Geun-Ho Park

Analysis of Bistatic Range and Velocity Tracking Performance according to Dynamic Models in Passive Bistatic Radar

This paper analyzes the bistatic range and velocity tracking performance of a target according to the dynamic model of the Kalman filter in a passive bistatic radar (PBR). The bistatic range and velocity can be derived using the time difference and Doppler frequency, respectively. In order to improve the detection performance of the location and velocity of the target in the PBR, time difference and Doppler frequency need to be precisely estimated. This can be achieved by tracking the state of an object with the use of a Kalman filter, the tracking performance of which is affected by the used dynamic model. In this paper, constant velocity model and constant acceleration model are used for analyzing the tracking performance of bistatic range and velocity obtained by the Kalman filter in target movement with constant velocity and acceleration.

Performance Analysis of the Cyclic-periodogram-based Signal Detector in Cognitive Radio

Spectrum sensing in cognitive radio aims to quickly and accurately detect communication signals of primary or secondary users in frequency domain. One of the well-known spectrum sensing techniques is a periodogram-based energy detection method. Unlike the conventional detection scheme which draws one detection result in the observed samples in one time window, the periodogram-based energy detector compares the value of the periodogram to the pre-determined threshold on each FFT (fast Fourier transform) bin. Another spectrum sensing technique considered in the cognitive radio area is a cyclostationary detector. The cyclostationary detector is generally known for outperforming the energy based detector. However, the cyclostationary detector has not been applied to the periodogram-based detection scheme. In this paper, we analyze the performance of the cyclic-periodogram detector which derives the detection results on each FFT bin. Simulation results show that the detection performance of the multi-cycle detector using the multiple cyclic frequencies outperforms the single-cycle detector and the periodogram-based energy detector.

Performance Analysis of Reference Channel Equalization Using the Constant Modulus Algorithm in an FM-based PCL system

A frequency-modulation (FM)-based passive coherent location (PCL) system is a passive radar system for detecting a target using commercial FM broadcasting signals. A cross-correlation function between the direct-path signal propagating line-of-sight of the FM transmitter and the receiver, and the target echo signal, can be derived to detect the target. When clutter is received on the reference channel, the target detection probability can be reduced. In order to improve the detection performance, the direct-path signal on the reference channel should be essentially recovered. In this paper, we apply the constant modulus algorithm (CMA) to remove the clutter received on the reference channel and analyze the amount of removed clutter by simulation. Furthermore, we show that the reference channel equalization plays a very important role in removing ghost targets in the cross-correlation function.

Computationally Efficient TDOA/FDOA Estimation for Unknown Communication Signals in Electronic Warfare Systems

The cross ambiguity function (CAF) has been commonly used to find time difference of arrival (TDOA) and frequency difference of arrival (FDOA). In most cases, direct computation of the CAF by using a conventional method such as fast Fourier transform is too computationally intensive. Thus, a two-stage approach consisting of a coarse mode to find rough TDOA/FDOA estimates and a fine mode for precise estimation was introduced. However, there has been no methodology for selecting an interpolation factor determined by the sampling frequency and target precision which significantly affects the computational complexity. In addition, even if the computational complexity can be reduced by using the optimal interpolation factor, the huge transmission data through the datalink between sensors and the central station still remains to be an obstacle for an electronic warfare (EW) system. In this respect, we derive an optimal interpolation factor and then propose a new two-stage TDOA/FDOA estimation algorithm using a resampling block to reduce the computational complexity and the data size simultaneously in EW systems. In the proposed method, the optimal interpolation factor can be used irrespective of the sampling frequency and the target precision. Simulation results show that the optimal interpolation factor efficiently reduces the computational burden without the loss of estimation performance.

Performance Analysis on a Decoupled Maximum Likelihood Angle Estimator in an FM Based Passive Bistatic Radar

We analyze the performance of a decoupled maximum likelihood (DEML) angle estimator in an FM based passive bistatic radar. Under the assumption that the bistatic range, the Doppler frequency estimates, and the transmitted signal emitted from an illuminator are given, we analyze the sensitivity of the DEML estimator against the range and Doppler frequency errors from the analytic expressions and simulation results. As a result, the performance of the DEML estimator may be mainly degraded by the Doppler frequency errors and we derive a condition that the root-mean-square error of the DEML estimator diverges.

CFAR Detection in a Passive Coherent Location System Using FM Signals

Recently, interest in a passive coherent location (PCL) system using commercial broadcasting signals has been increased since it exploits the existing broadcasting facilities without revealing the receiver’s location. To estimate positions of multiple targets by using the PCL system, constant false alarm rate (CFAR) detection, whose input is the samples of the range-Doppler map, has to be preceded, so that the parameters of the CFAR detector are influenced by the range-Doppler map. However, the characteristics of the range-Doppler map vary with bandwidth of the used broadcasting signals and its collection time. Therefore, algorithm parameters for the CFAR detector have to be properly determined considering those characteristics. To achieve this goal, we analyze the range-Doppler map in a PCL system using commercial FM broadcasting signals and then derive mathematical descriptions for the algorithm parameters of the number of window cells and that of guard cells. We also present which axis out of the range and the Doppler axes is better for CFAR detection.