Abstract:
The SAW sensor in a stainless steel button package having a diaphragm and mounted on a threaded port. Package can hermetically seal a sensor and RFID-antenna assemblies from media. Sensor diaphragm is exposable to media. Sensor and RFID antennas communicate electrically with SAW sensor and RFID device, respectively, for sensor measurements and identification. Antennas receive RF interrogation signal from a nearby interrogator/transceiver and send reflected RF signals back to the interrogator unit containing sensor measurement and sensor ID. TRF signal excites a SAW resonator inside the sensor and causes the SAW to resonate wherein resonant frequency changes with pressure and temperature applied to the sensor. Antennas could be printed circuit board antennas, helical antennas, loop antennas, any other commercially available off-the-shelf antennas or a combination of these.

Description:
RELATED PATENT APPLICATIONS 
   This application is a Continuation-In-Part (CIP) under 25 U.S.C. §120 of U.S. patent application Ser. No. 11/966,076, filed on Dec. 28, 2007, and incorporated herein by reference in its entirety. 

   TECHNICAL FIELD 
   Embodiments are generally related to sensors, and in particular pressure and temperature sensors and systems. Embodiments are also related to surface acoustic wave (SAW) devices, bulk acoustic wave (SAW) devices and, more particularly, to a pressure and/or temperature sensor assembled as a self-contained batteryless, transmitterless system. Embodiments are additionally related to wireless and batteryless pressure and/or temperature sensors used in mobile and industrial applications. 
   BACKGROUND OF THE INVENTION 
   Surface acoustic wave (SAW) devices used as sensors in measurement systems are known. For example, a tire pressure monitoring system (TPMS) helps to improve fuel economy and improve handling and safety by warning the driver about low tire pressure. TPMS is a vehicle-embedded system detecting the tire pressure by analyzing the difference between the wheel speeds or by direct measurement of pressure and temperature. Systems like a direct TPMS system typically consists of one central transceiver in the vehicle and four sensors mounted on the wheel rim, or valve stem to sense pressure and temperature inside the tire, and to organize data transmission to/from the central transceiver. 
   Various other SAW sensor applications are known in the art. In particular, many different techniques have been proposed for sensing the temperature of a component in an industrial process or system. SAW based pressure and temperature sensors, can be used in industrial and commercial systems to convey pressure and temperature values during processing operations such as filling, pumping, drilling, evacuating, dispensing, sealing, machine control, and condition monitoring applications in automotive, food and beverage, dairy, petroleum, medical, aircraft and surface transportation applications. 
   The majority of prior art sensors are direct active systems, some utilizing a silicon micro-electro-mechanical system (MEMS) capacitive or piezo-resistive based sensor powered by a battery. Where several sensors are utilized throughout a target system, pressure and temperature information is transmitted by radio frequencies from each sensor location (e.g., each of the wheels on a motor vehicle) to a central transceiver, located in or around the electronic control unit (ECU) and displayed as either a number or a warning indicator. The problem associated with using such prior art systems in, for example, a TPMS environment is that the need to remove the tire for access to the batteries, and the need to rebalance the tires after battery replacement, together with the disposal of worn out batteries are the major shortcomings of direct sensing systems. Batteries inside tires add weight, have limited life and cannot be replaced. Furthermore, they have inherent battery related performance issues such as temperature dependent voltage and current variations of the battery. These type of variations can cause inaccuracy in the sensor output that result in pressure or temperature reading errors. 
   Conventional wireless systems are not durable and are expensive to design and produce. The sensors and transmitters must also be able to withstand the harsh environment, such as when used inside a vehicle tire that includes high and low temperatures, shock and vibration, and centrifugal forces from tire rotation. Although they also feature wireless communication of the pressure and temperature values to a remotely placed central transceiver, they are difficult to install and service, and have significantly more electronics along with a battery in the wheel sensor to enable communications. More electronics in the wheel sensor and the previously mentioned battery voltage and current errors tend to make these types of devices less reliable. Also the wireless sensors utilizing a battery are not suitable for applications requiring intrinsically safe operations such as for e.g. petrochemical industry. 
   A need therefore exists for an improved wireless and batteryless sensor apparatus and easy to install packaging system, which can be integrated into a moving or rotating object such as for e.g. tire, industrial apparatus etc. and interrogated wirelessly, and that the sensors are ultimately more efficient and more reliable with fewer components than presently implemented sensors. Such an apparatus is described in greater detail herein. 
