Fabiola Colone

A Multistage Processing Algorithm for Disturbance Removal and Target Detection in Passive Bistatic Radar

The paper examines the problem of cancellation of direct signal, multipath and clutter echoes in passive bistatic radar (PBR). This problem is exacerbated as the transmitted waveform is not under control of the radar designer and the sidelobes of the ambiguity function can mask targets including those displaced in either (or both) range and Doppler from the disturbance. A novel multistage approach is developed for disturbance cancellation and target detection based on projections of the received signal in a subspace orthogonal to both the disturbance and previously detected targets. The resulting algorithm is shown to be effective against typical simulated scenarios with a limited number of stages, and a version with computational savings is also introduced. Finally its effectiveness is demonstrated with the application to real data acquired with an experimental VHF PBR system.

Cancellation of clutter and multipath in passive radar using a sequential approach

The paper deals with the cancellation of direct signal, multipath and clutter echoes in passive radar, where the transmitted waveform is not under control of the radar designer and the sidelobes of the ambiguity function mask even targets largely displaced in range and Doppler from the disturbance. A sequential approach is presented for disturbance cancellation and target detection based on projections of the received signals in a subspace orthogonal to both disturbance and previously detected targets. Modeling the clutter spread on few Doppler bins allows complete clutter cancellation. The approach is shown to be effective against typical scenarios with a limited number of iterations.

Comparison of Clutter and Multipath Cancellation Techniques for Passive Radar

In this paper we address the problem of clutter and multipath cancellation in passive radar. Different adaptive techniques are considered based on both well known approaches and innovative strategies proposed by the authors. The performance comparison allows to understand the particular behaviour of each technique in a practical scenario. The proposed innovative strategies are shown to be very appealing solutions for disturbance cancellation in passive radar.

WiFi-Based Passive Bistatic Radar: Data Processing Schemes and Experimental Results

The practical feasibility of a WiFi transmissions based passive bistatic radar (PBR) is analyzed here. The required data processing steps are described including the adopted techniques for 1) the control of the signal autocorrelation function (ACF) usually yielding a high sidelobe level, and 2) the removal of the undesired signal contributions which strongly limit the useful dynamic range. The performance of the proposed techniques is firstly evaluated against simulated data generated according to the IEEE 802.11 Standards. Moreover the results are presented against a real data set collected by an experimental setup when using the conventional dual (reference and surveillance) channels PBR receiving scheme. This allows us to demonstrate the potentialities of a WiFi-based PBR for local area surveillance applications, where vehicles and people can be detected and tracked. Based on the digital nature of the exploited signals of opportunity, the attractive possibility is also investigated of avoiding the use of a dedicated receiving channel for the reference signal, by synthesizing it from the surveillance channel. This approach is shown to yield comparable performance with respect to the conventional PBR approach while yielding a remarkable saving in terms of system complexity.

Ambiguity Function Analysis of Wireless LAN Transmissions for Passive Radar

Wireless transmission is becoming an increasingly widely available source of transmissions for passive radar detection. In this paper, we present a detailed analysis of the ambiguity function (AF) of a range of typical IEEE 802.11 signals obtained during a series of experimental trials. Theoretical analysis has been used to identify the average properties of basic signal types in terms of resolution and sidelobe levels in both the range and Doppler domains. The theoretical model of a range of typical 802.11 transmissions has been verified and range and Doppler resolutions have been investigated for a range of transmission types. It has been found that using Doppler with a suitable integration time can enable detection of typical personnel targets. A number of issues relating to the use of these transmissions have been identified during this study.

Experimental results for OFDM WiFi-based passive bistatic radar

In this paper the practical feasibility of a WiFi transmissions based passive bistatic radar (PBR) is analyzed. The required data processing steps are described there including the adopted techniques for: (i) the control of the signal Ambiguity Function usually yielding a high sidelobe level and (ii) the removal of the undesired signal contributions which strongly limit the useful dynamic range. The performance of the conceived system is evaluated with reference to typical signals broadcasted by a IEEE 802.11 access point exploiting an OFDM modulation. The achievable results are presented against a real data set collected by an experimental setup. This allowed us to preliminarily demonstrate the potentialities of a WiFi-based PBR for local area surveillance applications.

Efficient Detection and Imaging of Moving Targets in SAR Images Based on Chirp Scaling

An innovative scheme is presented for moving target detection and high-resolution focusing that exploits a bank of chirp scaling algorithms (CSA), each one matched to a different along track target velocity component. The new scheme is thought for multichannel (MC) synthetic aperture radar systems, to provide a high-resolution focusing of the moving targets. Adequate target detection capability is ensured by integrating the aforementioned bank of CSA with a post-Doppler space-time adaptive processing clutter cancellation step. The presented scheme is very efficient from a computational point of view and is able to achieve sub-clutter visibility for the moving targets. The effectiveness of the proposed techniques is shown with reference to an emulated MC data set.

Multifrequency integration in FM radio-based passive bistatic radar. Part I: Target detection

After summarizing the problems related with the variability of the characteristics of the waveforms received by PBR, especially when operating in the FM radio band, the concept of the MF integration has been introduced, aiming at (i) increasing the global SNR and (ii) making the detection performance robust w.r.t. the program content of the individual radio stations.

Performance analysis of a multi-frequency FM based Passive Bistatic Radar

In this paper we evaluate the target detection performance improvement of a multi-frequency approach for FM radio based passive bistatic radar. Specifically, we consider the high diversity of the FM radio signals received over different carrier frequencies spanning the 88-108 MHz band since it represents the basis for the request of a multi-frequency operation. The joint exploitation of the waveforms of opportunity received on multiple FM radio channels is shown to yield better performance in terms of detection capability. To demonstrate the effectiveness of the proposed approach two experimental prototypes of FM radio based passive radar receivers have been developed and fielded at the INFOCOM Dept. of the University of Rome ldquoLa Sapienzardquo. The two prototypes are based on two different design approaches: direct RF sampling and signal down-conversion & baseband sampling. The acquisition campaigns that have been carried out with the two prototypes are described together with the collected data analysis and processing. Finally, the results obtained over the collected data set for the single FM channels and after the proposed multi-frequency integration procedure are reported and compared with live air traffic control registrations.

Space-based passive radar enabled by the new generation of geostationary broadcast satellites

In this paper we investigate the possibility to develop a passive radar system for mid-range air target surveillance using, as illuminator of opportunity, a high EIRP level geostationary broadcast transmitter. These satellites are being introduced recently for Satellite Mobile Digital TV broadcast purpose. Since they are designed to allow mobile users to receive satellite TV without large antennas, a sufficiently high signal power is being transmitted, making them suitable as illuminators of opportunity in a passive radar system. The possibility to resort to a quasi-stationary transmitter is shown to highly simplify the signal processing required by the passive radar system. A preliminary evaluation of the achievable SNR is conducted, showing that mid-range target detection can be achieved with reliable performance. In addition, a detailed analysis of the Doppler frequency contributions is conducted. Specifically, the Doppler frequency contribution due to the motion between target and transmitter is shown to be locally independent over the target position. The overall bistatic Doppler frequency behavior is evaluated for several possible target trajectories and some critical trajectories are identified. Finally, some remarks referred to the 2D Cross Correlation Function (2D-CCF) evaluation are reported.