US Government As Represented by the Secretary of the Army

Elio A Mariani

Richard A Stern

William J Skudera, Jr

Arthur D Ballato

Raymond C McGowan

Richard W Babbitt

Clinton S Hartmann

Stuart D Albert

James T Stewart

A surface acoustic wave (SAW) sensing device for remotely sensing structu integrity of a physical structure. The sensing device includes a piezoelectric substrate with a notch formed part way in the bottom of the substrate and along the width thereof. The substrate is mounted to a physical structure of interest. An antenna is coupled to the RF circuit on the substrate and is capable of receiving and transmitting a RF signal. Interdigital input and output transducers are disposed on the upper surface of the substrate. The input transducer is located adjacent one end of the substrate and the output transducer is located adjacent an opposing end of the substrate. Bus bars connect the input and output transducers. The input transducer provides a complementary first response upon receipt of an RF expanded linear/nonlinear FM signal from the antenna and transmits this compressed pulse to the output transducer. The output transducer provides a second response upon receipt of the first response and transmits the same to the antenna via the bus bar. When the substrate is strained beyond a predetermined critical level, the substrate is fractured along the notch and the first response emitted by the input transducer is prevented from being transmitted to the output transducer indicating SAW sensor failure and that structural integrity has been compromised.

Remote sensing of structural integrity using a surface acoustic wave

A Passive Surface Acoustic Wave Identification Tag ('SAW-ID tag') device utilizes pulse compression techniques and a large number of coding possibilities for identifying articles at enhanced ranges. The SAW-ID tag device provides a piezoelectric substrate having bus bars, spaced electrode taps between the bus bars and a built-in antenna, with an input chirped SAW transducer having a dispersive, complementary matched filter response to an input expanded chirp signal from an expanded linear FM chirp waveform actively generated by a nearby chirp transmitter. The input expanded chirp signal is fed into the input chirped SAW transducer through the built-in antenna, to compresses the input expanded chirp signal into a narrow, compressed pulse signal propagating toward the electrodes taps. The spacing of the electrode taps establishes the desired unique time-ordered coding. The electrode taps sample the narrow, compressed pulse signal and provide narrow, compressed pulse samples propagating a coded, pulse train output transmitted via the antenna to a nearby interrogation means to identify the tagged article. The preferred embodiment is an SAW-ID tag device with a piezoelectric quartz substrate about 1 inch long, a built-in dipole antenna and five (5) spaced electrode taps, establishing several million coding possibilities. Also disclosed are methods of identifying articles using an SAW-ID tag device, and methods of selectively disconnecting and connecting electrodes to facilitate mass production.

Passive SAW-ID tags using a chirp transducer

A planar, magnetically-tunable, band-rejection filter comprising a slot-l having at least one magnetically tunable, dielectric resonator-stack positioned on its top surface. The core of each resonator stack is filled with ferrite material. As a result, the filter provides a higher 'Q', and thus provides greater suppression of unwanted microwave and millimeter-wave signals than the prior art.

Planar magnetically-tunable band-rejection filter

A planar preselector filter with tunable narrowband excision composed of a errite substrate having a microstrip line with a fixed-tuned bandpass filter on one surface and a plurality of slotline resonators etched in a ground plane on an opposing surface. The fixed tuned bandpass filter is composed of short resonant elements of microstrip, having a length that is one-half the guide wavelength at the center frequency of its passband. The slotline resonators are positioned on the opposing surface of the substrate such that it suppresses or excises a predetermined narrowband of frequencies within the passband of the fixed-tuned bandpass filter. Moreover, the center frequency of the narrowband excision is varied by applying a tunable magnetic bias field of a predetermined strength across the ferrite substrate.

Preselector filter with tunable narrowband excision

Two wide dynamic range detection circuits are disclosed, which are capable of detecting low-level desired signals in the presence of nearby strong interfering signals. Each circuit includes an attenuator scheme for attenuating the interfering signal while passing the desired signal. The first attenuator scheme uses a YIG filter in combination with an automatic gate arrangement. The second attenuator scheme uses a two-channel arrangement. The first channel uses a chirp-Z processor to derive a pulse-type transform signal in response to the strong interference signal. The second channel includes a YIG filter followed by a programmable notch filter which is controlled by the interference-signal pulse from the first channel. Following the programmable notch filter in the second channel is a chirp-Z processor followed by a gate arrangement wherein the gates are switched 'OFF' under control of the interference-signal pulse from the first channel.

