System and methods for detecting change in a monitored environment

A security system for detecting changes in a monitored environment, the system comprising:

• a plurality of means for responding to an interrogation signal with a unique identifier, the plurality of means for responding being distributed about the monitored environment;
• means for transmitting interrogation sequences of interrogations signals over a plurality of different frequency bands at a plurality of power levels;
• means for determining response patterns for each of the plurality of RF sensors to the interrogation sequences;
• means for determining if response patterns vary outside a predetermined background baseline;
• and
• means for providing an indication if response patterns vary outside the predetermined background baseline.

A method for detecting changes in a monitored environment, the method comprising:

• distributing a plurality of radio frequency (RF) sensors about the monitored environment, each RF sensor configured to respond to an interrogation signal with a unique identifier;
• repeatedly transmitting interrogation sequences of interrogations signals over a plurality of different frequency bands at one or more power levels for a given time period;
• determining response patterns for each of the plurality of RF sensors to the interrogation sequences to determine a background baseline;
• determining and storing change thresholds from the determined background baseline;
• repeatedly transmitting the interrogation sequences of interrogations signals over the plurality of different frequency bands at one or more power levels during a security monitoring time period to determine changes in the monitored environment;
• and
• transmitting a change detection indicator if at least one of the determined response patterns vary outside the change thresholds.