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Mobile Phone Patent Abstract
The switchable up-conversion loop device for a transmitting stage
of a mobile phone having multiple transmitting frequency bands includes
a phase detector (21) for generating a phase detector output signal
in response to a phase difference between an input signal and a
mixing product signal, multiple switchable voltage controlled oscillators
(35, 37; 100, 101, 102; 111, 112; 120), each connected to the phase
detector (21) and each generating an output oscillating signal,
the frequency of which depends on the phase detector output signal,
and a coupling device (44; 110; 119; 121) for coupling the output
oscillating signal to a mixer (26) for mixing said output oscillating
signal with a locally generated oscillating signal to produce the
mixing product signal.
Mobile Phone Patent Claims
We claim:
1. A switchable up-conversion loop device for a transmitting stage
of a mobile phone having multiple transmit frequency bands, said
up-conversion loop device comprising: a phase detector (21) generating
a phase detector output signal in response to a phase difference
between an input signal and a mixing product signal, multiple switchable
voltage controlled oscillators (35, 37; 100, 101, 102; 111, 112;
120), each of said voltage controlled oscillators being connected
to the phase detector (21) via a low pass filter (32) for generating
an output oscillating signal at a frequency which depends on the
phase detector output signal, and coupling means (44; 110; 119;
121) for coupling the output oscillating signal to a mixer (26)
for mixing said output oscillating signal with a locally generated
oscillating signal to produce said mixing product signal.
2. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, further comprising
a switching unit (40) including means for connecting or interrupting
a supply voltage to said multiple switchable voltage controlled
oscillators in order to switch the multiple switchable voltage controlled
oscillators (35, 37; 100, 101, 102; 111, 112; 120) on or off by
means of the switching unit (40).
3. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 2, wherein the multiple
switchable voltage controlled oscillators (35, 37; 100, 101, 102;
111, 112; 120) include one-band voltage controlled oscillators (35;
100, 101, 102) covering one transmit frequency band and/or multiple-band
voltage controlled oscillators (37; 112; 120) covering a plurality
of transmit frequency bands.
4. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 3, wherein said multiple-band
voltage controlled oscillators (37; 112; 120) are switchable between
said transmit frequency bands in response to a band switch control
signal.
5. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 4, further comprising
a control unit (23) including means for generating the band switch
control signal.
6. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 2, further comprising
a control unit (23) connected to said switching unit (40) and said
control unit (23) connects or interrupts a supply voltage to said
voltage controlled oscillators (35, 37; 100, 101, 102; 111, 112;
120) in response to an oscillator switching control signal from
said control unit (23).
7. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 6, wherein said multiple
switchable voltage controlled oscillators (37; 112; 120) comprise
at least one multiple-band voltage controlled oscillator (135) consisting
of an oscillator transistor (135), multiple resonance circuits (130a,
130b, . . . 103n) forming an oscillator circuit device together
with the oscillator transistor (135), and a switching element (132)
responsive to said oscillator switching control signal; and wherein
a respective one of said resonance circuits is connectable to said
oscillator transistor (135) by means of said switching element (132)
according to said oscillator switching control signal.
8. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, wherein the coupling
means (44; 110; 109; 121) couples the output oscillating signal
into said mixer (26).
9. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 8, wherein said mixer
(26) multiplies said locally generated oscillating signal with the
output oscillating signal received from said coupling means (44;
110; 109; 121).
10. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, further comprising
a loop filter (32) connected between said phase detector (21) and
said multiple switchable voltage controlled oscillators.
11. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, further comprising
a modulation means (5) for generating an input signal for said phase
detector (21).
12. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 11, wherein said modulation
means (5) is a minimum shift keying modulator.
13. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 12, further comprising
frequency dividing units (20,24) for dividing respective frequencies
of the input signal and the mixing product signal and wherein said
control unit (23) includes means for controlling the frequency dividing
units.
14. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 3, wherein each of said
multiple-band voltage controlled oscillators is a two-band voltage
controlled oscillator (37;112) covering two transmit frequency bands.
15. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 3, wherein each of the
multiple-band voltage controlled oscillators is a three-band voltage
controlled oscillator (120) covering three transmit frequency bands.
16. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 3, wherein three of
said one-band voltage controlled oscillators (100, 101, 102) are
connected to said phase detector (21) each covering one transmit
frequency band.
17. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 3, wherein one of said
one-band voltage controlled oscillators (35; 111 ) covering one
transmit frequency band and one two-band voltage controlled oscillator
(37; 112) covering two transmit frequency bands are connected to
said phase detector (21).
18. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 15, wherein said three-band
voltage controlled oscillator (120) covering three transmit frequency
bands is connected to said phase detector (21).
19. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, wherein said transmit
frequency bands are transmit frequency bands of a GSM system.
20. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 19, wherein said transmit
frequency bands of said GSM system consist of GSM 900, GSM 1800
and GSM 1900.
21. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, further comprising
a power amplifier (53,55) including means for amplifying the output
oscillating signal from said coupling means (44; 110; 119; 121)
to form an amplified output oscillating signal.
22. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, wherein the amplified
output oscillating signal is input to an antenna switching unit
(66) which switches said amplified output oscillating signal to
a transmitting antenna (67) according to an antenna control signal
from said control unit (23).
23. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, further comprising
a low pass filter (28) for filtering the mixing product signal produced
by said mixer (26) to suppress unwanted mixing products.
24. The switchable up-conversion loop device for a transmitting
stage of a mobile phone as defined in claim 1, further comprising
a PLL circuit (49) for generating the locally generated oscillating
signal in response to a controlling signal generated by said control
unit (23).
Mobile Phone Patent Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switchable up-conversion loop
device for a transmitting stage of a mobile phone.
2. Prior Art
Although applicable to any digital mobile phone system, the present
invention and its underlined problems will be discussed with particular
reference to a GSM mobile phone system.
The Global System for Mobile Telecommunication GSM is designed
as an international digital cellular service. Originally, the 900-Megahertz
band was reserved for GSM services. Since GSM first entered commercial
service in 1992, it has been adapted to work at 1800 MHz for the
Personal Communication Networks PCN in Europe, and at 1900 MHz for
Personal Communications Services PCS in the United States. Accordingly,
there are three main GSM-standards, i.e. GSM 900, GSM 1800 (PCN),
and GSM 1900 (PCS). Each GSM standard specifies different frequency
bands for the uplink frequency band, i.e. the communication from
the mobile phone to the base station, and the downlink frequency
band, i.e. the frequency band reserved for communication from the
base station to the mobile stations. The uplink frequency bands
or transmit frequency bands of GSM 900, GSM 1800 and GSM 1900 are
respectively 890 to 915 MHz, 1710 to 1785 MHz and 1850 to 1910 MHz.
In view of the increasing mobility of people, especially of business
men doing trade in different countries and continents, a mobile
phone adapted to the GSM 900 standard cannot be used within a region
where the GSM 1900 standard is employed. If, for instance, a business
man travels from Europe where GSM 900/1800 is installed, he might
not be able to communicate with this mobile phone in the United
States where GSM 1900 is used.
Accordingly, it is desired to provide a switchable transmitting
stage for a mobile phone, which is able to switch between different
GSM standards while at the same time the complexity of the mobile
phone and the additional production costs are kept at a minimum.
SUMMARY OF THE INVENTION
The invention provides a switchable up-conversion loop device for
the transmitting stage of a mobile phone having the features of
claim 1.
The switchable up-conversion loop device for a transmitting stage
of a mobile phone having multiple transmit frequency bands according
to the present invention comprises a phase detector generating a
phase detector output signal in response to the phase difference
between an input signal and a mixing product signal, multiple switchable
voltage controlled oscillators, each connected to the phase detector
via a low pass filter for generating an output oscillation signal
at a frequency which depends on the phase detector output signal,
a coupling means for coupling the output oscillation signal to a
mixer for mixing said output oscillation signal with a locally generated
oscillating signal to produce said mixing product signal.
The principal idea of the present invention resides in that a plurality
of switchable voltage controlled oscillators are provided in the
up-conversion loop of a transmitting stage by means of which switching
between the different transmit frequency bands is achieved.
Preferred embodiments of the present invention are listed in the
dependent claims.
According to a preferred embodiment, the multiple switchable voltage
controlled oscillators are switched on/off by means of a switching
unit which connects/interrupts the supply voltage to said voltage
controlled oscillators.
This has the advantage that reliable switching without additional
switching components in the signal path is achieved.
