GB2461556A - Controlling throughput to control temperature in an ultrawideband (UWB) transceiver circuit - Google Patents

Abstract

The invention relates to a temperature control system and method in a first ultrawideband (UWB) transceiver circuit which is in radio data communication with a second, remote UWB transceiver circuit. The method comprises: sensing a temperature of the first UWB transceiver circuit; determining whether the temperature exceeds a threshold temperature; determining, in response to the temperature exceeding the threshold temperature, an upper data throughput limit for the radio data communication; and controlling one of the first and the second UWB transceiver circuits to bring a throughput of the radio data communication below the upper data throughput limit, to control the temperature of the first UWB transceiver circuit. Preferably the controlling does not (or does not only) involve reduction of the on-air data rate as such a reduction can actually result in higher temperatures due to the transceiver circuit operating for longer. Preferably, the controlling reduces the duty cycle or average duration for which the transceiver is transmitting or receiving, by e.g. employing the MAC (medium access control) to reserve fewer time periods for communications, omitting acknowledgement messages, controlling RTS/CTS (request to sent/clear to send) signaling or employing a hibernation mode. The invention is particularly applicable to a circuit comprising a pair of integrated circuit dies mounted in a single package. A second invention relates to a UWB transceiver circuit including a power limitation system where a look up table stores data for linking an upper limit of desired power consumption, associated with a selectable operating mode, with an associated upper data throughput limit for radio data communication with a second, remote UWB transceiver circuit and where one of the UWB transceiver circuits is controlled to bring the radio data communication throughput below an upper limit to limit the power consumption of the first UWB transceiver circuit.

Description

Intellectual Property Office mm For Creetity and Innovation Application No. GBO8 12183.2 RTM Date:29 October 2008 The following terms are registered trademarks and should be read as such wherever they occur in this document: WiMedia UK Intellectual Property Office is an operating name of The Patent Office Ultrawideband Transceiver Systems

FIELD OF THE INVENTION

The invention relates to systems and methods for temperature control in ultrawideband (UWB) transceiver circuits. Other aspects of the invention relate to similar systems for limiting the maximum power consumption of a UWB transceiver.

BACKGROUND TO THE INVENTION

The MultiBand OFDM Alliance (MBOA), more particularly the WiMedia Alliance, has published a standard for a UWB physical layer (PHY) for a wireless personal area network (PAN) supporting data rates of up to 480 Mbps ("MultiBand OFDM Physical Layer Specification", release 1.1, July 14, 2005; release 1.2 is now also available). The WiMedia Alliance has also published standard for a UWB Medium Access Control (MAC) layer, "Distributed Medium Access Control (MAC) for Wireless Networks", release 1.01, December 15, 2006. The skilled person in the field will be familiar with the contents of these documents, which are not reproduced here for conciseness.

However, reference may be made to these documents to assist in understanding embodiments of the invention. Further background material may be found in Standards ECMA-368 and ECMA-369.

Broadly speaking a number of band groups are defined, for example one at around 30Hz and a second at around 6GHz, in Europe and the USA each comprising three 528MHz bands (in Japan the 6GHz use of the band group is more restricted). Figure 1 a, which is taken from ECMA-368, shows the band group allocation (band group 2 is effectively unavailable because it overlaps with WiFi (Registered Trade Mark)). The OFDM scheme employs 110 sub-carriers including 100 data carriers which, at the fastest encoded rate, carry 200 bits using DCM (dual carrier modulation). A 3/4 rate Viterbi code results in a maximum data under the current version of this specification of 480Mbps. Reduced signal strength, interference and like can reduce this data rate down to a specified minimum rate of approximately 53Mbps. The OFDM symbols are transmitted at 3.2MHz, that is about 3 per microsecond.

ECMA-368 defines a MAC standard including a distributed protocol for access and allocation of addresses. There is no central control node and instead a distributed reservation protocol (DRP) is employed, broadly a device observing which resources are used by other devices and then making a choice of address and channel time; a conflict resolution protocol is also provided. Frequency reuse is employed and each device beacons to its neighbour, mainly for the purposes of the MAC, inter alia to maintain synchronisation. A variable length beacon period is divided into 85 jis beacon slots and a device beacon provides information about the neighbours of a device (other devices it can "hear" -receive from) and therefore a received beacon can provide a device with information relating to its neighbour's neighbours including, in particular the occupancy of beacon slots. Broadly a device is able to transmit in a slot if it appears free and it also perceived as free by the device's neighbours' this enables spatial reuse of frequencies.

