HK1036704A - Non-linear distortion compensation circuit, transmitter device to be employed in the same and mobile communication unit - Google Patents

Description

Nonlinear distortion compensation circuit, transmitting device and mobile communication equipment

The present invention relates to a nonlinear distortion compensation circuit, a transmitting apparatus and a mobile communication device using the nonlinear distortion compensation circuit. More particularly, the present invention relates to a control system, a nonlinear distortion correction circuit for compensating for nonlinear distortion caused by nonlinearity of an amplifier or a frequency converter.

Conventionally, a linear circuit has been known as a nonlinear distortion correction circuit for compensating for nonlinear distortion caused by an amplifier, a frequency converter, and the like forming a transmitter to be used in radio communication. As a linear circuit, it is only to extract a nonlinear signal from a transmitted transmission signal and compensate for nonlinear distortion by subtracting the extracted nonlinear distortion signal, or to multiply a transmission signal by a signal having distortion compensation characteristics for compensating distortion before radio transmission processing such as frequency conversion, amplification and the like which is considered to cause nonlinear distortion in a transmitter.

On the other hand, it is known that nonlinear distortion caused by nonlinearity of an amplifier, a frequency converter, or the like forming a transmitter for radio communication appears as a leakage current in a channel band at the time of transmission and a leakage current in a band of an adjacent channel of the channel at the time of transmission, and the leakage current increases in accordance with an increase in transmission power. In particular, the power leaked to the adjacent channel is considered as the adjacent channel leakage power. The adjacent channel leakage power caused by the transmitter may affect another radio device communication using the adjacent channel, resulting in degradation of the reception characteristics.

Next, the influence of adjacent channel leakage power caused by a radio device employing a spread spectrum communication system (CDMA system: code division multiple access system) that performs multiplex communication by spreading the spectrum of a communication signal, as a communication system used in mobile communication, for other communication systems, will be discussed.

In a CDMA system, spreading of the spectrum of a communication signal is accomplished using a spreading code, such as a pseudo-random noise code (PN code) and the communication signal is identified by the spreading code. Thus, CDMA systems are given the ability for multiple channels and multiple radios to communicate simultaneously on the same frequency. The CDMA system is also characterized in that, in demodulating a received signal, if not multiplied by the same spreading code used for spreading at the transmitting side at the same time as at the transmitting side, demodulation of the received signal cannot be achieved, and at the receiving side, a received signal spread by a different spreading code or a received signal spread at a different time, i.e., a signal used for communication by other radio devices or a signal of another channel, is attenuated as noise in the current reception band.

Here, consideration is given to a case where one base station which gives mobile communication is given, a plurality of mobile stations are given at the position of the tip and the closest position of the base station, and communication is performed by the CDMA system. When a mobile station at the position of the tip and the closest position of the base station communicates with the base station using the same frequency and the same transmission power, the transmission power of the mobile station communicating at the closest position of the base station is higher than that of the mobile station communicating at the position of the tip, as viewed at the receiving end of the base station, so that the transmission signal of the mobile station at the position of the tip is buried in the transmission signal of the mobile station at the closest position. This was considered a far-near problem. In consideration of the characteristics of the CDMA system, even when the base station demodulates the signal transmitted from the top mobile station, since the signal of the closest mobile station is attenuated as noise for the reception frequency band, the transmission signal of the top mobile station cannot be correctly demodulated.

In CDMA systems, the near-far problem is solved by performing transmit power control with high accuracy and relatively frequently. That is, by performing the transmission power control, the transmission power of the closest mobile station is controlled to be a lower power, and the transmission power of the mobile station at the tip is controlled to be a higher power. For higher power transmissions by the mobile station, the frequency converter and/or amplifier forming the transmitter of the mobile station must operate in its non-linear region. As a result, at higher levels of transmit power, the nonlinear distortion of the transmitted signal increases. That is, adjacent channel leakage power transmitted from the transmitter increases. The effect of adjacent channel leakage power on other systems will be discussed with reference to fig. 6.

Fig. 6 illustrates a mobile communication system including a mobile station 101, a mobile station 102, a base station 103, a base station 104, a cell 105 and a cell 106. Here, a case is considered in which communication is performed using a CDMA system for the base station 103 and the base station 104, and carriers of the base station 103 and the base station 104 are different. Cell 105 represents the service area of base station 103 and is spread over the vicinity of base station 104. Cell 106, on the other hand, is the service area of base station 104.

