请问使用ST25R3911B可以保证通讯距离超过50cm吗？

亲爱的朱莱夫，
 
通信距离非常依赖于阅读器和标签。
只有当读卡器与标签之间存在良好的耦合时，才能保证良好的通信距离。这也将确保标签具有良好的LMA（负载调制幅度）。如果标签天线的尺寸与读取器天线相似，则给出良好的耦合。通常读卡器天线有点大。
使用的协议也会影响通信范围。例如，ISO15693允许比ISO14443 A或B更大的距离。根据经验，通信距离大约是方形天线的长度。这意味着如果你有一个10厘米×10厘米的天线，使用如上所述的标签，通信距离也应该至少为10厘米。此外，您的读者的Q因素在这里发挥作用。 Q因子越高，LC天线槽中的功率就会越大，并且越难以符合ISO标准，甚至产生可解码的波形。
 
达到50厘米后，您需要相应地升级标签和阅读器的天线尺寸。
另一种方法是增加额外的放大器电路，以提高1.4W以上的输出功率，并为RFI接收器路径增加额外的滤波。
 
BR Travis



以下为原文




Dear Zhulev,

The communication distance depends very much on both - reader and tag.
Only if there is a good coupling from reader to tag a good communication distance is guaranteed. This will also ensure that the tag has a good LMA (Load Modulation Amplitude). A good coupling is given, if the tag antenna is similar size than the reader antenna. Usually the reader antenna is a bit bigger.
Also the used protocol will have an influence on the communication range. ISO15693 for example will allow bigger distances than ISO14443 A or B. A rule of thumb says that the communication distance is approximately the length of a square antenna. Which means if you have a 10cm times 10cm antenna the communication distance should also be at least 10cm using a tag as described above. Also the Q-Factor of your reader plays a role here. The higher the Q-Factor will be, the more power will resonate in the LC antenna tank and the harder it will be to be ISO compliant or even produce decode-able wave shapes.

Achieving 50cm you will then need to upscale the antenna sizes for tag and reader accordingly.
An alternative would be to add additional amplifier circuit to boost output power beyond the 1.4W and add additional filtering to the RFI receiver path.

BR Travis