Passive Coherent Location Radar Systems Research Articles

Evaluating the Performance of FM-Based PCL Radar in the Presence of Jamming

In this paper, we examine an FM-based passive coherent location (PCL) radar system and attempt to quantify its performance in the presence of various different jamming waveforms namely broadband noise and a single tone on the carrier. It is shown that effective jamming can be achieved with relatively low jamming power. The importance of an effective direct signal canceller is also shown as a means of suppressing the jamming signal. The effect of these jamming scenarios is shown through simulation and then compared to a representative measured result from a real FM-based PCL radar system.

Antenna array characterisation and signal processing for an FM radio-based passive coherent location radar system

The design of passive coherent location radar, which exploits broadcasting transmitters of opportunity in the very high frequency (VHF) radio bandwidth, is presented. Here, the authors primarily focus on the system set-up and on the digital pre-processing steps. Emphasis is given to the antenna section analysis. The eight-element circular array, which is used for the signal acquisition, is analysed by means of simulations and measurements. Compensation for the mutual coupling effect between the different channels is achieved by applying a technique in the digital domain. An innovative digital beamforming algorithm is introduced to reduce the sidelobe level of the circular array pattern. Direct path interference suppression, range/Doppler data processing, greatest-of constant false alarm rate algorithm and range/Doppler-time plots extraction provide the final output of the processing chain. Experimental validation of the processing architecture is presented and the final detection results are compared with an automatic dependent surveillance broadcast data set.

Real Time Processing of Networked Passive Coherent Location Radar System

Real Time Processing of Networked Passive Coherent Location Radar SystemA Passive Coherent Location (PCL) Radar system, consisting of spatially distributed transmitters and receivers is currently being integrated at the University of Cape Town (UCT). The paper investigates the feasibility of real-time processing of PCL system signals using Graphic Processing Units (GPUs), specifically a study of two distinct clutter cancellation algorithms: ECA (Extensive Cancellation Algorithm) and NLMS (Normalised Least Mean Square). Clutter cancellation is the most computationally demanding part of PCL signal processing. This investigation compares the processing speed-up achieved by GPU over CPU implementations, with very encouraging results.

Passive coherent location radar systems. Part 2: Waveform properties

Resolution and ambiguity in both range and Doppler are parameters of fundamental importance in the design and subsequent performance of any radar system. In passive coherent location (PCL) systems these properties are determined by the transmitted waveform, the location of the transmitter, the location of the receiver and the location of the target. Consequently, the scope for radar design and optimisation would seem to be severely restricted as many factors are not within the control of the radar designer. In this paper practical measurements of transmitted waveforms are reported and used to illustrate their effects on the resulting system design and performance. In particular the ‘self-ambiguity’ which enables the limits on range and Doppler resolution to be evaluated is computed. The bistatic form of the ambiguity function is subsequently presented and used to illustrate how these best case parameters vary as a function of transmitter, receiver and target locations. Understanding the forms that these functions can take and subsequently the implications for system performance is most important if this type of radar is to be used effectively. It is shown that the radar designer does in fact have some limited freedoms to improve system performance. Finally the implications of transmitter waveform and bistatic geometry on target detection, location and imaging are discussed.

Passive coherent location radar systems. Part 1: Performance prediction

Passive coherent location (PCL) systems are a variant of bistatic radar that exploit ‘illuminators of opportunity’ as their sources of radar transmission. Dispensing with the need for a dedicated transmitter makes PCL inherently low cost, and hence attractive for a broad range of applications. Although a number of experimental and development examples exist, relatively little has been reported on the detailed performance of these systems and the resulting effects that these will have on the interpretation of backscatter and exploitation of derived information. In the paper a bistatic form of the radar range equation specifically tailored to PCL systems is developed. Realistic examples are used to examine and compare variations in sensitivity and coverage for three candidate transmitters of opportunity. These are analogue FM radio, cellular phone base stations and digital audio broadcast (DAB). These examples show that a wide and extremely useful set of detection ranges are achievable and also highlight some of the key issues underpinning more detailed aspects of predicting detection performance.