When mobile station 102 communicates with base station 104 at a position closest to base station 104, mobile station 101 communicates with base station 103 moving from the position closest to base station 103 to its distal position, and the transmission power of mobile station 101 and the leakage power of the adjacent channel increase as the position moves toward the distal position by the transmission power control of mobile station 101 by base station 103. When the mobile station 101 approaches the base station 104, the transmission power of the mobile station 101 and the leakage power of the adjacent channel reach the base station 104 at a higher power.

If the communication frequency used by base station 103 and the communication frequency used by base station 104 are adjacent to each other, the transmit power transmitted from mobile station 102 may be overwhelmed by the adjacent channel leakage power transmitted from mobile station 101. A problem encountered in this case is that the base station 104 cannot correctly receive the signal of the mobile station 102. This is because in the mobile station 102, the transmission power of the mobile station 102 is lower power for the transmission power control of the base station 104.

As a solution to this problem, linear circuits are used for compensating the nonlinear distortion of the transmitter. As explained above, as the linear circuit, it is only to extract a nonlinear signal from a transmitted transmission signal and compensate for nonlinear distortion by subtracting the extracted nonlinear distortion signal, or to multiply a transmission signal by a signal having a distortion compensation characteristic for compensating distortion before radio transmission processing such as frequency conversion, amplification, etc. which considers that nonlinear distortion is to be caused in a transmitter. The former is not practical due to the increased current consumption resulting from the increased circuit size and processing complexity. Therefore, the latter is mainly used as a nonlinear distortion compensation circuit. In particular, the latter linear circuit is called a predistortion type linear circuit.

A previously used predistortion type linear circuit is shown in fig. 7. It should be noted that the structure shown in FIG. 7 has been disclosed in Japanese unexamined patent publication No. Hei-10-23095. Referring to fig. 7, a transmission signal composed of two types of data, that is, digital I data and Q data, is supplied to the input terminals 21 and 22, respectively. These input data are supplied to a predistortion circuit 25 through FIR filters 23 and 24 to obtain digital I data and Q data which superimpose a nonlinear distortion inverse component caused by a variable power amplifier 29.

In addition to the I and Q data, a transmit power control signal from the transmit power controller 34 is provided to the predistortion circuit 25. The predistortion circuit 25 derives the inverse component of the nonlinear distortion by an arithmetic process on the basis of the transmission power control signal and the I and Q data. The resulting inverse components are superimposed on the I and Q data. The output data of the predistortion circuit 25 is converted into an analog signal by a D/a converter 26 and then modulated by a modulator 27 with the output of an oscillator 28. Thus, the I and Q signals (data) are modulated according to quadrature modulation. On the other hand, for the CDMA system, spreading processing using a spreading code is performed by the modulator 27.

The transmission signal thus modulated by the spreading is then supplied to the variable power amplifier 29 to be amplified by an amplifier gain determined by a transmission power control signal from the transmission power controller 34. By means of the amplifier 29, non-linear distortions can be caused. The amplified output is mixed with the oscillation frequency from the frequency synthesizer 31 in the mixer 30, and then amplified with a given gain by the amplifier 32, and transmitted as a radio signal from the antenna 33.

It should be noted that the transmission power control signal output from the transmission power controller 34 is generated on the basis of the power control information bit input from the terminal 35 and the reception level information signal from the terminal 36. Here, the power control information bit is power control information bit data contained in a signal transmitted from a partner (usually, a base station) to its own radio transmitter apparatus for communication. On the other hand, the reception level information signal is reception level information of a received signal transmitted from the base station.

Therefore, the occurrence of nonlinear distortion in the amplifier gain variable power amplifier 29 can be accurately judged by the predistortion circuit 25. Then, on the basis of the occurrence condition of the nonlinear distortion as the judgment, a compensation component may be generated as an inverse component of the nonlinear distortion. With this compensation component, even in the case where the amplifier gain is different according to the power amplifier 29, accurate distortion compensation corresponding to the amplifier gain can be performed.

Next, the correlation between the conventional transmitter shown in fig. 7 and the transmission power control for a mobile station (mobile communication apparatus) by a base station will be discussed. In the case of a CDMA system, a base station can distinguish a reception channel in communication or a mobile station in communication by a spreading code. Accordingly, the base station can distinguish the reception power of a desired wave from the power of other reception signals from the reception signal, and can thus derive the S/N (signal/noise ratio) of the reception channel. The transmission power control is performed according to the S/N ratio of the reception channel. That is, the base station derives the power of a desired wave and the power of an interference wave in order to derive the S/N ratio of the reception channel.

