Foliage penetrating sensor array for intrusion detection

A method of sensing an intruder in a protected area, the protected area defined by an array of field disturbance units, the method comprising:

• using a field disturbance unit to transmit a radio frequency signal, wherein the transmitted radio frequency signal is encoded with data;
• receiving the transmitted radio frequency signal at a different field disturbance unit, wherein the received radio frequency signal has a received signal strength;
• and
• analyzing the received radio frequency signal at the different field disturbance unit to determine the presence of an intruder within the protected area defined by the array of field disturbance units,
• wherein the step of analyzing includes converting the received radio frequency signal into a digital signal having an amplitude that is proportional to the received signal strength of the received radio frequency signal and wherein the step of analyzing further includes
• (a) determining the average amplitude of received signals, wherein the step of determining the average amplitude of received signals includes:
• subtracting a detection zone average amplitude memory value from the digital signal thereby creating a first output value, dividing the first output value by a first constant thereby creating a first quotient value, and adding the first quotient value with the detection zone average amplitude memory value thereby creating a second output value, storing the second output value in the detection zone average amplitude memory thereby replacing a previous detection zone average amplitude memory value;
• (b) determining the average variation of received signals, wherein the step of determining the average variation of received signals includes:
• taking the absolute value of the first output value thereby creating a positive value equivalent to the magnitude of the first output value;
• subtracting a detection zone average variation memory value from the absolute value of the first output value thereby creating a third output value, dividing the third output value by a second constant thereby creating a second quotient value, adding the second quotient value with the detection zone average variation memory value thereby creating a fourth output value, storing the fourth output value in the detection zone average variation memory thereby replacing a pervious detection zone average variation memory value;
• and
• (c) determining the presence of an intruder, the step including:
• multiplying the detection zone average variation memory value with a third constant thereby creating a first product, summing the first product with a minimum threshold value, thereby creating a fifth output value, comparing the fifth output value to the absolute value of the first output value to determine the presence of an intruder by presenting the fifth output value to the negative terminal of a comparator and presenting the absolute value of the first output value to the positive terminal of the comparator, wherein the comparator producing a positive value indicates the presence of an intruder.