Search

The objective of this work is to investigate the Ambiguity Function (AF) characterization of the Iridium L‐band downlink burst transmissions under single burst and multiband multi‐burst mode to demonstrate its suitability and capability as Signal of OPportunity (SoOP) for navigation. The Iridium bursts are collected and examined by demodulating without any prior knowledge for frame verification. The comprehensive analysis and theoretical model of the two mode AFs are presented and verified to evaluate the waveform properties with resolution and sidelobes in both the Doppler and delay domains. Degradation in AF resulting from signal model and multiband channel combination is characterized to exploit the trade‐offs for selection and utilization of the Iridium burst. It has been found that the single burst even with maximum length of 20.32 ms appears available but far from excellent for navigation, while the multiband mode produces significant improvements over the time delay and Doppler resolution as well as a certain degradation on the AF sidelobes. Issues relating to the Iridium bursts utilization have been identified. [ABSTRACT FROM AUTHOR]

Suppressing false alarms without impacting detection rate is an essential issue for search radars. Traditional threshold detection methods identify true targets by simply comparing the energy of target candidates with a threshold. In this work, a new data‐driven false‐alarm suppression approach is proposed based on a random forest model. It discriminates true targets and false alarms in the developed multi‐dimensional ambiguity feature spaces, instead of the time‐frequency features used in previous works, to fulfill short dwell‐time requirement of search radars. Evaluations through field experiments demonstrate that the proposed method can achieve as high as 98% validation accuracy and a significant improvement of detection performance compared to the conventional threshold detection. [ABSTRACT FROM AUTHOR]