2.4 GHz front-end multi-track AlN/α-Al2O3 SAW matched filter

Aluminum nitride (AlN) is a promising piezoelectric material for GHz surface-acoustic-wave (SAW) device application. We have reported the design and fabrication of the 2.4 GHz front-end AlN/α-Al₂ O₃ SAW matched filters and SAW delay lines. Furthermore, the implementation of a low-power 2.4 GHz spread spectrum (SS) wireless modem using the 2.4 GHz front-end AlN/α-Al₂ O₃ SAW matched filter has been reported. When the center frequency of the fabricated SAW matched filter is deviated from the designed center frequency due to the SAW velocity fluctuation of AlN/α-Al₂O₃ structure, the correlation intensity is degraded; this causes the degradation of demodulation performance of SS modem. The 3-dB correlator bandwidth of 2.4 GHz front-end AlN/α-Al₂O₃ SAW matched filter for 11-chip Barker code and 23-Mcps chip rate is found to be 1.2 MHz. Then we have estimated the correlator bandwidth is required to be 3-5 MHz for practical use. In order to expand the correlator bandwidth, we have proposed the multi-track SAW matched filter in which plural SAW matched filters are implemented on the AlN/α-Al₂O₃ substrate at the same time and are connected electrically in parallel. It has been shown that the 3-track SAW matched filter has the 3-dB correlator bandwidth of 3 MHz, which is sufficient for practical 2.4 GHz front-end AlN/α-Al₂O₃ SAW matched filter