![]() ![]() processing implementation for imaging across multiple distributed illuminators. A passive radar signal model is then developed and demonstrates one possible. A typical set of transmitters in the UHF and VHF bands based upon the local illuminators in the Columbus, Ohio region is presented to constitute a realistic passive imaging environment. Potential for imaging in passive multistatic radar systems is investigated primarily in terms of illuminator type and coherency. So far other research groups advanced in the field of bistatic/multistatic passive radars based on WIFI networks as illuminators of opportunity have not been found. At the end of the paper discussion about the results is presented. The main goal of this paper is to show how the amount of the illuminating signal impacts the range-Doppler matrix. Experiments were performed in the bistatic configuration in an outdoor environment using a two node WIFI network, the WIFIRAD as radar and a car as a reference target. This paper covers illuminating signal description, analysis of the duty factor impact on crossambiguity function shape and the results of experiments which show the impact of the duty factor on the radar’s performance. As WIFI signals are not continuous and the duty cycle depends on the amount of transmitted data, the paper is focused on the impact of the duty cycle on the quality of the detections obtained in the presented WIFIRAD. It utilizes the signals from WIFI networks as sources of illumination. ![]() WIFIRAD is a passive radar demonstrator developed in the Digital Signal Processing laboratories of the Warsaw University of Technology. Specifically, if the former is notably higher than the latter (by, e.g., 5 dB), there is a minor difference between the passive and active MLEs for the delay and Doppler estimation otherwise, the difference is non-negligible and increases with the SNR. Our results show that the signal-to-noise ratio (SNR) in the RC relative to the SNR in the SC has a significant impact on the passive MLE. The passive MLE is compared via numerical simulation with its active counterpart, which has exact knowledge of the waveform and uses it for cross-correlation. In addition, the Cramér- Rao Bound (CRB) is derived to benchmark the passive estimation performance. We present two implementations for the passive MLE, including a direct and, respectively, a fast implementation based on a twodimensional Fast Fourier Transform. Under this condition, the passive MLE is shown to reduce to a crosscorrelation and search process using the surveillance signal and a delay-Doppler compensated version of the reference signal. We examine the maximum likelihood estimator (MLE) for the passive estimation problem by modeling the unknown IO waveform as a deterministic process. The passive radar consists of a reference channel (RC), i.e., an antenna steered to the IO, and a surveillance channel (SC) that collects target echoes. We consider the problem of delay and Doppler frequency estimation of a moving target in passive radar using a non-cooperative illuminator of opportunity (IO). Keywords Passive radar systems, passive coherent location, passive bistatic radar, multistatic passive radio location, noise radars, WIFI signal decoding, frame detection, processing signal from wireless networks. This paper describes in details the algorithms and the results of the experiment for the multistatic passive radar based on the WIFI signal. After signal processing using Passive Coherent Location methods the target has been detected. The direct reference and reflected (surveillance) signals have been acquired and processed using specially developed algorithm presented in the paper. In the experiment the 3 wireless access points (AP) were communicating with each other and illuminating the radar scene (airfield). As a result of experiments conducted on 17th August 2013 at airfield Chrcynno a Cessna C208 airplane was detected using multistatic passive radar system based on low power signal from WIFI network nodes, which were acting as non-cooperative illuminators of opportunity. This paper presents the theory and experimental result of passive radar using WIFI transmitters as illumina-tors of opportunity. ![]()
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