CAJ | 학술논문

MAP/ML频率估计算法由于同时利用了幅度和相位信息,在信噪比较高时可得到极高的估计精度,但在低信噪比下估计性能不佳.对此分析了形成原因,并提出了结合FFT确定相干积分长度及无卷绕序列的最大似然(ML)估计方法.利用FFT的粗估计值对信号进行频移,从而将信号的频率和序列的相位变化限制到了一定范围内,据此推导了不同相干积分长度下的克拉美罗界(CRLB),确定了相干积分数据分段的最佳长度,通过相干积分提高信噪比保持高估计精度.依据相移后相位方差选择估计序列的方法,避免了解卷绕过程,从而消除了解卷绕对低信噪比下算法性能的影响.Monte Carl仿真实验结果表明本频率估计可达到非常接近CRLB界的估计性能.
MAP/ML빈솔고계산법유우동시이용료폭도화상위신식,재신조비교고시가득도겁고적고계정도,단재저신조비하고계성능불가.대차분석료형성원인,병제출료결합FFT학정상간적분장도급무권요서렬적최대사연(ML)고계방법.이용FFT적조고계치대신호진행빈이,종이장신호적빈솔화서렬적상위변화한제도료일정범위내,거차추도료불동상간적분장도하적극랍미라계(CRLB),학정료상간적분수거분단적최가장도,통과상간적분제고신조비보지고고계정도.의거상이후상위방차선택고계서렬적방법,피면료해권요과정,종이소제료해권요대저신조비하산법성능적영향.Monte Carl방진실험결과표명본빈솔고계가체도비상접근CRLB계적고계성능.
By using the information on both amplitude and phase,the frequency estimation algorithm MAP/ML can achieve high accuracy frequency estimation when the SNR is high.But the performance will be greatly degraded at a low SNR.Based on analyzing the reason,a new maximum likelihood(ML)estimation method is presented,which can confirm the coherent integration length and the unwound sequence combined with FFT.Using the coarse frequency estimation value for frequency shift,signal's frequency and the variation of sequence's phase are limited to a certain sphere,so that the Cramer-Rao lower bound(CRLB)limits with various coherent integration lengths are derived,and the optimal coherent integration length of data subsection is determined,which contributes to attaining the optimal balance between the estimation accuracy and the SNR gain.In addition,an estimation sequence selecting method based on the phase variance of the phase-shifted sequence is proposed,which avoids the phase unwraping process.Finally,the Monte Carlo simulation result shows that the performance of the estimator can approach the CRLB very closely.