Transversal filter
AssigneeEpcos AG
InventorsJacques Antoine Damy, Raphael Lardat, Michel Peracchia
Life of this patent
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Abstract
The filter includes at least one acoustic track formed on a piezoelectric substrate. At least one SAW input transducer and at least one SAW output transducer are arranged in each track. Each track has a RSPUDT structure and thus a distributed excitation. The excitation function includes sources arranged in a main lobe and a tail function including at least one tail lobe. A fine and precise approximation to the desired continuous excitation function is obtained by decreasing the excitation strength in the tail function by a factor of at least 2.
Claims20
A transversal filter, comprising
- a piezoelectric substrate;
- at least one acoustic track formed on the piezoelectric substrate;
- and
- at least one SAW input transducer and at least one SAW output transducer arranged in each track;
- wherein at least one input transducer and at least one output transducer has a distributed excitation comprising
- a continuous excitation function having a main lobe and at least one tail lobe with a sign of excitation different than the main lobe;
- and
- an excitation strength S in the main lobe being greater than an excitation strength G of the at least one tail lobe by a factor of x, where 8≧x≧2, x and x is a real number;
- wherein the at least one input transducer of each track is divided into a main lobe sub-transducer and a tail lobe sub-transducer by electrically separating at least one bus bar of the input transducer into two parts;
- wherein the main lobe and tail lobe sub-transducers adjoining each other in a longitudinal direction;
- and
- wherein the main lobe of excitation being assigned to the main lobe sub-transducer, the at least one tail lobe being assigned to the tail lobe sub-transducer.
A transversal filter, comprising:
- a piezoelectric substrate;
- at least one acoustic track formed on the piezoelectric substrate;
- and
- at least one SAW input transducer and at least one SAW output transducer arranged in each track;
- wherein at least one input transducer and at least one output transducer has a distributed excitation comprising
- a continuous excitation function having a main lobe and at least one tail lobe with a sign of excitation different than the main lobe;
- and
- an excitation strength S in the main lobe being greater than an excitation strength G of the at least one tail lobe by a factor of x, such that S=x G where 3≦x≦5.
A transversal filter, comprising:
- a piezoelectric substrate;
- at least one acoustic track formed on the piezoelectric substrate;
- and
- at least one SAW input transducer and at least one SAW output transducer arranged in each track;
- wherein at least one input transducer and at least one output transducer has a distributed excitation comprising
- a continuous excitation function having a main lobe and at least one tail lobe with a sign of excitation different than the main lobe;
- and
- an excitation strength S in the main lobe being greater than an excitation strength G of the at least one tail lobe by a factor of x, where 8≧x≧2, x and x is a real number;
- wherein each track comprises an input transducer and an output transducer, the input transducer and output transducer being similarly divided in sub-transducers;
- wherein a tail lobe sub-transducer of the input and output transducer directly adjoin each other;
- wherein the sub-transducers of the output transducer being circuited between two output terminals;
- and
- wherein an electrical connection of the sub-transducers between two input terminals is symmetrical to an electrical connection of sub-transducers between the two output terminals.
Dependencies are inferred from the claim text.