Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Utility Patent
1998-11-02
2001-01-02
Eisenzopf, Reinhard J. (Department: 2745)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S126000, C455S522000, C455S069000
Utility Patent
active
06169886
ABSTRACT:
FIELD OF THE INVENTION
This invention relates, generally, to power amplifiers of communication devices and, more particularly, to facilitating control of such power amplifiers according to a delayed waveform.
BACKGROUND OF THE INVENTION
Power amplifiers are used in wireless communication devices, such as cellular telephones, to facilitate transmission of communication signals. Many communication systems within which the wireless communication devices operate requires each wireless communication device to meet certain time and frequency requirements. One such system is the Global System for Mobile Communications (GSM) system. In the GSM system, multiple GSM cellular telephones share a single 200 kHz wide channel on which to transmit communication signals at different output power levels. Each GSM cellular telephone on a channel is allocated one 577 microsecond (&mgr;sec) time slot on a repetitive basis. During this time slot the cellular telephone ramps up its power amplifier to the proper frequency and output power level, transmits desired data and ramps down its power amplifier so as not to disturb or interfere with the other cellular telephone users sharing the same frequency. To ensure operation as described, the cellular telephones must, at all times, comply with a spectral frequency mask and a time mask. For example, time masks
100
and
102
corresponding to output power levels 13 dbm (power level in dB with respect to 1 milliwatt) and 33 dbm, respectively, are shown in dotted line in FIG.
1
. During the ramp-up of the power amplifier to the output power levels 13 dbm and 33 dbm, the output power of the power amplifier must at all times remain within the time masks
100
and
102
, respectively. Such is accomplished by, for example, ramping-up the power amplifier to the output power levels of 13 dbm and 33 dbm according to curves
104
and
106
of
FIG. 1
, respectively.
While the exact shape may vary, the curves
104
and
106
should initially have a somewhat steep ramp-up portion with an increasing slope, such as portion
108
of the curves
104
and
106
. A ramp-up portion, such as the portion
108
, is optimal to ensure that the power amplifier is not turned on and ramped-up too slowly, which can cause severe damage to the data to be transmitted, or turned on and ramped-up too quickly, which can cause large spectrum bursts that interfere with other cellular telephones operating at the same or similar frequencies.
Unfortunately, ramping-up the power amplifier to lower output power levels, such as 5 dbm, using the somewhat steep ramp-up portion with an increasing slope, such as the portion
108
, violates a time mask
110
of the 5 dbm output power level. The violation occurs at point
112
in FIG.
1
. Recently, the European Telecommunications Standards Institute defined the GSM Digital Telecommunication System (Phase 2) Mobile Station Conformance Specification (“GSM Phase 2”). GSM Phase 2requires that GSM cellular telephones be able to transmit at lower power levels, including but not limited to the 5 dbm level discussed above.
Therefore, what is needed is a way to facilitate transmission at lower power levels in a communication system defined by time and frequency spectrum requirements without sacrificing data integrity or causing spectrum interference.
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Black Gregory R.
Hietala Alexander W.
Eisenzopf Reinhard J.
Motorola Inc.
Nguyen Duc
Patrick Mark D.
Watanabe Hisashi D.
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