   BRIEF SUMMARY 
   The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed and is not intended to be a full description. A full appreciation of the various aspects of the embodiments can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
   It is, therefore, one aspect of the present invention to provide for improved sensor methods and systems. 
   It is another aspect of the present invention to provide for improved wireless, batteryless and transmitterless SAW pressure sensor with housing options. 
   The aforementioned aspects and other objectives and advantages can now be achieved as described herein. A wireless and batteryless pressure sensor apparatus comprises of a SAW sensor and a sensor antenna. The SAW sensor alone in combination with a sensor antenna can adequately operate from a nearby interrogator. SAW devices are resonators whose resonant frequency changes when strained. Working at radio frequencies, SAW sensing devices can be wirelessly excited with an interrogation pulse. The response (partial echo of the RF from the interrogator) from the SAW sensor can be measured to allow at least one of pressure and/or temperature to be calculated. 
   Optionally, A passive RFID device can be added to the SAW sensor system for sensor identification. An RFID device can be mounted on a printed circuit board with the SAW sensor. A SAW sensor antenna and an RFID antenna can be printed on the same or different printed circuit boards such that the antennas communicate electrically with the SAW sensor and the RFID device for sensor measurement and sensor identification (ID). As with the SAW sensor only solutions, the sensor can be interrogated utilizing a radio frequency, which can be used to excite a SAW resonator inside the sensor. The interrogation signal causes the SAW to resonate wherein the resonant frequency changes with the pressure and temperature that is applied to the sensor. 
   A SAW sensor can be designed in a button package which results in a full line of sensors for use with harsh media. The Sensor button can preferably sense the media pressure and/or temperature through direct contact of it&#39;s diaphragm with the media and is also capable of sensing the same through indirect means when pressure and/or temperature are indirectly applied to it&#39;s diaphragm through a transmission mean such as for, e.g., a flexible wall isolating the sensor from media in applications requiring cavity free installation. The sensor can be used in a wide variety of pressure ranges, port styles, and termination types. 
   The printed circuit board can be mounted on a threaded stainless steel or plastic port and over packaged with standard processes for sealing the sensor, and/or the sensor combined with an RFID device. SAW sensor button is mounted on port using welding process in case of a stainless steel port and using an O-ring elastomer or epoxy in case of a plastic port. The threaded port along with a plastic cover to seal the non-sensor side of the port completes the sensor housing. 
   Antennas are capable of receiving a radio frequency signal. When the antenna receives the particular signal associated with the sensor, or sensor+RFID device, the measurement generated by the sensor can be directed to and transmitted by the sensor antenna to the nearby transceiver/interrogator. 
   A wireless and batteryless pressure and/or temperature sensor apparatus comprises of a SAW sensor and an antenna for pressure and/or temperature data with an optional passive RFID device with an antenna for sensor identification (ID). The RF signal excites a SAW resonator inside the sensor and causes the SAW to resonate wherein a resonant frequency changes with the pressure and temperature that is applied to the sensor. Antennas could be printed circuit board antennas, helical antennas, loop antennas, any other commercially available off-the-shelf antennas or a combination of these. Housing and packaging methods results into a small size, light weight, easy to install wireless and batteryless pressure and/or temperature sensor apparatus which provides sensor data along with sensor ID for different applications. A threaded port can be made of either stainless steel material or plastic material apart from several other material options. Sensor buttons can be mounted on port using a welding process in case of a stainless steel port and using an O-ring elastomer or epoxy in case of a plastic port. 
   A sensor as will be further described herein can be adapted for use as a pressure and/or temperature sensing product for broad use in industrial, commercial, petroleum and automotive markets (e.g., TPMS). In a TPMS application, the sensor housing can be integrated with the valve stem inside the tire, strapped on the rim inside the tire, or mounted to the rim outside the tire. Such a sensor can also be utilized for moving parts such as tires, wheels, suspensions, rotary pumps, pistons, valves, and other pressure tanks or vessels. 
