Abstract: Embodiments of the invention relate to resonant circuits; particularly but not exclusively the embodiments relate to resonant circuits in RPID (radio frequency identification) responsive to a wide frequency range. A controllable electric resonator comprising an inductor coupled to a first capacitor to form a resonant circuit, the resonator further comprising a controllable element, a second capacitor controllable coupled across said first capacitor by said controllable element, and a control device to control said controllable element such that a total effective capacitance of said first and second capacitor varies over a duty cycle of an oscillatory signal on said resonator.

Abstract: Embodiments of the invention relate to the field of pet doors, particularly selective entry pet doors based on detection of RFID tags. An RFID pet door, the pet door comprising: an RFID reader to read an RFID tag on a pet; and a lock coupled to said RFID reader to control access through said pet door in response to an RFID signal from said tag; wherein said RFID reader has two modes, a first operational mode and a second, reduced power mode, and wherein said pet door further comprises: a pet proximity detector coupled to said RFID reader to identify when a pet is proximate said pet door and to control said RFID reader responsive to said identification such that when said pet is proximate said RFID is in said operational mode and such that said RFID reader is otherwise in said reduced power mode.

Abstract: Embodiments of the invention relate to the field of pet doors, particularly selective entry pet doors based on detection of RFID tags. We describe a pet door comprising: an RFID reader to read an RFID tag on a pet; and a lock coupled to said RFID reader to control access through said pet door in response to an RFID signal from said tag; wherein said RFID reader has two modes, a first operational mode and a second, reduced power mode, and wherein said pet door further comprises: a pet proximity detector coupled to said RFID reader to identify when a pet is proximate said pet door and to control said RFID reader responsive to said identification such that when said pet is proximate said RFID is in said operational mode and such that said RFID reader is otherwise in said reduced power mode.

Abstract: Embodiments of the invention relate to the field of RFID interrogators, particularly RFID interrogators that combine low loss with high rates of communication from the interrogator to a tag. Further embodiments relate to the field of active RFID tags and general radio transmitters. We describe a transmitter comprising a resonant circuit and a driver coupled to drive said resonant circuit, wherein said resonant circuit includes a resonance regeneration system such that during amplitude modulation of a resonant signal in said resonant circuit when an amplitude of said resonant signal is reduced energy from said reduction is stored and when said amplitude is increased said stored energy is used to regenerate said resonance signal.

Abstract: Embodiments of the invention relate to the field of RFID interrogators, particularly RFID interrogators that combine low loss with high rates of communication from the interrogator to a tag. We describe a transmitter comprising a resonant circuit and a driver coupled to drive said resonant circuit, wherein said resonant circuit includes a resonance regeneration system such that during amplitude modulation of a resonant signal in said resonant circuit when an amplitude of said resonant signal is reduced energy from said reduction is stored and when said amplitude is increased said stored energy is used to regenerate said resonance signal.

Abstract: A circuit block which comprises a non-linear capacitor with two different values of capacitance dependent on a value of a voltage of a resonant signal on the capacitor; a plurality of second capacitors each coupled to a respective switch to enable a said second capacitor to be switched in or out of parallel connection with the nonlinear capacitor; and a tuning control, coupled to the second capacitor switches, and sensing an amplitude of the resonant signal. The tuning control circuit is configured to control the second capacitor switches to successively switch the second capacitors in/out of parallel connection with the non-linear capacitor dependent on the amplitude of the resonant signal until the non-linear capacitor has substantially a single one of two different values, such that in a resonant circuit the circuit block then behaves as a fixed value capacitor.

Abstract: Embodiments of the invention relate to resonant circuits; particularly but not exclusively the embodiments relate to resonant circuits in RPID (radio frequency identification) responsive to a wide frequency range. A controllable electric resonator comprising an inductor coupled to a first capacitor to form a resonant circuit, the resonator further comprising a controllable element, a second capacitor controllable coupled across said first capacitor by said controllable element, and a control device to control said controllable element such that a total effective capacitance of said first and second capacitor varies over a duty cycle of an oscillatory signal on said resonator.

Abstract: An RFID reader for use in a pet door to control access for a pet bearing an RFID tag or implant. The RFID reader incorporates and is operable in two modes, a learn mode and a normal mode. In learn mode, the reader stores the ID code of an RFID transponder in the vicinity of the reader and also derives additional reader information corresponding to the RFID transponder. In normal mode, the reader compares the ID codes stored in memory to the RFID signal returned from an RFID transponder in the vicinity of said the reader. The RFID reader behavior is at least in part determined by the additional reader information corresponding to said ID codes stored in memory. We also describe a confidence threshold for acceptance of an ID code in learn mode and normal mode. The confidence threshold in normal mode may be less than in learn mode.

Abstract: Embodiments of the invention relate to the field of RFED (radio frequency identification). Some particularly preferred embodiments relate to a high-Q, so-called “full duplex” (FDX) RFID Reader. An RFID tag reader, the reader comprising: an electromagnetic (em) field generator for generating an electromagnetic (em) field for modulation by said tag, said modulation comprising modulated load of said em field by said tag; a detector system responsive to fluctuations in strength of said em field at said reader; a negative feedback system responsive to said detector system to provide a control signal for said em field generator for controlling said em field generator to reduce said detected fluctuations; and a demodulator responsive to said control of said em field to demodulate said em field modulation by said tag.

