| 摘要 |
<p>In a radio frequency identification (RFID) system using intelligent tags, amplitude and phase noise is minimized by using a low noise crystal oscillator (70) having an output frequency which is an integer multiple of the desired RF field frequency, then dividing this frequency using cascaded flip-flops for the frequency divider (72). Both outputs of the final stage flip-flop drive the transmitter antenna (34) to produce a continuous wave signal. Fiber optics (44) communicate analog tag response signals from the output of the receiver circuit (24) to the input of a tag response signal anlyzing module (20) including a digital signal processor (DSP 38), thus providing electrical isolation between these circuit elements, breaking ground loops, stopping internal switching noise from the DSP (38) from entering the receiver circuitry (24), and preventing common mode signals from interfering with the desired RFID tag signal.</p> |
