GB2613408A

GB2613408A - Temperature sensing device with antenna

Info

Publication number: GB2613408A
Application number: GB2204700.5A
Authority: GB
Inventors: Pereira da Cunha Mauricio; J Lad Robert; White Ian; Brüggemann Kurt; Downing Richard; Consola Maud
Original assignee: Airbus Operations SAS; Airbus Operations Ltd
Current assignee: Airbus Operations SAS; Airbus Operations Ltd
Priority date: 2021-11-30
Filing date: 2022-03-31
Publication date: 2023-06-07
Also published as: GB202204700D0

Abstract

Temperature sensing device for sensing aircraft wheel brake 200 temperature, the temperature sensing apparatus 300 comprising a surface acoustic wave, SAW, sensor element; and a planar sensor antenna electrically coupled to the SAW sensor element, the planar sensor antenna for receiving an interrogation signal and transmitting an output signal that is responsive to the interrogation signal, wherein the planar sensor antenna comprises two loops of a conductor material, the loops disposed on a surface of a substrate to provide the planar sensor antenna. Preferably the sensor element also comprises an interdigital transducer, IDT, and the planar sensor antenna is electrically coupled to the IDT. The sensor element may also comprise an input IDT and an output IDT with the planar sensor antenna is electrically coupled to both. A brake disc 202 comprising the temperature sensing device attached to the brake disc, an aircraft comprising the brake disc and a method of manufacturing a temperature sensing device is also claimed.

Description

TEMPERATURE SENSING DEVICE WITH ANTENNA

TECHNICAL FIELD

[0001] The present invention relates to sensing aircraft wheel brake temperature. More specifically, the present invention relates to features of a temperature sensing device.

BACKGROUND

[0002] When aircraft wheel brakes are applied to reduce the speed of an aircraft, the temperature of the aircraft wheel brakes rises. It can be advantageous to monitor the temperature of the aircraft wheel brakes, for example, to ensure that the brakes do not overheat. For example, temperature sensors such as thermocouples can be used to sense temperature.

SUMMARY

[0003] A first aspect of the present invention provided a temperature sensing device for sensing aircraft wheel brake temperature, the temperature sensing apparatus comprising: a surface acoustic wave (SAW) sensor element; and a planar sensor antenna electrically coupled to the SAW sensor element, the planar sensor antenna for receiving an interrogation signal and transmitting an output signal that is responsive to the interrogation signal, wherein: the planar sensor antenna comprises two loops of a conductor material, the loops disposed on a surface of a substrate to provide the planar sensor antenna.

[0004] Optionally, the SAW sensor element comprises an interdigital transducer (IDT); and the planar sensor antenna is electrically coupled to the [DT.

100051 Optionally, the SAW sensor element comprises an input IDT and an output [DT; and the planar sensor antenna is electrically coupled to both the input IDT and the output IDT 100061 Optionally, each of the loops of the planar sensor antenna forms a parallelogram.

100071 Optionally, each of the loops of the planar sensor antenna forms a rectangle or a square 100081 Optionally, the planar sensor antenna is electrically coupled to the SAW sensor element by a bond wire of diameter 1 millimetre.

100091 Optionally,the planar sensor antenna is electrically coupled to a tuning structure.

100101 According to a second aspect of the present invention, there is provided a brake disc for an aircraft wheel brake comprising the temperature sensing device according to the first aspect attached to the brake disc.

100111 According to a third aspect of the present invention, there is provided an aircraft comprising the brake disc according to the second aspect.

100121 According to a fourth aspect of the present invention, there is provided a method of manufacturing a temperature sensing device for sensing aircraft wheel brake temperature, the method comprising: producing a planar sensor antenna for receiving an interrogation signal and transmitting an output signal that is responsive to the interrogation signal, the planar sensor antenna comprising two loops of a conductor material, the loops disposed on a surface of a substrate to provide the planar sensor antenna: providing the temperature sensing device comprising the planar sensor antenna electrically coupled to a surface acoustic wave, SAW, sensor element.

100131 Optionally, the method according to the fourth aspect comprises providing the temperature sensing device comprises electrically connecting the planar sensor antenna to an input interdigital transducer (IDT) of the SAW sensor element, arid to an output IDT of the SAW sensor element.

