Dominant wave automatic frequency tracking numerical receiver

Abstract

The invention provides a dominant wave (DW) automatic frequency tracking numerical receiver. The numerical receiver not only has the function of radar numerical intermediate-frequency (IF) receiving, but also realizes numerical automatic frequency tracking and locking received by radar, and the system does not need traditional automatic frequency control loop circuits and external frequency adjustment components. The technical scheme of the invention is as follows: the IF DW and the IF echo wave channels of the receiver are received by wideband, the receiving bandwidth is determined according to the frequency coverage really needed by a radar system. The invention is mainly characterized in that the receiver carries out wideband sampling and buffers DW data received from the radar, the DW power spectrum is obtained by real-time numerical FFT transformation, the center of gravity of unilateral band spectrum is calculated, the frequency estimation of DW is obtained by the value of the center of gravity of spectrum and is converted into corresponding numerical control oscillator (NCO) frequency control word, the frequency control word obtained by calculation is used to control the frequency of NCO under synchronous trigger to realize automatic tracking of the DW frequency of NCO, AD sampling is carried out on the radar echo signal and then orthogonal down-conversion is carried out on the radar echo signal and the numerical frequency signal generated by NCO, the echo wave video IQ signal is obtained after IF matched filtering, and frequency adjustable components are only NCO. When DW frequency is calculated, the DW power is simultaneously calculated to judge whether the current DW input is valid or not, and if the DW is invalid, the search of system frequency is started. A timing sequence generating circuit generates AD sampling clock, generates DW sampling control sequence and data latching sequence according to trigger signals, and provides NCO clock.

Description

technical field [0001] The invention relates to a main wave automatic frequency tracking digital receiver, which is a receiver which uses real-time digital frequency spectrum analysis to realize the main wave frequency tracking, and belongs to the field of radar receiving and signal processing. Background technique [0002] The superheterodyne radar receiver converts the high-frequency signal into an intermediate frequency signal for amplification and filtering. The frequency of general IF amplifiers and filters is relatively fixed, and this IF frequency is called the rated IF frequency. In actual work, the frequencies of the magnetron transmitter and the local oscillator of the receiver are not coherent, and the transmission frequency of the magnetron transmitter will change with the change of the power supply voltage, ambient temperature, output load, etc. Its frequency drift range is different according to the radar operating band, generally between several megabytes and...

AI Technical Summary

Problems solved by technology

[0007] In addition to the receiving channel, the existing scheme also uses a separate self-frequency tuning loop. The front end needs an external frequency adjustable component (VCO or frequency adjustable transmitting tube), and the analog mode is used to control the VCO frequency or the mechanical mode to control the transmitter transmission frequency. The system The performance is limited, which increases the amount of equipment in the system. At the same time, because most of them are analog devices, the reliability of the system is reduced.

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