The apparatus for adjusting the efficiency of electric power amplification

Abstract: A current flowing from a power supply to a power amplification circuit is detected at two adjacent transmission periods having a non-transmission period therebetween. Between the two transmission periods, whether the current is increased or decreased is detected. When the increase is detected, an efficiency control signal is obtained to be supplied to the power amplification circuit by subtracting an increased amount between the two preceding transmission periods from an efficiency control signal used at the last preceding transmission period, and, when the decrease is detected, the efficiency control signal is obtained to be supplied to the power amplification circuit by adding the increased amount to the efficiency control signal used at the last preceding transmission period.

Description: This invention relates to an apparatus for adjusting the efficiency of RF power amplification, and more particularly to an adjusting apparatus of the RF power amplifying efficiency in which the power consumption of a mobile station is minimized in a TDMA (time division multiple access) radio communication system. A conventional apparatus for adjusting the efficiency of power amplification is used in a portable telephone set such as Cellular type telephone set in which transmission and receipt of signals are carried out simultaneously. In the conventional adjusting apparatus of the power amplification efficiency, an electric power is supplied via a control circuit to a power amplification circuit, and the control circuit detects the electric power to be supplied to the power amplification circuit, so that the electric power is minimized dependent on an efficiency control signal supplied from the control circuit to the power amplification circuit, provided that an output signal of the power amplification circuit is controlled to be constant by the control circuit. This is defined as "efficiency control", and the efficiency control is constantly carried out at the time of transmission. In the conventional adjusting apparatus of the power amplification efficiency, however, there is a disadvantage in that an optimum efficiency is difficult to be obtained in the case where transmission is carried out instantly in a burst mode. Further, there is a disadvantage in that noise is generated on a transmission output signal, and the transmission output signal is fluctuated, when a power amplification factor is adjusted during sinal transmission. US-A-4 811 421 discloses a transmission power control device according to which the power amplification efficiency is improved by decreasing the transmitting power. EP-A-0 402 952 suggests a method for automatically regulating the transmission power and quality by measuring values of signal strength and signal transmission quality. Accordingly, it is an object of the invention to provide an apparatus for adjusting the efficiency of power amplification in which the power amplification is carried out by an optimum efficiency, even in the case where signals are transmitted in a burst mode. It is a further object of the invention to provide an apparatus for adjusting the efficiency of power amplification in which noise carried on a transmission signal is reduced, and no fluctuation occurs in an output signal, even if an amplification factor is adjusted in an power amplification circuit during the signal transmission.These objects are achieved with an apparatus as specified in the independent claim 1. According to the invention, an apparatus for adjusting the efficiency of electric power amplification basically comprises: a power amplification circuit for amplifying a signal to be transmitted in a time division multiple access mode; and a control circuit for controlling the efficiency of power amplification in the power amplification circuit; wherein the efficiency is controlled in the control circuit to be an optimum value at a period not belonging to a period for the signal to be transmitted. The invention will be explained in more detail in conjunction with appended drawings, wherein: Fig. 1 is a block diagram showing a mobile station, Fig. 2 is a block diagram showing a conventional apparatus for adjusting the efficiency of power amplification included in the mobile station, Fig. 3 is a block diagram showing an apparatus for adjusting the efficiency of power amplification in a first preferred embodiment according to the invention, Fig. 4A is a timing chart explaining operation in the first preferred embodiment, and Fig. 4B is a graph explaining the relation between the efficiency control value and the efficiency. Fig. 1 shows a mobile station including a conventional apparatus for adjusting the efficiency of power amplification. The mobile station comprises a baseband signal processing circuit 211 for generating a baseband signal, a modulation circuit 210 for modulating the baseband signal by a signal to be transmitted, a power amplification circuit 202 for amplifying the modulated signal, a common use circuit 214 for supplying the amplified signal to an antenna 215, from which the amplified signal is transmitted, and for supplying a signal received by the antenna 215 to a low noise amplification circuit 213, in which the received signal is amplified by suppressing the generation of noise, a demodulator 212 for demodulating the received signal supplied from the low noise amplifier 213 to obtain a transmitted signal, and a control circuit 205 for controlling the power amplification circuit 202 to amplify the modulated signal by a controlled efficiency and the baseband signal processing circuit 211 to generate the baseband signal. Fig. 2 shows the conventional apparatus for adjusting the efficiency of power amplification which comprises the control circuit 205 as shown in Fig. 1, a power supply 204 and the power amplification circuit 202 as also shown in Fig. 1. In operation, a baseband signal is generated in the baseband signal processing circuit 211 by processing a received baseband signal supplied from the demodulator 212. The baseband signal thus generated is modulated in the modulation circuit 210 to provide the modulated signal by a signal to be transmitted from the antenna 215, and the modulated signal is amplified in the power amplification circuit 202 by the control circuit 205. In the control circuit 205, an electric power 203 supplied from the power supply 204 to the power amplification circuit 202 is detected, and the detected electric power 203 is controlled to be minimized by generating an efficiency control signal 201 to be supplied to the power amplification circuit 202. Consequently, a power amplification efficiency is adjusted in the power amplification circuit 202, so that an output signal of the power amplification circuit 202 is controlled to be constant during the whole time of a signal transmission period. Thus, a constant power of the modulated and amplified signal is transmitted via the common use circuit 214 from the antenna 215. In this explanation, a signal receiving operation is omitted, because it is self-explanatory. However, the aforementioned disadvantages occur in the conventional apparatus for adjusting the efficiency of power amplification. Next, an apparatus for adjusting the efficiency of power amplification in the preferred embodiment according to the invention will be explained in Fig. 3. The apparatus for adjusting the efficiency of power amplification comprises a power amplification circuit 102, a power supply 104, a current detection circuit 105, a sample and hold circuit 106, an analog to digital (A/D) converter 107, registers 108 and 109, a difference detection circuit 110, a decision circuit 111, and a digital to analog converter circuit 112, a weight addition circuit 113. In operation (to be explained in Fig. 4A), an input signal 101 is amplified in the power amplification circuit 102 to generate an output signal 103, wherein an electric power is supplied via the current detection circuit 105 from the power supply 104 to the power amplification circuit 102. A current value detected in the current detection circuit 105 is supplied to the sample and hold circuit 106, in which the current value is sampled at a rising edge of an input clock A generated at a transmission time TX and held at a falling edge of the input clock A. The current value held in the sample and hold circuit 106 is converted in the A/D converter 107 from an analog value to a digital value. A content of the register 108 is read to be stored in the register 109 at a rising edge of an input clock C generated prior to a receipt time RX, and supplied there from to the difference detection circuit 110 at the same time, and the register 108 reads a content of the A/D converter 107 at a rising edge of an input clock B generated at the receipt time RX. In other words, the content of the A/D converter 107 and the register 108 are transferred to the register 108 and the register 109, respectively, at a period prior to a subsequent transmission time TX. Then, the contents of the registers 108 and 109 are supplied to the difference detection circuit 110, so that a difference between the contents thereof is detected therein to be supplied to the decision circuit 111. The decision circuit 111 has stored an amount of increase between a former output value of the decision circuit 111 and an output value preceding the former output value, wherein the decision circuit 111 decides whether the detected current in the current detection circuit 105 is increased or not in accordance with the difference supplied from the difference detection circuit 110. Here, it is assumed that the power amplification circuit 102 has a property as shown in Fig. 4B. Thus, when it is detected in the decision circuit 111 that, the detected current is increased, an output value (present control value) of the decision circuit 111 is a value obtained by adding a polarity-inverted value of the increased (stored) amocnt to the former output value, and, when it is detected in the decision circuit 111 that the detected current is decreased, the output value (present control value) of the decision circuit 111 is a value obtained by adding the increased (stored) amount to the former output value. The present control value is supplied to the D/A converter 112, in which an analog control signal is obtained, and the analog control signal is amplified in the weight addition circuit 113, so that the amplified control signal is supplied as an amplification efficiency control signal D to the power amplification circuit 102. This control is repeated to provide an optimum power amplification efficiency. Although the invention has been described with respect to specific embodiment for complete and clear disclosure, the appended claim is not to be thus limited but is to be construed as embodying all modification and alternative constructions that within the scope of the claim.