Wide dynamic range detection circuit

A sensor for chemical vapor detection using a surface acoustic wave (SAW) ray that provides a means for simultaneously detecting several chemical agents. The sensor has a piezoelectric substrate and a bidirectional surface acoustic wave transducer on the substrate. Also on the substrate are several pairs of identical acoustic sensing and reference channels each on opposite sides of the transducer in a mirror image fashion. Each channel pair has a thin film capable of absorbing a chemical vapor to be monitored and a metallic surface acoustic wave grating reflector capable of receiving and reflecting surface acoustic waves through the thin film and back to the transducer. An acoustic absorber separates each channel. The reference channels are protected from ambient conditions while the sensing channels are exposed to such conditions. An RF signal is applied to the transducer causing the propagation of an acoustic signal into each of the sensing channels and reference channels. Output signals from the transducer are then detected. The array is preferably in a miniature configuration which is suitable for wearing on a person's wrist or arm.

Surface acoustic wave (SAW) chemical multi-sensor array

A dual channel flexural device is fabricated on a gallium arsenide (GaAs) bstrate that includes a pair of elongated active vibrating (GaAs) bars formed in the substrate that serve as acoustic waveguides. One of the bars serves as a reference channel, while the other bar is covered with a chemically sensitive coating and operates as a sensing channel. A pair of pseudo-surface acoustic wave (SAW) transducers serving as input and output transducers are located at each end of the bars. Each of the transducers is comprised of discontinuous U-shaped elements having dimensions and mutual separations of one half the acoustic operating wavelength formed on one side of the substrate while ground electrodes are formed thereunder on the opposite side of the substrate. When the transducers are energized, a flexural motion in the bars is set up, causing the bars to vibrate. The vibration of the chemically coated bar changes in response to absorption of vaporous contaminants providing a device which operates in a differential mode for chemical vapor sensing.

Dual-channel flexural acoustic wave chemical sensor

A planar tunable YIG filter assembly comprising a first substrate having on one side thereof spaced ridges, a first conductor spaced from and between the ridges, a dielectric spacer and YIG disk is mounted on said spacer whereby, a bandpass filter is established between said first conductor and a second conductor that is orthogonal with said first conductor and on a second substrate that is in contact with the ridges when means are provided for producing a magnetic field that is perpendicular to the substrate in the area of intersection of the first and second conductors.

Planar tunable YIG filter

A low-loss, wideband SAW transducer operating on a piezoelectric substrate with a longitudinal axis of propagation. The SAW transducer has a plurality of tapered interdigital electrodes that are mounted on the substrate transverse to the propagation axis. The electrode widths and spacings are constant along lines parallel to the axis and are tapered in the direction transverse to the axis. An acoustic-wave reflector having a plurality of elongated, tapered discontinuities or reflective fingers is located on the substrate adjacent one end of the transducer. The spacings and widths of the reflective fingers are similar to those of the electrodes, i.e., the finger widths and spacings are tapered in the direction transverse to the axis and are constant along lines parallel to the axis. Because of the taper, the fingers reflect wideband acoustic waves parallel to the axis.

Unidirectional surface acoustic wave transducer

Disclosed is a coplanar waveguide (CPW) which is connected directly into a balanced SAW transducer' via a tapered coplanar transmission line. Preferably, the CPW transition feeds directly into the 'balanced transducer' such that the ground planes of the CPW taper directly into the outer (grounded) bus bars of the SAW transducer and the center conductor of the CPW feeds directly into the 'hot' center electrode structure of the SAW transducer. This preferred structure is shown in FIG. 1. This balanced SAW transducer configuration provides better electrical shielding for lower electromagnetic feedthrough suppression and lower spurious signal levels. Moreover, the acoustic wave generated by this 'balanced transducer' configuration provides a more uniform acoustic power distribution because the center conductor of the SAW transducer provides a waveguide effect wherein the acoustic energy tends to follow the slow velocity metal structure, thus forming an acoustic waveguide.