100141 Optionally, the method according to the fourth aspect comprises: producing the planar sensor antenna such that each of the loops of the planar sensor antenna forms a parallelogram.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [0016] Figure 1 is a simplified schematic view of an aircraft on which examples may be deployed; [0017] Figure 2 is a simplified schematic view of a brake and a wheel of an aircraft landing gear assembly according to an example, [0018] Figure 3 is a simplified schematic block diagram of a temperature sensing device according to a first example; [0019] Figure 4 is a simplified schematic plan view of a surface acoustic wave sensor element, according to an example; [0020] Figure 5 is a simplified schematic block diagram of a temperature sensing system according to an example; [0021] Figures 6 is a simplified schematic block diagram of a second temperature sensing device, according to a second example, [0022] Figures 7 is a simplified schematic block diagram of a third temperature sensing device, according to a third example; [0023] Figure 8 is a flow diagram of a method of manufacturing a temperature sensing device, according to an example.

DETAILED DESCRIPTION

100241 The following disclosure relates to a temperature sensing device for sensing aircraft wheel brake temperature.

100251 Figure 1 is a simplified schematic view of an aircraft 100. The aircraft 100 comprises a plurality of landing gear assemblies 102. The landing gear assemblies may include main and nose landing gears that are deployed or extended during take-off and landing. Each landing gear assembly 102 includes wheels 104. The aircraft 100 comprises a computing system 106, which, for example, comprises one or more processors and one or more computer readable storage media. The aircraft 100 may also comprise instruments 108, such as instruments or sensors for measuring characteristics or parameters related to the aircraft, and instruments or sensors for measuring environmental characteristics.

100261 Figure 2 is a simplified schematic view of an aircraft wheel brake 200 associated with the wheel 104 of the aircraft 100. The wheel brake 200 applies a braking force to inhibit the rotation of the wheel 104 when applied. Each of the wheels of the aircraft 100 may have a wheel brake 200 associated with it. In this example, the wheel brake 200 comprises a plurality of brake discs 202 including a pressure plate 204, a reaction plate 206, and a number of rotors 208 and stators 210. In this example, the brake discs 202 include a plurality of rotors and stators, and the wheel brake 200 is therefore a multiple disc brake. In other examples, the wheel brake 200 may not be a multiple-disc brake: there may be only one disc 208, for example, between a pressure plate 204 and a reaction plate 206. In some examples, the brake discs 202 may include up to 9 discs or 11 discs, or any other number which is suitable for a wheel brake of an aircraft. The brake discs 202 may collectively be referred to as a heat pack. The components of the wheel brake 200 (hereafter, for brevity, the wheel brake 200 is referred to simply as the brake 200) such as the brake discs 202 may be housed in a wheel brake housing (not shown). As referred to herein, the term brake is used as if to include such a wheel brake housing.

100271 It will be understood that the type of wheel brake used in an aircraft landing gear depends on the characteristics of the aircraft in question, such as size, carrying capacity and the like. The following may be applied to any wheel brakes suitable for use as aircraft wheel brakes which heat up when applied to reduce aircraft speed, as discussed in the following.

100281 When the aircraft 100 travels along the ground supported by the landing gear assembly 102, the rotors rotate with the wheel 104 (the rotors are keyed to the wheel 104), whereas the stators, the pressure plate 204 and the reaction plate 206 do not rotate with the wheel 104 (the stators, the pressure plate 204 and the reaction plate 206 are keyed to a torque tube 218 associated with the wheel 104 which does not rotate with the wheel 104) When braking is applied, the pressure plate 204 is urged towards the reaction plate 206 so that the brake discs 202 come into contact with one another (as shown in box 212 of Figure 2) and friction acts to inhibit the rotational motion of the rotors, thus generating a braking force. When the brake 200 is applied, some of the kinetic energy of the aircraft 100 is absorbed into the brake discs 202 as heat (by the action of friction). Accordingly, the brake 200 heats up when it is applied to cause the aircraft 100 to slow down.

100291 Any one or more of the rotors, stators, pressure plate 204 and the reaction plate 206 may be composed of Carbon-Carbon (CC) composites. A brake including brake discs composed of CC composites may be referred to as a carbon brake. For example, the brake discs 202 may be composed of a graphite matrix reinforced by carbon fibers.

100301 Those skilled in the art will appreciate that the environment of the brake discs 202 may be harsh due to vibration and/or physical shock during application of braking for example The environment of the brake discs 202 may be harsh due to high temperatures reached by the brake discs 202, for example 100311 In this example, the aircraft 100 comprises a braking system 214 which controls the operation of the brake 200. The braking system 214 causes the brake 200 to be applied in response to a braking request (e.g. when a pilot of the aircraft 100 presses a brake pedal). For example, the brake 200 may be hydraulically actuated in which case the braking system 214 includes a hydraulic system (not shown) operationally connected with the brake 200, h) other examples, the brake 200 may be electrically actuated in which case the braking system 214 includes an electronic brake actuation system. The braking system 214 may be controlled by the computing system 106.

