Systems and methods for forward-scatter sensing

A method for passive sensing of unmanned aircrafts (UAs) within a target volume using radio frequency (RF) signals transmitted by satellites and/or aerostats, the method comprising:

• receiving RF-transmitting satellite or aerostat (RTSA) resultant signals originating from one or more RTSAs using one or more passive RF sensor units, wherein each of the one or more passive RF sensor units employs one or more concurrent reception beams, wherein at least one of the one or more concurrent reception beams has a beam direction that matches a present location of one of the one or more RTSAs and a beam width that matches an angular width of a forward scatter region, wherein each of the one or more RTSAs is one of a satellite and an aerostat, which transmits RF signals, and wherein the RTSA resultant signals are signals transmitted by the one or more RTSAs after traversing a medium between the one or more RTSAs and the one or more passive RF sensor units;
• and
• processing the received RTSA resultant signals, wherein the processing further comprises performing target detection based on the forward scatter effect using one or more of the following:
• applying auto-correlation to the received RTSA resultant signal, and detecting deviations between an auto-correlation output and an auto-correlation output expected in the absence of targets;
• defining one or more RTSA resultant signal attributes, computing values of the one or more RTSA resultant signal attributes for one or more time-swaths during a reception beam, and detecting deviations from expected values of the one or more RTSA resultant signal attributes;
• estimating a transmission resultant signal, and detecting differences between the received RTSA resultant signal and the estimated transmission resultant signal, wherein the transmission resultant signal is the RISA resultant signal after subtracting contributions of signals resulting from reflection and/or scattering from targets;
• estimating a transmission resultant signal, applying cross-correlation between the received RTSA resultant signal and the estimated transmission resultant signal, and detecting peaks in a cross-correlation output other than a peak corresponding to a zero time-delay;
• and
• estimating a transmission resultant signal, computing a difference between the received RTSA resultant signal and the estimated transmission resultant signal to obtain a resultant signal difference, computing a cross-correlation between the resultant signal difference and the estimated transmission resultant signal, and detecting peaks in a cross-correlation output.

A method for passive sensing of unmanned aircrafts (UAs) within a target volume using radio frequency (RF) signals transmitted by satellites and/or aerostats, the method comprising:

• receiving RF-transmitting satellite or aerostat (RTSA) resultant signals originating from one or more RTSAs using one or more passive RF sensor units, wherein each of the one or more passive RF sensor units employs one or more concurrent reception beams, wherein each of the one or more RTSAs is one of a satellite and an aerostat, which transmits RF signals, and wherein the RTSA resultant signals are signals transmitted by the one or more RTSAs after traversing a medium between the one or more RTSAs and the one or more passive RF sensor units;
• and
• processing the received RTSA resultant signals, wherein the processing further comprises performing target detection based on the forward scatter effect using one or more of the following:
• applying auto-correlation to the received RTSA resultant signal, and detecting deviations between an auto-correlation output and an auto-correlation output expected in the absence of targets, that meet certain predefined criteria;
• defining one or more RTSA resultant signal attributes, computing values of the one or more RTSA resultant signal attributes for one or more time-swaths during a reception beam, and detecting deviations from expected values of the one or more RTSA resultant signal attributes that meet certain predefined criteria;
• estimating a transmission resultant signal, and detecting differences between the received RTSA resultant signal and the estimated transmission resultant signal that meet certain predefined criteria, wherein the transmission resultant signal is the RTSA resultant signal after subtracting contributions of signals resulting from reflection and/or scattering from targets;
• estimating a transmission resultant signal, applying cross-correlation between the received RTSA resultant signal and the estimated transmission resultant signal, and detecting peaks in a cross-correlation output other than a peak corresponding to a zero time-delay that meet certain predefined criteria;
• and
• estimating a transmission resultant signal, computing a difference between the received RTSA resultant signal and the estimated transmission resultant signal to obtain a resultant signal difference, computing a cross-correlation between the resultant signal difference and the estimated transmission resultant signal, and detecting peaks in a cross-correlation output that meet certain predefined criteria.