Surface wave transversal frequency filter

Claim 2

A transversal frequency filter comprising: a piezoelectric substrate, a first filteR section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, switching means for coupling to said filter sections, said switching means having a first position for coupling in phase to said first and second sections and a second position for coupling to one of said sections with a 180* phase displacement from the signal of said other section, and means for providing an electrical connection for said filter.

Claim 3

A transversal frequency filter as set forth in claim 1 wherein the overlap length of the electrodes of each tap of said first and second filter sections varies in accordance with an approximation of the function sin x/x.

Claim 4

A transversal frequency filter as set forth in claim 1 wherein the first tap of each additional tap of said first filter section are oriented in a first direction on said substrate, and the first tap of each additional tap of said second filter section are oriented in a direction opposite to taps of said first section.

Claim 5

A transversal frequency filter as set forth in claim 1 wherein the spacing between electrodes of said taps is related to the center frequency of the filter bandwidth.

Claim 6

A transversal frequency filter as set forth in claim 1 wherein the overlapping length of each additional tap of said filter sections after said first tap is related to a given time harmonic.

Claim 7

A transversal frequency filter as set forth in claim 1 wherein the overlapping length of the electrodes of each tap of said filter sections forms a pattern related to the bandwidth of frequencies passed by said filter.

Claim 8

A transversal frequency filter system, comprising: a piezoelectric substrate, a first filter having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, a second filter having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate, each tap spaced a predetermined distance from said first tap, switching means coupled to said first and second filters for selectively controlling the phase relationship of input signals applied to said first and second filters, and means coupled to said substrate for detecting the output signal generated by said filter system.

Claim 9

A transversal frequency filter system, comprising: a piezoelectric substrate, a first filter having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, a second filter having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate, each tap spaced a predetermined distance from said first tap, switching means coupled to said first and second filters for selectively controlling the phase relationship of input signals applied to said first and second filters, and means coupled to said substrate for detecting the output signal generated by said filter system.

Claim 10

A transversal frequency filter system as set forth in claim 7 wherein the overlap length of the electrodes of each tap varies in accordance with an approximation of the function sin x/x.

Claim 11

A transversal frequency filter system as set forth in claim 8 wherein the outline of the overlapping electrodes as varying in accordance with the function sin x/x is related to the overall bandwidth of the passed frequency for each filter.

Claim 12

A transversal frequency filter system as set forth in claim 7 wherein the spacing between electrodes of said tap is related to the desired center frequency of each of said filters.

Claim 13

A transversal frequency filter system as set forth in claim 7 wherein the electrodes of each additional tap of said filters has an overlapping length related to a time harmonic of the periodicity of a band pass - band stop periodicity in the frequency domain.

Claim 14

A transversal frequency filter system, comprsing: a pieZoelectric substrate, a first filter including a first filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate, each spaced a predetermined distance from said first tap, said first filter further including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, a second filter including a first filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, said additional filter further including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, and first and second coupling means one connected to the first and second filter sections of each of said filters, each of said coupling means having a first position for connecting a signal to each of said filter sections in phase and having at least one additional position for connecting a signal to the first of said sections in each filter with a phase displacement from the signal supplied to the second section of each filter.

Claim 15

A transversal frequency filter system, comprsing: a pieZoelectric substrate, a first filter including a first filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate, each spaced a predetermined distance from said first tap, said first filter further including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, a second filter including a first filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, said additional filter further including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, and first and second coupling means one connected to the first and second filter sections of each of said filters, each of said coupling means having a first position for connecting a signal to each of said filter sections in phase and having at least one additional position for connecting a signal to the first of said sections in each filter with a phase displacement from the signal supplied to the second section of each filter.

Claim 16

A transversal frequency filter system as set forth in claim 12 including: a second piezoelectric substrate, a first filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said second substrate for generating a signal responsive condition in said crystal, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said second substrate each spaced a predetermined distance from said first tap for generating an additional signal responsive condition, a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said second substrate for generating a signal responsive condition in said crystal, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said second substrate each spaced a predetermined distance from said first tap for generating an additional signal responsive condition, switching means connected to said coupling means of said second filter for coupling a signal to said filter sections on said second substrate, said switching means having a first position for applying the input signal in phase to said first and second sections on said second substrate and at least one additional position for applying the signal to one of said sections to produce a phase displacement from the signal applied to said other section, and means defined for providing an electrical connection for said filter system.

