초록 ▼

A swept frequency theft detection system for detecting different resonant circuit targets which are resonant at different frequencies. The system comprises arrangements to generate swept frequency transmitter signals centered at different frequencies but which are swept in synchronism. Also provided

A swept frequency theft detection system for detecting different resonant circuit targets which are resonant at different frequencies. The system comprises arrangements to generate swept frequency transmitter signals centered at different frequencies but which are swept in synchronism. Also provided are antennas formed by offset loops, with the loops of different frequency antennas lying along different diagonal lines.

대표청구항 ▼

A swept frequency detection system for detecting resonant circuit targets attached to articles of merchandise located in an interrogation region, said targets being resonant, respectively, at different frequencies, said system comprising means for supplying, simultaneously, a plurality of swept freq

A swept frequency detection system for detecting resonant circuit targets attached to articles of merchandise located in an interrogation region, said targets being resonant, respectively, at different frequencies, said system comprising means for supplying, simultaneously, a plurality of swept frequency alternating electrical signals centered, respectively, at different frequencies, a plurality of transmitter antennas connected respectively, to receive an associated one of said alternating electrical signals centered at an associated one of said different frequencies and to produce corresponding electromagnetic waves, simultaneously, in an interrogation region, each transmitter antenna being formed in a plurality of loops offset from each other along a diagonal line such that the loops along each diagonal line produce electromagnetic waves centered about an associated one of said different frequencies, the diagonal lines of the respective transmitter antennas crossing each other, and a receiver arranged to detect disturbances to said electromagnetic waves produces by the presence in said interrogation region of a resonant circuit which is resonant within the frequency sweep of any of said alternating electrical signals.