According to a further preferred embodiment, the multiple voltage
controlled oscillators are selected from a group consisting of a
one-band voltage controlled oscillator covering one transmit frequency
band and multiple-band voltage controlled oscillators covering a
plurality of transmit frequency bands.
According to a further preferred embodiment, the multiple band
voltage controlled oscillator is switchable between different transmit
frequency bands in response to a band switch control signal.
This has the particular advantage that the switching is performed
within one voltage controlled oscillator having a plurality of transmit
frequency bands thus avoiding the necessity for a set of voltage
controlled oscillators which leads to a reduction of production
costs.
According to a further preferred embodiment, the band switch control
signal is generated by a control unit.
According to a further preferred embodiment, the switching unit
is connected to said control unit which connects/interrupts the
supply voltage to said voltage controlled oscillators.
According to a further preferred embodiment, said multiple-band
voltage controlled oscillator consists of an oscillator transistor
and multiple resonance circuits which are switchable to said oscillator
transistor by means of a switching element which is controlled by
said band switch control signal.
According to a further preferred embodiment, the coupling means
couples the output oscillation signal either inductively or capacitively
to said mixer, and normally via a directional coupler which is transmission
lines.
According to a further preferred embodiment, the mixer multiplies
said locally generated oscillating signal with the signal received
from said coupling means.
According to a further preferred embodiment, a loop filter is provided
between said phase detector and said multiple switchable voltage
controlled oscillators.
According to a further preferred embodiment, the input signal of
the phase detector is generated by a modulator.
According to a further preferred embodiment, the modulator is a
minimum shift keying modulator.
According to a further preferred embodiment, the frequency of the
input signal and of the mixing product signal are both dividable
by means of frequency dividing units which are controlled by said
control unit.
According to a further preferred embodiment, said multiple band
voltage controlled oscillator is a two-band voltage controlled oscillator
covering two transmit frequency bands.
According to a further preferred embodiment, said multiple band
voltage controlled oscillator is a three-band voltage controlled
oscillator covering three transmit frequency bands.
According to a further preferred embodiment, the three one-band
voltage controlled oscillators are provided and connected to the
phase detector, wherein each one-band voltage controlled oscillator
covers one transmit frequency band.
According to a further embodiment, there is provided one one-band
voltage controlled oscillator covering one transmit frequency band
and one two-band voltage controlled oscillator covering two transmit
frequency bands, wherein both voltage controlled oscillators are
connected to said phase detector via the low pass filter.
According to a further embodiment, there is provided one three-band
voltage controlled oscillator covering three different transmit
frequency bands, wherein the three-band voltage controlled oscillator
is connected to said phase detector.
According to a further preferred embodiment, the transmit frequency
bands are transmit frequency bands of a GSM system.
According to a further preferred embodiment, there are provided
three different transmit frequency bands being the transmit frequency
bands of GSM 900, GSM 1800 and GSM 1900.
According to a preferred embodiment, the output oscillation signal
from the coupling means is amplified by a power amplifier.
According to a further preferred embodiment, the amplified output
oscillation signal is input to an antenna switching unit which switches
said amplified output oscillation signal to a transmitting antenna
according to a control signal from said control unit.
According to a further preferred embodiment, the mixing product
signal produced by the mixer is filtered by a low pass filter to
suppress unwanted mixing products.
According to a further preferred embodiment, the locally generated
oscillation signal is generated by a PLL-circuit in response to
a control signal from said control unit.
According to a further preferred embodiment, the supply voltage
of the pre-stage amplifier is switched on/off by a switch in response
to a control signal from said control unit.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood by the
following detailed description of the preferred embodiments thereof
in conjunction with the accompanying drawings, in which:
FIG. 1 is a block diagram of a preferred embodiment of the present
invention, wherein a one-band voltage controlled oscillator and
a two-band switchable voltage controlled oscillator are provided
in the up-conversion loop of a transmitting stage for a mobile phone;
FIGS. 2A to 2C are respective block diagrams of three different
embodiments of a switchable up-conversion loop device for a transmitting
stage of a mobile phone which is switchable between three different
transmit frequency bands using three one-band voltage controlled
oscillators, using a one-band voltage controlled oscillator and
a two-band switchable voltage controlled oscillator and a three-band
voltage controlled oscillator, respectively; and
FIG. 3 is a block diagram of a multiple-band voltage controlled
oscillator which is switchable between different transmit frequency
bands.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a preferred embodiment of the switchable up-conversion
loop device for a transmitting stage of a mobile phone according
to the present invention.
