Surface wave devices

Claim 2

In a continuous wave broadcast signal receiver having a tunable input stage for selecting a program signal for application to a signal reproducing device, an acoustic filter system defining a band-pass signal-translating channel for translating to said reproducing device a program signal selected by said input stage, said filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; a first interaction device, comprised of interleaved combs of a predetermined number of conductive elements actively coupled to a first surface portion of said body and having input terminals coupled to said input stage, for responding to said selected program signal to launch acoustic surface waves along said body, the number of said conductive elements being selected to establish for said first device a first predetermined response characteristic over a given frequency band; and a second interaction device similarly comprised of interleaved combs of conductive elements actively coupled to a second surface portion of said body but differing in number from said conductive elements of said first device and having output terminals coupled to said reproducing device, for responding to said launched acoustic surface waves to deliver to said reproducing device signal energy translated by said acoustic waves, the number of said conductive elements in said second interaction device being selected to establish for said second device over said frequency band a second predetermined response characteristic which is different from said characteristic of said first device and in conjunction therewith establishes for said filter system a frequency response characteristic having a null point at a predetermined frequency in said band.

Claim 3

An acoustic filter system in accordance with claim 1 in which an edge of said body which is disposed transversely of the direction of propagation of said surface waves is slanted to define with the propagating surface an angle other than 90* .

Claim 4

An acoustic filter system in accordance with claim 1 in which said first interaction device launches a pair of acoustic surface waves which propagate in opposite directions along said body, in which said second interaction device is disposed in the propagation path of one of said pair of waves, and in which a third interaction device, structurally the same as said second interaction device including the same number of said conductive elements, is disposed in the propagation path of the other of said pair of waves.

Claim 5

An acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; and a surface wave interaction device actively coupled to a surface portion of said body and having a maximum interaction with said body at a predetermined frequency, said device being composed of interleaved combs of conductive elements each having the configuration of a segment of a circle and with the spacing between interleaved elements being effectively one-half the length of acoustic waves at said frequency.

Claim 6

An acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; and a surface wave interaction device actively coupled to a surface portion of said body and having a maximum interaction with said body at a predetermined frequency, said device being composed of interleaved combs of conductive elements each having the configuration of a segment of a circle and with the spacing between interleaved elements being effectively one-half the length of acoustic waves at said frequency.

Claim 7

An acoustic filter system in accordance with claim 4 including a second similar interaction device disposed concentrically within said first device and actively coupled to said body.

Claim 8

An acoustic filter system in accordance with claim 5 in which the outermost one of said concentric interaction devices has a greater number of conductive elements than the other of said devices.

Claim 9

In a continuous wave broadcast signal receiver having a tunable input stage for selecting a program signal for application to a signal reproducing device, an acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; a first electrode array, comprised of interleaved combs of conductive elements actively coupled to a first surface portion of said body and having input terminals coupled to said input stage, for responding to said program signal to launch acoustic surface waves along said body, said array being predominantly responsive at a frequency which bears a predetermined relation to the frequency of said program signal and the spacing between said elements of said combs being effectively one-half the length of acoustic surface waves at said predominant frequency; interaction means, comprised of a second similar electrode array coupled to a second surface portion of said body and having output terminals coupled to said reproducing device, for responding to said launched acoustic surface waves to deliver to said reproducing device signal energy translated by said waves; and a pair of inductors connected, respectively, to said electrode arrays to tune out the clamped capacitance thereof, the frequency of maximum response of one of said arrays and the frequency at which said inductor resonates with the clamped capacitance of said one array being different from, but related to, the corresponding frequencies of the other of said arrays to establish a predetermined frequency response for said system. 8. An acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; a surface wave interaction device actively coupled to a surface portion of said body and having a maximum interaction with said body at a predetermined frequency, said device being composed of interleaved combs of conductive elements with the spacing between said elements being effectively one-half the length of acoustic waves at said frequency and said device exhibiting a predetermined clamped capacitance; and an inductor coupled across said combs having a value for resonating with said capacitance at said frequency.

Claim 10

In a continuous wave broadcast signal receiver having a tunable input stage for selecting a program signal for application to a signal reproducing device, an acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; a first electrode array, comprised of interleaved combs of conductive elements actively coupled to a first surface portion of said body and having input terminals coupled to said input stage, for responding to said program signal to launch acoustic surface waves along said body, said array being predominantly responsive at a frequency which bears a predetermined relation to the frequency of said program signal and the spacing between said elements of said combs being effectively one-half the length of acoustic surface waves at said predominant frequency; interaction means, comprised of a second similar electrode array coupled to a second surface portion of said body and having output terminals coupled to said reproducing device, for responding to said launched acoustic surface waves to deliver to said reproducing device signal energy translated by said waves; and a pair of inductors connected, respectively, to said electrode arrays to tune out the clamped capacitance thereof, the frequency of maximum response of one of said arrays and the frequency at which said inductor resonates with the clamped capacitance of said one array being different from, but related to, the corresponding frequencies of the other of said arrays to establish a predetermined frequency response for said system. 8. An acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; a surface wave interaction device actively coupled to a surface portion of said body and having a maximum interaction with said body at a predetermined frequency, said device being composed of interleaved combs of conductive elements with the spacing between said elements being effectively one-half the length of acoustic waves at said frequency and said device exhibiting a predetermined clamped capacitance; and an inductor coupled across said combs having a value for resonating with said capacitance at said frequency.

