Design And Research Of Antenna Impedance Matching System Of Spaceborne Radio Plasma Imager

In recent decades,some multifunctional spaceborne active radars have been launched one after another,such as the RADIO PLASMA IMAGER carried by the IMAGE satellite;MARSIS carried by the Mars Express;and carried by the Demonstration and Science Experiments(DSX)spacecraft.WPIx etc.Under modern conditions,"Spaceborne radio plasma detection system" is a light weight,low power consumption,multi-functional spaceborne radio remote sensing instrument and signal processing software platform,used to detect plasma density distribution,structure,space and the dynamics of plasma space-time evolution.Signal parameters for learning characteristic information.In view of the difference in plasma density in different areas of space,in order for the radar to be able to image the space plasma in different areas,it needs to cover the detection range of space plasma from 30 kHz to 3MHz.Due to the fixed size of the transmitting antenna,only a few resonance points of the antenna itself are far from satisfying the detection target.Therefore,it is necessary to design a tunable broadband impedance matching system for the antenna,so that the satellite-borne radio plasma imager can have a wide frequency band and high emission.High efficiency and low return loss for plasma imaging in space.In this paper,the following researches are carried out on the design of the tunable impedance matching system of the spaceborne antenna:Aiming at the ultra-low radiation impedance and high capacitive reactance characteristics of the space-borne antenna in the electrically small state,a broadband impedance matching method based on the optimized real frequency method is designed.In the impedance matching experiment of the classic RLC passive load circuit,comparing some traditional and intelligent matching algorithms,the results show that the optimized real-frequency method has the characteristics of fast calculation convergence and good impedance matching characteristics.It also gives a theoretical design for simultaneous tuning and optimization of multiple frequency bands,which can better serve multiple applications such as GSM900,GSM1800,UMTS,and Wi Fi.In the scaled dipole antenna experiment,5% radar frequency step is used to divide the tuning frequency points.According to the different input impedance states of the antenna,the Non-Foster circuit,fractional L-type and LC-type impedance matching network models and intelligence are adopted.With the combination of broadband impedance matching algorithms,a set of tunable impedance matching network is designed,and the simulation experiment verifies that the Non-Foster circuit has the advantage of broadband S11 characteristic curve in the state of electric small dipole antenna.And use the vector network analyzer and the USRP N210 equipped with UBX-160 daughter board to carry out the radio open-loop actual measurement experiment,which verified that the multi-order impedance matching network calculated by the optimized real frequency method has the characteristics of wideband and improved Sparameters,which is comparable to the introduction of impedance converters.The LC network obtains a wider frequency band,but it also consumes a certain amount of received power.In the simulation experiment of the satellite antenna,the standard RADIO PLASMA IMAGER frequency step is 5% to divide the tuning frequency points,and a set of 141 tuning frequency points tunable impedance matching network system is designed for the 120-meter monopole antenna.Meet the needs of spaceborne antennas for the detection of plasma imaging frequencies in space.And given the complete design framework,such as power amplifier,control circuit,impedance conversion circuit,tuning circuit,antenna module.And according to the design idea of RADIO PLASMA IMAGER,the 250-meter monopole antenna matching network is matched.After analyzing the two experiments,it is found that the long dipole antenna has poor radiation performance in the electrically small state,and almost no signal is radiated below 100 kHz.The design of the network often chooses LC circuit tuning,and try not to introduce impedance converter;and the proposed broadband impedance matching network model combined with intelligent optimization algorithm can achieve better matching effect than L-type above 300 kHz,and it can also achieve adaptive keying.The purpose of tuning.