Foreground subject-identifying apparatus

摘要

A foreground subject-identifying apparatus comprises a sweep signal generator for issuing a sweep signal having frequencies fs falling within a prescribed range; a carrier wave generator for producing a carrier wave having a frequency f0; a first frequency mixer for mixing output signals from the sweep signal generator and carrier wave generator to generate an output signal having a frequency f0+/-fs; a first antenna through which to transmit an output signal from the first frequency mixer; a second antenna mounted on the foreground subject to receive an output signal sent forth from the first antenna; a coding circuit carried on the foreground subject which is provided with a plurality of resonance circuits resonating at different frequencies fT and adapted to form a specified code from a combination of these different resonance frequencies; a signal mixer for detecting an output signal from the second antenna to supply a signal having frequencies fs to the coding circuit and modulating the signal having a frequency f0 by resonance signals from the coding circuit to deliver a signal having a frequency f0+/-fT to the second antenna; a second frequency mixer for mixing an output signal having a frequency f0 from the carrier wave generator, and a signal having a frequency f0+/- fT received from the signal mixer through the second and first antennas and thereby issuing a signal having a frequency fT; and a coded signal interpreting circuit for detecting resonance frequencies out of a signal delivered from the second frequency mixer, thereby interpreting a coded signal supplied from the coding circuit.