Measuring tag side bands in ETSI and ISO
RAIN RFID is based on ISO/IEC 18000-63 / GS1 EPC UHF Gen2. For the deployment of RAIN RFID products and system several other standards are available. Besides the conformance standards we have performance standards and radio regulations.
One important radio regulations standard is ETSI EN 302 208, which is referred by the RED (Radio Equipment Directive). EN 302 208 requires tag sideband measurements for RFID tags in order to ensure that the tag sidebands do not exceed a certain level. The tag sidebands are relevant for the co-existence of multiple RF devices, like RFID tags and SRDs (Short Range Devices) in the same channel. Due to physics tag sidebands are appearing on both sides of RFID Reader transmit channels. An SRD, or another RF device, will always use one channel only. For that reason the sideband measurements as defined in EN 302 208 are always only considering ONE sideband.
RFID performance tests are done according to ISO/IEC 18046-2 for readers and ISO/IEC 18046-3 for tags. Different to the ETSI standard these standards consider BOTH sidebands of the tag response when defining performance criteria. A RAIN RFID reader benefits of 3 dB more signal, when considering both sidebands, which results in more communication range. However, it is also essential that the reader also filters away (or applies even advanced methods) the carrier itself, which may come from reflection of the tag. The carrier in the reader receiver is like-self jamming and reduces the sensitivity of the reader by overloading the receiver.
Summarizing, this means that the ETSI EN 302 208 standard measurements are done in respect to interference and therefore only one tag sideband needs to be considered, as only one sideband could fall into a single channel. For ISO/IEC 18046 performance testing it is relevant to consider exactly and just both sidebands as they provide all power where the data of the tag response is contained.