Precise Carrier Frequency Estimation Method for High Dynamic pcm/fm Signals

Abstract

The invention discloses a method for accurately estimating the carrier frequency of a high-dynamic PCM / FM signal, and aims to provide an estimation method with high carrier frequency estimation accuracy and small measurement error. The present invention is realized through the following technical solutions: a PCM / FM signal frequency measurement system is composed of a filter sampling module, a frequency modulation frequency positive and negative compensation parallel branch, a peak search module, and a frequency calculation module; the high dynamic PCM / FM signal passes through a band After passing through the filter module, the arbitrary down-sampling process is completed, and the down-sampled data enters the frequency modulation frequency positive and negative compensation parallel branch respectively; the sampling data is sequentially subjected to frequency modulation frequency pre-compensation, carrier Doppler change rate compensation, and mode control to complete carrier recovery; After FFT frequency measurement and non-coherent integration and accumulation, the peak search module finds the largest peak value and the corresponding change rate sub-slot in the integration result; the frequency calculation module estimates the carrier Doppler of the high dynamic PCM / FM signal according to the peak value result Le frequency shift, carrier Doppler rate of change, search time and other information.

Description

technical field [0001] The invention belongs to the technical field of wireless communication, and relates to a method for accurately estimating the carrier frequency of a high dynamic PCM / FM signal in a remote control telemetry system. [0002] technical background [0003] Large dynamic Pulse Code Modulation / Frequency Modulation (PCM / FM) telemetry signal, as a commonly used telemetry system, is a widely used signal type in the current remote control telemetry system. Because PCM / FM signal has The advantages of high precision, flexible format, and convenient data processing at both ends of the transceiver play a vital role in the aerospace field. The existing PCM / FM FM system usually uses a continuous phase frequency shift (Continuous Phase Frequency) with a frequency modulation index of h. Shift Keying, CPFSK) system, the CPFSK signal can be expressed as: [0004] [0005] In the above formula, A is the signal amplitude; f c is the center frequency of the carrier; f d...

AI Technical Summary

Problems solved by technology

The energy center of gravity method estimates the center of gravity of the spectrum energy according to the integrated peak spectral line and n spectral lines before and after it, thereby estimating the carrier frequency; the maximum value method uses the frequency point corresponding to the spectral peak as the current estimated value of the carrier frequency; the two The methods must rely on the spectral peak to adapt to different SNR scenarios, but the estimation accuracy is low, and the estimation performance deteriorates seriously when the spectral peak is far away from the central frequency point

The median method uses the symmetry of the frequency spectrum to estimate the frequency at the midpoint of the two frequency points corresponding to a specific amplitude threshold. The spectrum under the noise ratio is seriously affected by noise, which will lead to a serious decrease in estimation performance

[0012] When the aircraft carrier performs a large maneuvering movement, the carrier frequency of the received signal will produce a large Doppler frequency shift and its rate of change. Traditional carrier frequency estimation methods regard it as a chirp signal in a short period of time to estimate parameters. However, since the received signal is extremely dynamic and severely attenuated by various channel losses, using the carrier frequency as a single-frequency signal in the frequency measurement process will seriously reduce the estimation accuracy of the carrier frequency, and at the same time, it will not be able to meet the needs of weak signal environments. It is difficult to maintain advantages in high dynamic stress, weak signal environment and high estimation accuracy at the same time

In high dynamic and weak signal scenarios, if the carrier frequency of the received signal cannot be accurately estimated, or the estimated carrier Doppler frequency, Doppler change rate and other information have large errors, the difference between the copied signal and the received signal The frequency error exceeds the pull-in range of the tracking loop, and the tracking loop usually cannot lock in quickly and stably

[0013] In the above-mentioned traditional frequency measurement method, after the frequency measurement system filters and samples the received signal, it first directly performs Fast Fourier Transform (FFT), and then uses different methods to search for peak spectral lines, thereby solving the carrier frequency , the frequency measurement performance of each method has its own advantages and disadvantages, but none of them can meet the performance requirements of high dynamic stress, weak SNR and high estimation accuracy at the same time. Therefore, in complex scenarios such as high dynamics and weak signals, in order to realize the tracking loop How to accurately and quickly estimate the carrier frequency of the PCM / FM signal has become a technical difficulty that needs to be solved urgently

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