Communications in the MAC layer are organised into superframes, each superframe comprising 256 medium access slots each of 256 ps (a total of 65 ms). A device may use one or more MAS slots depending upon the requirements of a communication channel between devices. Figure ib, which is taken from ECMA-368, shows the MAC superframe structure and Figure ic shows details of a beacon period (BP).

Figure 1 d shows the general format of an example MAC frame for a beacon including from 1 to N information elements (JEs) for BPO (Beacon Period Occupancy) and DRP (Distributed Reservation Protocol) data, as well as other information elements. The MAC header comprises, in addition to control information and information identifying the type of frame (0 for a beacon frame), a source and destination address each specified by a 16 bit device address (DevAddr) which is generated locally by a device, essentially randomly avoiding addresses known to be used by neighbours and neighbour's neighbours. Most (but not all) devices also have a globally unique 48 bit extended unique identifier (EUI48TM) and provision is also made for including this value in a beacon.

The BPO information element (BPOIE) provides information on the beacon period (see Figure ic) as observed by the device sending the BPOIE. The BPOIE includes a bit map of occupied beacon slots, formatted as a variable length array with each element corresponding to a beacon slot and the DevAddrs corresponding to the beacon slots encoded as occupied in the beacon slot information bit map (in sending beacon slot order). Beacon slots 0 and 1 are signalling slots used for a device to advertise when a slot is used, since the length of the beacon period (in terms of number of slots) is variable, for power saving, and thus devices extend their view of the beacon period as necessary.

As mentioned above, different applications have different requirements in terms of throughput and maximum delay (latency), and this translates into a repetition rate of an allocated time slot within a single superframe having a slot duration of n MAS periods, repeated in subsequent superframes. The pattern of MASs depends upon the type and priority of data -for example real time delay data requires a low latency whereas for bulk data transmission the delay is of little consequence but a large channel time is desirable.

The MAC co-ordinates access within a superframe. The DRP protocol enables an initiating device ("owner") to make a claim for channel time between the owner and another device ("target). Broadly the owner device decides on the request and inserts a DRP information element in its outgoing beacon claiming some MASs which it believes are free DRP IFs in the beacons from other devices. Thus the owner sends a DRP and qualifies the target with a target address (DevAddr). The target device is responsible for granting the request and for providing ongoing reconfirmation during the period of use that the channel time requested by the owner remains free.

Details of a DRP reservation request and response can be found in BCMA-368 sections 16.5.1 and 16.5.2 (hereby incorporated by reference) and details of the DRP TB can be found in ECMA-368 sections 16.8.6 and 16.8.7 (also hereby incorporated by reference).

Details of the DRP IE are shown in Figure le (upper); details of the "DRP Control" field in the DRP 1E are shown in Figure 1 e (lower), both taken from ECMA-368; the DRP IE is used to negotiate a reservation of MASs and to announce reserved MASs. In the DRP Control field the reservation status bit indicates the status of the negotiation process (zero under negotiationlconflict; set to one by a device granting or maintaining a reservation). The owner bit indicates if the device transmitting the DRP TB is the reservation owner; the conflict tie-breaker bit is set to a random value when a reservation request is made; the Unsafe bit indicates when any of the MASs identified in the DRP Allocation fields is considered in excess of reservation limits (the reservation is unsafe because part of the reservation may be seized by another device).

As explained in ECMA-368 section 16.8,6, the DRP lB contains one or more DRP Allocation fields each encoded using a zone structure.

The inventors have recognised that the MAC of a UWB transceiver may be employed to address problems of temperature control, which become particularly acute at high data rates when the instantaneous power consumption is high, especially as there is a continuing drive to reduce the physical size of the transceiver circuitry.

SUMMARY OF THE INVENTION

According to the present invention there is therefore provided a method of controlling temperature in a first ultrawideband (UWB) transceiver circuit, wherein said first UWB transceiver circuit is in radio data communication with a second, remote UWB transceiver circuit, the method comprising: sensing a temperature of said first UWB transceiver circuit; determining whether said temperature exceeds a threshold temperature; determining, in response to said temperature exceeding said threshold temperature, an upper data throughput limit for said radio data communication; and controlling one of said first and said second UWB transceiver circuits to bring a throughput of said radio data communication below said upper data throughput limit, to control said temperature of said first UWB transceiver circuit.

