Matsushita Electric Industrial Co., Ltd.

Masao Akimoto

Toshiharu Tanaka

Kenroku Tani

Daishiro Hayakawa

Katsumi Narita

Comb filter having a comb like band pass characteristic curve by using an ultrasonic delay line (9) is improved to reduce its size. An input signal is given through an impedance element 13 to a single terminal 10a of an improved delay line 9, wherein the single terminal serves as the input terminal and at the same time as the output terminal. Signals at both ends of the impedance element 13 are given to a mixing circuit 15 for summing or subtracting thereby. In the improved delay line 9, the ultrasonic wave radiated from the input terminal travels twice the conventional delay line and comes back to the original terminal, and thereby a sufficient propagation distance is obtainable in a small delay line.

Comb filter

Herein disclosed is a reed type electromechanical filter device which comprises a vibrator element having a pair of spaced parallel arm portions adapted to vibrate in lateral directions, a pair of piezoelectric ceramic plates or electromechanical transducer elements mounted on the arm portions of the vibrator element, and a pair of elastic metal members respectively mounted on the outer side faces of the arm portions and/or a pair of elastic metal members respectively mounted on the inner side faces of the arm portions. The elastic metal members are effective to prevent the arm portions from directly striking against each other and/or the inner faces of side walls of a housing enclosing the vibrator element in the event the filter device is subjected to a violent impact which would otherwise cause deterioration of the performance quality of the filter device.

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Kadoma, Japan

Masao Akimoto