FIG. 1 is a block diagram of a transmitting stage of a mobile phone,
wherein the receiving stage is only indicated in the lower part
of the block diagram in dashed lines. An information-carrying signal
which is to be transmitted by the transmitting stage is supplied
via lines 1, 2 to mixers 3, 4 of a modulation means 5. The modulator
5 receives via line 6 a locally generated oscillation frequency
from a dividing unit 7 which divides the frequency supplied via
line 8 from a voltage controlled oscillator 9. The divided locally
generated oscillation frequency is supplied via line 6 to the modulator
5 and branched at a branching node 10 via line 11 to a phase shifter
12 and via line 13 to the mixer 4. The supplied oscillation frequency
signal is phase-shifted by the phase-shifting means 12 by 90.degree.
and delivered to the mixer 3 on line 14. The mixer 3 multiplies
the signals received on lines 1, 14 to a first mixing product signal
which is supplied to a summing means 15 on line 16. The mixer 4
multiplies the signal received on lines 2, 13 to a second mixing
product signal which is output to the summing means 15 on line 17.
The modulator 5 shown in FIG. 1 is used as a Gaussian minimum shift
key modulator.
The modulated information-carrying signal is output from the modulator
5 on line 18 to a dividing unit 20 and a phase detector 21. The
dividing unit 20 divides the frequency received from the modulator
by a fixed or predetermined integer number in response to a control
signal received via a control line 22 from a control unit 23. The
phase detector 21 consists of a device that produces an output voltage
proportional to the phase difference of the signals input from the
first frequency dividing unit 20 and second frequency dividing unit
24. The second frequency dividing unit 24 is connected to the phase
detector 21 via a line 25 and divides the frequency of a mixing
product signal received from a mixer 26 via line 27, a low-pass
filter 28 and a connecting line 29 in response to a control signal
sent to the frequency dividing unit 24 via a control line 30. The
loop filter 32 is a low pass filter that is used to control the
PLL dynamics, and therefore the performance of the system. The output
signal of the loop filter 32 is branched at node 33 via line 34
to a first voltage controlled oscillator 35 and via line 36 to a
second voltage controlled oscillator 37.
In the embodiment shown in FIG. 1, the first voltage controlled
oscillator 35 is a one-band voltage controlled oscillator covering
one transmit frequency band, and the second voltage controlled oscillator
37 is a two-band voltage controlled oscillator covering two transmit
frequency bands. Accordingly, the switchable up-conversion loop
device for a transmitting stage shown in FIG. 1 covers three different
transmit frequency bands.
The first voltage controlled oscillator 35 is supplied with the
supply voltage via a power supply line 38, and the second voltage
controlled oscillator 37 is supplied with a supply voltage via power
supply line 39. The power supply lines 38, 39 of the first and second
voltage controlled oscillators 35, 37 are switchable by means of
a switching unit 40 which connects or interrupts the supply voltage
to the voltage controlled oscillators 35, 37 in response to a switching
control signal from the control unit 23 on control line 41.
According to the switch control signal on line 41, both voltage
controlled oscillators 35, 37 are switched independently on or off.
There is only one voltage controlled oscillator switched on at the
same time. While the switching between the different voltage controlled
oscillators 35, 37 is performed in response to the switch control
signal on control line 41, the switching between the different transmit
frequency bands within the two-band voltage controlled oscillator
37 is performed in response to a band switch control signal which
is received by the two-band voltage controlled oscillator 37 on
control line 42 from the control unit 23. On the output side, the
two voltage controlled oscillators 35, 37 are connected by output
lines 42, 43 to a coupling means 44. In the embodiment shown in
FIG. 1, the coupling means 44 consists of three striplines or microstriplines
45, 46, 47, wherein the first stripline 45 is connected to the output
line 42 of the first voltage controlled oscillator 35 and the third
stripline 47 is connected to the output line 43 of the second voltage
controlled oscillator 37. The second stripline 46 of the coupling
means 44 couples part of the signal from 45 or 47 via a signal coupling
line 48 to mixer 26.
