Abstract: A monitoring system, particularly suitable for monitoring conditions (e.g. pressure or temperature) of a vehicle tire comprises a passive sensor (102, 104), an antenna (106) associated with said passive sensor, and switching means (108) for controlling the connection between the passive sensor and the antenna such that, in a first state of said switching means, said antenna is prevented from transmitting a signal generated by the passive sensor, and, in a second state of said switching means, said antenna is permitted to transmit a signal generated by the passive sensor. The switching means is operated remotely by means of a control signal. The control signal may be derived from the sum or difference of RF signals (F1 and F2) applied to a filter (112) In alternative embodiments the control signal is the modulating frequency of an AM or FM modulated radio signal or a radio signal carrying a digital code.

Abstract: A vibratory gyroscope is provided that includes a vibratory element; a vibration inducing device for inducing a mode of vibration into the vibratory element; and a processing device for generating, in response to a change in strain detected in the vibratory element, a signal indicative of a rate of rotation about an axis of the vibratory element corresponding to a rotation imparted to the vibratory element subsequent to an inducing of the vibration. The vibration inducing device includes an acoustic signal source provided at a location spaced from the vibratory element. Undesirable effects associated with mounting the vibration inducing device to the vibratory element are thereby avoided.

Abstract: A rotary signal coupler for providing signal coupling to a Surface Acoustic Wave (SAW) device (4) mounted on a shaft (5) includes a first electrically conducting loop (21) mounted on a disc (23) and connected to the SAW device (4), and a second electrically conductive loop (22) mounted on a disc (24) and connected to external electronic circuitry. The disc (23) is fixed relative to the shaft (5) and the disc (24) is fixed relative to the structure in which the shaft (5) rotates so that the loops (21, 22) are inductively coupled. A grounded screen (27), which preferably takes the form of a plurality of radially extending fingers is located on the disc (23) and positioned between the loops (21, 22) to eliminate capacitive coupling therebetween.

Abstract: A vibratory gyroscope is provided that includes a vibratory element; a vibration inducing device for inducing a mode of vibration into the vibratory element; and a processing device for generating, in response to a change in strain detected in the vibratory element, a signal indicative of a rate of rotation about an axis of the vibratory element corresponding to a rotation imparted to the vibratory element subsequent to an inducing of the vibration. The vibration inducing device includes an acoustic signal source provided at a location spaced from the vibratory element. Undesirable effects associated with mounting the vibration inducing device to the vibratory element are thereby avoided.

Abstract: The present invention relates to a rotary signal coupler, that is to say a device for providing signal coupling between two components which are rotatable relative to each other. A coupler is provided comprising a first substantially circular track secured to a first support and a second substantially circular track secured to a second support which is rotatable relative to the first support. The first and second tracks are coaxial with the axis of rotation of the rotatable second support and are adjacent each other so as to provide signal coupling therebetween. The second track has at least two gaps therein which form electrical discontinuities between separated track portions. The separated track portions are electrically connected to one another. Signal coupling with a rotatable support having a relatively large diameter may be thereby improved.

Abstract: Apparatus for determining the resonant frequency of a passive sensor, for example a saw device, includes a device (5, 7, 3) for transmitting signals of a plurality of frequencies to the passive sensor (2); a device (3, 7) for receiving signals from the passive sensor simultaneously with the transmitting of signals; a device (7) for comparing the received signals with the transmitted signals to identify a characteristic change in the relationship between the received signals and the transmitted signals which occurs when the sensor is being driven at its resonant frequency. As the frequency at which the passive sensor is driven passes through the resonant frequency of the sensor the phase and/or amplitude of the signal generated by the passive sensor will change. By identifying this change of phase and/or amplitude the point at which resonance occurs can be detected.

Abstract: A wheel, particularly for a vehicle, includes at least a portion formed from non-metallic material which incorporates at least one sensor indicative of a condition sensed. A wheel is molded from a fiber reinforced plastics material and incorporates passive sensors capable of indicating conditions of the wheel or the tire associated with it (e.g., tire pressure or torque transmitted). The sensor output is processed by an ASIC device to provide an output signal to a communications device also mounted on the wheel. The ASIC and communications device are powered by a virtual battery which is charged by, e.g., using electrical pulses generated by strain within the wheel itself. An id tag may be provided to identify the wheel in question.

