| 摘要 |
<p>The method and apparatus are intended to trace household pets who have run away, to follow animals for biological research and other purposes whereby objects and persons need to be followed or traced. The use of energy by a marker (1) employed is minimal, so that such a marker can function for a very long time uninterruptedly without its battery having to be changed. Use is made of radio frequency back scatter technique, which involves radio frequency identification. An additional feature is that in spite of simple antenna arrangements, by means of a doppler measurement the direction to the marker can be determined rapidly adn positively. An antenna (2) functions in the frequency band of the investigaging signal, for example, a dipole, a marker modulator (3) and a signal source (4) which produces a sub-carrier wave with a frequency of preferably 66.5 kHz, which is then fed to the high frequency modulator. The modulator comprises a diode (5), which joins the two halves of the dipole. The impedance of the antenna is modulated in the rhythm of the sub-carrier wave frequency and therewith the amplitude and/or phase of the reply signal. A battery (6) feeds the electronic circuitry in the marker. A code generator (7) generates a data signal with an identification number, which is then modulated on the sub-carrier wave by a code modulator (8).</p> |
