中文摘要：

提出利用步进频信号作为宽带测井信号,讨论步进频信号在随钻电磁波测井中的应用.用数值模式匹配算法（NMM）和快速傅里叶变换（FFT）,建立步进频信号在地层中的测井数值模型.利用FFT和NMM对步进频信号的每个窄带脉冲进行计算,得到各个接收线圈的接收信号,再利用相敏检波的方法得出各个频点下的幅度和相位信息.用IFFT进行接收信号的合成处理,完成脉冲综合,提高峰值信噪比（PSNR）,峰值点处的幅度和相位作为测井响应.电磁波传播测井中,2个接收线圈的幅度比和相位差作为测井响应.数值仿真结果显示,利用步进频信号作为测井信号的测井方法,较单频信号的测井方法能够有效提高信噪比和纵向分辨率,比线性调频连续波在硬件上更容易实现宽带,有效抑制相关噪声.

英文摘要：

A novel broadband electromagnetic propagation logging method with the stepped frequency signal as the well-logging signal is proposed for logging while drilling （LWD）. The logging responses of the layered media to the stepped-frequency signal in the noise environment are modeled numerically by using Numerical Model Matching （NMM） and Fast Fourier Transform （FFT）. Based on the frequency spectrum of each narrow band pulse of the stepped frequency signal, the NMM is used first to calculate both the amplitude and phase of the signals in receiving coils, and then FFT is applied to convert them to the logging responses in time domain. After that, the phase-sensitive detection is used to calculate the amplitude and phase of every stepped frequency. And the pulse synthesis is realized by Inverse Fast Fourier Transform （IFFT） of the amplitude and phase of stepped frequencies. And the peak signal to noise ratio （PSNR） is improved significantly. As the logging response of the electromagnetic propagation logging tool, the amplitude ratio and phase difference between the compressed signals from two separated coils in the peak point are obtained respectively. It has been shown from the simulation results that the use of the stepped-frequency signal as the wideband logging signals can improve the signal to noise ratio （SNR） and the logging resolution remarkably, especially under the condition with correlated noise which restrains the SNR and logging resolution strongly in traditional logging with single frequency continuous wave. Moreover, compared to the linear frequency modulation continuous waves, the stepped-frequency signal is easier to achieve broadband in the hardware and improve SNR.