P2N-7 Wide Bandwidth SAW Chirp Filters with Improved Magnitude Response

Three wideband SAW chirp filters are reported. They are 1 GHz central frequency with 400 MHz bandwidth and 10 mus chirp duration, 1.5 GHz central frequency with 600 MHz bandwidth and 10 mus chirp duration, and 2 GHz central frequency with 800 MHz bandwidth and 6 mus chirp duration, respectively. With our regular design and fabrication, the passband has a 2~3 dB peaking at the high frequency end for these wide bandwidth chirp filters. To suppress the peaking, some extra grooves are inserted before the reflective gratings, which partially diffracts the acoustic wave at the peaking frequency. This method has been proven effective and has little degradation on other performances. A chirp transform spectrometer (CTS) based on the 400 MHz bandwidth chirp filters has been built and the spectrum output shows good compressed pulse