Research On Ultra-Long Wave Active Receiving Antenna Based On Non-Foster Circuit

Ultra-long wave(Extremely Low Frequency,ELF),also known as ultra-low frequency electromagnetic wave,refers to the 30Hz?300Hz spectrum in the electromagnetic wave spectrum.Because of its low propagation attenuation rate and strong anti-interference ability,it is very suitable for ultra-long-distance communication.It plays an important role in civil fields such as medical and health,geographic exploration,and military fields such as remote control diving equipment and underwater communications.Among them,the underwater ultralong wave communication is the most strategic.Although the development prospects of underwater ultra-long-wave communication technology are very broad,as an important part of the ultra-long-wave communication system,the ultra-long-wave receiving antenna mainly faces two problems in practical applications.On the one hand,according to the antenna half-wavelength theory,the size of the ultra-long wave receiving antenna is bound to reach the kilometer level,which is very inconvenient for the concealment and navigation of the underwater vehicle.On the other hand,antennas that work in the ultra-long wave frequency band are electrically small antennas,so the bandwidth of the ultra-long wave receiving antenna is very narrow and the gain is low,resulting in extremely slow information receiving rate and very weak received signal strength.At the same time,there are all kinds of complex ultra-low frequency noise in the underwater environment,which will interfere with the received signal and need to be considered.Therefore,research on miniaturized,wide-band,and ultra-long wave receiving antenna systems that can cope with underwater ultra-low frequency noise interference is of great significance for promoting the development of underwater ultra-long wave communication technology and improving the performance of underwater vehicles.At present,the optimization of bandwidth expansion and size reduction of most antennas is realized by external loading of the antenna,changing the antenna structure,designing passive broadband matching network and other technical methods,but subject to the constraints of gain bandwidth theory,the optimization effect of the above methods is limited.Therefore,from the perspective that the combination of active circuit and antenna can broaden the antenna's working frequency band,reduce the size of the antenna and increase the antenna gain,this article has carried out the study of the ultra-long wave active receiving antenna based on the non-Foster circuit.The main work and innovations done include:1.Aiming at the problems of the traditional ultra-long wave receiving antenna with narrow bandwidth and slow communication rate,a method of matching electric small antennas with a non-Foster circuit with a negative impedance converter(NIC)as the core is proposed.Use negative impedance transformation to generate negative capacitance or negative inductance that is exactly the opposite of the reactance characteristics of passive components to cancel or reduce the input reactance of the electrically small antenna.This can achieve antenna resonance in a larger frequency range and break through the gain bandwidth theory.To achieve the purpose of widening the working frequency band of the antenna.2.Aiming at the problem of the large size of the traditional ultra-long wave receiving antenna,a method of constructing a negative impedance converter with an operational amplifier as the core and adding deep negative feedback to establish a non-Foster circuit is proposed.Through the non-Foster matching electric small antenna and negative feedback to adjust the amplification factor,while reducing the size of the antenna,it can obtain higher gain than the original electric small antenna,which will compensate for the decrease of the gain due to the decrease of the effective height of the antenna.To achieve the goal of better performance after the antenna is miniaturized.3.Aiming at the problem of ultra-low frequency electromagnetic noise dominated by 50 Hz power frequency interference in the marine environment,a filtering method combining passive low-pass filter and active notch filter is proposed.Through the resonance frequency selection and active filter circuit,it can have a good filtering effect on signal frequencies greater than 300 Hz and 50 Hz power frequency interference,and achieve the purpose of reducing the interference suffered by the ultra-long wave receiving antenna.4.After the preliminary design of the ultra-long wave active receiving antenna circuit,the simulation software is used to simulate and analyze the overall circuit,optimize and adjust the parameters of the components in the circuit,and finally determine that the designed ultra-long wave active receiving antenna based on the non-Foster circuit meets the performance index requirements.Compared with the traditional ultra-long wave receiving antenna,the antenna size is reduced,the antenna working frequency band is expanded,and the ability to resist underwater ultra-low frequency noise interference is enhanced.