Saw transducer with coplanar waveguide transition

A method and apparatus directed to a thin film piezoelectric resonator deposited on a support layer of dielectric material and being configured in the form of a cantilever structure having a base portion formed on an integrated circuit substrate and having an overhanging beam portion joined at one end to the base portion, with the opposite end being unsupported with an air-gap intermediate the beam portion and the substrate. In the fabrication of the resonator, a thin film of dielectric material, e.g. zinc oxide (ZnO) is first deposited on the substrate, but is subsequently removed from beneath the beam portion resulting in the air-gap which is open on three sides and thus results in a greater ease of fabrication. A completely monolithic chemical detector is implemented utilizing a matched pair of these cantilevered air-gap thin film resonators, with one of the resonators further including a coating on one of its electrodes and which is responsive to a predetermined chemical to cause a frequency shift in the presence of the chemical to be detected. In one embodiment of the chemical detector, the frequency outputs of the two resonators are compared with the difference frequency providing an indication of the chemical being detected.

Cantilevered air-gap type thin film piezoelectric resonator

Amplitude error compensation is provided for a surface acoustic wave (SAW) reflective array correlator (RAC) device having a first reflective array grating fed by an input interdigital transducer and a second reflective array grating which feeds the reflected SAW signal output from the first array grating to an output interdigital transducer. A third or auxiliary reflective array grating is disposed between the first and second array gratings to reflect a portion of the SAW signals reflected from the first array grating to the second array grating to an acoustic absorber. The portion of the SAW signals reflected to the acoustic absorber are those SAW signals which when present in the output of the second array grating which is fed to the output transducer produce the unwanted amplitude errors. The third reflective array grating is fabricated of a photosensitive polymer material so that the frequency and amplitude selective configuration of the grating may be obtained by using photolithographic techniques.

Saw reflective array correlator with amplitude error compensating

An amplitude error compensated surface acoustic wave reflective array corator is provided having an input interdigital transducer feeding a first slanted reflective array grating, a second slanted reflective array grating feeding an output transducer and a third, amplitude error compensation slanted reflective array grating feeding the output transducer. The third array grating receives only the leakage surface acoustic waves leaking past the second array grating from the first array grating and has a frequency and amplitude selective configuration which enables it to select those leakage surface acoustic wave signals which when added to the output of the second array grating by means of a multistrip coupler and fed to the output transducer provide an amplitude error compensated output RF signal. The frequency and amplitude selective configuration of the third array grating is obtained by forming the grating of discreet packets of reflectors, controlling the spatial location of the packets along the length of the array, the number and length of the reflectors in each packet and, if reflective grooves are employed, the depths of the grooves.

Amplitude error compensated saw reflective array correlator

Amplitude error compensation is provided for a surface acoustic wave (SAW) lanted array correlator (SAC) device having an input interdigital dispersive slanted array transducer feeding a plurality of frequency dispersed SAW signals to an output interdigital dispersive slanted array transducer over a plurality of parallel, frequency dispersed first paths. A reflective array grating having a frequency and amplitude selective configuration is disposed between the input and the output transducers to reflect along a second path to an acoustic absorber a portion of the SAW signals sent from the input transducer to the output transducer. The second path is perpendicular to and traverses the plurality or first paths. The portion of the SAW signals reflected to the acoustic absorber are those SAW signals which when present in the output of the output transducer produce the unwanted amplitude errors. The reflective array grating is fabricated of a photosensitive polymer material so that the frequency and amplitude selective configuration of the grating may be obtained by using photolithographic techniques.

Saw slanted array correlator with amplitude error compensating polymer

A low-cost SAW device package comprises a ceramic or glass carrier chip, a SAW device substrate mounted on the carrier chip via a conventional adhesive and a package cover mounted over the SAW device by a glass frit. The glass frit provides a tight vacuum seal for the SAW device so that outside contamination is prevented. The package cover is fabricated of a low-cost nonmetallic, non-single crystalline material (i.e. glass) having thermal characteristics similar to or the same as those of the SAW device substrate. The packaged SAW device is mounted into a circuit or subsystem using conventional bonding techniques.

Growing community of inventors

Hamilton Square, NJ, United States of America

Elio A Mariani