Claim 17

A transversal frequency filter system as set forth in claim 13 wherein the overlap length of each electrode in the taps of said filters varies in accordance with an approximation of the function sin x/x.

Claim 18

A transversal frequency filter system as set forth in claim 14 wherein the overlap length of each electrode in the taps of said filters is related to the overall bandwidth of the frequencies passed by each of said filters.

Claim 19

A transversal frequency filtering system as set forth in claim 15 wherein the spacing between electrodes of each tap of said filter is related to the desired center frequency of each filter bandwidth.

Claim 20

A transversal frequency filtering system as set forth in claim 13 wherein said switching means includes a switch having a first position for applying an input signal in phase to said first and second sections of said filter and a second position for applying the signal to one of said sections to produce a 180* phase displacement from the signal applied to said other section.

Claim 21

A surface wave frequency filtering system, comprising: a first filter including a first filter section having a first tap of substantially parallel spaced interdigital electrodes defined on a substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on the same substrate each spaced a predetermined distance from said first tap, said filter further including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on the same substrate each spaced a predetermined distance from said first tap, said filter further including means for providing an electrical connection to said filter sections, said means having a first position for connecting in phase to said first and said second sections and a second position for connecting to one of said sections with a 180* phase displacement from said other sections, and means for providing an output terminal for said filter, at least one additional filter each including a first section having a first tap of substantially parallel spaced interdigital electrodes defined on a substrate for, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on the substrate each spaced a predetermined distance from said first tap, said additional filter including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on the same substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, each of said additional filters further including output means defined on the substrate for providing an output terminal for said filter, and means for coupling each of said additional filters to said first filter in a ''''tree'''' arrangement, said means coupling to the filter sections and having a first position for applying a signal in phase to the first and second sections of a respective filter and a second position for applying a signal to one of said sections of the respective filter to produce a 180* phase displacement from the signal applied to said other sections.

Claim 22

A surface wave frequency filtering system, comprising: a first filter including a first filter section having a first tap of substantially parallel spaced interdigital electrodes defined on a substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on the same substrate each spaced a predetermined distance from said first tap, said filter further including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on said substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on the same substrate each spaced a predetermined distance from said first tap, said filter further including means for providing an electrical connection to said filter sections, said means having a first position for connecting in phase to said first and said second sections and a second position for connecting to one of said sections with a 180* phase displacement from said other sections, and means for providing an output terminal for said filter, at least one additional filter each including a first section having a first tap of substantially parallel spaced interdigital electrodes defined on a substrate for, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on the substrate each spaced a predetermined distance from said first tap, said additional filter including a second filter section having a first tap of substantially parallel spaced interdigital electrodes defined on the same substrate, and at least one additional tap of substantially parallel spaced interdigital electrodes defined on said substrate each spaced a predetermined distance from said first tap, each of said additional filters further including output means defined on the substrate for providing an output terminal for said filter, and means for coupling each of said additional filters to said first filter in a ''''tree'''' arrangement, said means coupling to the filter sections and having a first position for applying a signal in phase to the first and second sections of a respective filter and a second position for applying a signal to one of said sections of the respective filter to produce a 180* phase displacement from the signal applied to said other sections.

Claim 23

A surface wave frequency filtering system as set forth in claim 18 wherein the overlap length of each electrode in the taps of each filter varies in accordance with an approximation of the function sin x/x.

Claim 24

A surface wave frequency filtering system as set forth in claim 19 wherein the spacing between electrodes of each tap of said filters is related to the desired center frequency of each filter bandwidth.

Claim 25

A transversal frequency filter comprising: a piezoelectric substrate, a first filter section having a first tap including a first set of substantially parallel electrodes defined on said substrate, a second set of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second arrays of electrodes, said first filter section including at least one additional tap each having a first set of substantially parallel electrodes defined on said substrate, a second set of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second sets of electrodes, each additional tap spacEd a predetermined distance from said first tap, a second filter section having a first tap with a first array of substantially parallel electrodes defined on said substrate, a second array of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second sets of electrodes, said second filter section having at least one additional tap with a first set of substantially parallel electrodes defined on said substrate, a second set of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes, and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second sets of electrodes, each additional tap spaced a predetermined distance from said first tap, means for coupling an input signal to said filter sections, said means having a first position for applying an input signal in phase to said first and second sections, a second position for applying a signal to one of said sections with a 120* phase displacement from a signal applied to said other section, and a third position for applying a signal to one of said sections with a 240* phase displacement from the signal applied to said other section, and means defined on said substrate for providing a connection for said filter.

