Compensation of Diffraction Effects on Group Delay Time and Stop-Band Rejection

Abstract

SAW bandpass filters for application in IF stages of microwave radio systems have to satisfy very strict quality requirements in respect of minimum amplitude and phase distortions. Diffraction effects severely degrade stop-band and group delay time performance and demand compensation in filter design. Correction of phase errors by changing finger positions is not accurate enough because of limited precision in the manufacturing process. A method for compensating amplitude and phase errors, a pplicable on split-finger transducers, is demonstrated, which does not affect electrode positions. Theoretical analysis and experiments show that the described method works well. A filter, having high stop-band attenuation and minimum group delay t ime ripple,is presented.