Abstract: Embodiments of the invention relate to the field of pet doors, particularly selective entry pet doors based on detection of RFID tags. We describe a pet door comprising: an RFID reader to read an RFID tag on a pet; and a lock coupled to said RFID reader to control access through said pet door in response to an RFID signal from said tag; wherein said RFID reader has two modes, a first operational mode and a second, reduced power mode, and wherein said pet door further comprises: a pet proximity detector coupled to said RFID reader to identify when a pet is proximate said pet door and to control said RFID reader responsive to said identification such that when said pet is proximate said RFID is in said operational mode and such that said RFID reader is otherwise in said reduced power mode.

Abstract: Embodiments of the invention relate to the field of RFID interrogators, particularly RFID interrogators that combine low loss with high rates of communication from the interrogator to a tag. Further embodiments relate to the field of active RFID tags and general radio transmitters. We describe a transmitter comprising a resonant circuit and a driver coupled to drive said resonant circuit, wherein said resonant circuit includes a resonance regeneration system such that during amplitude modulation of a resonant signal in said resonant circuit when an amplitude of said resonant signal is reduced energy from said reduction is stored and when said amplitude is increased said stored energy is used to regenerate said resonance signal.

Abstract: We describe RFID tags that incorporate a nonlinear resonator that self-adapts to the driving frequency of a reader. More particularly we describe an RF tag for sending data to a tag reader by modulating energy drawn from an RF field of said tag reader, the tag comprising: an antenna; a resonant circuit coupled to said antenna to resonate at a frequency of said RF field; a local power store to store power extracted from said RF field; a modulation system to modulate one or both of the resonance amplitude and a relative phase of a signal in said resonant circuit with respect to said RF field; and a feedback circuit coupled to said resonant circuit and to said local power store to control one or both of said resonance amplitude and said relative phase to control transients in said resonance amplitude caused by said modulation.

Abstract: A loudspeaker comprising a bending wave panel-form acoustic radiator having a first portion and at least one further portion a transducer for exciting bending waves in the radiator, the transducer being coupled to the further portion of the radiator to cause the radiator to radiate an acoustic output, and means confining low frequency radiation to the further portion of the radiator.

Abstract: Audio apparatus (30) comprising a piezoelectric transducer (44) and coupling means (54) for coupling the transducer to a user's pinna (32) whereby the transducer excites vibration in the pinna (32) to cause it to transmit an acoustic signal from the transducer (44) to a user's inner ear, characterised in that the transducer is embedded in a casing (42) of relatively soft material and the casing (42) is mounted to a housing (34) of relatively hard material such that a cavity (48) is defined between the casing (42) and housing (34).

Abstract: Embodiments of the invention relate to the field of RFID interrogators, particularly RFID interrogators that combine low loss with high rates of communication from the interrogator to a tag. We describe a transmitter comprising a resonant circuit and a driver coupled to drive said resonant circuit, wherein said resonant circuit includes a resonance regeneration system such that during amplitude modulation of a resonant signal in said resonant circuit when an amplitude of said resonant signal is reduced energy from said reduction is stored and when said amplitude is increased said stored energy is used to regenerate said resonance signal.

Abstract: A contact sensitive device includes a member capable of supporting bending waves and a plurality of sensors mounted on the member for measuring bending wave vibration in the member. The sensors measure the bending wave signals and by calculating a phase angle for each measured bending wave signal and a phase difference between the phase angles of at least two pairs of sensors so that at least two phase differences are calculated, the location of the contact can be determined.

Abstract: A contact sensitive device includes a member capable of supporting bending waves and a plurality of sensors mounted on the member for measuring bending wave vibration in the member. The sensors measure the bending wave signals and by calculating a phase angle for each measured bending wave signal and a phase difference between the phase angles of at least two pairs of sensors so that at least two phase differences are calculated, the location of the contact can be determined.

Abstract: A contact sensitive device includes a member capable of supporting bending waves and a plurality of sensors mounted on the member for measuring bending wave vibration in the member. The sensors measure the bending wave signals and by calculating a phase angle for each measured bending wave signal and a phase difference between the phase angles of least two pairs of sensors so that at least two phase differences are calculated, the location of the contact can be determined.

Abstract: A loudspeaker comprising a panel-form acoustic member adapted for operation as a bending wave radiator and an electrodynamic moving coil transducer having a voice coil mounted to the acoustic member to excite bending wave vibration in the acoustic member. The junction between the voice coil and the acoustic member is of sufficient length in relation to the size of the acoustic member to represent a line drive such that the acoustic member has a mechanical impedance which has a rising trend with bending wave frequency.

Abstract: Disclosed is a touch input device that determines touch position by sensing vibrations propagating in a touch plate that are indicative of a touch to the touch plate. Vibration sensing devices such as piezoelectric sensors are used to sense the vibrations. Selecting the size, shape, placement position and orientation of the sensors on the touch plate can enhance sensitivity of the sensors to vibration and yield symmetric response with respect to the direction of vibration propagation. Also disclosed is a method of making a vibration sensing touch input device.