   The SAW pressure sensor apparatus disclosed herein can therefore sense pressure and temperature for use in harsh media, applications with moving/rotating objects and is resistant to the effects of shock, vibration and hostile environments. The sensor is more reliable due to absence of electronic circuitry on the sensor side and also due to the fact that it&#39;s batteryless. This also makes a good candidate for applications requiring intrinsically safe operations such as for e.g. petrochemical industry. The overall housing and packaging methods mentioned herein results into a small size, light weight, easy to install, wireless and batteryless pressure and/or temperature sensor apparatus which provides sensor data along with sensor ID for different applications. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the embodiments and, together with the detailed description, serve to explain the embodiments disclosed herein. 
       FIG. 1A  illustrates a top view of a SAW sensor button package, which can be implemented in accordance with a preferred embodiment; 
       FIG. 1B  illustrates a side view of the SAW sensor button package, which can be implemented in accordance with a preferred embodiment; 
       FIG. 2  illustrates a perspective view of the sensor antenna assembly mounted on a stainless steel port, in accordance with a preferred embodiment; 
       FIG. 3  illustrates an perspective view of a sensor antenna assembly including a SAW sensor and RFID component which can be implemented in accordance with a alternative embodiment; 
       FIG. 4  illustrates a perspective view of the sensor antenna assembly of  FIG. 3  mounted on a stainless steel port, in accordance with an alternative embodiment; 
       FIG. 5  illustrates a perspective view of a packaged pressure sensor apparatus, in accordance with a preferred embodiment; 
       FIG. 6  illustrates a perspective view of the pressure sensor apparatus with flush mount port, in accordance with an alternative embodiment; 
       FIG. 7  illustrates a perspective view of a miniature port style pressure sensor apparatus, in accordance with an alternative embodiment; and 
       FIG. 8  illustrates an exploded view of a tire sensor system, which can be implemented in accordance with an alternative embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   The particular values, configurations and applications discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. Note that in  FIGS. 1-8  identical parts or elements are generally indicated by identical reference numerals. 
   Referring to  FIG. 1A  a top view of a SAW sensor button package  150  is illustrated, which can be implemented in accordance with a preferred embodiment. Pressure sensor package  150  generally includes a package cover  160  that includes a dimple  162  formed at the center of cover  160 . Pressure sensor package  150  can be implemented as a SAW pressure and/or temperature sensor. 
   Referring to  FIG. 1B  a side view of the SAW sensor button package  150  is illustrated, which can be implemented in accordance with a preferred embodiment. Cover  160  thus generally includes a dimple  162  formed at the center of cover  160 . A quartz sense element  164  can be located below proximate to dimple  162  and between mounting pins  168  and  172 . Pressure sensor  150  can be implemented as a SAW pressure sensor that includes a quartz sense element  164  (e.g., a SAW chip), and a package base  166 . The sensor diaphragm  174  can be hermetically welded to the front end of the base  166  The pressure sensor  150  described herein can be utilized to measure pressure and temperature inside monitored systems, such as a vehicle tire (e.g., a passenger car tire or truck tire). When used as A TPMS, the pressure sensor  150  should preferably possess a low cross sectional area and thickness, and be generally lightweight in configuration to be compatible for truck tires and passenger car tires. 
   Referring to  FIG. 2  an exploded view of a SAW sensor system  100  in accordance with a preferred embodiment of the invention. The sensor system  100  can include a printed circuit board  110 . that can be formed from a high-performance polyimide film material that is currently available and utilized in the electronics arts such as, for example, Kapton®. Kapton® is a registered trademark of the E. I. DuPont de Nemours and Company. The SAW sensor system as depicted includes a SAW sensor  150  and sensor antenna assembly  120  as illustrated, and which can be implemented in accordance with a preferred embodiment of the present invention. The SAW sensor  150  is combined with an antenna  120  on the printed circuit board  110  and assembled in a stainless steel port package  310  for use in various applications. The sensor and antenna portions can then be packaged to protect them from debris, as will be described in more detail below. 
