Hand-held spherical antenna system to detect transponder tagged objects, for example during surgery
A hand-held antenna system allows medical personnel to ascertain the presence or absence of objects (e.g., medical supplies) tagged with transponders in an environment in which medical procedures are performed. In use, the hand-held antenna system may be positioned proximate a patient at a time after a medical procedure, such as after child birth, so the system can scan the patient's body to determine the presence of objects tagged with transponders. The antenna system includes three antenna elements arranged mutually orthogonal to each other to transmit and receive signals in three coordinate directions. A controller is coupled to the antenna elements to transmit signals to the transponders and to receive response signals. The antenna system may operate in a static scan mode wherein the antenna system is held in a fixed position by a user and a dynamic scan mode wherein the antenna system is moved by a user.
1 . A computer-implemented method of operating an interrogation and detection system, comprising:
controlling each of a first antenna element, a second antenna element, and a third antenna element of a spherical hand-held antenna, each of the first, second, and third antenna elements is a coil orthogonal to the other antenna elements, and a hollow interior to emit wideband interrogation signals in time-wise succession during a transmit portion of respective transmit and detection cycles;
receiving an electromagnetic signal during a noise detection portion of a detection cycle of the respective transmit and detection cycles;
determining a noise value during the detection cycle that is indicative of a noise level corresponding to a highest of N samples of the received electromagnetic signal, wherein N is a positive number; and
adjusting a signal detection threshold based at least in part on the noise value of the detection cycle.
2 . The computer-implemented method of claim 1 , further comprising:
emitting an interrogation signal during the transmit portion of the respective transmit and detection cycles.
3 . The computer-implemented method of claim 2 , further comprising:
receiving a second signal during a response portion of the detection cycle.
4 . The computer-implemented method of claim 3 , further comprising:
determining a presence or an absence of a transponder based at least in part on a number of M samples of received signals and on the adjusted signal detection threshold, wherein M is a positive number.
5 . The computer-implemented method of claim 4 , further comprising:
comparing a maximum value of a plurality of matched filter outputs with the adjusted signal detection threshold.
6 . The computer-implemented method of claim 4 , wherein a ratio of N:M is equal to or greater than 4.
7 . The computer-implemented method of claim 1 , further comprising:
converting the received signal from a time domain to a frequency domain spectrum.
8 . The computer-implemented method of claim 1 , wherein the electromagnetic signal includes an unmodulated electromagnetic signal.
9 . The computer-implemented method of claim 8 , wherein, when determining the noise value indicative of the noise level, the computer-implemented method further comprises:
setting the noise value based on the highest one of a predetermined number of samples of the unmodulated electromagnetic signal received during the noise detection portion of the detection cycle.
10 . The computer-implemented method of claim 1 , wherein, when adjusting the signal detection threshold, the computer-implemented method further comprises:
adjusting the signal detection threshold based at least in part on:
a first number of determined noise values indicative of the noise level during at least one noise detection portion that occurred before the received response portion of a first one of the detection cycles; and
a second number of determined noise values indicative of a noise level during at least one noise detection portion that occurred after the received response portion of the first one of the detection cycles.
11 . An interrogation and detection system, comprising:
a processor; and
a memory, including instructions stored thereon, which when executed by the processor cause the system to:
control each of a first antenna element, a second antenna element, and a third antenna element of a spherical hand-held antenna, each of the first, second, and third antenna elements is a coil orthogonal to the other antenna elements, and a hollow interior to emit wideband interrogation signals in time-wise succession during a transmit portion of respective transmit and detection cycles;
receive an electromagnetic signal during a noise detection portion of a detection cycle of the respective transmit and detection cycles;
determine a noise value during the detection cycle that is indicative of a noise level corresponding to a highest of N samples of the received electromagnetic signal, wherein N is a positive number; and
adjust a signal detection threshold based at least in part on the noise value of the detection cycle.
12 . The system of claim 11 , wherein the instructions, when executed, further cause the system to emit an interrogation signal during the transmit portion of the respective transmit and detection cycles.
13 . The system of claim 12 , wherein the instructions, when executed, further cause the system to receive a second signal during a response portion of the detection cycle.
14 . The system of claim 13 , wherein the instructions, when executed, further cause the system to determine a presence or an absence of a transponder based at least in part on a number of M samples of received signals and on the adjusted signal detection threshold, wherein M is a positive number.
15 . The system of claim 14 , wherein the instructions, when executed, further cause the system to compare a maximum value of a plurality of matched filter outputs with the adjusted signal detection threshold.
16 . The system of claim 11 , wherein the instructions, when executed, further cause the system to convert the received signal from a time domain to a frequency domain spectrum.
17 . The system of claim 11 , wherein the electromagnetic signal includes an unmodulated electromagnetic signal.
18 . The system of claim 17 , wherein when determining the noise value indicative of the noise level the instructions, when executed, further cause the system to set the noise value based on the highest one of a predetermined number of samples of the unmodulated electromagnetic signal received during the noise detection portion of the detection cycle.
19 . The system of claim 11 , wherein when adjusting the signal detection threshold, the instructions, when executed, further cause the system to adjust the signal detection threshold based at least in part on:
a first number of determined noise values indicative of the noise level during at least one noise detection portion that occurred before the received response portion of a first one of the detection cycles, and
a second number of determined noise values indicative of a noise level during at least one noise detection portion that occurred after the received response portion of the first one of the detection cycles.
20 . A non-transitory computer-readable storage medium which stores a program causing a computer to execute a computer-implemented method of operating an interrogation and detection system, the computer-implemented method comprising:
controlling each of a first antenna element, a second antenna element, and a third antenna element of a spherical hand-held antenna including three orthogonal coils and a hollow interior to emit wideband interrogation signals in time-wise succession during a transmit portion of respective transmit and detection cycles;
receiving an electromagnetic signal during a noise detection portion of a detection cycle of the respective transit and detection cycles, by a spherical hand-held antenna including three orthogonal coils and a hollow interior;
determining a noise value during the detection cycle that is indicative of a noise level corresponding to a highest of N samples of the received electromagnetic signal, wherein N is a positive number; and
adjusting a signal detection threshold based at least in part on the noise value of the detection cycle.