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Refleksi RFID

Teknologi RFID didasarkan pada pengetua saintifik yang jelas. Tag mengumpulkan tenaga yang diunjurkan gelombang radio dalam medan elektromagnet. Teg kemudian mencerminkan isyarat yang diubah menggunakan teknik yang dipanggil
back-scatter which the antennas receive. Because it is a science, it is often assumed that an expert can accurately predict both the read performance of a tag on any item and the distance it can be read from, just by looking at the system. Unfortunately, reality is much more complex, making RFID operation seem like black magic. In most

Wizard RFID

persekitaran, RFID menghasilkan hasil yang pelik. - kerap melawan intuitif. Biasanya, hasilnya akhirnya masuk akal sebaik sahaja disiasat, tetapi jarang sekali yang anda harapkan.

Terima kasih kepada RR Donnelley & Sons Co. kerana menghantar sampel label RFID Custom Wave mereka. Kini semua orang tahu tentang percetakan antena adat RR Donnelley? (Awak tidak? Baik awak patut. Semak artikel ini mengenai mereka dalam RFID Journal!)

Kami menerima empat tag UHF pasif yang berbeza yang kami uji dalam dua persekitaran yang berbeza.

  1. Di dalam gudang
  2. Di luar tempat letak kereta terbuka

Di bawah adalah hasil ujian jarak jauh.

CW-100-04U7CW-100-08MR6
Inlay04U701MR6
Ukuran Inlay18 mm * 44 mm22 mm * 60 mm
Julat Baca Gudang2.2 meter6.22 meter
Julat Baca Luar2.13 meter3.35 meter

CW-100-01MR6CW-100-05U7
Inlay08MR605U7
Ukuran Inlay95 mm * 8 mm50 mm * 30 mm
Julat Baca Gudang6.83 meter9.19 meter
Julat Baca Luar4.72 meter5.18 meter

Why is there such a significant difference in read range between the two environments if we are using the same reader and the same tags? Most likely the answer is due to reflection of RF energy. The diagram below shows the environment in our warehouse which we tested. The tags were being read down a corridor bordered by pallets of paper products. The image shows how the RF field might be reflected to improve our range.

Diagram Ujian Gudang

Grafik artikel Refleksi RFID

The warehouse test diagram illustrates a reader with energy reflected down the corridor. Only a small amount of the energy output from the reader is able to escape through space between the pallets and up into space above the pallets. In this warehouse trial, the tag was able to be read from further away because there was more RF energy available to power the tag than there would have been in the open. Additionally, the large metal door behind the tag could have reflected energy back towards the tag, which would give the tag a double dose of RF energy.

Outside, most of the RF energy that was not oriented directly at the tag was lost because it escaped into space. The RF energy around the tag was weaker and it could not power the tag at the longer distances.

Refleksi tidak hanya mengubah keupayaan anda untuk membaca tag, tetapi juga mencipta situasi membaca tag aneh. Semasa ujian luar, kami mendapati apa yang kami fikir adalah julat bacaan maksimum untuk CW-100-05U7 pada 4 meter. Di 4.5 meter, kami tidak dapat membaca teganya. Walau bagaimanapun, di 5 meter, pembaca menemui tag lagi. Mengapa pembaca dapat membaca dari 5 meter tetapi tidak 4.5 meter? Sudah tentu jawapannya adalah pantulan. Imej di bawah menunjukkan fenomena yang kita lihat.

Bidang Tenaga RF

Bidang tenaga RF

Passive UHF tags are dormant until they are powered by enough energy to send a response. In the example above, the RF energy is powerful enough to read a tag anywhere in the first area without any reflection. Then there is a small gap between fields. There is likely energy in the gap between the blue areas, but it is not enough to power the tag. In the small blue areas to the right of the large oval, the RF energy is enhanced via reflected RF waves increasing the energy available to the tags. In this situation, it may have reflected from the ground or nearby vehicles, as shown in the image below.

Refleksi RF

Bounce RFID

Apa yang boleh kita ambil dari ini?

Testing is critical as it is almost impossible to consider all factors which you may see in your actual environment. More than focusing solely on the tag and reader, consider the places where the field will be at its weakest and adjust the tag or antenna locations if possible.

Anda boleh melihat video tentang cara ini berfungsi dalam praktik di bawah. Papan LED yang menunjukkan kekuatan medan dengan Teleeris UHF Sensor.

RF reflection is one of many aspects of an RFID system to consider. For more information on RFID systems please contact sales@telaeris.com. Untuk maklumat lanjut mengenai label RFID Custom Wave, lihat laman web mereka di http://www.rrdonnelley.com/printed-electronics/customwave/.

Note: Handheld RFID readers are not usually the best solution for long distance scanning. Fixed readers and antennas will typically provide a longer read range as the readers project more RF energy.

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