100321 Figure 3 is a simplified schematic view of a temperature sensing device 300. The temperature sensing device 300 is for sensing aircraft wheel brake temperature (for example, the temperature of the brake 200). For example, the temperature sensing device 300 may be attached to a component of the brake in order to sense the temperature of that component of the brake 200. For example, the temperature sensing device 300 may be attached to one of the brake discs 202. In the example of Figure 2, the temperature sensing device 300 is attached to one of the stators. For example, the temperature sensing device 300 is attached to a first stator 210a, as schematically shown.

100331 The temperature sensing device 300 may be attached to the first stator 210a in a manner that can withstand the high temperatures expected to occur at the first stator 210a. For example, the temperature sensing device 300 may be attached to the first stator 210a by means of a ceramic adhesive. Ceramic adhesive may be intended to withstand high temperatures, for example in excess of 1000°C. For example, the ceramic adhesive may be applied between the first stator 210a and the temperature sensing device 300 and cured such that the temperature sensing device 300 is bonded to the first stator 210a using cured ceramic adhesive material (for example, ceramic epoxy adhesive material). In some examples, the first stator 210a comprises a first formation (for example, one or more grooves). The first formation may be formed by cutting, grinding, drilling, or boring the first formation into the material of the first stator 210a. In such examples, a second formation may be formed from the ceramic adhesive to interlock with the first formation. For example, the ceramic adhesive with the second formation may be an attachment element for attaching the temperature sensing device 300 to the first stator 210a. For example, the second formation is complementary to the first formation. For example, the first formation is a groove formed in the first stator 210a and the second formation is a spike which fits into the groove to inhibit movement between the first stator 210a the attachment element along an axial direction and a circumferential direction of the first stator 210a. In some examples, providing the attachment element as described comprises applying uncured ceramic adhesive material to the surface of the first formation to create the second formation.

100341 It will be appreciated that the temperature sensing device 300 may be attached to a brake disc in a number of ways. Alternatively, or in addition to the use of ceramic adhesive, other fasteners such as ceramic bolts may be used to attach the temperature sensing device 300. For example, a ceramic bolt may be passed through a through hole in the temperature sensing device 300 and engage with a threaded hole in the first stator 210a. In some examples, an appropriately shaped clip (for example, a metal clip) may be used as an attachment element. For example, the clip may comprise through holes and may be attached to the first stator 210a using bolts. Those skilled in the art will appreciate the various ways of attaching components to withstand high temperatures.

100351 The temperature sensing device 300 comprises a surface acoustic wave (SAW) sensor element 302. In the example of Figure 3, the temperature sensing device also comprises a sensor antenna 304, which is electrically coupled to the SAW sensor element 302. The temperature sensing device 300 may be a passive device in that it does not require electrical power to operate. It will be understood that the SAW sensor element 302 works based on SAWs generated in the SAW sensor element 302. For example, the SAW sensor element 302 comprises a transducer which converts an input signal (for example, an electrical signal) into a surface acoustic wave that resonates in the SAW sensor element 302. The SAW sensor element 302 also, for example, comprises a transducer to convert the SAW into an output signal (for example, an output signal) 100361 It will be understood that the SAW sensor element 302 works based on SAWs generated in the SAW sensor element 302. For example, the SAW sensor element 302 comprises a transducer which converts an input signal (for example, an electrical signal) into a surface acoustic wave that resonates in the SAW sensor element 302. The SAW sensor element 302 also, for example, comprises a transducer to convert the SAW into an output signal (for example, an output signal). Physical properties (such as temperature, for example) of the SAW sensor element may be determined based on the output signal.

100371 The input signal may be referred to as an interrogation signal. That is because the interrogation signal causes the output signal based on which, for example, temperature can be determined. The interrogation signal therefore acts to query the SAW sensor element 302 to provide an output signal. The interrogation signal may be wirelessly received by the temperature sensing device 300. The output signal may be wirelessly transmitted by the temperature sensing device 300.

100381 The SAW sensor element 302 comprises one or more interdigital transducers (IDTs). The IDTs are for converting between a SAW and, for example, an electrical signal The functioning of an IDT is described further below. In some examples, the SAW sensor element 302 is a one-port SAW sensor. In such examples, the SAW sensor element 302 has one IDT. For example, the SAW sensor element 302 may have one IDT and reflectors either side of the IDT to reflect the SAW. In such examples, the one IDT converts an input signal into a SAW and also converts the SAW back into an electrical signal as a response (output) signal.

100391 In some examples, the SAW sensor element 302 is a two-port SAW sensor. In such examples, the SAW sensor element 302 comprises two IDTs spaced apart from one another. There is an input IDT which converts an input signal into a SAW. The SAW travels from the input IDT to an output IDT. The output IDT converts the SAW into an output signal. Those skilled in the art will appreciate the various configurations of a SAW sensor element.

