Simultaneous Gen2 Inventory and Angle of Arrival Measurement of Backscatter Signals with Multiple Commodity SDRs
Simultaneous Gen2 Inventory and Angle of Arrival Measurement of Backscatter Signals with Multiple Commodity SDRs
复制标题
使用多种商品 SDR 同时进行第二代库存和反向散射信号到达角测量
DOI：
10.1109/jrfid.2021.3079299
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发表时间：
2021
影响因子：
3.1
通讯作者：
Jin Mitsugi and Yuusuke Kawakita
中科院分区：
文献类型：
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作者：
Jin Mitsugi and Yuusuke Kawakita
在物品搜索应用中，迫切需要UHF射频标签的同步库存和到达角（AoA）测量。现有射频标签的高精度AoA测量主要采用由多天线和相干接收器组成的无线电来产生同步的多个IQ流。这种无线电是用专用的硬件和软件实现的，不适合用于新想法的原型设计。本文提出了一种利用带有四个接收天线的两个商品软件定义无线电（sdr）实现同时库存和AoA测量的方法。通过使用两个RF开关从四个天线中依次选择两个天线，并使用RF开关物理切换这两个天线和接收器的组合，可以消除两个sdr之间的互相偏移。这样就可以在盘点过程中进行SDR接收机相位校准，无需人工干预。四个天线单元的AoA测量只需要两个sdr就可以实现，但会影响AoA测量的敏捷性。利用空间平滑来解决多径问题。天线交换集成到基于双射频端口USRP开发的SDR Gen2询问器中。外部RF开关与Gen2库存进度同步控制，使用Gen2协议功能称为动作和目标。通过对商用Gen2射频标签进行有线和无线实验，评估了相位偏移抵消的准确性。实验表明，在衰减稳定的情况下，在室内环境下，使用4根接收天线同时进行AoA测量，测量精度在±15度以内。
Simultaneous inventory and angle of arrival (AoA) measurement of UHF RF tags is strongly demanded in item searching applications. Existing high-accuracy AoA measurements of RF tags mainly employ a radio comprised of multiple antennas and a coherent receiver to produce synchronized multiple IQ streams. Such radios are realized as dedicated hardware and software, which is not suitable for prototyping new ideas. This paper proposes a method to realize simultaneous inventory and AoA measurement with two commodity software defined radios (SDRs) with four receiving antennas. The mutual phase offset between the two SDRs is canceled by sequentially selecting two antennas from the four antennas with two RF switches and physically switching the combination of these two antennas and the receivers with an RF switch. In this way, the SDR receiver phase calibration can be performed during the process of inventory without human intervention. AoA measurement with all four antenna elements can be realized only with two SDRs with a penalty on the AoA measurement agility. Spatial smoothing is applied to counter the multipath problem. The antenna switching is integrated into an SDR Gen2 interrogator developed on a dual RF-port USRP. The external RF switch is synchronously controlled along with Gen2 inventory progress using Gen2 protocol features called action and target. The accuracy of the phase offset cancellation is evaluated by conducting wired and wireless experiments with commercial Gen2 RF tags. The experiments reveal that the AoA measurement can be simultaneously performed with Gen2 inventory achieving within ±15 degree accuracy with four receiving antennas in an indoor environment when the fading is stable over the measurement duration.