Research On Tunable Matching Network Of Communication Antenna

In the HF and VHF communication systems of military platforms,due to the requirements of broadband and miniaturization,communication antenna will inevitably lead to problems such as increased standing waves and reduced radiation efficiency,thereby reducing the radiation performance of the antenna,which will affect the communication distance.Therefore,it is of great significance to study the tunable matching network of communication antenna.In this thesis,passive and active matching technologies are used to design the tunable matching network of the HF/VHF communication antenna.For the antenna to be matched,the circuit design scheme and structural implementation method of adjustable narrowband matching and fixed broadband matching are proposed,and the physical processing is completed on this basis,and two automatic tuning methods of antenna are refined as follows:(1)The transmission line theory and the basic theories of electrically small antennas involved in tunable matching network of communication antenna are systematically summarized,and the basis of active devices and SCM are introduced in detail.A passive LC-tuned matching network is designed for the VHF broadband antenna,different circuit forms are analyzed and compared,and finally the matching circuit is designed by Smith chart method combining(38)and inverted(38)structures,and at the same time,the design of the antenna tunable matching system which can be controlled by computer is completed with the SCM circuit,including the schematic and PCB design of the hardware circuit and the writing of the software part of the program,finally the actual matching network board is optimized,processed and tested to achieve fixed frequency narrowband matching and frequency hopping broadband matching in the 30-88 MHz and 108-400 MHz bands.The VSWR is reduced to below 1.5in the fixed frequency narrowband matching mode and below 3 in the frequency hopping broadband matching mode.(2)A broadband matching network based on active non-Foster circuit is designed for an electrically small whip antenna.Firstly,the gain bandwidth limiting theory and the principle of non-Foster circuit are introduced and analyzed,based on which the matching network is simulated and designed with the performance of the antenna itself,and selecting appropriate components for matching network schematic and PCB layout design,combined with the SCM circuit and computer control program to complete the hardware circuit processing test and software control of the tunable matching system,to achieve the ultra-wideband matching effect of an electrically small whip antenna in the frequency band of 10-85 MHz and 108-600 MHz.(3)According to the automatic tuning requirement of communication antenna,two kinds of antenna automatic tuning methods based on VSWR detection and data acquisition principle are compared and analyzed,and automatic tuning algorithm is written.The former can complete the detection of VSWR according to the principle of detection of standard network combined with algorithm;the latter collects the real-time data of VSWR in the VNA through the program combined with automatic tuning algorithm to finally realize the automatic tuning and matching of the antenna.