100401 Figure 4 illustrates a particular example of the SAW sensor element 302. In this example, the SAW sensor element 302 is a two-port SAW sensor, and comprises an input IDT 402 and an output IDT 404. Each of the input IDT 420 and the output IDT 404 comprises two interlocking comb-shaped arrays of electrodes, deposited on the surface of a piezoelectric substrate 406 to form a periodic structure. The electrodes may be metallic electrodes, for example In this example, the input EDT 402 comprises a first periodic electrode structure 402a and the output IDT 404 comprises a second periodic electrode structure 404a. The input IDT 402 is provided at a first location of the piezoelectric substrate 406 and the output EDT 404 is provided at a second location of the piezoelectric substrate 406 such that there is a space between the input EDT 402 and the output DT 404.

100411 Those skilled in the art will appreciate that a piezoelectric material can generate an electric charge in response to mechanical stress. Furthermore, a piezoelectric material can deform and generate mechanical stress in response to an applied electric field. An alternating electrical signal can be applied to the input DT 402 such that adjacent electrodes have opposite polarities and the polarity of each electrode alternates according to the applied alternating electrical signal. Such a signal causes there to be a region of compressive stress next to a region of tensile stress, and each region alternates between compressive and tensile stress. As a result of this alternating compressive and tensile stress, there is generated a mechanical wave. This mechanical wave is what is referred to as a surface acoustic wave (SAW), as described above. SAWs in the SAW sensor element 302 are generated at the resonant frequency of the SAW sensor element 302.

100421 In the example of Figure 4, the SAW travels from the input IDT 402 to the output IDT 404. The alternating regions of compressive and tensile stress caused by the SAW at the output [DT cause there to be alternating electric fields. These alternating electric fields generate an electrical signal in the output IDT such that the polarities of adjacent electrodes of the output IDT 404 alternate in the manner described above for the input IDT 402. In other words, an electrical signal is generated at the output IDT 404 by the reverse of the process which took place at the input EDT 402 to generate the SAW from the input electrical signal.

100431 As previously described, the physical properties (such as temperature, for example) of the SAW sensor element may be determined based on the output signal. The characteristics of the SAW in the SAW sensor element 302 depend on the physical properties of the SAW sensor element such as temperature. Therefore, by detecting the characteristics of the SAW, the temperature of the SAW sensor element 302 can be determined. For example, the characteristics of the SAW are detected using the output signal generated by the output 1DT 404 in response to an interrogation signal received at the input 1DT 402.

100441 Various characteristics of the SAW may be detected. For example, a delay relating to the transmission of the interrogation signal and receipt of the output signal in response from the temperature sensing device 300, a phase shift response of the SAW sensor element 302, and/or a resonant frequency of the SAW sensor element 302 may be detected. For example, the frequency of the output signal corresponds to the frequency of the SAW and therefore the resonant frequency of the SAW sensor element 302. A desired physical property of the SAW sensor element 302 (such as temperature) may then be determined from the detected characteristic of the SAW sensor element 302.

100451 A predefined relationship between the detected characteristic (for example, the resonant frequency) of the SAW sensor element 302 and the temperature of the SAW sensor element 302 may be stored in a computer readable memory (for example, in the computing system 106) on the aircraft 100, for example. The predefined relationship specifies what the detected characteristic of the SAW sensor element 302 is expected to be at various different temperatures (for example, obtained from calibration and/or testing of the SAW sensor element 302). For example, from a given resonant frequency, the temperature of the SAW sensor element 302 is determined from the predefined relationship. The predefined relationship may be stored in the form of a look-up table, rule, correlation equation, graph, etc. 100461 The predefined relationship may be determined by performing calibration or other test on the SAW sensor element 302. For example, test may be performed to cause the SAW sensor element 302 to resonate at different temperatures and determine the resonant frequencies at those temperature in order to establish the predefined relationship.

100471 As previously described, the temperature sensing device 300 is attached to one of the brake discs 202. In the example of Figure 2, the temperature sensing device is attached to one of the stators 210. Therefore, the temperature of the SAW sensor element 302 corresponds to the temperature of the brake disc to which it is attached.

100481 The interrogation signal may be wirelessly received by the temperature sensing device 300. The temperature sensing device 300 may comprise (as in the example of Figure 3) a sensor antenna 304 configured to wirelessly receive the interrogation signal, and supply the interrogation signal to the SAW sensor element 302. For example, the sensor antenna 304 receives the interrogation signal in the form of radio waves and converts the radio waves into an electrical signal. The SAW sensor element may be configured to, responsive to the interrogation signal, output a signal as a response (the described output signal), the output signal indicative of the resonant frequency of the SAW sensor element 302, to the sensor antenna 304. For example, the sensor antenna 304 may be configured to wirelessly transmit the output signal. For example, the sensor antenna 304 converts the electrical output signal into radio waves.

