Performance Comparison of RFID Tag at UHF Band and Millimeter-Wave Band

Abstract

The ultra high frequency (UHF) band spectrum will likely be congested in near future since the next generation wireless as well as Radio Frequency Identification (RFID) system users will witness the use of UHF band technology with increased demand of bandwidth, bit rate, frequency spectrum and power consumption. The alternate solution is the use of millimeter-wave band technology. It is possible to improve data throughput, range resolution and multi-user capability in mm-wave band RFID system. ‘Higher power reception efficiency and lower side lobe level (SLL) of radiation pattern’ is required for RFID system that will increase the tag range and transmission bit rate. At the same time lower SLL will minimize the interference level. Beam pointing error is another problem of UHF band antenna which reduces the tag range and bit rate. These problems can be minimized by using large number of antenna elements. But with UHF band signal it is practically difficult to construct large array antenna; since the array size becomes tremendously larger with the increase of antenna elements. ‘Higher power reception efficiency and lower SLL’ can practically be obtained by using non-uniform power distribution of large number of antenna elements in millimeter wave band. A new and technically better method of beam forming by implementing the concept of staircase power distribution (SPD) of antenna elements at 60 GHz has been investigated and presented in the paper. The SPD method is compared with Gaussian edge tapering method. It was found that the maximum SLL (MSLL) is the lowest in case of SPD. The beam efficiency of SPD is also equivalent to that of Gaussian edge tapering method. It is easier to fabricate a larger number of antenna elements within smaller area with SPD at 60 GHz system; since the antenna size is smaller and the number of different power distribution in SPD case is less and stepwise uniform. Uniform and less number of different power distribution of SPD also minimizes other technical errors.