multiple antennas are installed to meet the technical requirements,this will have a very large impact on the movement and concealment of field vehicles.To this end,this paper takes the design of ultra-wideband miniaturized antennas in practical engineering applications as the research goal,and takes into account its gain while meeting the standing wave ratio.The main contents of the study are as follows:1.Research on VHF-UHF band vehicle-mounted ultra-wideband small antenna.The antenna is a three-segment integrated rod-shaped structure.The first section is the VHF band and uses a mid-feed antenna;the second section is the VHF-UHF band and uses a dipole antenna;the third section is the UHF band and also uses dipoles antenna.Because the antenna is a long rod-shaped structure,the three band-frequency antennas are all fed by coaxial lines.Based on the loading characteristics of a general broadband monopole antenna,the loading of ferrite magnetic loops with different permeability at different positions in the feed-forward antenna and the L,C loading of the feed-forward antenna with one arm to the ground are studied.For the effect of the input impedance and gain of the center-feed antenna,a center-feed antenna with ultra-wideband miniaturization is designed.Based on the study of the impedance characteristics of the dipole antenna,the dipole antenna is loaded with a composite ? type L and C lossless matching network technology and the magnetic beads are used to load the choke technology to improve the broadband performance of the dipole antenna.The prototype test results show that the antenna achieves gains of-5d Bi,-4d Bi,and-4d Bi within 5.8,1.8,and 1.6 octave,and the standing wave ratio of the whole band is less than 3.2.Research on 2GHz-6GHz broadband asymmetric dipole loaded antenna.The antenna adopts an asymmetrical radiation structure with an upper radiator and a lower radiator.Based on the principle of the thick vibrator antenna and the antenna loading technology,the radiator on the antenna adopts a cross "dry" structure with a wide vibrator plane.Through the change of the upper radiator wide oscillator parameters and the effect of "dry" shape loading on its frequency band characteristics to realize the miniaturized design of the antenna.According to the principle of the sleeve antenna,the lower radiator is a coaxial feeder outer conductor that coaxially feeds the antenna,and is loaded with a short-open sleeve.Its structure is that the open sleeve surrounds the lower radiator coaxial feeder outer conductor,and A short-circuit disc is loaded between the lower radiator and the open sleeve.By studying the influence of the structural parameters of the short-open sleeve on the impedance characteristics and gain performance of the antenna,the miniaturized design of the antenna is realized.Finally,the measured antenna samples are in the range of 2GHz-6GHz,the standing wave ratio is less than 3,and the gain is greater than 0d Bi. |
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