| 摘要 |
<p>PURPOSE:To correctly read reflective response information from a moving information card by multiplying a received signal by a signal expressed in a different phase by 90 deg. from a carrier or in the same phase as the carrier, extracting a low frequency component, then squaring and adding the received signal. CONSTITUTION:In an information reader 21, a carrier signal W1 at a prescribed frequency is outputted, the carrier signal W1 is reflected by an information card 4 in a discriminating area, and returned to the information reader 21 as a reflective information signal W2. The signal received by the information reader 21 is multiplied by multiplying signals SCOS and SSIN expressed in the different phase by 90 deg. from the carrier and in the same phase with the carrier by multiplying circuits 23 and 24, it is transmitted through LPFs 25 and 28, squared by squaring circuits 26 and 29, and added by an adding circuit 30. Thus a Doppler shift component included in the received signal is eliminated, and the reflective response information signal from the moving information card can be correctly read.</p> |
