Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-04-22
2001-07-03
Chang, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S084000, C455S314000, C455S553100
Reexamination Certificate
active
06256511
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a dual mode radio architecture and, in particular, relates to the same for use in a mobile radio handset.
BACKGROUND ART
Personal communication networks are being deployed extensively worldwide using mobile radio systems. Early cellular networks, still in operation, use analogue modulation formats for the radio air interface protocol. These analogue networks exhibit the problem of call saturation in high usage areas. The North American AMPS system is typical of such an analogue system.
To overcome this problem higher capacity air interface protocols using digital modulation format networks have been introduced, oftentimes operating in tandem with analogue networks, providing cellular radio coverage that by both systems. Examples of digital moblie phone networks currently in operation are the PCS1900, DCS1800 and GSM systems, which are national and supra-national standardised radio air interface protocols (AIPs).
Nevertheless, these networks exhibit the problem of not having global operation. To overcome this problem, additional global radio air interface protocols using digital modulation format networks via satellite have been introduced, such as the digital ODYSSEY system. Furthermore, short range cordless networks, such as the digital CT2 version of the US unlicensed UPCS band, or DECT are becoming increasingly employed.
In a large country such as the United States or Canada the early standardised analogue network known as AMPS has reached a fairly universal coverage of the populated North American continent. The newer digital networks tend to be deployed in areas of high usage. A result of this is that there are areas of digital network coverage overlaying a universal analogue network coverage. Additionally different air interface protocol standards of digital networks have been deployed regionally, since different telecommunications operators have developed their own protocols or have developed such protocols in line with national and sometimes international standards authorities, for example, the GSM protocol.
Whilst it is reasonable to suppose that handsets operable for different radio communications protocols are similar from the users point of view, it is not possible, in particular, to use a digital mobile radio for use in an analogue cellular region and vice versa. This stems from the fact that whilst both types of handsets possess antennas, radio front end transmitter, receiver and baseband circuits, they operate on different air interface protocols with different radio carrier frequencies, duplex timing and modulation formats, which are incompatible.
Therefore it can be seen that each individual personal communications system user will need a dual network service for complete coverage. Consequently the user requires a handset that will not only function throughout the coverage area of the specific subscribed-to digital network, but also have a switched alternative mode to operate on the universal analogue network.
There is a likely deployment scenario where the mobile terminal user wishes to access the two communication operating systems. Therefore there is a need for a dual-mode PCS1900/AMPS, PCS/UDCS, PCS/ODYSSEY, DCS1800/GSM, GSM/DECT, DCS1800/DECT, JDC/Handyphone and JDC/ODYSSEY handsets, to name but a few.
The problem of implementing a dual mode handset has been considered to be surmountable by two different approaches: The first solution uses two separate radio transceivers piggybacked and combined at the antenna and at the man-machine interface (keyboard and audio); The second solution uses two separate radio sections piggybacked and combined at the digital signal processing part of the radio transceiver. These two approaches have problems in that they are complicated and unwieldy, and it is clear that a dual-mode radio architecture with an increased functional commonality of circuits would be the most cost effective solution.
OBJECT OF THE INVENTION
The present invention seeks to provide a dual mode radio architecture.
STATEMENT OF INVENTION
In accordance with one aspect of the present invention, there is provided a radio front end transceiver operable to receive and transmit radio signals in different frequency bands and modulation formats, the transceiver comprising; receive and transmit paths for each modulation format, wherein common receive and transmit intermediate frequency circuitry is employed and the local oscillator requirements for the intermediate frequency to baseband conversion are derived from a single frequency synthesiser.
Preferably, the first local oscillator requirements for the intermediate frequency to radio frequency conversion are derived from a single frequency synthesiser.
Preferably, a single first local oscillator is used and the required dual mode operation is achieved by using a dual band voltage controlled oscillator and a programmable synthesiser. The first local oscillator can employ overlap tuning in order to constrain the voltage controlled oscillator tuning range appropriate for the dual band.
The transceiver can comprise a single second local oscillator, wherein the required dual mode operation is achieved by integer division of the second local oscillator to derive the required local oscillator input signals. Two first local oscillators can be used and the required dual mode operation can be achieved by operating each of the required RF front-ends from a specific first local oscillator.
The higher frequency radio system local oscillator bands can be arranged to overlap, by switching intermediate frequencies, whereby the tuning range is constrained to avoid retuning between transmit and receive.
Preferably the transceiver is provided with a means to determine the operational mode. Alternatively, switch means may be provided to effect a change in operational mode.
In accordance with another aspect of the present invention, there is provided a radio transceiver comprising a combination of functional block circuits and frequency plan,
wherein, in a first circuit, disparate radio air interface signals are downconverted, with a first local oscillator, and filtered with switched separate intermediate frequency filters, amplified and converted using a second local oscillator, to in-phase and quadrature baseband signals, in a common sub-system of functional blocks,
wherein, in a second circuit, disparate baseband modulation format in-phase and quadrature signals are upconverted to their respective disparate radio air interface signals in a common subsystem of functional blocks configured as a phase lock loop upconverting modulator, which uses a common first local oscillator to the receive circuit and a reference derived from the prime second local oscillator,
wherein, the frequency synthesis is arranged so that only two phase locked voltage controlled oscillators are required, with the two receive second local oscillator frequencies integer relationship derived from the prime second local oscillator, itself phase locked to the frequency reference, and the first local oscillator frequencies all derived from the same frequency reference, with the higher frequency radio system local oscillator bands arranged to exactly overlap, by switching intermediate frequencies, so as to constrain the tuning range to avoid retuning between transmit and receive.
The present invention also provides a handset incorporating a dual band transceiver.
In accordance with another aspect of the invention, there is provided a method of operating a radio front end transceiver operable to receive and transmit radio signals in different frequency bands and modulation formats, wherein for each modulation format the same receive and transmit intermediate frequency circuitry is employed and the local oscillator requirements for the intermediate frequency to baseband conversion are derived from a single frequency synthesiser.
In accordance with another aspect of the invention, there is provided a method of operating a radio front end transceiver operable to receive and transmit radio signals in different fre
Ansorge Christian
Brown David Alan
Edwards Fraser Murray
Nisbet John Jackson
Appiah Charles N.
Chang Vivian
Lee Mann Smith McWilliams Sweeney & Ohlson
Nortel Network Limited
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