Research And Application Of Four-channel Integrated Short-wave Receiving Front-end

The short-wave timing is to modulate the time signal to four short-wave carrier frequency points of 2.5 MHz,5 MHz,10 MHz,and 15 MHz,and the receiver receives the signal and performs local time-frequency calibration.The conventional short-wave timing receiving front end usually uses an electric antenna,and thus is bulky,resulting in poor maneuverability of the receiving front end and less applicable scenarios.In addition,the traditional short-wave timing system has poor anti-interference ability and has a serious multipath effect due to the use of an amplitude modulation system.The short-wave timing system based on the direct sequence spread spectrum system can solve these two problems well,but it has high requirements on the stability of the local oscillator source at the receiving front end.In order to adapt to the short-wave timing based on direct sequence spread spectrum system,this paper analyzes the basic theory of the receiving front-end,and combines the characteristics of short-wave timing to design a four-channel short-wave receiving front-end with miniaturization,strong anti-interference ability and high stability local oscillator.The main research results of this paper are summarized as follows:Firstly,the effects of dynamic magnetization characteristics,ferrite material properties,ferrite size structure,coil turns and coil winding mode on the receiving performance of the antenna are studied,and the simulation design is carried out using FEKO simulation software.Furthermore,a vertically polarized short-wave ferrite receiving antenna is designed,which has a volume of only 10 cm×1 cm×1 cm.Secondly,the basic principle of short-waveband low-noise amplifier and the basic matching method of high-frequency circuit are studied.A low-noise amplifier coupling with magnetic antenna is designed.The noise coefficient is as low as 0.8dB and the gain is 14 dB.Thirdly,the basic method of short-wave frequency source design and filter theory are studied.A four-channel local oscillator circuit with controllable frequency and amplitude is fabricated,and a harmonic suppression filter is designed to shape the waveform into a standard sine wave.The experimental test shows that the frequency phase noise generated by the local oscillator circuit can be as low as-113dBc@10kHz.Finally,the basic theory of the mixer,IF amplifier,and AGC modules in the receiving front end is studied.The relevant modules that meet the system requirements are designed,and the whole receiving system circuit fabrication and debugging is completed.Laboratory tests and field tests are conducted.The test results showed that the entire receiving front-end system is working properly and in line with expectations.