On-chip correlation-a new approach to narrow band SAW identification tags

SAW devices are characterized by particularly good coding and correlation capabilities which are used in matched filter application. If the signal code given to such a device corresponds to a code implemented in a correlation device there will be generated a typical correlation peak at its output. In the case of an “on-chip-correlation” (OCC) device the correlation function is used to create a peak in form of a surface acoustic wave on the chip. The first test device consists of two different PSK coded SAW structures which are connected to the antenna over a common signal bus. When the device is interrogated by a coded RF signal the input transducer generates a wave pulse (OCC peak). Passing the second PSK transducer the impulse will generate a PSK signal corresponding to the structure of the second transducer. The coded signal will be transferred back to the interrogation unit and thus identify the measured object. It is ensured that the interaction between different transducer codes does not falsify the output signal. The advantage of the new device is an “impulse-free” interrogation so that the used bandwidth does not oversize the allowed 1.74 MHz bandwidth and the European ISM standard can be fulfilled. The design, simulation and experimental results of the 80 MHz and the 433.92 MHz device setup were introduced and discussed