Claim 11

An acoustic filter system in accordance with claim 8 in which an impedance, comprising a signal source or a load, is coupled across said interaction device and in which the Q of the circuit including said inductor and said impedance is small relative to the effective Q of the circuit which is the electrical analogue of the combination represented by said interaction device in coupled relation with said body.

Claim 12

An acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; a first surface wave interaction device actively coupled to a surface portion of said body and having a maximum interaction with said body at a predetermined frequency; and a second surface wave interaction device actively coupled to a surface portion of said body and spaced from said first device, in a direction parallel to the direction of surface wave propagation, by effectively one-quarter surface wavelengths at said frequency, both of said interaction devices being composed of interleaved combs of conductive elements with the spacing between the elements thereof effectively one-half wavelength of the acoustic surface wave for which said devices exhibit maximum interaction respectiveLy.

Claim 13

An acoustic filter system comprising: a body of piezoelectric material propagative of acoustic surface waves; a first surface wave interaction device actively coupled to a surface portion of said body and having a maximum interaction with said body at a predetermined frequency; and a second surface wave interaction device actively coupled to a surface portion of said body and spaced from said first device, in a direction parallel to the direction of surface wave propagation, by effectively one-quarter surface wavelengths at said frequency, both of said interaction devices being composed of interleaved combs of conductive elements with the spacing between the elements thereof effectively one-half wavelength of the acoustic surface wave for which said devices exhibit maximum interaction respectiveLy.

Claim 14

A system as defined in claim 10 including a signal source for applying a given signal to both said interaction devices but with a phase difference of pi /2 radians. kappa )

Claim 15

An acoustic filter system in accordance with claim 11 in which the corresponding conductive elements of said first and second interaction devices are spaced (P+ kappa s/2, where P is an integer and lambda s is the length of the acoustic waves at said frequency.

Claim 16

An acoustic filter system in accordance with claim 11 in which the spacing of the conductive elements in one of said devices is modified from the half wavelength relation to displace the potential developed across the combs thereof approximately pi /4 radians in one direction relative to the current therein, while the spacing of the conductive elements in the other of said devices is modified from the half wavelength relation to displace the potential across the combs thereof approximately pi /4 radians in the opposite direction relative to the current therein.

Claim 17

An acoustic filter system in accordance with claim 3 in which said interaction devices have a predetermined clamped capacitance, in which inductors are coupled to said interaction devices to tune out the clamped capacitances thereof, and in which the clamped capacitances of said second and third interaction devices are tuned out at a common frequency having a value different from that at which the clamped capacitance of said first interaction device is tuned out.

Claim 18

An acoustic filter system in accordance with claim 3 in which the middle one of said three interaction devices has a maximum interaction at one frequency while the remaining two devices have a maximum interaction at a common frequency which is different from said one frequency.

Claim 19

An acoustic filter system in accordance with claim 1 in which said body has a relative permittivity epsilon r and in which said electrode array is removably coupled to said body and is spaced from the surface thereof by a distance not exceeding d/ epsilon r, where d is the spacing between conductive elements in said array.

Claim 20

An acoustic filter system in accordance with claim 16 in which the conductive elements of one comb of the electrode array are nonuniformly spaced from the interleaved conductive elements of the other comb and in which said electrode array is mechanically coupled to a low acoustic impedance member movable relative to said body to selectively dispose different portions of said electrode array in active coupling relationship with said body.

Claim 21

An acoustic filter system in accordance with claim 17 in which the conductive elements of said one comb fan apart while the conductive elements of the other comb fan together.

Claim 22

An acoustic filter system in accordance with claim 8 in which said interaction device has a maximum interaction with said body at one frequency and in which said inductor resonates with said clamped capacitance at another frequency related to said frequency of maximum interaction to establish a predetermined frequency response for said system.

Claim 23

A wave signal receiver comprising a plurality of cascade-connected acoustic filter systems, individually in accordance with claim 3, in which the interaction devices of said systems exhibit a clamped capacitance, in which an inductor is connected to each such device to resonate with the clamped reactance thereof, and in which the frequency of maximum interaction of the interaction devices of said systems and the frequencies at which the clamped capacitances thereof are resonated are selected relative to one another to provide a predetermined frequency response for said receiver.

Claim 24

A wave signal receiver comprising at least two cascade-connected acoustic filter systems, individually in accordance with claim 1, in which the number of conductive elements and the frequency of maximum interaction of the interaction devices constituting saId filter systems are different from one another.

Claim 25

A wave signal receiver in accordance with claim 21 in which each of said filter systems comprises three interaction devices with the center one serving as a transmitter and with the remaining two serving collectively as a pickup and in which the two transducers of each such pickup have the same number of conductive elements and a common frequency of maximum interaction.