100491 For example, the sensor antenna 304 supplies the interrogation signal to the input IDT 402 of the SAW sensor element 302. The interrogation signal as received at the input IDT 402 is an alternating electrical signal which causes the input IDT 402 to generate a SAW as previously described. The SAW sensor element 302 provides an output signal (generated by the output IDT 404 as previously described). For example, the output signal is supplied from the output IDT 404 to the sensor antenna 304. The sensor antenna 304 transmits the output signal. For example, the sensor antenna 304 is electrically coupled to the input IDT 402 and the output IDT 404. The origin of the interrogation signal and the components which receive and process the output signal are described later.

100501 A change in temperature of the SAW sensor element 302 causes a change in the resonant frequency. For example, as the temperature of the SAW sensor element 302 increases, the resonant frequency of the SAW sensor element decreases The frequency of the SAW depends on the spacing between the electrodes of the 1DTs. The spacing between adjacent electrodes is referred to as the pitch of the IDT in question. The pitch determines the wavelength of the SAW generated by the IDT. The pitch is equal to half of the wavelength of the SAW generated by the IDT Therefore, the desired frequency resonant frequency of the SAW sensor element 100511 The frequency of the SAW depends on the propagation velocity of the SAW and the wavelength of the SAW according to Equation (1) below. (1)

100521 In Equation (1), f represents the frequency of the SAW, 17.s. represents the propagation velocity of the SAW in the SAW sensor element in question, and A represents the wavelength of the SAW.

100531 The frequency of the SAWs generated in the SAW sensor element 302 can be referred to as the resonant frequency of the SAW sensor element. It will be appreciated that, for a given propagation velocity of the SAW in the SAW sensor element 302, the resonant frequency of the SAW sensor element 302 can be configured by selecting an appropriate pitch for the 1DTs of the SAW sensor element 302 100541 The temperature of the SAW sensor element 302 may be determined by detecting the resonant frequency of the SAW sensor element 302 as indicated by the output signal 100551 Figure 5 schematically illustrates an example of a temperature sensing system 500 for sensing aircraft wheel brake temperature. The temperature sensing system 500 comprises the temperature sensing device 300 according to any of the described examples. The temperature sensing system 500 also comprises a wireless relay device 502 for delivering the interrogation signal for wirelessly interrogating the SAW sensor element 302. The wireless relay device 502 delivers the interrogation signal by wirelessly transmitting the interrogation signal to the temperature sensing device 300. The wireless relay device 502 also wirelessly receives the described output signal. The wireless relay device 502 is hereafter simply referred to as the relay 502.

100561 In some examples, the relay 502 comprises a relay antenna 504. The relay antenna wirelessly transmits the interrogation signal and wirelessly receives the output signal. In some such examples, the relay 502 is simply a device for communicating wirelessly with the temperature sensing device 300. As described, the temperature sensing device 300 may be attached to one of the brake discs 202. The relay 502 may be attached to a component of the brake 200 or wheel 104 such that it can wirelessly communicate with the temperature sensing device 300 attached to a brake disc. For example, the relay 502 may be mounted so as to maintain line of sight with the temperature sensing device 300.

100571 The wireless communication between the temperature sensing device 300 and the relay 502 can be implemented, for example, by electromagnetic, inductive or capacitive coupling of the relay 502 to the temperature sensing device 300. For example, each of the sensor antenna 304 and the relay antenna 504 may be configured to convert electrical signals to radio waves and vice versa, with the radio waves being transmitted between the respective antennas.

100581 In some examples, the temperature sensing device 300 is attached to the first stator 210a and the relay 502 is attached to the torque tube 218 to which the first stator 210a is keyed. In such examples, the relay 502 is attached to the torque tube at a position so as to be in the line of sight of the temperature sensing device 300 on the first stator 210a. In other examples, the temperature sensing device 300 may be attached to a different brake disc or a different component of the brake 200, and the relay 502 may be attached to an appropriate location to maintain line of sight with the temperature sensing device 300.

