RFID Readers for the HDX Protocol


Posted on Feb 6, 2014

Upper traces show voltages VOUT, lower traces show transients. Frequency transition at 500 us. Figure 16. Upper: baseband signal from simulator in FDX mode retrieved by reader. Middle: digital signal on simulator LOADMOD line that generated the upper trace. Lower: baseband signal retrieved from an FDX tag. Figure 20. Upper: input signals VIN12 and VIN2 fed one after the


RFID Readers for the HDX Protocol
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other to the same system. The traces above the signals show the trigger provided by the simulator. Lower: signals superimposed for displaying overlap condition Figure 21. Effect on transients on bit decoding. Upper traces: signal amplified by reader. Middle traces: transient induced by transition (note that only the part that follows the transition represents the transient). Lower traces: trigger at transition provided by simulator. Figure 22. Scope visualization of frequency transition generated with the tag simulator, after application of equalization of bit amplification. Traces have same meaning as in figure 21. Previous work ( Gelinotte et al. , 2006 ; Vuza et al. , 2007 ; Vuza et al. , 2009 ) presented the contribution of the present authors to the development of readers for communication with tags according to the FDX protocol. Readers produced so far by Frosch Electronics were classified as voltage-driven and current-driven ( Vuza et al. , 2009 ), according to which circuit variable is controlled by the reader and which is controlled by the tag (and sensed by the reader). A voltage-driven reader powers the antenna with an AC voltage of constant amplitude. The FDX tag transmits data by load modulation, which causes the variation of the voltage at the tap point (the junction between the antenna coil and the tuning capacitor). The reader senses the latter voltage and extracts the baseband signal that contains the...




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