Counter-intuitively, in a UWB transceiver reducing the on-air data rate can result in the circuit becoming hotter since although the peak power is reduced the transceiver circuit operates for longer. Thus reducing the on-air data rate could result in thermal runaway and therefore, in preferred embodiments, a UWB transceiver circuit is controlled to reduce the overall data throughput without, or not only by, reducing the on-air data rate.

In embodiments, however, communications operate at substantially a maximum on-air data rate for a negotiated perceptible packet or frame error rate, given the throughput limit. This helps to achieve minimum power consumption for a desired throughput.

Without a constraint on throughput there can in effect be conflicting requirements arising from the twin aims of minimising power consumption and controlling temperature so that it does not exceed a determined limit, although this is not obvious since one might expect controlling operation to minimise power consumption would.

automatically minimise the risk of overheating.

In some preferred embodiments the controlling comprises controlling an average duration, or duty cycle of transmit/receive, for which one or both of the first and second UWB transceiver circuits is transmitting or receiving, Preferably this control comprises controlling an operational mode of the UWB transceiver circuit via the MAC interface of the circuit.

This again is counter-intuitive since although one might expect transmitting to employ more power than receiving, in embodiments of UWB transceiver circuits receiving and transmitting use similar amounts of power. In embodiments of the method, therefore, the controlling may comprise controlling an average duration for which a transmitter of the first UWB transceiver circuit is operating and/or sending a signal from the first UWB transceiver circuit to the second UWB transceiver circuit, to control a duration to which a transmitter of the second UWB transceiver circuit is operating. (In this context controlling of the operation of a UWB transceiver circuit preferably comprises controlling a clock signal applied to the circuit, although the controlling may additionally or alternatively comprise controlling power applied to a transceiver circuit).

In the first, local transceiver circuit the skilled person will appreciate that a range of teclmiques may be employed to control when this circuit is transmitting. In embodiments of the method, to control when the local transceiver is receiving a message is, in effect, sent to the remote transceiver to control transmissions from this device. One approach is simply to omit acknowledgements sent by the first UWB transceiver to the second, remote transceiver; another possibility is to control the RTS/CTS (request to send/clear to send) signalling since RTS is employed to announce to a recipient device that a frame is ready for transmission, requesting confirmation of ability to receive, and the CTS response is required to confirm that the recipient is ready to receive. A further option is to employ a Hibernation Mode, as specified in the standard ECMA-368, in which a device indicates that it will go into hibernation for one or more superframes, intending to wake later (and in which DRP reservations with the device are maintained. The address of a device in hibernation mode is still advertised and unicast traffic for the device is buffered until it once more becomes active. As mentioned above, however, preferred implementations do not adapt the on-air data rate as this could result in thermal runaway, for example the error rate increasing resulting in a reduced data rate and hence increased heating due to increasing on time.

The invention also provides a carrier processor control code to implement the above-described methods, for example code for a hardware description language such as Verilog (Trade Mark) or VHDL (Very high speed integrated circuit Hardware Description Language) or SystemC, although alternatively the code may additionally or alternatively comprise source, object or executable code in a conventional programming language (interpreted or compiled) such as C, or assembly code, or code for setting up or controlling an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). As the skilled person will appreciate such code and/or data may be distributed between a plurality of coupled components in communication with one another.

In a related aspect the invention provides an ultrawideband (UWB) transceiver circuit including a temperature control system, wherein said UWB transceiver circuit is able to be in radio data communication with a second, remote UWB transceiver circuit, the temperature control system comprising: a sensor to sense a temperature of said UWB transceiver circuit; a system to determine whether said temperature exceeds a threshold temperature; a system to determine, in response to said temperature exceeding said threshold temperature, an upper data throughput limit for said radio data communication; and a system to control one of said UWB transceiver circuit and said second, remote UWB transceiver circuit to bring a throughput of said radio data communication below said upper data throughput limit, to control said temperature of said UWB transceiver circuit.