Claim 26

A transversal frequency filter comprising: a piezoelectric substrate, a first filter section having a first tap including a first set of substantially parallel electrodes defined on said substrate, a second set of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second arrays of electrodes, said first filter section including at least one additional tap each having a first set of substantially parallel electrodes defined on said substrate, a second set of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second sets of electrodes, each additional tap spacEd a predetermined distance from said first tap, a second filter section having a first tap with a first array of substantially parallel electrodes defined on said substrate, a second array of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second sets of electrodes, said second filter section having at least one additional tap with a first set of substantially parallel electrodes defined on said substrate, a second set of substantially parallel electrodes defined on said substrate interleaved with said first set of electrodes, and a third set of substantially parallel electrodes defined on said substrate interleaved with said first and second sets of electrodes, each additional tap spaced a predetermined distance from said first tap, means for coupling an input signal to said filter sections, said means having a first position for applying an input signal in phase to said first and second sections, a second position for applying a signal to one of said sections with a 120* phase displacement from a signal applied to said other section, and a third position for applying a signal to one of said sections with a 240* phase displacement from the signal applied to said other section, and means defined on said substrate for providing a connection for said filter.

Claim 27

A transversal frequency filter as set forth in claim 21 wherein said first, second and third sets of electrodes respectively for each of said filter section taps has a periodicity corresponding to one acoustic wavelength of the center frequency of a filtering bandwidth.

Claim 28

A transversal frequency filter as set forth in claim 21 wherein the overlap length of the electrodes of each tap of said first and second filter sections varies in accordance with an approximation of the function sin x/x.

Claim 29

An acoustic surface wave transversal frequency filter comprising: a piezoelectric substrate, a plurality of filter sections defined on said substrate along a common acoustic channel at preselected spaced loctions, each of said filter sections defined by a plurality of interleaved parallel electrodes defining a preselected center frequency, the electrode overlap of adjacent electrodes in each filter section defining a selected weighting function corresponding to the desired filter function, preselected ones of said plurality of filter sections spaced on said substrate at loctions corresponding to harmonics of said center frequency, the overlap of respective electrodes of said preselected filters defining a fraction of the corresponding electrode overlap of filter sections disposed at locations corresponding to the fundamental mode of said center frequency, means coupled to said filter sections for simultaneously applying an input signal thereto, said filter sections effective responsive to said input signal, to generate an acoustic surface wave in said substrate corresponding to the filter function defined by said filter sections; and means disposed on said substrate along said acoustic channel for detecting acoustic surface waves propagating therealong and providing electrical output signals responsive thereto.

Claim 30

An acoustic surface wave transversal frequency filter comprising: a piezoelectric substrate, a plurality of filter sections defined on said substrate along a common acoustic channel at preselected spaced loctions, each of said filter sections defined by a plurality of interleaved parallel electrodes defining a preselected center frequency, the electrode overlap of adjacent electrodes in each filter section defining a selected weighting function corresponding to the desired filter function, preselected ones of said plurality of filter sections spaced on said substrate at loctions corresponding to harmonics of said center frequency, the overlap of respective electrodes of said preselected filters defining a fraction of the corresponding electrode overlap of filter sections disposed at locations corresponding to the fundamental mode of said center frequency, means coupled to said filter sections for simultaneously applying an input signal thereto, said filter sections effective responsive to said input signal, to generate an acoustic surface wave in said substrate corresponding to the filter function defined by said filter sections; and means disposed on said substrate along said acoustic channel for detecting acoustic surface waves propagating therealong and providing electrical output signals responsive thereto.

Claim 31

A transversal frequency filter as set forth in claim 24 wherein said plurality of filter sections comprise: first and second filter sections disposed on said substrate adjacent one another along a common acoustic channel, thereat defining the fundamental mode of said center frequency; adjacent electrodes thereof defining a maximum overlap corresponding to a preselected weighting function; and third and fourth filter sections disposed along said acoustic channel respectively adjacent said first and second sections, spaced therefrom by a distance corresponding to a preselected harmonic of said center frequency, the overlap of adjacent electrodes of said third and fourth sections defining A fraction of said maximum overlap of corresponding adjacent electrodes of said first and second sections.

Claim 32

A transversal frequency filter as set forth in claim 25 wherein said preselected weighting function substantially corresponds to the function sin x/x.

Claim 33

A transversal frequency filter as set forth in claim 24 wherein said means for coupling an input signal to said filter sections includes switching means for selectively controlling the phase relationship between respective filter sections.