Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation
Reexamination Certificate
1998-12-07
2002-06-11
Hunter, Daniel (Department: 2684)
Telecommunications
Receiver or analog modulated signal frequency converter
Local control of receiver operation
C455S078000, C455S086000, C455S086000, C455S343200
Reexamination Certificate
active
06405025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method according to the preamble of claim
1
for selecting the frequency range in radio communication devices operating in several frequency ranges, so called multiband radio communication devices.
The invention also relates to a multiband radio communication device.
2. Description of the Prior Art
Of the existing digital cellular networks, the GSM (Global System for Mobile telecommunications) is the most extensively used at the moment. Because the networks suffer from congestion, the GSM system, which originally had an operating frequency of 900 MHz, has been extended to 1.8 GHz. There are also cellular networks of other standards widely used in the world. Because the mobility of people and communications between people are increasing, there is a need for combined telephones, which operate on several different networks, depending on which network is available and/or which network offers services to the users at the lowest price.
In addition, in the so called third generation cellular systems (UMTS/FLPMTS, Universal Mobile Telecommunication System/Future Public Land Mobile Telecommunication System) it is possible to use several frequency ranges within the same system. Because of these reasons, efforts have been made to develop radio communication devices which can operate in several different frequency ranges and/or in network systems of different standards. In order to simplify the explanation, the frequency ranges used by different systems are handled in this patent application as if they were always different frequency ranges, although in some cases it is possible that different systems use the same frequency ranges.
In radio communication devices operating in many different frequency ranges, the duplexing and multiple access methods of different systems must be matched. Duplexing means separating communications in the transmit and receive direction from each other in a data transfer connection between two transceiver devices. Common methods are Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD). Multiple access means dividing the capacity of the system or a part of it (such as a base station) between many terminal devices (such as radio communication devices). Common methods are Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA). In addition, different multiplexing methods are applied in the systems, whereby one device directs information received from several sources to a common transfer channel and separates the transmissions from one another e.g. by Time Division Multiplexing (TDM) or Frequency Division Multiplexing (FDM), for example.
A prior art radio communication device operating in two directions by time or frequency division multiplexing contains many RF and intermediate frequency filters both on the transmit (TX) and receive (RX) side.
FIG. 1
shows a prior art GSM communication device
100
. In the GSM system, the transmission and reception take place in different time slots and at different frequencies. The communication device
100
includes the receiver (RX) branch
11
and the transmitter (TX) branch
12
. The selection of whether the communication device operates in the reception state or the transmission state can be performed by means of an antenna switch (not shown) placed e.g. between the inputs of the branches
11
and
12
and the antenna
21
, whereby the selected branch is connected to the antenna
21
. The antenna switch that connects the antenna to the transmitter branch
11
and the receiver branch
12
in turn, is used in radio communication devices for separating the signals if the system has time division duplexing (TDD). If the transmission and reception take place in different frequency ranges, a filter
22
like the duplex filter used in analog telephones can be used as the separating unit, as in the solution shown in FIG.
1
.
The duplex filter
22
is a circuit device with three gates, comprising a reception branch filter
22
RX between the antenna and reception gate and a transmission branch filter
22
TX between the transmitter and antenna gate. The operating frequencies of the filters have been selected so that a transmission frequency signal does not get to the receiver gate and a reception frequency signal does not get to the transmission gate. The frequency properties of the filters can be adjustable.
On the reception side
11
, the GSM communication device
100
includes a Low Noise Amplifier (LNA)
32
, the input gate of which is connected to the duplex filter
22
. The amplifier
32
is followed by a bandpass filter
33
, which filters the received signal. The output gate of the filter
33
is connected to a mixer
34
, in which the received signal is mixed with the first mixing signal coming from the synthesizer
23
. The intermediate frequency signal produced as the mixing result is directed to the RF circuit
35
of the receiver for further processing.
The signal
45
produced in the transmitter part
12
of the communication device
100
at the pre-stage of the transmitter (not shown) is mixed in the mixer
44
with the first mixing signal. The output of the mixer
44
is taken to the bandpass filter
43
, which is generally situated before the power amplifier
42
of the transmitter. The output of the power amplifier
42
is coupled through the duplex filter
22
to the antenna
21
. Between the power amplifier
42
and the duplex filter
22
there is often a directional coupler (not shown), by which the power level of the signal going to the antenna can be measured.
FIG. 2
shows a prior art dual mode radio communication device
200
operating in two different frequency ranges as an example of multiband radio communication devices operating in several frequency ranges. In the radio communication device
200
, both frequency ranges share the same antenna
21
. An antenna switch
50
connects the shared antenna
21
to the component chain (a or b) forming the desired transmitter-receiver according to the frequency range used. The operations of the selected component chain are mainly the same as shown in FIG.
1
and in the case of the component chain a they comprise a duplex filter
22
a
and in the reception branch RXa an amplifier
32
a
and a bandpass filter
33
a
, and in the transmission branch TXa a bandpass filter
43
a
and a power amplifier
42
a
. Correspondingly, when another frequency range/system is used, the components being used are the duplex filter
22
b
and the signal path going through the amplifier
32
b
of the reception branch RXb and the filter
33
b
, or the signal path going through the filter
43
b
of the transmitter branch TXb and the amplifier
42
b.
Switch
51
on the reception side and switch
52
on the transmission side operate synchronously with the antenna switch
50
and connect the selected transmission and reception branches via mixers
34
and
44
to the common modulation and demodulation components of a dual mode telephone, and through them to other components of the communication device.
The prior art solution shown in
FIG. 2
above has the problem of attenuation in the switches
50
,
51
,
52
and in the duplex filters
22
a
and
22
b.
SUMMARY OF THE INVENTION
An object of the invention is to provide a new method for selecting the frequency range of a radio communication device that operates i.e. transmits and/or receives in at least two different frequency ranges.
Another object of the invention is to provide a new radio communication device, especially a new mobile station.
A method according to the invention for selecting one of the frequency ranges of a radio communication device operating in at least two different frequency ranges, comprises the step of activating an amplifier in a signal path corresponding to said frequency range among the group of the amplifiers placed in the signal paths of a signal branch of the radio communication device. In a preferred embodiment of the invention the activating of
Gantt Alan T.
Hunter Daniel
Nokia Mobile Phones Limited
Perman & Green LLP
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