Preferably the transceiver circuit is implemented on two dies, a digital/mixed signal die and an RF (radio frequency) die, both mounted within a single package. This is a useful technique for manufacturing a UWB transceiver, but the temperature control problems in such an arrangement can be particularly acute -and therefore embodiments of the invention are particularly advantageous in the context of such an arrangement. The temperature sensor may be implemented, for example, as a semiconductor junction on one of the dies.

According to a further related aspect of the invention there is provided an ultrawideband (LTWB) transceiver circuit, wherein said UWB transceiver circuit is in radio data communication with a second, remote UWB transceiver circuit, the UWB transceiver circuit including a power limitation system comprising: a power mode select input to receive data for selecting one of a plurality of different operating modes of the UWB transceiver, each with an associated upper-limit of desired power consumption of said UWB transceiver circuit; a lookup table storing, for each of said operating modes, data for linking a said upper-limit power consumption with an associated upper data throughput limit for said radio data communication; and a power control system coupled to said power mode select input and to said lookup table, to control one of said IJWB transceiver circuit and said second, remote UWB transceiver circuit to bring a throughput of said radio data communication below said upper data throughput limit to limit a power consumption of said UWB transceiver circuit.

In some preferred embodiments the operating modes include at least one mode in which the power consumption is substantially unlimited by the power control system, and the second mode in which an upper-limit of the power consumption of the UWB transceiver circuit is limited by limiting a maximum throughput of the LTWB radio data communications between the transceiver and the second, remote transceiver circuit.

Preferably the power control system is implemented in or coupled to a medium access control (MAC) system of the UWB transceiver circuit, in particular to control an average duration for which a transmitter of the UWB transceiver circuit is operating.

However in some particularly preferred embodiments the power control system also includes a mechanism to control power in a receive circuit of the TJWB transmitter, in particular by sending a signal to the second, remote UWB transceiver or by omitting to send a response to this second, remote transceiver, in order to reduce an average time for which the second, remote transceiver is transmitting to the receive circuit of the local UWB transceiver.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will now be further described, by way of example only, with reference to the accompanying figures in which: Figures la to le show, respectively, band group and band allocation in MB-OFDM UWB, a MAC superframe structure, details of a beacon period (BP), a general format of an example MAC frame for a beacon including beacon period occupancy (BPO) and distributed reservation protocol (DRP) data, and a DRP IE and details of the DRP

Control field;

Figures 2a to 2c show, respectively, an outline functional diagram of a UWB communications system according to an embodiment of the invention, an outline block diagram of a UWB transceiver configured to implement an embodiment of the invention, and example physical arrangements of UWB dies on a substrate; Figures 3a to 3c show, respectively, a detailed block diagram of an MAC system of a UWB transceiver configured to implement an embodiment of the invention, a flow diagram of a UWB transceiver temperature control procedure according to an embodiment of the invention, and TJWB transceiver MAC sub-system implementing a power consumption limitation system according to an embodiment of an aspect of the invention; Figure 4 shows a block diagram of a UWB transmitter sub-system suitable for use with embodiments of the invention; Figure 5 shows a block diagram of a UWB receiver sub-system suitable for use with embodiments of the invention; and Figures 6a and 6b show, respectively, a block diagram of a PHY hardware implementation for an OFDM UWB transceiver, and an example RF front end for the transceiver of Figure 6a.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Broadly speaking we will describe a UWB transceiver communication system in which, if the temperature becomes too high, the transmit/receive time or duty cycle is reduced to cool an IC (integrated circuit) implementation of the transceiver. However embodiments do not reduce the on-air data rate but instead reduce the throughput, thus allowing use of an on-air data rate which is substantially the maximum possible without thermal runaway. Embodiments do not simply control the on-air data rate, which could result in thermal runaway; instead in preferred implementations the MAC is employed to effectively reserve fewer time periods for communications. This can be considered as reducing the proportion of a duty cycle during which the transmitter and/or receiver of the transceiver operates (or is clocked). To reduce the receive duty cycle the MAC is employed to signal to the transmitter end to, in effect, control the local receive duty cycle by signalling to control transmissions by one or more remote UWB transceivers transmitting to the local T.JWB receiver.

