FI89648C - FOERFARANDE OCH ANORDNING FOER STYRNING AV EN RADIOSAENDARE - Google Patents

Description

λ 89648

Method and apparatus for controlling a radio transmitter

The invention relates to a method and a device for controlling a radio transmitter. According to the method, the radio-5 transmitter is alternately controlled to the ON state, where the RF power output from the transmitter is of the desired magnitude, and to the OFF state, where the RF power is not transmitted, and in the ON state, the RF power is determined by a power control signal controlling the transmitter amplifiers. The device according to the invention in turn is in accordance with the preamble of claim 10.

The method and device according to the invention are intended for use in a base station of a GSM mobile telephone network, but it can equally well be applied to other types of radio systems in which the transmitter is keyed on the basis of varying transmission needs. However, the greatest benefit of the invention is achieved in networks such as the GSM system, where the speed requirements are high.

The GSM radio system uses dynamic transmission power control at both the base station and the mobile station-20a. The power control word is four bits long, so 16 power levels are available. The interval between two consecutive power levels is 2 dB, so the total power control range is 30 dB. In the so-called TX-on time slot in which the transmission takes place, the transmission power in each time slot of the frame 25 is determined according to the above-mentioned power control word to one of sixteen different power levels. The so-called TX-off time slot, in turn, is the time slot when no transmission takes place (RF power is zero).

The GSM specifications specify the required rate of power increase from transmitter 30 as the TX-on time slot occurs after the TX-of-f time slot. However, the required rate of ascent is not easy to achieve without worse side effects, the most significant of which is spectrum propagation.

It is an object of the present invention to provide a method and apparatus capable of facilitating the control of the power rise rate of 89648 2. With the method according to the invention, this is achieved in such a way that the power control signal is kept non-zero even in the OFF state of the transmitter. The device according to the invention, in turn, is characterized by what is described in the characterizing part of claim 2.

The basic idea according to the invention is also to keep a certain non-zero (small) value of the power control signal in the OFF state of the transmitter, in which no RF power is thus transmitted, whereby when the TX-on time interval comes, the transmission power quickly rises to its desired value.

By means of the solution according to the invention, e.g. the rate of increase in transmitter power required by the GSM specifications can be easily achieved without the above-mentioned negative side effects.

In the following, the invention will be explained in more detail with reference to the examples according to the accompanying drawing, in which Fig. 1 shows a block diagram of a GSM system base station transmitter in terms of the invention, and Fig. 2 shows a more detailed implementation of power control according to the invention.

Figure 1 is a block diagram of a portion of a GSM base station transmitter to which the present invention pertains. Reference numeral 1 denotes a separator circuit to which a digital data signal D is applied to the weather inputs si-25. In addition, the separator circuit receives a byte clock BCK and a slot clock SLCK for system synchronization (a byte clock is an internal clock incoming data, and the slot clock is a clock that gives one pulse per slot so that it is up during the pulses given by the byte clock). The information on the respective desired power level (power control control word) is included in the digital data signal D. In the isolator circuit 1 35, this power level information is separated and converted to an analog power control voltage Vc / corresponding to that level 8 9 6 4 8 3. which controls the gain of the transmitter preamplifier 3. The preamplifier 5 is connected to the transmitter power amplifier 4, which supplies RF power to the transmitter antenna 5. The TX on / off data separated from the data stream D is also output from the isolator circuit 1 to the power control unit 2, which disconnects the voltage to the preamplifier 3 in the TX off position. VX. The serial da-10 level signal D1, which no longer contains power level information, is fed by a separator unit 1 to a quadrature modulator 1 ', the I and Q components generated by which are fed to an immersion converter 6, which raises the signals to a higher frequency and feeds them to a preamplifier 4. In addition, information about the advancing power is provided to the PE power control unit 2, whereby the power control is able to adapt to, for example, changes in the gain in the transistor stages.

Figure 2 shows in more detail how the power control voltage Vc supplied to the power control unit 2 is generated in the isolator circuit 1. The power control control word mentioned at the beginning, denoted PD and first separated from the incoming data stream D, controls the EPROM circuit 7 containing different power levels. voltages in digital form. The EPROM circuit also includes the shape of the curve (cosine curve) according to which the power increases for each power level. The output signal in digital form of the EPROM circuit is fed to a D / A converter 8, which converts the to the analog form of the output signal. This analog power control voltage Vc 30 is then supplied to the power control unit 2, as shown in Fig. 1. According to the invention, the EPROM circuit 7 is also controlled by an address generator 9, which receives at its inputs a time slot clock SLCK, an octave bit clock OBCK (Octal Bit Clock) and a TX on / off signal which is separated from the data stream. The address generator 9 is one of these 4

3 9 6B

a counter controlled by the input signals, which operates so that when the TX-off time comes after the TX-on time slot it points to the first rising curve address, the corresponding control voltage Vc according to the invention being much lower than the lowest power level control voltage Vc indicated by the control word PD. In practice, the control power PD has a control voltage of about 1 V for the lowest power level indicated, while the control voltage in a TX-off situation is about 50 mV.

With the power control unit 2, the control voltage Vc goes to the operative amplifier, which, thanks to the above-mentioned "biasing", has time to react quickly to changes when the TX-on time interval comes.

Although the invention has been described above with reference to the example according to the accompanying drawing, it is clear that the invention is not limited thereto, but can be modified in many ways within the scope of the inventive idea set forth in the appended claims. In the structural example described above, the "biasing" could in principle also be performed by the power control unit 2, since said unit 20 receives information about when there is a TX-off time interval. In practice, however, it is simpler to adapt the "biasing" to the same memory circuit used to generate the power level control voltage in the TX-on time slot, as described above.

Claims (3)

89648 A method for controlling a radio transmitter, the method comprising varyingly controlling the radio transmitter 5 to the ON state, where the RF power output from the transmitter is of the desired magnitude, and to the OFF state, where the RF power is not transmitted, and in the ON state, the RF power is determined by the power control signal (Vc) controlling the gain of the transceivers (3, 4). that the power control signal (Vc) is kept non-zero even in the OFF state. 2. An apparatus for controlling a radio transmitter, the apparatus comprising means for alternately controlling the radio transmitter to an ON state in which the RF power output from the transmitter is desired and an OFF state in which no RF power is transmitted, wherein in the ON state the RF power is determined by the transceivers ( 3, 4) by means of a power control signal (Vc) controlling the gain, characterized in that it comprises biasing means (9, 7) by which the power control signal (Vc) is given a non-zero value even in the OFF state of the transmitter. Device according to claim 2, characterized in that the biasing means comprise a memory (7) containing information on the value of the OFF power control signal (Vc) and means (9, 8) forming a power control signal (Vc) from the contents of the memory (7). transmitter in OFF-25 mode. 6 a964t> Patentkrav