Reconstructed Reference Signal Research Articles

Improved 2D Ground Target Tracking in GPS-Based Passive Radar Scenarios.

Global Positioning System (GPS) satellites offer promising opportunity for Passive Radar systems due to their global coverage and the availability of multiple satellites throughout the world. However, their low power at ground level limits system coverage. In this paper, a GPS based Passive Radar which exploits a single illumination source, and uses digital array processing for ground targets localization is presented. To face signal power problems, a processing scheme combining reconstructed reference signals, adaptive filtering techniques and spatial filtering is implemented. Conventional beamforming techniques are used to increase the level of the target echo before the detection stage, and high resolution DoA estimation techniques are applied to estimate targets azimuth. Ground target localization in local Cartesian space is performed taking into account the system geometry, range and azimuth information. Both synthetic and real radar data are used to analyse system operation. During the measurement campaign, a cooperative vehicle was used for validation purposes. Results confirm that ground targets detection and localization are feasible using a single GPS transmitter.

LTE-based passive multistatic radar for high-speed railway network surveillance: design and preliminary results

AbstractWith the aim of performing perimeter surveillance of high-speed railway networks, this paper presents the design of a passive multistatic radar system based on the use of Long-Term Evolution (LTE) downlink signals as the illumination of opportunity. Taking into account the specifications and standard of the LTE system, the ambiguity function of measured downlink signals is analyzed in terms of range and Doppler resolution, ambiguities, and sidelobe level. The deployment of the proposed passive radar is flexible and scalable, and it is based on multichannel software defined radio receivers that obtain the reference and surveillance signals by means of digital beamforming. The signal processing and data fusion are based, respectively, on the delay-Doppler cross-correlation with the reconstructed reference signals and a two-stage tracking at sensor and central level. Finally, the performance of the proposed system is estimated in terms of its maximum detection range and simulation results of the detection of moving targets are presented, demonstrating its technical feasibility for the short-range detection of pedestrians, vehicles, and small drones.

Performance of the least squares filter for passive radar interference cancellation applications

For passive radar interference cancellation, least squares (LS) filter is a popularly used method, which projects the surveillance signal in a subspace orthogonal to interference subspace. Under the assumption of ideal reference signal reconstruction, LS filter is simple and effective to implement. However, there is a limited understanding of its performance in passive sensing environments with non-negligible multipath and noise in reference signal. This study examines such effects on the performance of interference cancellation by LS filter. Since transmitted signal is beyond access in passive radar, modulation error rate (MER) is introduced to characterise the direct-path signal noise ratio (SNR) of the reference signal. Closed-form expression for cancellation loss ratio (CLR) is derived, which quantifies to what extent the SNR and interference noise ratio of reference signal and surveillance signal should be achieved to guarantee an acceptable SNR loss of interested target after interference cancellation. Moreover, a modified-MER scheme is proposed to cope with the noise residual in the reconstructed reference signal so as to improve cancellation performance. Effectiveness is verified by both simulated and experimental collected passive radar data using digital terrestrial multimedia broadcasting waveform. These results are useful in practical data processing for passive radar sensing.

Parameter Estimation of Co-Channel AIS Signal Using Ambiguity Function

A new data-aided algorithm for parameter estimation of the co-channel AIS signal transmitted over the additive white Gaussian noise channel is proposed in this paper. The co-channel signal consists of a strong signal with high power and a weak signal with low power. The parameters of the strong signal are estimated by searching the ambiguity function of the co-channel signal in two dimensions. A reference signal is therefore reconstructed with the estimated parameters and the aided data. By removing the ambiguity function of the reconstructed reference signal from that of the original co-channel signal, a new co-channel signal ambiguity function is obtained, from which the parameters of the weak signal are estimated. The simulation results illustrate that the proposed algorithm can estimate the parameters of the co-channel AIS signal effectively.

Robust decentralized output regulation with single or multiple reference signals for uncertain heterogeneous systems

SummaryWe consider the problem in which N coupled heterogeneous uncertain linear systems aim at tracking one or more reference signals generated by given exosystems under the restriction that not all the systems are directly connected to the exosystems. To tackle this problem, the reference signals are reconstructed via local interaction of the systems among themselves and the exosystems in accordance with the given communication graph. Then, decentralized robust controllers using the reconstructed reference signals are designed and shown to result in a closed‐loop system whose outputs track the prescribed reference signals. Copyright © 2014 John Wiley & Sons, Ltd.

Carrier Synchronization and Detection of Polyphase Signals

Digital communication networks used for the distribution of high-speed digital information are currently the subject of design studies for many civil and military applications. This paper presents results that are useful in such studies as well as in network planning. In particular, the paper is concerned with the problems of carrier synchronization and noisy reference detection of polyphase signals. Reconstruction of coherent references for the detection of polyphase [ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> -ary phase-shift-keyed (PSK)] signals is considered and analyzed for three carrier reconstruction loops, namely, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> th power (multiply-and-divide) loops, generalized Costas ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I-Q</tex> ) loops, and extensions of data-aided (modulation wipeoff) loops. General expressions for the error probability are developed when the reconstructed reference signals are noisy. These expressions are evaluated numerically for cases of practical interest and compared with differentially coherent reception.