Research On DSSS System Of Power Meter Reading And FPGA Implementation

As an important part of the energy Internet,the power meter reading system plays a vital role in the construction of the energy Internet.The direct sequence spread spectrum has the advantages of anti-interference,anti-interception,anti-multipath fading,co-channel operation and multi-access communication,etc.Therefore,it has unique advantages to choose direct sequence spread spectrum technology as the modulation method of power meter reading system.In this thesis,we focus on synchronization and narrowband interference suppression under the overall framework of power meter reading direct spread spectrum system,and design the communication system scheme to meet the project requirements,and finally implement the whole communication system.Specifically,it includes:1.First of all,this thesis introduces the principle of DSSS acquisition,deeply studies the segment correlation algorithm,PMF-FFT（Partial Matched Filter-Fast Fourier Transform）algorithm and delayed dual correlation algorithm,and analyzes their performance.Because the delayed dual correlation has the characteristics of anti-frequency offset and low complexity,this thesis chooses the delayed dual correlation algorithm to implement.On this basis,the Tong detection algorithm with near-neighbor constraint is introduced to improve it,so that the false alarm probability of delayed dual correlation algorithm capture is reduced to below 10^-5.Secondly,for the carrier synchronization algorithm of burst communication,this thesis compares the traditional carrier synchronization algorithm with the delayed dual correlation.The delayed dual correlation achieves the same estimation accuracy as the M&M algorithm with lower complexity.Finally,according to the above discussion,this thesis proposes an overall synchronization scheme.2.Secondly,this thesis investigates the time domain adaptive filtering,focusing on the minimum mean square algorithm and the normalized minimum mean square algorithm.At the same time,this thesis analyzes the performance of the adaptive multi-threshold algorithm in the frequency domain interference suppression technique,and finds that the adaptive multi-threshold algorithm is more damaging to the useful signal than the time domain normalized mean square algorithm.Therefore,the normalized mean square algorithm is selected and the quantization bit width of the filter weights is determined to be16 bits by fixed-point simulation.3.Finally,based on the above algorithm and design scheme,this thesis adopts the top-down design idea to implement the power meter reading,and makes full use of the idea of time-division multiplexing to reduce the resource occupation of the system while ensuring the correct timing.The functional verification is carried out by Modelsim to ensure the correct functionality and timing of the design.The test shows that the false frame rate of the system is less than 7%when the reception sensitivity is-125d Bm.