Telecommunications – Transmitter – With feedback of modulated output signal
Patent
1995-07-10
1998-04-07
Pham, Chi H.
Telecommunications
Transmitter
With feedback of modulated output signal
455127, 330279, H04B 104
Patent
active
057376972
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to communications systems which are available far digital mobile communications systems and which prevent the transmission power from overshooting at the beginning of transmission or at the time of changing the transmission power to a lower level.
BACKGROUND ART
Conventionally, cellular digital mobile communications systems have been adopting a TDMA (time division multiple access) method. In the TDMA method, transmission and reception between communications systems utilizing the method are carried out in a time slot associated with the transmission and reception frequency, which is so cold intermittent transmission (or burst transmission) in which stabilization of the transmission power is promoted.
Specifically, the field strength received at a cell base station receiving a transmitted radio wave from a mobile station varies as the mobile station moves within a cell, and accordingly the level of the transmission power from the mobile station is controlled so that it is changed on the basis of an instruction signal from the cell base station. For example, if a mobile station is near from the base, the transmission power of the mobile station is lowered so as to avoid input saturation (cross modulation) caused by a strong electric field at the cell base station receiving a transmission radio wave from the mobile station.
If a mobile station is far from the base, the transmission power of the mobile station is raised so as to make higher the field strength received by the cell base station receiving the transmitted radio wave from the mobile station to maintain a stable reception state. Further, in a mobile station, after having its level controlled, the transmission power is controlled by means of a closed loop so as to make its level constant, preventing the transmission power from changing. Specifically, when the transmission power of the mobile station is comparatively high, a fall in the output power caused by calorification of last-stage power amplifier devices and a variation in the power supply voltage is checked to keep a stable transmission state in a radio circuit formed between the mobile station and the cell base station.
FIG. 1 is a block diagram showing a structure of a conventional communications system in which the transmission power is closed-loop-controlled. In FIG. 1, a radio transmission signal Pa is received in the communications system and is fed through an input terminal 1 to a variable-gain circuit 2. A power amplifier 3 outputs a transmission power Po which is an amplified version of the radio transmission signal Pa from the variable-gain circuit 2. The transmission power Po from the power amplifier 3 is sent to an antenna 6 through a branch circuit 4, such as a directional coupler, adapted to make a signal branch and a multiplexer 5 for sharing the antenna. The transmission power Po is sent out from the antenna 6 as radio wave
On the other hand, radio wave Wb from the cell base station (not shown) is received at the antenna 6 to provide a receive signal, which is input to a receiving portion 10 through the multiplexer 5. In the receiving portion 10, frequency conversion, demodulation, etc. are performed to provide a demodulated signal. The demodulated signal includes transmission power change instruction information Sa for specifying the level of the transmission power from the mobile station carrying this system on the basis of the field strength at the time when the cell base station received radio wave Wa from the mobil station. The transmission power change instruction information Sa is fed to a controller 12 including a CPU etc. Also, a branch circuit 4 makes the transmission power Po branch and feed a detector circuit 7. The detector circuit 7 envelope detects a high frequency signal which has branched off at the branch circuit 4, and applies a detected signal Sb exhibiting the level of the high frequency signal to an input terminal of an error amplifier 8.
Also, supplied from a D/A converter 13 to the other input terminal of the erro
REFERENCES:
patent: 5438683 (1995-08-01), Durtler et al.
patent: 5507016 (1996-04-01), Okuhara
Pham Chi H.
Toshiba Corporation
LandOfFree
Transmission power control circuit for a communication system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmission power control circuit for a communication system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmission power control circuit for a communication system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-28232