100591 The temperature sensing system 500 may comprise an interrogation apparatus 506. The interrogation apparatus 506 may form part of the computing system 106 of the aircraft 100. In such examples, the interrogation apparatus 506 forms a communication link (which may be wireless or wired) with the relay 502. The interrogation apparatus 506 comprises a controller 508 configured to provide the interrogation signal. For 1:3 example, the controller 508 may provide the interrogation signal based on a command signal received from another component of the computing system 106. The command signal may comprise the interrogation signal, and the interrogation signal may simply be retransmitted towards to the relay 502. In other examples, the command signal may be an instruction for the controller 508 to generate the interrogation signal 100601 In the example of Figure 5, the interrogation apparatus 506 comprises a transceiver 510 for transmitting the interrogation signal to the relay 502 and receiving the described output signal from the relay 502. The transceiver 510 may communicate with the relay 502 via a wired communication link or wirelessly. For example, for wireless communication, respective antennas may be provided as part of the relay 502 and the interrogation apparatus 506.

100611 The SAW sensor element 302 has a resonant frequency within a frequency range between 175 megahertz (MHz) and 190MHz at a predetermined temperature. A frequency range between 175MHz and 190N1Hz is not limited to a range having 175i\THz as a lower limit and 190MHz as an upper limit. For example, the frequency range may be any range that falls between 175 MHz and 190 MHz (for example, 175 MHz to 180 MHz, 176 MHz to 188 MHz, 180 MHz to 190 MHz, etc.). In some examples, the resonant frequency of the SAW sensor element 302 is within the frequency range when the temperature of the SAW sensor element 302 is within a predetermined temperature range (for example, 24°C to 1000°C).

100621 According to examples, the temperature sensing device 300 comprises the SAW sensor element 302 and the sensor antenna 304. The sensor antenna 304 is electrically coupled to the SAW sensor element 302. The sensor antenna 304 is for receiving an interrogation signal and transmitting an output signal that is responsive to the interrogation signal 100631 In some examples, the sensor antenna 304 is a planar sensor antenna.

100641 Figure 6 is a schematic plan view of a planar sensor antenna 600. The planar sensor antenna 600 is a more specific example of the previously described sensor antenna 304 100651 The planar sensor antenna 600 comprises two loops of a conductor material. The planar sensor antenna 600 comprises a double loop of the conductor material. As referred to herein, two loops of a conductor material mean that the conductor material forms a continuous track which loops around twice in order to form the planar sensor antenna 600. The planar sensor antenna 600 comprises a first conductive loop 600a and a second conductive loop 600b of the conductor material. As shown in Figure 6, the first conductive loop 600a is continuous with the second conductive loop 600b. The loops are, for example, disposed on a surface 602 of a substrate 604 to provide the planar sensor antenna 600. In some examples, the loops are formed on the surface 602 of the substrate 604 by, for example, depositing the conductor material. In some examples, pre-formed conductor material (for example, a wire) is disposed on the surface 602 of the substrate 604 to provide the planar sensor antenna 600. Figure 6 also shows the SAW sensor element 302. In some examples, there is provided a tuning stmcture 606 on the sensing device substrate 604, described in further detail later. The sensing device substrate 604 may carry components (not shown in Figure 6) of the temperature sensing device 300 other than the planar sensor antenna 600, and the SAW sensor element 302 and the tuning structure 606.

100661 The conductor material may be any conductor material suitable for providing an antenna. For example, the conductor material may copper, aluminium, another conductive metal, or a non-metallic conductor material. In some examples, the planar sensor antenna 600 comprises a wire arranged to form the planar sensor antenna 600. In some examples, the wire is a bond wire.

100671 The substrate 604 may be or comprise a layer of a ceramic material As described, the sensor antenna 600 is electrically coupled to the SAW sensor element 302 (any electrical connections that may be present are not shown in Figure 6). The substrate 604 therefore carries electronic components of the temperature sensing device 300 which contribute to sensing temperature. The substrate 604 may also be referred to as the sensing device substrate 604.

100681 The surface 602 of the sensing device substrate 604 is a planar surface. Therefore, by arranging the conductor material on the surface 602 to form an antenna as described, the planar sensor antenna 600 is provided. In some examples, the planar sensor antenna 600 is a printed antenna.

100691 For example, conductor material is arranged on the surface 602 of the sensing device substrate 604 to form the first conductive loop 600a and the second conductive loop 600b on the planar surface 602 so that the resultant antenna is planar. For example, a wire (for example, a bond wire) is so arranged to form the planar sensor antenna 600.

100701 Two loops of the conductor material may advantageously provide a stronger signal to and from the SAW sensor element 302 than a different number of loops of the conductor material. For example, Figure 7 is a simplified schematic plan view of an alternative planar sensor antenna 700. The alternative planar sensor antenna 700 comprises four loops disposed on the surface 702 of the sensing device substrate 704. The four loops are provided by a continuous track of conductor material which loops around four times in order to form the planar sensor antenna 700. Other electronic components which may be present (e.g. a SAW sensor element and a tuning structure) are not shown in Figure 7.