Claims: An apparatus for adjusting the efficiency of a power amplification circuit, comprising: a power amplification circuit (102) for amplifying a signal to be transmitted in a time division multiple access mode; and a control circuit comprising: a) a circuit (105) for detecting an electric current supplied from a power supply (104) to said power amplification circuit (102), b) a first register (108) for storing said electric current value at a first transmission period, c) a second register (109) for storing said electric current value at a second transmission period, said second transmission period following said first transmission period by allocating a first non-transmission period between said first and second transmission periods, d) a difference detection circuit (110) for detecting a difference between contents of said first and second registers (108,109), said difference indicating an increase or decrease of said electric current as said change of said electric current, and e) a decision circuit (111) for supplying an efficiency control signal to said power amplification circuit (102) by subtracting a difference between said efficiency control signal used at said first transmission period and said efficiency control signal used at said second transmission period from said efficiency control signal used at said second transmission period, when said increase is detected in the difference detection circuit (111), or by adding said difference to said second efficiency control signal used at said second transmission period, when said decrease is detected in the difference detection circuit, wherein said efficiency control signal is determined at a second non-transmission period following said second transmission period for a third transmission period following said second transmission period by allocating said second non-transmission period between said second and third transmission periods.

Inventors: NORIMATSU HIDEHIKO, NORIMATSU, HIDEHIKO, NORIMATSU, HIDEHIKO, C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1993
Main classification: H04B7
IPC codes: H03G3, H04B7