Abstract: A monitoring system, particularly suitable for monitoring conditions (e.g. pressure or temperature) of a vehicle tire comprises a passive sensor (102, 104), an antenna (106) associated with said passive sensor, and switching means (108) for controlling the connection between the passive sensor and the antenna such that, in a first state of said switching means, said antenna is prevented from transmitting a signal generated by the passive sensor, and, in a second state of said switching means, said antenna is permitted to transmit a signal generated by the passive sensor. The switching means is operated remotely by means of a control signal. The control signal may be derived from the sum or difference of RF signals (F1 and F2) applied to a filter (112) In alternative embodiments the control signal is the modulating frequency of an AM or FM modulated radio signal or a radio signal carrying a digital code.

Abstract: The present invention relates to an apparatus and method for detecting the condition of an item and, particularly, but not exclusively, to an apparatus and method for detecting a specific condition of a motor vehicle tire. The invention provides apparatus comprising a structure for radiating radio frequency energy in response to a reception by said structure of radio frequency energy; said structure having a first configuration which, in use, is changed to a second configuration in response to said item attaining said specific condition; said change in configuration producing a detectable difference in radio frequency energy radiated from said structure. Apparatus according to the present invention thereby allows for the remote interrogation of the condition of an item.

Abstract: A rotary signal coupler for providing signal coupling to a Surface Acoustic Wave (SAW) device (4) mounted on a shaft (5) comprises a first electrically conducting loop (21) mounted on a disc (23) and connected to the SAW device (4), and a second electrically conductive loop (22) mounted on a disc (24) and connected to external electronic circuitry. The disc (23) is fixed relative to the shaft (5) and the disc (24) is fixed relative to the structure in which the shaft (5) rotates so that the loops (21, 22) are inductively coupled. A grounded screen (27), which preferably takes the form of a plurality of radially extending fingers, is located on the disc (23) and positioned between the loops (21, 22) to eliminate capacitive coupling therebetween.

Abstract: The present invention relates to a rotary signal coupler, that is to say a device for providing signal coupling between two components which are rotatable relative to each other. A coupler is provided comprising a first substantially circular track secured to a first support (not shown) and a second substantially circular track (102) secured to a second support (10) which is rotatable relative to the first support. The first and second tracks are coaxial with the axis of rotation of the rotatable second support (10) and are adjacent each other so as to provide signal coupling therebetween. The second track (102) has at least two gaps (106, 108) therein which form electrical discontinuities between separated track portions. The separated track portions are electrically connected (110) to one another. Signal coupling with a rotatable support having a relatively large diameter may be thereby improved.

Abstract: A method and apparatus for measuring the torque transmitted by a member comprises a SAW device (66) secured to the member such that mechanical stress in the member due to torque transmitted thereby induces bending of the SAW device. Means are provided for measuring the change in resonant frequency of the SAW device induced by bending. In one embodiment, a hole (52) is formed in the member (50) and the SAW device is mounted in a pair of diametrically opposite slots provided in the hole (52). The SAW device comprises a substrate on which electrode pairs are laid down, the electrode pairs being in a position such that bending of the SAW device results in compression of the zone containing one electrode pair and tension in a zone comprising another electrode pair. In an alternative arrangement the member is formed with a recessed portion in the surface thereof and the SAW device is mounted in a pair of slots formed by opposite walls of the recess.

Abstract: An apparatus for tracking the varying resonant frequency of an electrically resonant structure, characterized by: a variable frequency oscillator providing an excitation signal of a variable frequency encompassing the possible resonant frequency range of the resonant structure, a bidirectional RF transmission line connecting the variable frequency oscillator and the resonant structure, the transmission line incorporating a directional coupler which generates a directional coupler signal proportional to the reflected signal from the resonant structure, the directional coupler signal being conditioned by a processor to provide a feedback signal to the input of the variable frequency oscillator, such that the mean frequency of the excitation signal is caused to continuously track the varying resonant frequency resonant structure.

