Transmitting power control circuit

Abstract: A transmitting power control circuit comprising a control unit (4) which recognizes the period of transmitting the voice signal and issues instruction to the reference signal generating unit (3) to output a lower output reference value during such period and a reference value generating unit which has, as the one output reference value, an output reference value corresponding to a lower output level in the higher power level of the adjacent power levels and an output reference value corresponding to a higher output level in the lower power level and prepares, as a result of it, a lower number of output reference values and thereby outputs the output reference value during transmission of data signal in each power level and the output reference value during transmission of voice signal.

Description: The present invention relates to a transmitting power control circuit comprising a transmitting output unit for outputting a transmitting signal of a predetermined level, a reference value generating unit providing at least two different reference levels, an output level detector, and a transmitting output control unit for controlling the level of the transmitting signal to the predetermined level on the basis of the output signals of the reference value generating unit and the output level detector. Such power control circuits are used in mobile radio equipment or the like, and are, for instance, known from GB-A-2 213 002. Fig. 6 is a block diagram indicating a part of the transmitting side of a conventional mobile radio equipment. In this figure, the reference numeral 1 denotes a main apparatus of radio equipment; 2, a transmitting output unit for outputting a transmitting signal of the predetermied level; 41, a control unit which controls starting of transmitting output unit 2; 5, an antenna for sending a transmitting signal; 8, a reference signal generator for generating an output reference value. In addition, 21, a high frequency signal amplifier (hereinafter referred to as amplifier) for amplifying the transmitting signal to the predetermied level in accordance with an instruction signal; 22, an output level detector for allowing the transmitting signal of the predetermined level to pass and outputting a level signal in accordance with such predetermined level; 23, a transmitting output control unit for comparing the level signal and output reference value and applying a current depending on difference of such signals to the amplifier 21 as an instruction signal. Next, operations will be explained. The amplifier 21 amplifies a transmitting signal in accordance with the instruction signal and outputs a transmitting signal of the predetermined level. The amplified transmiting signal is transmitted from the antenna 5. The level of amplified transmitting signal is detected by the output level detector 22. The output level detector 22 outputs a level signal in accordance with the detected level. The transmitting output control unit 23 compares the output reference value input from the reference value generator 8 and level signal and outputs a difference current to the amplifier 21 as the instruction signal. Accordingly, the transmitting output control unit 23 controls the amplifier 21 so that the level signal matches with the reference value. The output level of amplifier 21 is thus kept constant. Moreover, since the level of transmitting signal of a mobile radio equipment is determined depending on the system used, the output reference value is set so that the output level becomes equal to a level in the specified range. Fig. 7 is a circuit diagram indicating an example of the transmitting output control unit 23. As shown in Fig. 7, the level signal is input to an input terminal 27. Meanwhile, the output reference value is input to the input terminal 28. The comparator 24 generates a voltage depending on a voltage difference of a couple of input voltages. Moreover, a base current flows into a transistor 25 depending on such voltage and thereby resultant collector current flows. Next, the collector current of transistor 25 becomes a base current of transistor 26. Therefore, the transistor 26 allows flow of the collector current depending on the collector current of transistor 25. This collector current flows into the output terminal 29 as an instruction signal. As explained above, the transmitting output control unit 23 applies an instruction signal to the amplifier 21 depending on the level signal in order to control an output level of the amplifier 21. Fig. 8 shows a relationship between power level and output level of a mobile station of the Advanced Mobile Phone Service: AMPS in the USA. In this case, the power level of eight (8) steps (six kinds) is defined. Accordingly, a reference value generator which generates six kinds of output reference value (values depending on the output level indicated by black points in Fig. 8) is required in place of the reference value generating unit 8. Moreover, the control unit 41 issues an instruction to the reference value generating unit 8 to output the output reference value depending on the power level instructed from a base station. In an ordinary mobile radio communication system, change of field depending on the location of a mobile station, called fading, is generated. Fig. 9 shows an example of the fading. This profile is observed in the side of mobile station, but when a mobile station is moving, similar phenomenon can also be observed in the base station. In Fig. 9, it is assumed that the receivable field level in the receiving side is A. In this case, if it changes to show the field distribution as shown by B with the predetermined transmitting level in the transmitting side by the fading, reception becomes impossible in some cases. Therefore, it is required in the transmitting side that a signal higher level than such transmitting level is transmitted in order to obtain the field distribution, for example, C in the receiving side. Here, the mobile station transmits the data signal to be used for incoming and outgoing calls and the voice signal. The data signal is required to show the distribution C of receiving field in