100711 The inventors surprisingly found that the planar sensor antenna 600 comprising two loops of the conductor material provided a SAW sensor element signal at -29.0dB, whereas the planar sensor antenna 700 comprising four loops of the conductor material provided a SAW sensor element signal at -31.6dB. In other words, the inventors surprisingly found that the planar sensor antenna 600 comprising two conductive loops provides a stronger SAW sensor element signal than the planar sensor antenna 700 comprising four conductive loops 100721 Providing a stronger SAW sensor element signal means that the planar sensor antenna 600 converts more of the wirelessly received interrogation signal into an electrical signal provided to the SAW sensor element 302 Providing a stronger SAW sensor element signal also means that the planar sensor antenna 600 converts more of the output signal output by the SAW sensor element 302 into a wirelessly transmitted signal (for example, a radio frequency (RF) signal).

100731 The planar sensor antenna 600 is electrically coupled to the one or more IDTs of the SAW sensor element 302 (electrical connections between the planar sensor antenna 600 and the SAW sensor element 302 are not shown). In some examples, the planar sensor antenna 600 is electrically coupled to the SAW sensor element by a bond wire of diameter 1 millimetre (mm). For example, the planar sensor antenna 600 is electrically coupled to the one or more IDTs by a lmm bond wire. In the case of the example two-port SAW sensor element of Figure 4, the planar sensor antenna 600 is electrically coupled to both the input IDT 402 and the output IDT 404.

100741 In some examples, each of the conductive loops of the planar sensor antenna 600 forms a parallelogram. In some such examples, each of the loops of the planar sensor antenna forms a rectangle or a square. In the particular example shown in Figure 6, the first conductive loop 600a forms a rectangle, and the second conductive loop 600b forms a rectangle. The surface 602 may be a parallelogram such as a rectangle or a square. The loops of the planar sensor antenna 600 being in the form of a parallelogram therefore make better use of the available surface 602 than, for example, circular or elliptical loops. For example, for a rectangular surface, a greater part of a rectangular antenna loop may be close to the boundaries of the rectangular surface.

100751 In some examples, the planar sensor antenna 600 is electrically coupled to the tuning structure 606 (any electrical connections that may be present are not shown in Figure 6) In such examples, the planar sensor antenna 600 may be electrically coupled to the one or more IDTs of the SAW sensor element 302 via the tuning structure 606. For example, the tuning structure 606 is introduced in series (for example, in terms of electrical connection) between the planar sensor antenna 600 and the SAW sensor element 302. Those skilled in the art will appreciate that the tuning structure 606 may improve power transfer between the SAW sensor element 302 and the planar sensor antenna 600 by matching the impedance of the SAW sensor element 302 to the impedance of the planar sensor antenna 600, for example 100761 There may be provided a brake disc for an aircraft wheel brake comprising the temperature sensing apparatus 300 comprising the planar sensor antenna 600, according to any of the described examples, attached to the brake disc. There may be provided an aircraft comprising such a brake disc 100771 The substrate 604 carrying the described electronic components may be packaged or housed in a housing to provide the temperature sensing device 300. For example, the sensor antenna is an internal antenna and is not provided on an external surface of the temperature sensing device 300. Instead, the sensor antenna is an internal component of the temperature sensing device 300.

100781 In some examples, the relay antenna 504 may comprise any of the features described in relation to the sensor antenna. For example, the relay antenna 504 may comprise two loops of a conductor material, the loops formed on a surface of a substrate to provide a planar relay antenna.

100791 Figure 8 is a flow diagram illustrating a method 800 of manufacturing a temperature sensing device comprising the described planar sensor antenna 600 according to any of the described examples. At block 802 of the method 800, a planar sensor antenna for receiving an interrogation signal and transmitting an output signal that is responsive to the interrogation signal is produced. The planar sensor antenna comprises two loops of a conductor material, the loops formed on a surface of a substrate to provide the planar sensor antenna. In the following description of the method 800, reference is made to the features shown in Figure 6.

100801 For example, performing block 802 involves arranging the conductor material on the planar surface 602 to form the planar sensor antenna 600. For example, block 802 involves printing the planar sensor antenna 600 on the planar surface 602 using the conductor material. For example, the conductor material is printed onto the surface 602 of the sensing device substrate 604 For the printing, any suitable technique used in printing circuit components and/or connections onto a printed circuit board may be used. For example, photolithographic techniques may be used to print the planar sensor antenna 600 onto the surface 602 of the sensing device substrate 604. In some examples, a wire is arranged on the surface 602 of the sensing device substrate 604 in order to form the planar sensor antenna 600.

