Band-pass filter with surface acoustic wave devices
AssigneeRockwell International Corporation
InventorCarmine F. Vasile
Life of this patent
Estimating the term…
Abstract
At least one of several transducers on a piezoelectric substrate is externally short-circuited by a series resonance circuit for suppression of triple transit echoes. The resonance circuit is additionally connected to an amplifier via a high input or output impedance. In multi-transducer systems any two transducers are prevented from communicating via echo signals by such resonance circuits. In filter cascades several resonance circuits may be included in the interstage coupling circuit or between the input and output amplifiers on the one hand and the cascade on the other hand.
Claims28
In an electric band pass filter circuit using at least one solid state acoustic surface wave filter device having at least one transmitting transducer coupled to a piezoelectric substrate and at least one receiving transducer coupled to the same substrate to receive surface acoustic waves transmitted by the transmitting transducer, the filter circuit including a drive circuit for and connected to the transmitting transducer and an output circuit for and connected to the receiving transducer, the improvement comprising:
- one of the drive circuit and output circuit being power-matched to the filter device, the respective other one including a resonance circuit resonating at a frequency in the pass band thereby effectively shortcircuiting the respective transducer at least for the one frequency in the filter pass band, so that upon reception of surface waves by the respective transducer the said transducer retransmits at a most neglectable echo;
- and
- said other circuit including a high impedance effective across the capacitor of the resonance circuit, the resonance circuit acting as load impedance converter for said respective transducer.
An electric band pass filter comprising:
- a surface acoustic wave filter having a transmitting transducer coupled to a piezoelectric substrate for launching acoustic surface waves therein, further having a receiving transducer coupled to said substrate for receiving said surface waves;
- and
- circuit means connected to at least one of said transducers for establishing short circuit load impedance across said transducer, for a frequency in the pass band of said filter, for inhibiting the one transducer from launching surface waves in response to electrical signals generated in the one transducer in response to any surface waves received.
An electrical high frequency band pass filtering circuit comprising:
- a surface acoustic wave filter having a piezoelectric substrate cooperating with at least one surface wave transmitting transducer and at least one surface wave receiving transducer, the transducers being acoustically coupled to each other by said substrate;
- first circuit means connected to said transmitting transducer for providing thereto electrical signals driving said transmitting transducer for launching surface waves on said substrate;
- second circuit means connected to said receiving transducer for being responsive to electrical signals generated by the receiving transducer upon receiving said launched surface waves;
- and
- a resonance circuit resonating at a frequency in the pass band of the filter and being included in one of said first and second circuit means to establish short circuit load conditions across the respective one of the transducers as connected to the one circuit means, at least for signals having said frequency so that the respective transducer retransmits at most neglectable surface waves in response to electrical signals generated by the respective transducer in response to surface waves received.
In an electric high frequency band pass filter circuit which connects a source means for such signals to an output and amplifying means, the combination comprising:
- a first surface acoustic wave filter having input and output transducers acoustically coupled by a piezoelectric body;
- first circuit means for connecting the input transducer to said source means;
- a second surface acoustic wave filter having input and output transducers acoustically coupled by a piezoelectric body;
- second circuit means for connecting the output transducer on the second filter to said output and amplifying means;
- third circuit means connecting the output transducer of the first filter to the input transducer of the second filter;
- and
- at least one of said first, second and third circuit means including resonating circuit means for shortcircuiting at least some of the transducers for pass band signal frequencies to inhibit retransmission of a received surface wave signal.
An electrical band pass filter comprising:
- a piezoelectric substrate;
- a plurality of transducers coupled to the substrate, at least one of the transducers provided for launching acoustic surface waves, all of the transducers capable of receiving acoustic surface waves, generating electrical signals in response thereto and retransmitting acoustic surface waves in direct response to the generated electrical signals;
- first circuit means connected to said one transducer for providing thereto electrical signals so that the one transducer launches surface waves;
- second circuit means connected to at least one other of the transducers of the plurality for extracting therefrom pass band signals resulting from stimulation of the one other transducer upon receiving surface waves;
- and
- resonance circuit means included in at least one of the first and second circuit means for short circuiting at least some of said transducers for pass band frequencies thereby retransmitting at most neglectable surface waves so that said second circuit means is stimulated by surface waves only which do not result from any retransmission of surface waves.
Dependencies are inferred from the claim text.