C. Bongioanni

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.

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.

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.

Multifrequency integration in FM radio-based passive bistatic radar. Part II: Direction of arrival estimation

The concept of MF operation introduced in [1] has been extended to the target DoA estimation stage, aiming at the same time to (i) increase the angular localization accuracy and (ii) make the DoA estimation performance robust w.r.t. the time-varying characteristics of the waveforms received by PBR, especially when operating in the FM radio band.

Direction of arrival estimation for multi-frequency FM-based Passive Bistatic Radar

In this paper we introduce a multi-frequency approach for improving target Direction of Arrival (DoA) estimation in FM radio based Passive Bistatic Radar (PBR). The joint exploitation of the waveforms of opportunity received on multiple FM radio channels in the 88÷108MHz band is shown to yield better performance in terms of detection capability and DoA estimation accuracy, since it is robust with respect to both the broadcasted radio program content and to the propagation channel conditions. To demonstrate the effectiveness of the proposed approach an experimental FM-based PBR prototype has been developed and fielded at the DIET Dept. of the University of Rome “La Sapienza”. The acquisition campaigns that have been carried out 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 DoA estimation technique are reported and compared with live air traffic control registrations.

PBR activity at INFOCOM: Adaptive processing techniques and experimental results

The paper describes the results achieved at the INFOCOM Department of the University of Rome ldquoLa Sapienzardquo on passive bistatic radar (PBR). The developed adaptive signal processing techniques are introduced for: improved disturbance cancellation, multipath removal, and multifrequency target detection. The development of experimental wide-band PBR prototypes is described, as opposed to single frequency channel PBR systems, giving special attention to the system design guidelines and test procedures. The experimental results achieved using the wide-band PBR prototypes are shown, there including the demonstration of effectiveness of the techniques above. The results are shown to be largely consistent with live air traffic control registrations.

Passive radar components of ARGUS 3D

Combining the detection range capability of passive radar using FM radio emissions with the range resolution obtained through the use of DVB-T signals and the elevation coverage capability provided by DAB Tx yields a high-performance hybrid passive radar sensor. Increasing the coherent integration time of the high-resolution DVB-T component in a track-before-detect approach, cued by the Doppler information obtained through the FM radio component, provides high-range resolution at extended detection ranges. In addition, the DAB-using component, cued by Doppler information provided by FM radio, extends the high-resolution detection volume to elevation ranges not illuminated by DVB-T. The heart of such a hybrid passive radar sensor will be the cued track-before-detect procedure, which is currently being developed at Fraunhofer Institute for High Frequency Physics and Radar Techniques in Wachtberg, Germany.

A flexible receiver architecture for multi-band Passive Bistatic Radar

In this paper a flexible receiver architecture is described for a Passive Bistatic Radar (PBR) that can exploit any of the many broadcast signals available in the frequency spectrum, going from the FM and VHF-UHF bands (DAB/DVB-T) to the S-band (WiFi/WiMax/LTE). Specific front-ends receiver sections are foreseen for each selected waveform of opportunity, while a common part of the system performs the I&Q demodulation and the Analog-to-Digital (A/D) conversion. The scheme can be used both for a direct I&Q conversion and for a double conversion (up-conversion stage from Radio Frequency-RF-to a high Intermediate Frequency -IF- and down-conversion from IF to Base Band -BB-) of the received signals for PBR applications. This allows to remove the image frequency even in the wide bandwidth occupied by the digital TV signals. A prototype of the proposed concept has been developed and fielded, with proper laboratory tests and real data acquisition campaigns, at DIET Dept. of the University of Rome “La Sapienza”. The results obtained with the receiver, in three possible configurations, are reported and discussed: FM-based PBR (for medium/long-range air targets surveillance), DAB/DVB-T (for medium range air and sea surveillance) and WiFi-based PBR (for short-range human target localization).