The mixer 26 multiplies the received coupling signal with a locally
generated oscillation signal from a PLL circuit 49 which generates
an oscillation signal in response to a controlled signal received
from the control unit 23 on control line 50. A connecting line 51
connects the PLL circuit 49 with mixer 26. The output signal of
the first voltage controlled oscillator 35 passes on line 42 via
the first coupling stripline 45 and a line 52 to a power amplifier
53. The output signal of the second voltage controlled oscillator
37 passes via line 43 the third coupling stripline 47 and via line
54 to a power amplifier 55.
The output signals of the power amplifiers 53, 55 are passed via
lines 64, 65 to a switching means 66 which selectively switches
the output signal on lines 64 or 65 to a transmitting/receiving
antenna 67 in response to a control signal from control unit 23
wherein said control signal is received by the switching means 66
via control line 68. The control signal on control line 68 controls
whether one of the output signals on the output signal lines 64,
65 are transmitted by the antenna 67 or whether the antenna is used
as a receiving antenna which outputs a received signal via a received
signal line 69 to the receiving stage of the mobile phone.
The locally generated oscillation signal produced by the PLL circuit
49 in response to the control signal on control line 50 and the
second locally generated oscillation signal generated by the PLL
circuit 9 in response to a control signal on control line 70 are
generated depending on which GSM standard is used, i.e. which transmit
frequency band is to be used. Accordingly, the frequency dividing
unit 7, 20, 24 are controlled via control lines 71, 22, 30 to divide
the received signals by a predetermined integer number depending
which GSM-standard operation mode is selected by the control unit
23.
The switchable up-conversion loop device for a transmitting stage
of a mobile phone shown in FIG. 1 has three transmit frequency bands,
i.e. one transmit frequency band covered by the first voltage controlled
oscillator 35 and two different transmit frequency bands covered
by the second voltage controlled oscillator 37. In a preferred embodiment,
the three transmit frequency bands are the transmit frequency bands
of GSM 900, GSM 1800 and GSM 1900 which are 890 to 950 MHz for GSM
900, 1710 to 1785 MHz for GSM 1800 and 1850 to 1910 MHz for GSM
1900.
If the switchable up-conversion loop device for a transmitting
stage is used for a mobile phone which is switchable between the
three different GSM standards, the first voltage controlled oscillator
35 covers the transmit frequency band of GSM 900, while the switchable
two-band voltage controlled oscillator 37 covers the transmit frequency
band of GSM 1800 and the transmit frequency band of GSM 1900. In
case that the control unit selects the GSM 900 operation mode, the
first voltage controlled oscillator 35 is switched on by switching
means 40 in response to the control signal on control line 41, and
the second voltage controlled oscillator 37 is switched off at the
same time. The PLL circuit 49 generates a first locally generated
oscillation frequency determined by the selected output intermediate
frequency on line 27 on the selected transmitting channel within
the transmit frequency band in response to the control signal on
control line 50. The frequency synthesizer 9 generates a second
locally generated oscillation signal equal to the frequency at 25,
given by the intermediate frequency at 27 divided by divider 24,
times the dividers 7 and 20.
In case that the GSM 1800 operation mode is selected by control
unit 23, the first voltage controlled oscillator 35 is switched
off by switch 40, while at the same time the second voltage control
oscillator 37 is switched on by switch 40 in response to the control
signal on control line 41. Further, the second switchable voltage
controlled oscillator 37 which covers two transmit frequency bands
is switched to its first transmit frequency band being the transmit
frequency band of GSM 1800, i.e. 1710 to 1785 MHz. At the same time,
the PLL circuit 49 generates another first locally generated frequency
signal corresponding to the selected transmit channel in response
to the control signal on control line 50 and the intermediate frequency
on line 27 selected for the GSM 1800 design. The voltage control
oscillator 9 again generates a second locally generated frequency
signal in response to control signal and control line 70.
In case that the GSM 1900 operation mode is selected by control
unit 23, the second voltage controlled oscillator 37 is switched
on while the first voltage controlled oscillator 35 is switched
off. Within the second voltage controlled oscillator 37, the second
transmit frequency band, i.e. the transmit frequency band of GSM
1900 is selected which is 1850 to 1910 MHz. At the same time, the
PLL circuit 49 generates another first locally generated oscillation
frequency signal depending on the selected transmit channel. The
PLL circuit 9 again generates a second locally generated oscillation
signal which is divided by a factor 2 by the frequency signal dividing
unit 7 and supplied to the modulator 5 via line 6.
