Telecommunications – Transmitter – With feedback of modulated output signal
Patent
1996-12-03
1998-11-03
Vo, Nguyen
Telecommunications
Transmitter
With feedback of modulated output signal
455 69, H04B 1112
Patent
active
058323732
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an output power control device for a radio device, for changing a target transmission output power gradually or continuously, for example, an output power control device mounted in a mobile terminal of a car phone system, a mobile phone system, etc.
BACKGROUND ART
Generally, in mobile communication systems, such as car phones etc., in order to limit power consumption or reduce interference to other mobile terminals, the output power level of a mobile terminal is subjected to output power control so as to change either in multiple stages or continuously depending on a base station instruction. For example, a mobile terminal of a car phone system of the North American Analog Cellular System controls the output power in six stages (PL2-PL7), with +28 dBm as the largest output.
FIG. 2 is a block diagram showing the basic construction of a conventional output power control device for carrying out such a power control operation.
In FIG. 2, a carrier wave signal generated by an oscillator 1 is input to a power amplifier 3 by being converted to a transmission signal through various processing circuits, such as a driver amp 2. A transmission signal that has been power amplified by this power amplifier 3 is input to an antenna resonator 8 through a coupling transmission path (directional coupler) 4 etc., and after undesired waves have been eliminated by the antenna resonator 8, the signal is radiated into space from an antenna 9 used for both transmission and reception (hereafter simply called antenna).
A received signal, which is converted to an electrical signal as a result of the antenna 9 capturing a radio wave has undesired frequency bands eliminated by the antenna resonator 8. The received signal is then pre-amplified by the preamp 10 and input to a received signal processing system. A receive signal from such a base station includes transmission output power level instruction information.
The coupling transmission path 4 mentioned above is comprised of a main transmission line 4a, coupling transmission line 4b and termination resistance 4c. Only traveling waves from the transmission signal from the power amplifier 3 are input to a detection circuit 5 by being extracted from one end of the coupling transmission line 4b. In the detection circuit 5, this transmission signal is biased according to bias resistor 5a and rectified by being input to a detection diode 5c via coupling capacitor 5b. Thereafter, the signal is made into smooth d.c. using smoothing capacitor 5d and load resistor 5e to provide a detection power output (detection signal). This detection signal is input to a feedback control circuit 6 as a TSSI (Transmission Signal Strength Indication) signal corresponding to an actual output level radiated from the antenna 9.
The controller 7 supplies a control signal representing a specified output power level to a feedback control circuit 6, according to an instruction from a base station (not shown). As a result of this, the feedback control circuit 6 forms and outputs a feedback signal (hereafter called FB signal) for reducing the difference between an actual output level recognized from the TSSI signal and a target power level to be controlled. The FB signal is input to, for example, the Vcont input terminal of a power amplifier 3 whose output power level can be varied.
As described above, an output power level feedback loop is formed, and in this feedback loop, the controller 7 provides an output power target value to be controlled, and the output power level is controlled to become that target power level.
Further, there have recently been many cases where digital processing has also been applied to parts of output power control devices, as shown in FIG. 3. That is, the TSSI signal from the detection circuit 5 is converted to digital data by the A/D converter 11 and input to the controller 7. The FB signal data is formed by computation in the controller 7 which also provides the function of the feedback control circuit 6. This FB signal data is conv
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Nakanishi Eiichi
Onodera Tetsuo
Aoki Makoto
OKI Electric Industry Co., Ltd.
Vo Nguyen
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