order to eliminate error but the voice signal is not always required to show such distribution. For instance, if the receiving field distribution B is obtained, communication is not disturbed, although a momentary noise is generated during communication. In the case of mobile radio equipment, the power is almost consumed in the amplifier 21. Fig. 10 shows relationship between an output power of amplifier 21 and current dissipation. For example, when the amplifier 21 is operated in output of 30 dBm, current dissipation is 600 mA. When a battery with capacity of 0.6 Ah is used, it can serve for an hour. When the amplifier is operated in output of 29 dBm, current dissipation is 500 mA and the battery can serve for 1.2 hours. As explained above, an output of the amplifier 21 is set as low as possible within the specified range in order to suppress power consumption but it will result in a problem to lower the output of amplifier 21 in view of preventing an error of data signal as explained above. The existing transmitting power control circuit is structured as explained above. Therefore, an output level of amplifier 21 is constant and such constant value is set to a rather higher value in the specified range considering transmision of data signal. Namely, since a high output level required for transmission of data signal is used in direct also for transmission of voice signal, following problems arise, that is, current dissipation increases, a large capacity battery is required for long term communication and the apparatus becomes large in size. From GB-A-2 213 002, as already mentioned, a transmitting power control circuit is known which contains two switching circuits to provide variable output power for a transmitter. In order to save battery power, the normal output values are only generated when a voice signal is present. If no voice signal is present, a signal from an unvoice identifier is fed to the switching circuits in order to reduce the output power, and accordingly the battery power consumption. It is an object of the present invention to eliminate the problems as explained above in connection with the transmission of data signals. It is particularly an object of the present invention to provide a transmitting power control circuit which suppresses the power consumption of an apparatus, realizing a long term communication using a small capacity battery and reducing the size of the apparatus, without endangering the safe transmission of data signals during set-up of a connection. According to the invention, a transmitting power control circuit is characterized in that during initial set-up of a connection between a mobile station and a base station for transmission of data signals a higher reference level is enabled by a control unit, whereas a lower reference level is enabled during subsequent transmission of voice signals. Preferable embodiments are defined in the dependent claims. Fig. 1 is a block diagram indicating a mobile radio equipment utilizing the transmitting power control circuit as the first embodiment of the present invention. Fig. 2 is a timing diagram indicating switching of the output levels. Fig. 3 is a block diagram indicating a mobile radio equipment utilizing the transmitting power control circuit of the second embodiment of the present invention. Fig. 4 is a diagram for explaining relationship between power level and output level. Fig. 5 is a block diagram indicating a mobile radio equipment utilizing the transmitting power control circuit of a third embodiment of the present invention. Fig. 6 is a block diagram of a mobile radio equipment utilizing conventional transmitting power control circuit. Fig. 7 is a circuit diagram indicating an example of the transmitting output control unit. Fig. 8 is a diagram for explaining relationship between power level and output level. Fig. 9 is a diagram for explaining an example of the fading, and Fig. 10 is a diagram for indicating an example of relationship between current dissipation and output power of amplifier. PREFERRED EMBODIMENTS OF THE INVENTION An embodiment of the present invention will be explained with reference to the accompanying drawings. In Fig. 1, the reference numeral 3 denotes a reference value generating unit comprising an analog switch 3a having two contacts a, b. The resistance values of respective resistors are preset so that a voltage applied to the trasnsmitting output control unit 23 when the contact a is conductive is higher than the voltage applied to the transmitting output control unit 23 when the contact b is conductive. Both voltages are output reference values and correspond to the values within the specified range of output levels. The reference numeral 4 denotes a control unit which operates as the conventional control unit and applies a switching signal for the switch to the reference value generating unit 3. The other elements are denoted by the like reference numerals similar to that shown in Fig. 6. Next, operations will be explained with reference to the timing diagram of Fig. 2. In the case of generating an outgoing call, the control unit 4 selects an idle originating call control channel (channel A) based on the receiving level received by the receiver (not illustrated). The control unit 4 applies an originating call signal after tuning the transmitter (not illustrated) to the channel A. The originating call signal is modulated in the transmitter, amplified in the amplifier 21 and is then transmitted from the antenna 5 to the base station. In this case, the control unit 4 gives a switching signal to instruct closing of the contact a to the reference value generating unit 3. Accordingly, the output level is set to a higher level (refer to Fig. 2D). The base station notifies the channel number of communication channel (channel V) to be used, using the channel A. Upon obtaining such channel number through the receiver, the control unit 4 sets both transmitter and receiver to the transmitting condition by the channel V designated. Here, the mobile radio equipment receives a continuity test signal (SAT) from the base station and enters the voice communication condition after returning such SAT to the base