| 摘要 |
PCT No. PCT/SE90/00526 Sec. 371 Date Feb. 18, 1992 Sec. 102(e) Date Feb. 18, 1992 PCT Filed Aug. 15, 1990 PCT Pub. No. WO91/03109 PCT Pub. Date Mar. 7, 1991.A method for the contactless transmission of information between a transmitter/receiver unit and a transponder. The transmitter/receiver unit is caused to transmit a first and a second carrier wave which have mutually different frequencies (f1, f2), forming the difference frequency, of the two different frequencies ,in the transponder, dividing the third signal, (the difference frequence) (f3) to a fourth signal (f4) having half the difference frequency, causing the fourth signal to modulate the two carrier waves received in the transponder as a result of being applied to a diode or like device, so that the received carrier waves are reflected back from the transponder to the transmitter/receiver unit, mixing the signal received back in the transmitter/receiver unit with one of the first or the second carrier wave frequencies, and bringing forward each of the two sidebands on respective sides of the carrier wave frequency with which mixing is effected, such sidebands differing from the last mentioned carrier wave frequency by a frequency which is equal to half the difference frequency (f4), that sideband of the sidebands which has a frequency that lies between the carrier wave frequencies is a combined or combination sideband which is caused to have an amplitude that differs from the amplitude of the other sideband, and the pair of sidebands then being filtered and the information content of the sidebands being detected in the detecting circuit of the transmitter/receiver unit. |
