Research On Coherent DOA Estimation Algorithm Based On TC-OFDM Signal

Direction of Arrival(DOA)estimate of the signal is one of the important research contents of array signal processing.By processing the array signal data matrix to identify the direction of arrival of the signal,it has been widely used in the research of radar,sonar and astronomy.Time&Code Division-Orthogonal Frequency Division Multiplexing(TC-OFDM)signals can achieve high-precision indoor and outdoor positioning by multiplexing communication signal resources.In the actual environment,due to interference and other reasons,there are coherent signals,and the performance of classical DOA estimation algorithm declines and is not applicable to TC-OFDM broadband signals.Therefore,the coherent DOA estimation algorithm based on TC-OFDM signals is studied theoretically in this paper.The main research contents include:(1)The direction of arrival estimation algorithm is based on the array signal model,and the array signal models of narrowband signals,coherent signals and TC-OFDM signals are established respectively.The traditional DOA estimation algorithm is discussed and introduced.When there is a coherent signal,the algorithm cannot identify its DOA value and needs to be decoherent.This paper proposes the Invariant Property of Noise Subspace Smoothness(IPNSS)algorithm,which divides the received signal data matrix into sub-arrays before and after,and calculates the algorithm average of the data covariance matrix.By adding a virtual signal source and searching from various angles,the algorithm space spectrum is constructed by using the invariant characteristics of the noise subspace to estimate the DOA of the coherent signal.Compared with the classic DOA estimation algorithm for coherent signals,this algorithm has more obvious spatial spectrum peaks and better algorithm stability under low signal-to-noise ratio conditions.(2)Based on the TC-OFDM array signal model,this paper uses the focus transform method to focus the wideband TC-OFDM signal on the same frequency from the frequency domain.In order to avoid the loss of signal-to-noise ratio in the focus transformation,a focus change matrix model that satisfies its construction principles is proposed.On this basis,the data covariance matrix after the focus transformation is obtained,and the invariant noise subspace smoothing algorithm is used to process it to obtain the direction of arrival of the TC-OFDM signal.In this paper,DOA estimation algorithm based on TC-OFDM signal is analyzed to identify the spatial spectrum characteristics of the algorithm from multiple angles.The stability of the algorithm under different SNR,antenna number and snapshot number is calculated through many experiments.This algorithm can accurately identify DOA of TC-OFDM signals.(3)The software radio platform is used to implement and verify the DOA estimation algorithm based on TC-OFDM signals,and the USRP(Universal Software Radio Peripheral)general software radio and National Instruments(NI)supporting equipment are used to build.The program is designed based on the Lab VIEW program platform,and the phase compensation between the USRP devices is performed to realize the DOA estimation algorithm.The experimental data verifies the DOA estimation performance of the DOA estimation algorithm for signals from different directions.