The invention further contemplates a UWB transceiver, for example as described with reference to aspects and embodiments of the invention, which dispenses with sensing a temperature and determining a maximum throughput in response to a sensed temperature, instead determining a maximum throughput in response to a desired upper-limit on power consumption. In embodiments this may be employed to implement a plurality of different operational modes each corresponding to a different upper-limit power consumption, for example a maximum throughput mode for when, say, mains power is available for powering the UWB transceiver, and one or more reduced power modes for when, say, the UWB transceiver is operated by battery power.

Referring now to Figure 2a, this shows a simplified, conceptual diagram of a UWB communication system incorporating first and second UWB transceivers 202a, b configured to implement data throughput-based temperature control in accordance with a preferred embodiment of the invention. Figure 2b shows an outline block diagram of a UWB transceiver 202 of Figure 2a. The receiver comprises a MAC subsystem 204 coupled to a PHY sub-system 206 and to an I/O processor 208 providing an external datalcontrol interface for the transceiver. A management sub-system 210 is coupled to MAC 204; this incorporates a temperature control procedure 212, as described further later, responsive to sensed temperature of one or more dies on which the UWB transceiver is implemented.

Figure 2c shows, schematically, example physical layouts for the UWB transceiver of Figure 2b which, as illustrated, comprises first and second dies on a common substrate.

A first die (Die 1) may carry digital/mixed signal circuitry and in embodiments may dissipate for example of order 0.5 Watt; the second die (Die 2) may be an RF die dissipating perhaps 0.7 Watts on average. Inside their package with no heat sink and an ambient temperature of order 25°C the die temperature is at risk of exceeding the maximum permitted junction temperature of, say, around 80°C. This is a particular risk in the flip-chip mounted die configuration illustrated on the right hand side of Figure 2c.

In preferred embodiments of the UWB transceiver, therefore, one or both of Die 1 and Die 2 incorporate an on-die temperature sensor, for example a semiconductor junction, which is able to be read via a register on the chip in order to implement a temperature control procedure for either or both of the dies to inhibit overheating.

Returning to Figures 2a and 2b, if the temperature is greater than a threshold then management sub-system 210 is able to signal to MAC 204 to reduce a percentage of time for which the transceiver is either or both of transmitting and receiving. However this is not done by controlling the on-air data rate since it is likely that standards-based control procedures dictate this. Similarly in embodiments there is no direct control of the time for which the receiver and/or transmitter circuits are on (power and/or clock supplied) since typically circuitry is already implemented to control these and associated base band circuits in an efficient manner. Thus indirect control, via data throughput, is employed, thus enabling embodiments of the invention to be retroactively applied without necessitating a redefinition of lower level UWB operating procedures.

Referring now to Figure 3a, this shows a medium access control (MAC) system 300 for a UWB transceiver (the physical layers of which are described below with reference to Figures 4 to 6), the MAC system 300 being configured to implement a temperature limitation procedure according to an embodiment of the invention, as described above.

The MAC system 300 comprises a message parsing interface (MPI) 302 with a bidirectional data and control connection, "X" to the physical layer hardware shown in Figures 4 to 6. The MPI 302 is coupled to an MPI controller 304, which also interfaces to AES (Advanced Encryption Standard) hardware 306, which has a separate connection to MPI 302. The MPI controller 304 is coupled to a hi-directional data and control bus 308 to which are coupled a plurality of DMAC (Direct Memory Access Control) units including an MPT DMAC 310, an EDT (Electronic Data Interchange) DMAC 312, an SPI (Serial Peripheral Interface) DMAC 314, a serial DMAC 316, a USB (Universal Serial Bus) DMAC 318 and an SDIO (Secure Digital I/O memory card) DMAC 320. Each of DMACs 312 -320 is coupled to a respective controller and then to a corresponding interface. Bus 308 is also coupled to an AHB (Advanced High- Performane Bus) interface 322 which in turn is coupled to memory 324 including non-volatile code and data memory Boot ROM 324a, code memory (RAIVI) 324b and data memory (RAM) 324c; bus 308 is also coupled to shared memory (RAM) 326.

In embodiments of the MAC system 300 the boot and/or code memory 324a,b stores code to implement a temperature controller 212. One or more temperature sensors 214a, b are read by temperature controller 212 which controls the power consumption of the UWB transceiver to inhibit overheating.

