Improved Trapezoidal SAW Filter with On-Chip Inductance
The performance of small-volume surface acoustic wave(SAW)filters is significantly affected by packaging.To solve this problem,a new SAW trapezoidal filter circuit topology is proposed.By analyzing the phe-nomenon of the upturn of the remote rejection caused by the packaging of the filter at high frequency,the layout de-sign is changed from the circuit structure to realize the on-chip inductance.The circuit topology that combines the conventional trapezoidal filter structure with the special grounding structure of the longitudinally coupled dual-mode resonator type filter(DMS)contributes to out-of-band rejection and design flexibility.The optimal topology of the high-order RF SAW filter with a center frequency of 2 580 MHz,bandwidth of 50 MHz,and an insertion loss of less than 2.5 dB is obtained via simulation analysis on a standard 42°Y-X lithium tantalate(LiTaO3)substrate.
packagesurface acoustic wave(SAW)filteron-chip inductancedual-mode resonator type filter(DMS)structuretransmission zeroout-of-band inhibition
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