Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Reexamination Certificate
1999-08-13
2003-12-02
Urban, Edward F. (Department: 2746)
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
C455S165100, C455S076000, C455S168100, C331S00100A
Reexamination Certificate
active
06658240
ABSTRACT:
FIELD OF INVENTION
The present invention relates to the dead time reduction for multiband synthesizer frequency jumps. In particular, the present invention relates to the dead time reduction for multiband synthesizers allowing to generate output signals in at least two frequency bands.
BACKGROUND OF INVENTION
Multiband synthesizer units are typically used in mobile phones. Here, the output signal of the multiband synthesizer is supplied to different mixer stages for sending and receiving signals in mobile phones, e.g., for the modulation of sending signals and the demodulation of received signals.
FIG. 11
shows a related frequency generation unit
200
. Here, the object is to tune the frequency of a voltage-controlled oscillator
202
after frequency division thereof such that it is coincident to a frequency of a basic oscillator
204
. As shown in
FIG. 11
, the basic oscillator
204
comprises a reference oscillator
206
that feeds a first programmable divider
208
to convert the frequency generated in the reference oscillator
206
into a control frequency for the operation of the voltage-controlled oscillator
202
.
As also shown in
FIG. 11
, a second programmable divider
210
is provided to convert the frequency generated by the voltage-controlled oscillator
202
into a frequency suitable for comparison with the reference frequency of the basic oscillator
204
. A phase detector
212
enables a comparison of the output signal of the second programmable divider
210
and the reference frequency. A detected phase error is then supplied to a loop filter
214
wherein an integration takes place. Using this integrated error signal the voltage-controlled oscillator
202
is controlled until the phase difference vanishes. Usually, the first programmable divider
208
, the second programmable divider
210
and the phase detector
212
form the frequency synthesizer
216
of the frequency generation unit
200
of the PLL type.
FIG. 12
shows the embedding of this frequency generation unit
200
into a single band frequency generation device.
As shown in
FIG. 12
, the frequency generation unit
200
is connected to a control unit
218
provided for the operation and the programming of the frequency generation unit
200
. This control unit
218
supplies different control signals and programming data signals to the frequency generation unit
200
either during operation or programming thereof.
Therefore, there is provided a signal line for the selection of an appropriate channel in the frequency band and a programming strobe line to indicate a programming mode. In case the programming strobe signal is supplied related data for the programming of the first programmable divider
208
and the second programmable divider
210
are supplied to the frequency generation unit
200
so as to select an appropriate channel in the single frequency band.
Still further, in case the frequency generation unit
200
should not output a frequency signal, it is set into the standby mode via the standby control line to reduce the amount of power consumed in the frequency generation unit
200
.
After reprogramming of the frequency generation unit
200
a phase detector
212
detects a phase difference between the signals at the outputs of the first programmable divider
208
and the second programmable divider
210
. Therefore, the phase detector
212
will drive the loop filter
214
until this phase difference vanishes. In other words, during the transition from the previously programmed output frequency to the newly programmed output frequency, there exists a transition time period wherein the phase detector drives the loop filter
214
such that the voltage-controlled oscillator
202
is tuned to the newly programmed operation frequency.
To this end, the phase detector comprises two parts, i.e. the actual phase difference detector and a charge pump (not shown).
As shown in
FIG. 13
, the phase detector unit works on the zero crossings of the input signals to the phase detector
212
. One solution is to output a pulse with the same length as the time difference between the zero crossings of the input signals. In other words, this means that the output of the phase detector unit is proportional to the phase difference of the input signals supplied thereto.
Further, the phase detector unit has two different outputs, one for a positive phase difference and one for a negative phase difference. The respective output signals are supplied to a related charge pump that produces positive and negative current pulses with constant amplitude but different length which may then be processed through the loop filter
214
.
In case the frequency generation unit
200
is locked to the frequency specified through the control unit
218
, the phase detector
212
works in its linear region, as shown in FIG.
14
. Before the frequency generation unit
200
is locked, the non-periodic behaviour of the phase detector
212
will force the frequency of the voltage-controlled oscillator
202
into the linear region of the phase detector
212
so that a locking of the frequency generation unit
200
is always guaranteed. For large initial frequency errors the phase detector operates in a frequency discriminator mode. Once the error is within the linear pull-in-range, it operates as a coherent phase detector, as shown in FIG.
14
.
While the design illustrated with respect to
FIG. 11
to
FIG. 14
is adapted to, e.g., mobile phones being operated in a single frequency band this single band operation is no longer suitable for the increasing number of subscribers and the limited number of communication channels in existing cellular mobile networks. To the contrary, a combination of technical advantages being related to different frequency bands seems to be necessary, e.g., in particular through providing multiband cellular networks and multiband mobile phones being related thereto through combining, e.g., the GSM 900, GSM 1800 and PCS frequency bands, respectively.
However, a prerequisite is an effective frequency generation in a plurality of frequency bands and in particular an effective transition between these frequency bands within minimal time periods.
As shown in
FIG. 15
wherein those parts being identical to those shown in
FIG. 11
are denoted with same reference numerals, one approach is to use a plurality of voltage-controlled oscillators
220
-
1
, . . . ,
220
-n, i.e. one voltage-controlled oscillator for each frequency band of the multiband frequency generation unit
222
. The output of each voltage-controlled oscillator
220
-
1
, . . . ,
220
-n is then coupled to the input of the second programmable divider via a coupling unit
224
achieving an appropriate supply of the output signals of the voltage-controlled oscillators
220
-
1
, . . . ,
220
-n to the second programmable divider
210
.
FIG. 16
shows a further approach to the multiband frequency generation that differs over the frequency generation unit as shown in
FIG. 15
in that a loop filter
214
-
1
, . . . ,
214
-n is provided for each of the voltage-controlled oscillators
220
-
1
, . . . ,
220
-n. This leads to an additional advantage in that the transient behaviour for each single frequency band may be determined separately in compliance with frequency band specific requirements.
Therefore, using either approach shown in
FIG. 15
or
FIG. 16
, it is not only necessary to switch between different channels in a single frequency band but also to switch between different bands in the frequency generation unit or equivalently to carry out frequency band jumps. This may require a re-programming of the first programmable divider
206
and the second programmable divider
210
, and further to switch off the voltage-controlled oscillator in the old frequency band and to switch on the voltage-controlled oscillator in the new frequency band.
One example for such a transition would occur in a mobile phone that during a single GSM TDMA frame is active on three time slots. One is used for receiving, one for transmitting, and one for monitoring, res
Gesesse Tilahun
Nixon & Vanderhye
Telefonaktiebolaget LM Ericsson
Urban Edward F.
LandOfFree
Multiband frequency generation device and related method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multiband frequency generation device and related method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiband frequency generation device and related method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3166708