100811 In some examples, the planar sensor antenna 600 is produced at block 802 such that each of the loops of the planar sensor antenna 600 forms a parallelogram. For example, the first loop 600a forms a rectangle and the second loop 600b also forms a rectangle. Producing the planar sensor antenna 600 at block 802 may involve producing the planar sensor antenna 600 according to any of the described examples. Those skilled in the art will appreciate the various techniques which may be used to deposit or otherwise provide conducting material on the planar surface 602 in order to produce electronic components such as the described planar sensor antenna 600.

100821 At block 804 of the method 800, the temperature sensing device (e.g., the temperature sensing device 300) comprising the planar sensor antenna 600 (e.g., as produced at block 1302) electrically coupled to a SAW sensor element (e.g., the described SAW sensor element 302) is provided. For example, the planar sensor antenna 600 is electrically coupled to the input IDT 402 and the output IDT 404 of the SAW sensor element 302. The SAW sensor element 302 may be provided on, or as part of, the sensing device substrate 604. In such examples, the sensing device substrate 604 with the planar sensor antenna 600 and the SAW sensor element 302 electrically coupled to the planar sensor antenna 600 may be provided as part of the temperature sensing device 300.

100831 In some examples, block 804 comprises providing the tuning structure 606 electrically coupled to the planar sensor antenna 600. For example, the tuning structure 606 is electrically couples the SAW sensor element 302 to the planar sensor antenna 600. The tuning structure 606 may be formed by depositing the same conducting material used for the planar sensor antenna 600 (or a different conducting material) onto the planar surface 602 in an appropriate pattern. Those skilled in the art will appreciate the configuration of a tuning structure between an antenna and an electronic device which receives and/or outputs a signal to that antenna.

100841 Certain components are described as being electrically coupled to other components. In some examples, components may be electrically coupled by virtue of an electrical connection. Those skilled in the art will appreciate that electronic components may also be capacitively or inductively coupled, for example. The type of electrical coupling depends on the characteristics of the electronic components and the particular application.

100851 It should be noted that the Figures show simplified schematic views for the purpose of illustration. The Figures are intended to illustrate the described concepts and are not intended to convey dimensions, relative sizes of components and the like In some cases, certain components are not shown for simplicity, as will be appreciated by those skilled in the art 100861 Although the invention has been described above with reference to one or more preferred examples, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1.
A temperature sensing device for sensing aircraft wheel brake temperature, the temperature sensing apparatus comprising: a surface acoustic wave, SAW, sensor element; and a planar sensor antenna electrically coupled to the SAW sensor element, the planar sensor antenna for receiving an interrogation signal and transmitting an output signal that is responsive to the interrogation signal, wherein: the planar sensor antenna comprises two loops of a conductor material, the loops disposed on a surface of a substrate to provide the planar sensor antenna.
The temperature sensing device according to claim 1, wherein: the SAW sensor element comprises an interdigital transducer, IDT and the planar sensor antenna is electrically coupled to the IDT The temperature sensing device according to claim 2, wherein: the SAW sensor element comprises an input IDT and an output MT; and the planar sensor antenna is electrically coupled to both the input IDT and the output IDT.
4. The temperature sensing device according to any one of the preceding claims, wherein: each of the loops of the planar sensor antenna forms a parallelogram.
The temperature sensing device according to claim 4, wherein: each of the loops of the planar sensor antenna forms a rectangle or a square.
6. The temperature sensing device according to any one of the preceding claims, wherein: the planar sensor antenna is electrically coupled to the SAW sensor element by a bond wire of diameter 1 millimetre.
7. The temperature sensing device according to any one of the preceding claims, wherein: the planar sensor antenna is electrically coupled to a tuning structure.
8. A brake disc for an aircraft wheel brake comprising the temperature sensing device according to any one of claims 1 to 7 attached to the brake disc.
An aircraft comprising the brake disc according to claim 8
10. A method of manufacturing a temperature sensing device for sensing aircraft wheel brake temperature, the method comprising: producing a planar sensor antenna for receiving an interrogation signal and transmitting an output signal that is responsive to the interrogation signal, the planar sensor antenna comprising two loops of a conductor material, the loops disposed on a surface of a substrate to provide the planar sensor antenna: providing the temperature sensing device comprising the planar sensor antenna electrically coupled to a surface acoustic wave, SAW, sensor element.
1 1. The method according to claim 10 comprising: providing the temperature sensing device comprises electrically coupling the planar sensor antenna to an input interdigital transducer, IDT, of the SAW sensor element, and to an output IDT of the SAW sensor element.
12. The method according to claim 10 or claim 11 comprising: producing the planar sensor antenna such that each of the loops of the planar sensor antenna forms a parallelogram.