Rfid detection system

Abstract

Systems and methods for use in detecting the presence of an RFID device are provided. One RFID detection system includes a detection circuit that includes an oscillating circuit. The detection circuit is configured to hold the RFID detection system in a low power mode in which the RFID detection system is configured to not actively attempt to communicate with nearby RFID devices. The detection circuit is further configured to monitor one or more parameters of a signal of the oscillating circuit and compare the one or more monitored parameters to one or more reference parameters. The detection circuit is further configured to, based on the comparison, determine whether to transition the RFID detection system from the low power mode into an active communication mode in which the RFID detection system is configured to actively attempt to communicate with nearby RFID devices.

1 . An RFID detection system, comprising:
 a detection circuit including:
 a single antenna configured to detect the presence of one or more RFID devices near the RFID detection system, the one or more RFID devices having a resonant frequency; and 
 an oscillation circuit configured to sweep an operating frequency of the detection circuit across a range of frequencies, the range of frequencies including the resonant frequency of the one or more RFID devices, the sweeping comprising performing a plurality of oscillation cycles, each oscillation cycle passing through the resonant frequency once; 
   a filter circuit configured to:
 receive a signal from the detection circuit; and 
 output one or more components of the signal in a band around the oscillation frequency; and 
   a comparator configured to:
 receive the one of more components of the signal from the filter circuit; 
 compare a voltage signal component of the one or more components appearing once during the complete oscillation cycle to a reference voltage level; and 
 switch the RFID detection system from a low power mode into an active communication mode in response to the voltage signal component appearing once during the complete oscillation cycle of the sweeping and the voltage signal component exceeding the reference voltage level. 
   
     
     
         2 . The RFID detection system of  claim 1 , wherein the detection circuit is configured to estimate a relative distance between the RFID detection system and one of the one or more RFID devices based on an amplitude of the voltage signal component appearing once during the complete oscillation cycle. 
     
     
         3 . The RFID detection system of  claim 1 , wherein the detection circuit is configured such that the presence of one or more RFID devices near the RFID detection system causes a substantial change in the voltage signal component near the resonant frequency of the one or more RFID devices and one or more objects other than the one or more RFID devices cause a change in the voltage signal component across the range of frequencies. 
     
     
         4 . The RFID detection system of  claim 1 , further comprising an amplifier configured to amplify the one or more components of the signal outputted by the filter circuit. 
     
     
         5 . The RFID detection system of  claim 4 , further comprising a rectifier and a filter configured to average the one or more components of the signal amplified by the amplifier and provide an averaged signal to the comparator. 
     
     
         6 . The RFID detection system of  claim 1 , wherein, in the low power mode, the detection circuit draws a current between 1 μA and 25 μA from an energy storage device of the RFID detection system. 
     
     
         7 . The RFID detection system of  claim 1 , wherein the RFID detection system is configured to actively attempt to communicate with nearby RFID devices when in the active communication mode. 
     
     
         8 . The RFID detection system of  claim 1 , further comprising a microprocessor configured to receive an output of the detection circuit and to set the RFID detection system in one of the low power mode or the active communication mode based on the output. 
     
     
         9 . The RFID detection system of  claim 1 , wherein the RFID detection system is configured to be embedded within a locking device and used in unlocking the locking device based on one or more signals received from the one or more RFID devices near the RFID detection system when the RFID detection system is in the active communication mode. 
     
     
         10 . The RFID detection system of  claim 9 , wherein the locking device comprises a padlock. 
     
     
         11 . A method, comprising:
 sweeping an operating frequency of a detection circuit with an oscillation circuit across a range of frequencies, wherein a single antenna of the detection circuit is configured to detect the presence of one or more RFID devices, wherein the one or more RFID devices have a resonant frequency, wherein the range of frequencies includes the resonant frequency of the one or more RFID devices, and wherein the sweeping comprises performing a plurality of oscillation cycles, each oscillation cycle passing through the resonant frequency once;   receiving, by a filter circuit, a signal from the detection circuit;   outputting, by the filter circuit, one or more components of the signal in a band around the oscillation frequency;   receiving, by a comparator, the one of more components of the signal from the filter circuit;   comparing, by the comparator, a voltage signal of the one or more components appearing once during the complete oscillation cycle to a reference voltage; and   switching the RFID detection system from a low power mode into an active communication mode in response to the voltage signal appearing once during the complete oscillation cycle of the sweeping and the voltage signal exceeding the reference voltage.   
     
     
         12 . The method of  claim 11 , further comprising estimating a relative distance between the RFID detection system and one of the one or more RFID devices based on an amplitude of the voltage signal appearing once during the complete oscillation cycle. 
     
     
         13 . The method of  claim 11 , wherein the detection circuit is configured such that the presence of one or more RFID devices near the RFID detection system causes a substantial change in the voltage signal near the resonant frequency of the one or more RFID devices and one or more objects other than the one or more RFID devices cause a change in the voltage signal across the range of frequencies. 
     
     
         14 . The method of  claim 11 , further comprising amplifying, by an amplifier, the one or more components of the signal outputted by the filter circuit. 
     
     
         15 . The method of  claim 14 , further comprising:
 averaging, by a rectifier and a filter, the one or more components of the signal amplified by the amplifier; and   providing, by the rectifier and the filter, an averaged signal to the comparator.   
     
     
         16 . The method of  claim 11 , wherein, in the low power mode, the detection circuit draws a current between 1 μA and 25 μA from an energy storage device of the RFID detection system. 
     
     
         17 . The method of  claim 11 , further comprising transmitting an output of the detection circuit to a microprocessor configured to set the RFID detection system in one of the low power mode or the active communication mode based on the output. 
     
     
         18 . The method of  claim 11 , wherein the RFID detection system is configured to be embedded within a locking device, and wherein the method further comprises unlocking the locking device based on one or more signals received from the one or more RFID devices near the RFID detection system when the RFID detection system is in the active communication mode. 
     
     
         19 . The method of  claim 18 , wherein the locking device comprises a padlock. 
     
     
         20 . An RFID detection system, comprising:
 a detection circuit including:
 a single antenna configured to detect a presence of one or more RFID devices near the RFID detection system, the one or more RFID devices having a resonant frequency; and 
 an oscillation circuit configured to sweep an operating frequency of the detection circuit across a range of frequencies, the range of frequencies including the resonant frequency of the one or more RFID devices, the sweeping comprising performing a plurality of oscillation cycles, each oscillation cycle passing through the resonant frequency once; 
   a filter circuit configured to:
 receive a signal from the detection circuit; 
 output one or more components of the signal in a band around the oscillation frequency; 
   an amplifier configured to amplify the one or more components of the signal outputted by the filter circuit;   a rectifier and a filter configured to average the one or more components of the signal amplified by the amplifier; and   a comparator configured to:
 receive an averaged signal from the rectifier and the filter; 
 determine an amplitude of a voltage signal component of the averaged signal appearing once during a complete oscillation cycle of the sweeping; 
 compare the amplitude to a reference voltage level; and 
 switch the RFID detection system from a low power mode into an active communication mode in response to the voltage signal component appearing once during the complete oscillation cycle of the sweeping and the amplitude exceeding the reference voltage level; 
   wherein the detection circuit is configured to estimate a relative distance between the RFID detection system and one of the one or more RFID devices based on the amplitude of the voltage signal component appearing once during the complete oscillation cycle of the sweeping.