   Referring to  FIG. 3  an exploded view of a SAW sensor system  200  is illustrated, which can be implemented in accordance with an alternative embodiment of the present invention. Sensor package  150  described in  FIG. 2  can be modified for use with radio-frequency identification (RFID) device  130 . The sensor antenna assembly  100  can therefore function as a combined SAW sensor  150  and RFID device  130  that permits proximity-based communications between the reader and the SAW sensor and RFID devices. Radio frequency identification device (RFID)  130  can be utilized to provide unique identification for a given sensor enabling tracking abilities for the sensor or apparatus that the sensor is mounted to. The sensor system  100  can include a printed circuit board  110 . that can be formed from a high-performance polyimide film material that is currently available and utilized in the electronics arts such as, Kapton®. The assembly  100  can also include a surface acoustic wave (SAW) sensor  150  and sensor antenna  120  and an RFID  130  and RFID antenna  140 , which can be electronically connected. The SAW sensor antenna  120  and the RFID antenna  140  can be a shared antenna and enable communication or electrical connection between the SAW sensor package  150  and the RFID device  130 . The SAW sensor package  150  can be configured from one or more SAW sensing elements. Such a configuration therefore permits wireless interrogation of SAW sensor package  150  from an external wireless source, such as, for example, a wireless data transmitter and receiver device (e.g., interrogator), which is located external to the sensor assembly  100 . 
   Antennas  120  and  140  can be printed on a polyimide substrate  112  such as, for example, Kapton®. Antennas  120  and  140  can therefore constitute flexible circuit antenna configurations and/or antenna ribbons. Antennas  120  and  140  can be printed onto a substrate  112  (or tape) formed from a polyimide film material such as, for example, Kapton®. It can be appreciated that other types of polyimide films can be utilized in place of Kapton® in accordance with alternative embodiments. The use of Kapton® is therefore discussed herein for general illustrative and edification purposes only and is not considered a limiting feature of the embodiments disclosed herein. 
   As utilized herein with respect to the invention, the term “RFID device,” and so forth, generally can refer to a device that includes a loop antenna of one or more turns coupled to an electronic device, wherein the electronic device both receives signals via the loop antenna and transmits signals via the loop antenna. Specific measurement parameters can also be extracted from certain SAW RFID configurations to produce a passive wireless sensor capable of conveying an identification code if required along with temperature, pressure or other similar measurements back to an interrogation reader. Such uniquely identifiable sensors can be well suited for the automotive industry where a single reader located in an automobile could communicate and monitor pressure, temperature and other useful parameters. 
   The received signals with respect to the wireless article may include signals for controlling and/or operating the electronic device and/or for being stored in a memory associated therewith, whether embodied in the same or a separate electronic chip. The transmitted signals with respect to the wireless article may include information that is stored in the memory of or associated with the electronic device and may include information previously received and stored therein. 
   Such device or other wireless article may be part of the object to be detected/identified, or may be made on a rigid or flexible substrate that is placed with and/or attached to such object, such as by adhesive or a strap or tie or the like, or by being packaged therewith, either permanently or releasable, as may be desired for a particular application. Where the object is metallic or otherwise electrically conductive, the wireless article can be spaced away from the object a sufficient distance, e.g., a few millimeters, to allow operation of its antenna for communication of signals. 
   Referring to  FIG. 4  a perspective view of the sensor antenna assembly  100  mounted on a stainless steel port  310  is illustrated, in accordance with an alternative embodiment. The sensor apparatus  300  includes the sensor antenna assembly  100  mounted on a stainless steel port  310 , such as, for example, a stainless steel material. The sense element  164  of the pressure sensor package  150  is bonded to the stainless steel port  310  in order to measure diaphragm deformations. 
   Referring to  FIG. 5  a perspective view of the sensor package assembly  400  with plastic cover  410  is illustrated, in accordance with an alternative embodiment. The sensor assembly  100  can be overpackaged with a plastic cover  410  once placed on the stainless steel port  310  for sealing the sensor package  150 , and the RFID device  130  when included with the SAW sensor in the package  400 . The dimensions of cover  410  may vary, depending on the needs and use of such a device. This SAW sensor package  150  can also be overpackaged by welded into a fitting, threaded port, or automotive style housing and can be utilized in food and beverage, dairy, kidney dialysis, infusion pumps, air compressors, hydraulic controls, transportation, aerospace, agriculture, oil refinery, refrigeration and general industrial applications. 
   The sensor apparatus  400  can be interrogated utilizing a radio frequency band of 434 MHz, which is the standard ISM (Industrial, Scientific and Medical) band. A portion of the interrogation signal can be used to excite the SAW sense element  164  inside the sensor  150  as shown in  FIG. 1B . 
