Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1997-12-18
2001-02-27
Le, Thanh Cong (Department: 2684)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S084000, C455S086000
Reexamination Certificate
active
06195563
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to a radio frequency receiver and a radio frequency transmitter. In particular, the present invention relates to a radio frequency (RF) receiver or radio frequency (RF) transmitter suitable for incorporating in a radio telephone operable in both terrestrial and satellite networks.
Current mobile telephone systems are mainly provided by ground based (terrestrial) cellular systems such as GSM (Global System for Mobiles), PDC 800 or AMPS (American Mobile Phone System). Other mobile telephone systems include the Inmarsat-M satellite system, in which subscribers use briefcase-sized mobile telephones to make calls via geo-stationary orbiting satellites.
Several new proposals for mobile satellite telephone systems are currently under development by major telecommunications companies. These global systems have been well publicised and are known commercially by the trade names ICO, IRIDIUM, GLOBALSTAR and ODYSSEY. In parallel with the launch of these new mobile satellite systems, several terminal equipment manufacturers are developing handheld mobile units for use by subscribers of these systems. Some terminal equipment manufacturers are proposing developing dual-mode handsets which operate on both the ground based cellular systems and the new mobile satellite systems.
WO 96/08883 discloses a dual mode telephone device which is operable on both satellite and land based cellular communication systems. The device includes one set of antenna and radio frequency circuits for receiving and transmitting signals in a satellite network, and another set of antenna and radio frequency circuits for receiving and transmitting in a terrestrial network. A dual mode frequency synthesiser provides for wide channel spacings when supplying the terrestrial radio frequency circuits and narrow channel spacings when supplying the satellite radio frequency circuits.
BRIEF SUMMARY OF INVENTION
According to a first aspect of the present invention there is provided a radio frequency receiver operable in a first mode and a second mode, the first mode being a terrestrial mode in which the receiver operates in a terrestrial network, the second mode being a satellite mode in which the receiver operates in a satellite network, the radio frequency receiver comprising: a first front-end RF stage for receiving a terrestrial signal of the terrestrial network and providing a first output signal characteristic of the terrestrial signal, a second front-end RF stage for receiving a satellite signal of the satellite network and providing a second output signal characteristic of the satellite signal, and a common RF stage including an input for receiving either the first output signal or the second output signal and including mixing circuitry for frequency down-converting the first or second output signal to enable subsequent decoding.
A dual mode receiver in accordance with the invention provides an advantage that radio frequency (RF) circuitry used in receiving the terrestrial signal may also be used in receiving the satellite signal. Thus a receiver in accordance with the invention may operate with a reduced component count when compared to existing dual mode receivers. A reduced component count may in turn reduce the cost of the receiver, and may also save space within the receiver. Furthermore, if the power consumption of the receiver is dependent on the number of components then by reducing the component count the power consumption of the receiver may accordingly be reduced.
The process of mixing is also referred to as frequency translation, frequency changing, or heterodyning.
In one preferred embodiment the first output signal is at a lower frequency than the frequency of the terrestrial signal. Accordingly, the first front-end RF stage may comprise mixing circuitry.
In another preferred embodiment the first output signal is at substantially the same frequency as the frequency of the terrestrial signal. In this case the first front-end RF stage may be a terrestrial antenna.
Ideally the first output signal and the second output signal are at substantially the same frequency. This provides an advantage that by being at the same frequency the first or the second output signals may be processed in the same manner by the common RF stage. For example, a bandpass filter which is used in the common RF stage may have the same frequency response when receiving the first or the second output signals. Also, a mixer circuit used in the common RF stage may be supplied with a local oscillator signal with the same frequency when receiving the first or the second output signals.
In a preferred embodiment the second output signal is at a lower frequency than the frequency of the satellite signal. Accordingly, the second front-end RF stage may comprise mixing circuitry.
Preferably, the first front-end, the second front-end, and/or the common RF stages include filtering means and amplifying means. The amplifying means may amplify the relatively weak satellite or terrestrial signal received from the satellite or terrestrial network. The filtering means may reject unwanted signals received from the satellite or terrestrial network or reject spurious signals produced inherently by the receiver circuitry.
In a preferred embodiment the mixing circuitry of the common RF stage frequency down-converts the first or second output signal via an intermediate frequency. After performing the frequency down-conversion the mixing circuitry may provide the frequency down-converted first or second output signal to a base band circuit which performs the subsequent decoding.
The common RF stage may include switching means for selectively receiving the first or second output signal.
According to a second aspect of the present invention there is provided a radio frequency transmitter operable in a first mode and a second mode, the first mode being a terrestrial mode in which the transmitter operates in a terrestrial network, the second mode being a satellite mode in which the transmitter operates in a satellite network, the radio frequency transmitter comprising: a common RF stage including mixing circuitry for frequency up-converting a modulation signal to an intermediate signal, and first and second outputs for providing the intermediate signal to a subsequent RF stage, a first terminal RF stage for receiving the intermediate signal from the first output and transmitting a terrestrial signal characteristic of the intermediate signal for reception by the terrestrial network, and a second terminal RF stage for receiving the intermediate signal from the second output and transmitting a satellite signal characteristic of the intermediate signal for reception by the satellite network.
A dual mode transmitter in accordance with the invention provides an advantage that radio frequency (RF) circuitry used in transmitting a modulation signal in the terrestrial network may also be used in transmitting a modulation signal in the satellite network. Thus a transmitter in accordance with the invention may operate with a reduced component count when compared to existing dual mode transmitter solutions. A reduced component count may in turn reduce the cost of the transmitter and may also save space within the transmitter. Furthermore, if the power consumption of the transmitter is dependent on the number of components then by reducing the component count the power consumption of the transmitter may be accordingly reduced.
In one preferred embodiment the terrestrial signal is at a higher frequency than the frequency of the intermediate signal. Accordingly, the first terminal RF stage may comprise mixing circuitry.
In another preferred embodiment the terrestrial signal is at substantially the same frequency as the frequency of the intermediate signal. In this case the first terminal RF stage may be a terrestrial antenna.
In a preferred embodiment the satellite signal is at a higher frequency than the frequency of the intermediate signal. Accordingly, the second terminal RF stage may comprise mixing circuitry.
Preferably,
Cong Le Thanh
Nokia Mobile Phones Limited
Perman & Green LLP
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