Uninformed Parameter Estimation for Passive Reception of Data Modulated LFM Waveforms

The data modulated linear frequency modulation (LFM) waveform is one typical communications and radar signal that supports dual-functional radar-communication system operation. This article considers a receiver detecting the main signal parameters of the data modulated LFM waveform. Earlier efforts have demonstrated that the discrete chirp-Fourier transform (DCFT) is capable of uninformed parameter estimation for standard LFM waveforms without data modulation. However, any phase modulation induced by the application of communications data to an LFM waveform may deteriorate the LFM phase information and the recovery of the LFM parameters can become inaccurate. Furthermore, in realistic applications, the transmitter will implement pulse shaping and the receiver may have no prior knowledge of the transmitted phase modulation. To achieve accurate parameter estimation for data modulated LFM waveforms, this article proposes a noncoherent discrete chirp-Fourier transform (NC-DCFT). Furthermore, based on the NC-DCFT method, we propose the integrated step and segment methods to estimate directly the symbol rate of the data modulated LFM waveform. The simulation section of this article demonstrates the performance of the NC-DCFT methods relative to the existing Hough transform method and confirms that the former performs better when their numerical computational complexities are roughly equal.