Only one path corresponding to one GSM output transmit frequency
band is switched to the transmitting antenna 67 at the same time.
In case that the first voltage controlled oscillator 35 generating
an output frequency within the transmit frequency band of GSM 900
is switched on by means of switch 40, the power amplifier 53 is
amplifying the signal received on line 52, while the power amplifier
55 is off. Further, switching means 66 switches the output signal
line 64 to the transmitting antenna 67.
The embodiment shown in FIG. 1 shows a switchable up-conversion
loop transmitting stage of a mobile phone having three transmit
frequency bands using the one-band voltage controlled oscillator
35 and a two-band voltage controlled oscillator 37. The embodiment
shown in FIG. 1 is only one possible way to construct a switchable
up-conversion loop for a transmitting stage according to the present
invention.
As can be seen from FIG. 2A, 2B, 2C, the circuit according to the
present invention may be varied to provide a transmitting stage
having three transmit frequency bands.
FIG. 2A shows a further embodiment of a transmitting stage having
three transmit frequency bands according to the present invention.
The output signal of the phase detector 32 is branched off at branching
node 33 to three different one-band voltage controlled oscillators
100, 101, 102, each covering one transmit frequency band and outputting
the voltage controlled oscillation signal via lines 103, 104, 105
to a triplexer 106 which outputs the received signals on an output
line 107 to a first stripline 108 which couples to a second stripline
109 of a coupling means 110, wherein the output signal of the second
stripline 109 is coupled via coupling line 48 to the mixer 26. The
three one-band voltage control oscillators 100, 101, 102 are switched
on/off by switching the corresponding supply voltage lines (not
shown).
FIG. 2B shows a further embodiment for a three-band transmitting
stage having three transmit frequency bands, wherein a one-band
voltage controlled oscillator 111 and a two-band voltage controlled
oscillator 112 covering two transmit frequency bands are employed
and output a respective output signal on output lines 113, 114 to
a diplexer 115 which outputs a voltage controlled output signal
on output line 116 to a first stripline 117 which couples to a second
stripline 118 which couples signals via line 48 to the mixer 26.
The first and second stripline 117, 118 form the coupling means
119. The switching between the one-band voltage controlled oscillator
111 and the two-band voltage controlled oscillator 112 is performed
by switching on/off the respective supply voltages, while the switching
between the two different frequency bands within the two-band voltage
controlled oscillator 112 is performed in response to control signal
from the control unit 23.
FIG. 2C shows a further embodiment of a three-band transmitting
stage having only one voltage controlled oscillator 120 which has
three different transmit frequency bands. The switching between
the three transmit frequency bands of the three-band voltage controlled
oscillator 120 is performed in response to a control signal from
the control unit 23, wherein the output voltage control signal is
supplied to coupling means 121 via a line 122. The coupling means
121 is formed by two coupled striplines 123, 124, wherein the stripline
124 couples the signal via line 48 to the mixer 26.
FIG. 3 shows a multi-band voltage controlled oscillator used in
the switchable up-conversion loop for a transmitting stage according
the present invention. The multiple-band voltage controlled oscillator
130 comprises a plurality of resonance circuits 130a-130n being
a part of the oscillator circuit. The resonance frequency of the
oscillator is determined by the selected resonance circuit.
The resonance circuits 130a-130n are connected via lines 130a-130n
to a switching means 132 connecting each of the resonance circuits
130a-130n in response to a control signal on a control line 133
via a connecting line 134 to an oscillator transistor 135 producing
an output signal on an output line 136 the frequency of which is
proportional to the input control voltage on an input line 137.
In case of a two-band voltage controlled oscillator, as for instance
voltage controlled oscillators 37, 112, there are provided two resonance
circuits 130a, 130b. In case of three-band voltage controlled oscillator,
as for instance a three-band voltage controlled oscillator 120 in
FIG. 2C, there are provided three resonance circuits 130a, 130b,
130c.
Although the present invention has been described with respect
to preferred embodiments thereof, it should be understood that many
modifications can be performed without departing from the scope
of the invention as defined by the appended claims.
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