Design and Development of Narrow-Band TCSAW Filter with Low Insertion Loss
A shunt-capacitance-type ladder-type topology was proposed by adding a shunt capacitance in a ladder-type topology to further reduce the insertion loss of a narrow-band filter.The shunt capacitance was used to modify the anti-resonant frequency of the resonator for reducing the bandwidth of the filter with sacrificing low insertion loss.A narrow-band temperature compensated SAW(TCSAW)filter with low insertion loss based on a SiO2/Cu/127°YX-LiNbO3 structure was developed successfully via resonator design and evolutionary algorithm optimization.The experimental results indicate that the center frequency of the filter,relative bandwidth,and passband insertion loss are 1 514 MHz,0.46%,and only 1.45 dB,respectively.Further,the attenuation at the frequency 20 MHz outside the passband decreases to 24 dB,remote out-of-band attenuation is greater than 30 dB,attenuation at the WiFi band is up to 48 dB,TCF is-20×10-6/℃,and the size of the device is 1.1 mm×0.9 mm.
TCSAW filterladder-type topologyshunt capacitancenarrow-bandlow insertion loss
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