Figure 3b shows an example of a control procedure in which, at step 250, controller 212 reads the temperature of one or both dies via sensors 214 and then determines (step 252) whether or not the temperature is greater than a permitted threshold. The step of determining whether the temperature is greater than a threshold is optional and may be omitted. Thus in the following step 254 the procedure uses a lookup table 256 to read a maximum permitted throughput (or data identifying this) from the table, corresponding to the determined temperature. The procedure then signals or controls the MAC to reduce the throughput, and hence temperature of the integrated circuit (step 258); the procedure then loops back to step 250.

The skilled person will be aware that there are a number of different ways in which the MAC may be controlled to reduce the proportion of time for which the transmitter of the UWB transceiver is operating, for example by controlling request of a fewer number of transmission slots. The procedure may signal to a remote, transmitting UWB transceiver in a number of different ways. For example, data acknowledgements expected to be sent by the receiving transceiver may simply be omitted or a more complex control procedure may be implemented, for example putting the local device into a hibernation mode by including a Hibernation Mode Information Element in a beacon that the device transmits before entering hibernation mode. In still other implementations the transmit request/acknowledgement protocol may be modified.

Figure 3c shows a medium access control (MAC) system 300 similar to that of Figure 3a (in which like elements are indicated by like reference numerals), and including a power limitation system 220 configured to implement a plurality of different maximum limited power consumption operating modes, as described above. Such a power limitation system may be in addition to or instead of a temperature control system as previously described.

In Figure 3c a power limitation system 220 is implemented as processor control code in memory 324. The power limitation system 220 receives an input comprising data defining a power limitation operational mode, for example via one or more of the interfaces illustrated in Figure 3c. The power limitation controller then reads maximum throughput data from a lookup table (not shown in Figure 3c, for simplicity) and controls the MAC to limit the throughput, and hence power consumption, in a way similar to that described above for limiting a maximum operating temperature of the integrated circuit.

Figures 4 to 6 described below show functional and structural block diagrams of an OFDM UWB transceiver for use with the MAC hardware described above.

Thus referring to Figure 4, this shows a block diagram of a digital transmitter sub-system 800 of an OFDM UWB transceiver. The sub-system in Figure 4 shows functional elements; in practice hardware, in particular the (I) FFT may be shared between transmitting and receiving portions of a transceiver since the transceiver is not transmitting and receiving at the same time.

Data for transmission from the MAC CPU (central processing unit) is provided to a zero padding and scrambling module 802 followed by a convolution encoder 804 for forward error correction and bit interleaver 806 prior to constellation mapping and tone nulling 808. At this point pilot tones are also inserted and a synchronisation sequence is added by a preamble and pilot generation module 810. An IFFT 812 is then performed followed by zero suffix and symbol duplication 814, interpolation 816 and peak-2-average power ratio (PAR) reduction 818 (with the aim of minimising the transmit power spectral density whilst still providing a reliable link for the transfer of information). The digital output at this stage is then converted to I and Q samples at approximately lGsps in a stage 820 which is also able to perform DC calibration, and then these I and Q samples are converted to the analogue domain by a pair of DACs 822 and passed to the RF output stage.

Figure 5 shows a digital receiver sub-system 900 of a UWB OFDM transceiver.

Referring to figure 5, analogue I and Q signals from the RF front end are digitised by a pair of ADCs 902 and provided to a down sample unit (DSU) 904. Symbol synchronisation 906 is then performed in conjunction with packet detectionlsynchronisation 908 using the preamble synchronisation symbols. An FFT 910 then performs a conversion to the frequency domain and ppm (parts per million) clock correction 912 is performed followed by channel estimation and correlation 914.

After this the received data is demodulated 916, de-interleaved 918, Viterbi decoded 920, de-scrambled 922 and the recovered data output to the MAC. An AGC (automatic gain control) unit is coupled to the outputs of a ADCs 902 and feeds back to the RF front end for AGC control, also on the control of the MAC.

Figure 6a shows a block diagram of physical hardware modules of a UWB OFDM transceiver 1000 which implements the transmitter and receiver functions depicted in figures 4 and 5. The labels in brackets in the blocks of figures 4 and 5 correspond with those of figure 6a, illustrating how the functional units are mapped to physical hardware.

