Design Of Electric Small Active Antenna Based On Non-Foster Circuit Matching

With the development of science and technology,the electrical properties of antennas in wireless communication systems are increasingly demanding,and the installation space of antennas in wireless communication equipment is limited.The performance of antennas is jointly constrained by gain-bandwidth-volume,and it is difficult to achieve miniaturization and broadband at the same time.For electrically small antennas,the commonly used passive matching method can broaden the bandwidth within a certain frequency range,but it will also be constrained by the three.Therefore,this paper uses the negative capacitance generated by the non-Foster circuit to offset the large input reactance of the electric small antenna,improve the impedance matching of the antenna,and realize the miniaturization and broadband of the antenna.The main work includes:1.A grounding non-Foster circuit based on OPA356 is designed.In Multisim,the time domain characteristics of the circuit:the phase of voltage and current are observed,and the phase relationship of voltage and current of negative capacitance,negative inductance and negative resistance is determined.In ADS,the single variable analysis of load capacitance and bias resistance in non-Foster circuit is carried out,and the influence of component parameters on circuit input impedance and equivalent capacitance is verified,which is consistent with the negative conversion principle of non-Foster circuit.In Multisim,the network analyzer is used to analyze the stability of the designed circuit.Through the simulation experiment,the problem of circuit instability is solved by paralleling the capacitor near the bias resistance.Finally,the grounding non-Foster circuit is processed and tested.The test results show that the grounding non-Foster circuit is suitable for cooperating with the antenna in parallel with the equivalent circuit model to broaden the antenna frequency band.2.An active dual-cone sleeve antenna operating in 3-30MHz band is designed.Because the equivalent circuit model of the dual-cone sleeve antenna is series of small resistance and small capacitance,a floating-ground non-Foster circuit is designed to match the antenna.The total length of the double-cone sleeve antenna is 150 mm,and the sleeve radius is 23 mm.First of all,two forms of passive matching are carried out on the antenna.The simulation results show that the traditional passive matching adopted by the antenna in the 3-30MHz band still cannot achieve broadband effective radiation.Secondly,the improved floating ground non-Foster circuit is applied to the antenna matching.The results show that the active matching can greatly improve the input reactance of the electrically small antenna,and the S11 can be significantly less than-6dB in the 12.5-30MHz band.Then,based on the active matching,the passive matching of the active antenna is carried out.The simulation results show that the passive matching can improve the input resistance of the electrically small antenna.Finally,the floating non-Foster circuit and double cone sleeve antenna are fabricated and tested,and the gain of active antenna is analyzed.The test results show that the floating-ground non-Foster circuit is suitable for the use of antenna with series equivalent circuit model,and the S11 is less than-8dB in the 3-30MHz band.