Research On Key Technologies Of C-Band Pulse Modulation Signal Source

In the field of wireless measurement,multipath effect is the main reason that affects positioning accuracy.Multipath effects are not completely eliminated at present,but high isolation pulse sources can reduce their effects.This paper takes the pulse modulation signal source as the research object,and focuses on the broadband frequency synthesis technology and time domain vector cancellation technology.The main research contents are divided into the following parts:Firstly,for the wideband requirements of frequency source,this paper successfully develops microwave broadband frequency source by phase-locked frequency synthesis technology.The output frequency range of frequency source is 1GHz-10 GHz,which is output in point frequency.The frequency source has the characteristics of stable output frequency,wide frequency band and small volume and so on.By comparing the advantages and disadvantages of microwave switching modulation and pulse power amplifier modulation,the microwave switching modulation method was selected and the microwave switching modulator was successfully designed.The designed modulator has a 50 dB isolation in the C-band,which has the characteristics of fast modulation speed and high isolation.Secondly,in view of the problem that the modulation scheme of traditional modulation scheme is not high,this paper uses the combination of time domain vector cancellation technology and microwave switching modulator to increase the isolation of pulse signal.The time domain vector cancellation system includes a microstrip Wilkinson power divider,an ultra-wideband planar balun,and so on.After simulation,optimization,processing and other steps,the Wilkinson power divider and ultra-wideband planar balun working in C-band were successfully designed.After physical testing,the microstrip Wilkinson power divider has an insertion loss of less than 1 dB in the C-band,a return loss of better than 15 dB,an isolation greater than 20 dB,and equal power and power synthesis performance;Output port of ultra-wideband planar balun in the C-band amplitude imbalance degree is less than 1dB,the phase difference is 180°,the error is less than 10°,and the output signal has the same amplitude inversion function.Finally,the entire system was tested and the effective cancellation frequency range of the time domain vector cancellation system ranged from 4.6 GHz to 6.4 GHz.The use of a time domain vector cancellation system can increase the isolation of a single microwave switching modulator by more than 10 dB;the use of a time domain vector cancellation system and a cascaded microwave switching modulator can achieve a modulation signal isolation of 80 dB.It meets the high isolation requirements of the pulse modulation signal source of this topic.