Abstract: Apparatus for determining the resonant frequency of a passive sensor, for example a saw device, comprises: means (5,7, 3) for transmnitting signals of a plurality of frequencies to said passive sensor (2); means (3, 7) for receiving signals from said passive sensor simultaneously with said transmitting of signals; means (7) for comparing the received signals with the transmitted signals to identify a characteristic change in the relationship between the received signals and the transmitted signals which occurs when the sensor is being driven at its resonant frequency. Typically, as the frequency at which the passive sensor is driven passes through the resonant frequency of the sensor the phase and/or amplitude of the signal generated by the passive sensor win change. By identifying this change of phase and/or amplitude the point at which resonance occurs can be detected.

Abstract: An apparatus for tracking the varying resonant frequency of an electrically resonant structure, characterized by: a variable frequency oscillator providing an excitation signal of a variable frequency encompassing the possible resonant frequency range of the resonant structure, a bidirectional RF transmission line connecting the variable frequency oscillator and the resonant structure, the transmission line incorporating a directional coupler which generates a directional coupler signal proportional to the reflected signal from the resonant structure, the directional coupler signal being conditioned by a processor to provide a feedback signal to the input of the variable frequency oscillator, such that the mean frequency of the excitation signal is caused to continuously track the varying resonant frequency resonant structure.

Abstract: The present invention relates to an apparatus and method for detecting the condition of an item and, particularly, but not exclusively, to an apparatus and method for detecting a specific condition of a motor vehicle tire. The invention provides apparatus comprising a structure for radiating radio frequency energy in response to a reception by said structure of radio frequency energy; said structure having a first configuration which, in use, is changed to a second configuration in response to said item attaining said specific condition; said change in configuration producing a detectable difference in radio frequency energy radiated from said structure. Apparatus according to the present invention thereby allows for the remote interrogation of the condition of an item.

Abstract: An electronic structure comprising an electrically conductive base member with a layer of piezoelectric material bonded thereon, characterised in that at least first and second interdigital arrays are bonded or otherwise attached to said layer, in use said first interdigital array relying on the piezoelectric properties of said layer and said second interdigital array relying on the dielectric properties of said layer. Typically the first and second interdigital array forms part of at least one oscillator, such as a surface acoustic wave (‘SAW’) resonator, a shallow bulk acoustic wave (‘SBAW’) resonator, or the like. The second interdigital array forms part of at least one directional coupler such as a Lange coupler.

Abstract: Apparatus for measuring the value of a physical quantity which affects the impedance of an electrically resonant structure, the apparatus comprising an electrically resonant structure, an RF electrical energy source, a bidirectional RF transmission line connecting the source to the structure, the directional coupler detecting the voltage or phase of a reflected signal returned from the resonant structure characterised in that the resonant structure is substantially non energy radiating and, at a given frequency of the source, has an impedance which varies continuously as a function of the value of the physical quantity. Typically the electrically resonant structure is at least partially composed of piezoelectric material.

Abstract: A method of, and apparatus for, measuring dynamic torque transmitted by a shaft having an axis of rotation is characterised by the steps of:1 locating on the shaft (S) a pair of transducers (T, T1, T2), each comprising an SAW resonator, as a complementary pair so that for a first direction of rotation (K) of the shaft (S) about the axis (A) one transducer (T1) is under compression and the other (T2) in tension and for a reverse direction of rotation of the shaft the one transducer (T1) is in tension and the other (T2) in compression, a signal input (C1) and a signal output (C2, C3) for either each transducer or a single signal output for a signal derived from both transducers, the signal input and signal output or outputs being located at discrete locations on or near the outside of the shaft (S) for rotation therewith,2 causing a driving signal to be applied to the signal input (C1);3 detecting at each or the signal outlet (C2, C3) at least an output resonant frequency of the transducer (T, T1, T2) when driv