| 主权项 |
1. A communication method, comprising:
controlling a communication distance between a first radio frequency (RF) device and a second RF device using a low-frequency magnetic field; and exchanging information between the first RF device and the second RF device within a predetermined distance range using RF channels; wherein, one of the first RF device and the second RF device receives a first low-frequency alternating magnetic field signal from the other of the first RF device and the second RF device to control the communication distance between the first RF device and the second RF device; wherein receiving the first low-frequency alternating magnetic signal to control the communication distance further includes: detecting the received first low-frequency alternating magnetic field signal; converting the first low-frequency alternating magnetic field signal into a first electrical signal; comparing the first electrical signal with a first preset threshold value; and controlling the communication distance between the first RF device and second RF device based on a comparison result; wherein the first RF device is a card reader, the second RF device is a card, the first electrical signal is a voltage signal, and the first threshold value is a voltage threshold Vt, wherein the voltage threshold Vt is determined by: under selected transmission parameters, measuring voltage-distance curves of a plurality of terminals and obstacles, the selected transmission parameters including a frequency of the low-frequency alternating magnetic field signal, a modulation mode, a coding mode, and a transmission magnetic flux density Be; obtaining a reference voltage-distance curve, the reference voltage-distance curve being an average value of curves of the terminals and obstacles; and selecting a voltage value at a distance point at half of a maximum valid card transaction range on the reference voltage-distance curve as Vt for the card reader. |
