Research On Wideband Active Transmitting Antennas Based On Negative Impedance Convertor

With the rapid development of wireless communication technology these years, therequirement of communication equipment broadband becomes higher and higher, whichrequires antenna in small size, wideband, etc. Negative impedance matching the activeElectrically Small Antenna (ESA) has drawn much attention for its unique advantages. Thisantenna can effectively break through the technology limits of low efficiency and narrowbandwidth in passive matching. Besides, it is easier for short wave antenna to realizeminiaturization and broadband.In this paper, we focus on the negative impedance matching active ESA related theory,then design and test the active transmitting antenna matched with negative impedanceconverter (NIC). Firstly, research background, development history and the advantages of thenegative impedance matching ESA is introduced; Secondly, basic principles of active antenna,impedance characteristics and working bandwidth of ESA and other related qualifications areanalyzed. Based on the tough fact that the passive matching ESA is hard to be realized, thecharacteristics of non-foster witch also named negative impedance is raised up with theanalysis of the foster reactance theorem. After theory analysis of negative impedancematching active transmitting antenna, we can conclude that this method is effective toenhance antenna’s working bandwidth, and can achieve a good match with the transmitter aswell.Intensive research has been launched on the basic principle and the stability of NIC.Then current inversion NIC (CINIC), voltage inversion NIC (VINIC) and float NIC (FNIC)are designed with operational amplifier. Theory analysis, software simulation and practiceverification work corresponding to the three converters also been carried out respectively,which lays a theoretical and practical basis for active negative impedance matching networkdesign.Finally, this paper brings up a design method of active broadband ESA based on negativeimpedance matching. The impedance parameters of antenna are simulated in HFSS, whichprovides backing for the parameters of active matching network.CINIC and FNIC matching network respectively, these two kinds of active matching network are designed, both circuits simple and with high stability.At last, the designed active antenna has been equivalent measured. The test resultsindicate that both match schemes can well match50coaxial cable and realize the purpose ofbroadband matching, with the bandwidth up to dozens of octaves, which proves thetheoretical analysis to be correct and the method to be feasible and effective.