Measuring and testing – Miscellaneous
Reexamination Certificate
2004-02-17
2004-11-09
Williams, Hezron (Department: 2856)
Measuring and testing
Miscellaneous
C310S31300R, C340S010100, C340S870030, C340S870160
Reexamination Certificate
active
06813947
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a product having a sensor, by means of which a measurement variable which corresponds to a reactance and which is within a measurement range can be supplied, having a matching network and having a surface acoustic wave element, with the sensor being connected via the matching network to a first reflector in the surface acoustic wave element, and the first reflector together with the matching network and the sensor forming a resonator.
The invention also relates to a method for determining a measurement variable, which corresponds to a reactance, within a measurement range by a sensor, which is connected via a matching network to a first reflector in a surface acoustic wave element, and which, together with the first reflector and the matching network, forms a resonator. The method comprises the following steps:
a) production of a surface acoustic wave which propagates on the surface acoustic wave element;
b) production of a first reflected acoustic wave by reflection of the surface acoustic wave on the first reflector;
c) reception of the first reflected surface acoustic wave; and
d) determination of the measurement variable from the first reflected surface acoustic wave.
The invention also relates to a corresponding arrangement.
A product such as this, a method such as this and an arrangement such as this are described in the article “SAW Delay Lines for Wirelessly Requestable Conventional Sensors” by R. Steindl, A. Pohl, L. Reindl and F. Seifert, IEEE Ultrasonics Symposium, Proceedings, pages 351 et seqq, see in particular FIGS. 1, 4 and 5 together with the associated description. Reference is additionally made to the article “Wirelessly Interrogable Sensors for Different Purposes in Industrial Radio Channels” by the same four authors who have been named, 1998 IEEE Ultrasonics Symposium, Proceedings, pages 347 et seqq, see in particular the chapter entitled “Radio Request Methods”, page 349 et seq. Finally, reference is made to the article “Funksensorik und Identifikation mit OFW-Sensoren” [Radio sensor systems and identification using SAW sensors] by L. Reindl, G. Scholl, T. Ostertag, F. Schmidt and A. Pohl, presented at the ITG/GMA specialist conference on “Sensors and measurement systems” between Mar. 9 and 11, 1998 at Bad Nauheim, a written script of which lecture was provided. FIG. 18 of the script together with the associated description is of particular interest.
The above significant technological background also includes the articles “Surface Acoustic Wave Filters for Digital Radio Relay Systems” by G. Riha, H. Stocker and P. Zibis, Telcom Report 10 (1987) Special “Radio Communication” 241 and “Reproducible Fabrication of Surface Acoustic Wave Filters” by W. E. Bulst and E. Willibald-Riha, Telcom Report 10 (1987) Special “Radio Communication” 247. The article “Programmable Reflectors for SAW-ID-Tags” by L. Reindl and W. Ruile, 1983 IEEE Ultrasonics Symposium, Proceedings, pages 125 et seqq is also of importance.
The technology of autonomous sensor modules which can be checked without the use of wires has developed in recent years on the basis of a requirement for monitoring measurement variables such as wear, pressure and temperature in the tires of a passenger or goods vehicle. A completely passive sensor module comprising a surface acoustic wave element, an antenna and a sensor as well as any matching networks that may be required promises particular advantages for this purpose. A sensor module such as this does not require its own power supply, since the measurement variable which is determined by the sensor can be checked at any desired time by means of a high-frequency pulse transmitted to the module. This is explained in detail in the articles mentioned initially. A sensor module such as this can be checked by an evaluation appliance at a distance of several meters using radio frequency signals from an appropriate frequency band (for example the frequency band around 434 MHz). Possible sensors include a temperature sensor and a pressure sensor, and the sensor module is sufficiently small and compact to allow it to be installed in a conventional automobile tire.
As is evident from the three documents cited initially, the amplitude of the signal which is reflected on the reflector (which is connected to the sensor) of the surface acoustic wave element is the variable to be evaluated for the measurement, and thus governs the achievable measurement resolution. A pressure sensor in particular has a reactance as the measurement variable and can be connected to the reflector via a matching network such that it forms a resonator which allows the amplitude of a surface acoustic wave which is reflected by the reflector to be varied in accordance with the variability of the measurement variable. The evaluation of the amplitude of the reflected surface acoustic wave has the disadvantage that it is necessary to take into account a measurement error which is a function of this amplitude. The smaller the amplitude, the smaller is the separation between the amplitude and the noise, which is always present, and, in a corresponding way, the poorer is the achievable resolution. Since a minimum separation between the signal and the noise (signal to noise ratio) must not be undershot for sensible evaluation, the measurement dynamic range is thus restricted. There is also a restriction with regard to the distance between the evaluation appliance and the sensor module, since the amplitude which can be received by the evaluation appliance falls as the distance increases. In a corresponding way, the present prior art excludes long range measurements and high resolution measurements.
SUMMARY OF THE INVENTION
The invention is thus based on the object of specifying a product, a method and an arrangement of the type mentioned initially, each of which avoids the described disadvantages and allows measurement of a measurement variable which corresponds to a reactance, and which measurement is not restricted by the necessity to reach a compromise between the achievable resolution and the achievable range.
In order to achieve this object, a product is specified having a sensor, by means of which a measurement variable which corresponds to a reactance and which is within a measurement range can be supplied, having a matching network and having a surface acoustic wave element, with the sensor being connected via the matching network to a first reflector in the surface acoustic wave element, and with the first reflector together with the matching network and the sensor forming a resonator. For a value of the measurement variable within the measurement range, the resonator has a resonance with respect to a reflection of a surface acoustic wave, which propagates on the surface acoustic wave element, on the first reflector.
In order to achieve this object, a method is specified for determining a measurement variable, which corresponds to a reactance, within a measurement range by a sensor, which is connected via a matching network to a first reflector in a surface acoustic wave element, and which, together with the first reflector and the matching network, forms a resonator, which resonator has, for a value of the measurement variable within the measurement range, a resonance with respect to a reflection of a surface acoustic wave, which propagates on the surface acoustic wave element, on the first reflector, comprising the following steps:
a) production of a surface acoustic wave which propagates on the surface acoustic wave element;
b) production of a first reflected acoustic wave by reflection of the surface acoustic wave on the first reflector;
c) reception of the first reflected surface acoustic wave; and
d) determination of the measurement variable from a phase of the first reflected surface acoustic wave.
In order to achieve this object, an arrangement is specified for determining a measurement variable, which corresponds to a reactance, by a sensor, which is connected via a matching network to a first reflector in a surface aco
Dollinger Franz
Schimetta Gernot
Baker & Botts L.L.P.
Miller Rose M.
Siemens Aktiengesellschaft
Williams Hezron
LandOfFree
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