Referring to figure 6a an analogue input 1002 provides a digital output to a DSU (down sample unit) 1004 which converts the incoming data at approximately 1 Gsps to 528Mz samples, and provides an output to an RXT unit (receive time-domain processor) 1006 which performs sample/cycle alignment. An AGC unit 1008 is coupled around the DSU 1004 and to the analogue input 1002. The RXT unit provides an output to a CCC (clear channel correlator) unit 1010 which detects packet synchronisation; RXT unit 1006 also provides an output to an FFT unit 1012 which performs an FFT (when receiving) and IFFT (when transmitting) as well as receiver zero-padding processing.

The FFT unit 1012 has an output to a TXT (transmit time-domain processor) unit 1014 which performs prefix addition and synchronisation symbol generation and provides an output to an analogue transmit interface 1016 which provides an analogue output to subsequent RF stages. A CAP (sample capture) unit 1018 is coupled to both the analogue receive interface 1002 and the analogue transmit interface 1016 to facilitate debugging, tracing and the like. Broadly speaking this comprises a large RAIVI (random access memory) buffer which can record and playback data captured from different points in the design.

The FFT unit 1012 provides an output to a CEQ (channel equalisation unit) 1020 which performs channel estimation, clock recovery, and channel equalisation and provides an output to a DEMOD unit 1022 which performs QAM demodulation, DCM (dual carrier modulation) demodulation, and time and frequency de-spreading, providing an output to an INT (interleave/dc-interleave) unit 1024. The INT unit 1024 provides an output to a VIT (Viterbi decode) unit 1026 which also performs de-puncturing of the code, this providing outputs to a header decode (DECHDR) unit 1028 which also unscrambles the received data and performs a CRC 16 check, and to a decode user service data unit (DECSDU) unit 1030, which unpacks and unscrambles the received data. Both DECHDR unit 1028 and DECSDU unit 1030 provide output to a MAC interface (MACIF) unit 1032 which provides a transmit and receive data and control interface for the MAC.

In the transmit path the MACIF unit 1032 provides outputs to an ENCSDU unit 1034 which performs service data unit encoding and scrambling, and to an ENCHDR unit 1036 which performs header encoding and scrambling and also creates CRC 16 data.

Both ENCSDU unit 1034 and ENCHDR unit 1036 provide outputs to a convolutional encode (CONY) unit 1038 which also performs puncturing of the encoded data, and this provides an output to the interleave (INT) unit 1024. The INT unit 1024 then provides an output to a transmit processor (TXP) unit 1040 which, in embodiments, performs QAM and DCM encoding, time-frequency spreading, and transmit channel estimation (CHE) symbol generation, providing an output to (I)FFT unit 1012, which in turn provides an output to TXT unit 1014 as previously described.

Referring now to figure 6b, this shows, schematically, RE input and output stages 1050 for the transceiver of figure 6a. The RE output stages comprise VGA stages 1052 followed by a power amplifier 1054 coupled to antenna 1056. The RE input stages comprise a low noise amplifier 1058, coupled to antenna 1056 and providing an output to further multiple VGA stages 1060 which provide an output to the analogue receive input 1002 of figure 6a. The power amplifier 1054 has a transmit enable control 1054a and the LNA 1058 has a receive enable control 1058a; these are controlled to switch rapidly between transmit and receive modes.

Broadly speaking we have described a UWB transceiver system which includes a control ioop to limit a maximum throughput in response to a measured temperature of a die or dies of integrated circuit implementation of the IJWB transceiver. In preferred embodiments the transceiver signals temperature control information to another end of a link to the UWB transceiver, to facilitate control of receiver as well as transmitter power consumption. In embodiments power consumption is controlled via a maximum permissible throughput, controlling a maximum permissible proportion of time for which a transmitter and/or receiver (and associated baseband circuitry) is operating (power and/or clock applied). We have also described UWB transceiver systems which implement a plurality of different operating modes with different power consumption limitations; these are able to operate over a range of different underlying standards.

Again in preferred embodiments power consumption limitationloperating mode information is signalled to a remote transceiver with which the local UWB transceiver has a link. The operating modes may define, for example, operational profiles such as mains-powered/on-charge, long-life, maximum throughput, battery exhausted and the like.

No doubt many effective alternatives will occur to the skilled person. It will therefore be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the spirit and scope of the claims appended hereto.