   After the sensor element  164  reaches resonation, a resonant frequency can be transmitted to the user through the SAW sensor antenna  120 . This resonant frequency changes with the pressure and temperature that is applied to the sensor apparatus  400 . In some SAW device embodiments, monitoring device frequency and any changes thereto provide sufficient information to determine parameters such as temperature and strain to which a SAW device is subjected. 
   Referring to  FIG. 6  a perspective view of a pressure sensor apparatus  500  with flush mount port  510  is illustrated, in accordance with an alternative embodiment. The dimple  162  translates external pressure to mechanical force against the sense element  164 . The flush mount port  510  is ideal for medical, beverage and food processing applications where stringent sanitation requirements are necessary. Note that flush mount port  510  can be configured from stainless steel. Referring to  FIG. 7  a photograph of a miniature port pressure and temperature sensor apparatus  600  is shown, in accordance with an alternative embodiment. The sensor antenna assembly  420  can be placed with and/or attached to a miniature port  610 . 
   Referring to  FIG. 8  an exploded view a tire sensor system  700  is illustrated, which can be implemented in accordance with an alternative embodiment of the present invention. System  700  can be implemented in the context of a tire  710  associated with, for example, a drum-type brake. It can be appreciated, however, that system  700  can be implemented in the context of other brake systems, such as disk brakes, and that the drum-type brake configuration is presented herein for general illustrative and edification purposes only. Tire  710  generally includes a tire rim  720 . System  700  includes a brake drum  730 , which can interact with a backing plate  740 , which in turn surrounds a vehicle axle  750 . 
   System  700  also incorporates sensor apparatus  400 ,  500  and  600 , which is described in greater detail herein with respect to  FIGS. 1-7 . System  700  can be utilized to monitor the temperature and pressure of tire  710  by locating sensor apparatus  400 ,  500  and  600  at a particular location within or on tire  710 . A wireless signal (e.g., radio frequency, low frequency, etc.) can be transmitted to sensor apparatus  400 ,  500  and  600 . Pressure and air temperature data can then be transmitted back for further collection and evaluation. 
   The sensor antenna assembly  100 / 200  and the stainless steel port  310  can be utilized as a wireless and batteryless pressure and temperature sensor that can be used in a wide variety of applications. The sensor apparatus  400  utilizes surface acoustic wave (SAW) technology for the sensor technology and, when used, a passive radio frequency identification (RFID) technology for sensor identification. The key applications may be in Tire Pressure Monitoring Systems (TPMS)  700  where the sensor apparatus  400  can be integrated with the valve stem inside the tire  710 , strapped on the rim  720  inside the tire  710  utilizing sensor apparatus  600 , and mounted to the rim  720  outside the tire  710  utilizing sensor apparatus  500 . 
   The sensor apparatus such as apparatus  400 ,  500  and  600  is ideal for equipment that has moving parts such as tires, wheels, suspensions, assembly machines, rotary filling machines, rotary pumps, pistons, valves, and other pressure tanks or vessels. These sensors can be ideal for mobile, portable, or un-stationary equipment. The sensor apparatus can be interrogated with low power RF signals and can be ideal for applications that require intrinsically safe and explosion proof components. The sensor apparatus  400 ,  500  and  600  is resistant to the effects of shock, vibration and hostile environments. A wide variety of pressure ranges, port styles, and termination types can be utilized with respect to the sensor antenna assembly  100 . The wireless technology allows the measurement of pressure and temperature from inside the tire  710  to help truck fleet managers accurately monitor tire pressure for improved fuel efficiency and extended tire life. 
   The invention described herein can be implemented, in accordance with one possible embodiment, as a product in a component in a wireless and batteryless tire pressure monitoring system (TPMS). Although described in detail as a possible application, TPMS should not be viewed as a limitation over the present invention as it will be appreciated that many other industrial and commercial applications are possible for the wireless, batteryless sensor described herein. Such an exemplary embodiment as TPMS can be configured as a small-size device, which is also lightweight and based on batteryless operation. The pressure sensor described herein does not consume power when implemented. Thus, the present invention can be embodied in a practical and low cost design solution. Such a design can be mass-produced for automotive, heavy-duty vehicles, and commercial markets. 
   It will, therefore, be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.