station. In this timing, the control unit 4 applies the switching signal to designate release of contact a and close of the contact b to the reference value generating unit 3. Therefore, the voice signal is transmitted with the lower output level (refer to Fig. 2D). As explained above, during the data communication, the transmitting signal has been transmitted with a high output level in the specified range in order to prevent data error by fading but since data communication is carried out only within a short period among total communication period, the current dissipation can be reduced considering total period of communication time. For instance, according to the example shown in Fig. 10, the output level is set to 30 dBm during the data signal transmission or to 28 dBm during the voice signal transmission. In case the data communication requires 5% of total communication period, a battery in capacity of 0.6 Ah will realizes communication for 1.4 hours. Namely, the communication period can be extended up to 1.4 times longer than the period in transmission of 30 dBm. Fig. 3 is a block diagram indicating a mobile radio equipment to be used when a plurality of power levels are used for transmitting signal. In this figure, the reference numeral 6 denotes a reference value output unit comprising an analog switch 6a having seven contacts a - g. Fig. 4 indicates power level of AMPS. The black points indicate output levels used by the mobile radio equipment to which the present embodiment is applied. For example, it is indicated when the second power level is designated from the base station, the data signal is transmitted in the output level of the point a (29 dBm), while the voice signal is transmitted in the output level of point b (25 dBm). In addition, output levels at the points a - g respectively correspond to the points a - g in Fig. 3. Therefore, the resistance values of respective resistors in the reference value generating unit 6 are set to generate output reference values corresponding to the output levels at the points a - g. For example, when the second power level is designated, the control unit 4a applies the switching signal to the reference value generating unit 6 to close the contact a during data signal transmission or close the contact b during voice signal transmission. As explained above, the reference value generating unit 6 having seven contacts a - g has realized setting of the high level corresponding to data signal and low level corresponding to voice signal within the specified range of the six kinds of power levels. In above each embodiment, the analog switches 3a, 6a have been used to generate output reference value but a D-A converter 7 may be provided as shown in Fig. 5. In this case, each output reference value is digitalized in the control unit 4b. The control unit 4b outputs the digital output reference value in the same timing as the output reference value setting timing in the first embodiment or in the second embodiment. The D-A converter 7 outputs the output reference value depending on such digital output reference value to the transmitting output control unit 23. As explained above, the effect which is same as the in each embodiment can be realized, circuit structure can also be simplified and the apparatus itself can also be reduced in size. As described previously, according to the present invention, the transmitting power control circuit comprises a reference value generating unit which generates a couple of output reference values depending on two output levels within the specified range and is structured so that any one output reference value is used depending on the transmission timing of the data signal and voice signal. Accordingly, current dissipation can be reduced and a battery may be used for a long period of time. In addition, according to the present invention, the transmitting power control circuit comprises a reference value generating unit which generates an output reference value corresponding to a couple of output levels within the specified range of each power level and is used in common with the output level of adjacent power levels and is structured so that any one output reference value is used depending on the transmission timing of the data signal and voice signal. Thereby, current dissipation of apparatus can be reduced and structure can be simplified considerably even when many kinds of power levels are used.

Claims: A transmitting power control circuit comprising a transmitting output unit (2) for outputting a transmitting signal of a predetermined level, a reference value generating unit (3, 6, 7) providing at least two different reference levels (a, b), an output level detector (22), and a transmitting output control unit (23) for controlling the level of the transmitting signal to the predetermined level on the basis of the output signals of the reference value generating unit (3, 6, 7) and the output level dector (22), characterized in that during initial set-up of a connection between a mobile station and a base station for transmission of data signals a higher reference level (a) is enabled by a control unit (4), whereas a lower reference level (b) is enabled during subsequent transmission of voice signals. Control circuit according to claim 1, in which different power ranges are provided, characterized in that the reference value generating unit (6, 7) is adapted to provide a plurality, larger than two, of different reference levels (a-g), and that for each power range two adjacent reference values (a, b; b, c; c, d ...) are used as the higher reference level and the lower reference level. Control circuit according to claim 1 or 2, characterized in that the reference value generating unit (3, 6) includes a voltage divider and a switch circuit (3a, 6a) controlled by the control unit (4). Control circuit according to claim 1 or 2, characterized in that the reference value generating unit (7) includes a D-A converter (7) controlled by the control unit (4).

Inventors: ADACHI KEIGO C O MITSUBISHI DE, ADACHI, KEIGO, C/O MITSUBISHI DENKI KABUSHIKI K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1990
Main classification: H04B7
IPC codes: H04B1, H03G3