Claims (15)

1. CLAIMS: 1. A method of controlling temperature in a first ultrawideband (UWB) transceiver circuit, wherein said first UWB transceiver circuit is in radio data communication with a second, remote IJWB transceiver circuit, the method comprising: sensing a temperature of said first UWB transceiver circuit; determining whether said temperature exceeds a threshold temperature; determining, in response to said temperature exceeding said threshold temperature, an upper data throughput limit for said radio data communication; and controlling one of said first and said second UWB transceiver circuits to bring a throughput of said radio data communication below said upper data throughput limit, to control said temperature of said first UWB transceiver circuit.
2. 2. A method as claimed in claim 1 wherein said controlling to bring said throughput below said upper data throughput limit does not comprise controlling to reduce an on-air data rate of said radio data communications.
3. 3. A method as claimed in claim 1 or 2 further comprising operating at substantially a maximum on-air data rate of said radio data communications for an established acceptable packet or frame error rate.
4. 4. A method as claimed in claim 1, 2 or 3 wherein said controlling comprises controlling an average duration for which a said UWB transceiver circuit is one or both of transmitting or receiving.
5. 5. A method as claimed in any one of claims 1 to 4 wherein said controlling comprises controlling an operational mode of a said UWB transceiver circuit via a MAC (Medium Access Control) interface of said circuit.
6. 6. A method as claimed in any one of claims 1 to 5 wherein said controlling comprises controlling an average duration for which a transmitter of said first UWB transceiver circuit is operating.
7. 7. A method as claimed in any one of claims 1 to 6 wherein said controlling comprises sending a signal from said first UVTB transceiver circuit to said second 1JVTB transceiver circuit to control a duration for which a transmitter of said second UWB transceiver circuit is operating.
8. 8. A method as claimed in any preceding claim wherein said controlling comprises controlling application of a clock signal to at least part of said first UWB transceiver circuit.
9. 9. A method as claimed in any preceding claim wherein said first UWB transceiver circuit comprises a pair of integrated circuit dies mounted within a single package, a first, digital circuit die and a second radio frequency circuit die, and wherein said sensing of a temperature comprises sensing a temperature of one of said dies.
10. 10. An ultrawideb and (LTWB) transceiver circuit including a temperature control system, wherein said UWB transceiver circuit is able to be in radio data communication with a second, remote UWB transceiver circuit, the temperature control system comprising: a sensor to sense a temperature of said UWB transceiver circuit; a system to determine whether said temperature exceeds a threshold temperature; a system to determine, in response to said temperature exceeding said threshold temperature, an upper data throughput limit for said radio data communication; and a system to control one of said UWB transceiver circuit and said second, remote UWB transceiver circuit to bring a throughput of said radio data communication below said upper data throughput limit, to control said temperature of said UWB transceiver circuit.
11. 11. An ultrawideband (LTWB) transceiver circuit, wherein said UWB transceiver circuit is able to be in radio data communication with a second, remote UWB transceiver circuit, the UWB transceiver circuit including a power limitation system comprising: a power mode select input to receive data for selecting one of a plurality of different operating modes of the UWB transceiver, each with an associated upper-limit of desired power consumption of said UWB transceiver circuit; a lookup table storing, for each of said operating modes, data for linking a said upper-limit power consumption with an associated upper data throughput limit for said radio data communication; and a power control system coupled to said power mode select input and to said lookup table, to control one of said UWB transceiver circuit and said second, remote UWB transceiver circuit to bring a throughput of said radio data communication below said upper data throughput limit to limit a power consumption of said UWB transceiver circuit.
12. 12. An ultrawideband transceiver circuit as claimed in claim 11 wherein said operating modes include at least a first operating mode in which said power consumption is substantially unlimited by said power control system, and a second operating mode in which a said upper-limit of power consumption is applied by said power control system.
13. 13. An ultrawideband transceiver circuit as claimed in claim 11 or 12 wherein said power control system coupled to a medium access control (MAC) system of said UWB transceiver circuit.
14. 14. An ultrawideband transceiver circuit as claimed in claim 11, 12 or 13 wherein said power control system is configured to control an average duration for which a transmitter of said UWB transceiver circuit is operating.
15. 15. An ultrawideband transceiver circuit as claimed in any one of claims 11 to 14 wherein said power control system includes a system to control power in a receive circuit of said UWB transmitter by sending a signal to or omitting to send a response to said second, remote UWB transceiver, to reduce an average time for which said second, remote UWB transceiver is transmitting to said receive circuit.