| 摘要 |
A radio frequency (RF) device includes an RF transceiver, an RF antenna, and a magnetic signal detector. The RF is selected to be in the very high frequency (VHF), ultrahigh frequency (UHF), or super high frequency (SHF) bands such that the shielding effect is reduced and the RF device can be configured as a SIM card disposed inside a cellular phone with an increased RF communication range. The magnetic signal detector is used to sense a magnetic field signal from an RF reader, which includes an RF transceiver, an RF antenna, and a magnetic signal transmitter. The longer communication range afforded by the VHF, UHF, or SHF bands is reduced by the sensing of the magnetic field, thereby providing a communication range control, while the RF device and the RF reader exchange information through the RF channel with improved security as a result of the range control. |