When the S/N ratio is less than or equal to a predetermined value, the base station transmits a control signal to the mobile station for increasing the power of a transmission signal of the mobile station. On the other hand, when the S/N ratio is larger than a predetermined value, the base station transmits a notification for reducing the transmission power so that the transmission power of the mobile station in communication will not interfere with the communication of the other mobile stations in communication. The calculation of the S/N ratio performed by the base station is done at each time slot forming a transmission frame transmitted by the base station.

Therefore, the transmission control information is updated every slot. The correlation between the transmission frame transmitted by the base station and the transmitted transmission power control information is as shown in fig. 8. A procedure of transmission power control to be performed will be discussed with reference to fig. 8.

Referring to fig. 8, one frame to be transmitted is composed of n time slots TS1 through TSn. One slot is composed of control information, transmission power control information, and communication data. Upon receiving a signal transmitted by a base station, a mobile station demodulates to extract transmission power control information from the demodulated received signal and performs transmission power control of a transmitter every time slot.

In this case, the nonlinear distortion compensation performed on the basis of the detection of the transmission power of the signal transmitted in the time slot TSi at a certain time can compensate for the distortion of the transmission signal transmitted in the next time slot TS (i + 1). However, since the transmission signal transmitted in the time slot TS (i +1) is differentiated from the transmission power in the time slot TSi by the transmission power control, correct nonlinear distortion compensation cannot be accomplished.

As explained above, in the prior art, the non-linear distortion compensation to be performed on the basis of the detection of the transmission power transmitted at a time in the time slot TSi is a distortion compensation acting on the transmission signal transmitted in the next time slot TS (i + 1). However, since the transmission power transmitted at the time slot TS (i +1) is different from that of the time slot TSi, correct nonlinear distortion compensation cannot be performed.

On the other hand, in order to do so accurately, it becomes important to perform distortion compensation by the predistortion circuit for each bit (symbol) constituting transmission data in each slot of a transmission signal. However, in the structure shown in fig. 7, compensation for each bit (symbol) is not considered at all.

An object of the present invention is to provide a nonlinear distortion compensation circuit, a transmitting apparatus and a mobile communication device employing the nonlinear distortion compensation circuit, in which a mobile station can accurately compensate distortion of each bit (symbol) due to nonlinearity of a transmitter even when a base station performs transmission power control for the transmitter of the mobile station.

According to a first aspect of the present invention, a nonlinear distortion compensation circuit in a transmitting apparatus for controlling transmission power based on transmission power control information external in digital signal transmission, comprises:

compensation component generating means for generating a compensation component for the nonlinear distortion based on the transmission power of each bit of the digital signal and the transmission power control information; and

a compensation apparatus for compensating for nonlinear distortion of a transmission signal by using a compensation component.

According to a second aspect of the present invention, a transmitting apparatus comprises:

a transmitter including a non-linear distortion inducing element;

a non-linear distortion compensating circuit in a transmitting apparatus for controlling transmission power based on transmission power control information to the outside in digital signal transmission, the compensating circuit comprising compensation component generating means for generating a compensation component for non-linear distortion based on the transmission power of each bit of digital signal and the transmission power control information, and compensating means for compensating for the non-linear distortion of a transmission signal with the compensation component.

According to a third aspect of the invention, a mobile communication device comprises:

a receiver for receiving a signal from a communication partner, the signal containing transmission power control information;

a transmitting device, comprising: a transmitter including a non-linear distortion inducing element; a nonlinear distortion compensation circuit in the transmitting apparatus for controlling transmission power based on transmission power control information transmitted as a digital signal to the outside, said compensation circuit comprising compensation component generating means for generating a compensation component for nonlinear distortion based on the transmission power of each bit of the digital signal and the transmission power control information; and comprises compensation means for compensating the non-linear distortion of the transmission signal with a compensation component.

The compensation component generating means may generate each bit compensation component, and may perform compensation of nonlinear distortion based on each bit compensation component. The compensation component generating means may calculate each bit of transmission power from the instantaneous transmission power value and the average value of the transmission power, and generate each bit of compensation component based on the calculation result and the transmission power control information. The compensation component generating means may include storage means for storing compensation data as the compensation component in advance, and address generating means for generating an address of the storage means based on the transmission power per bit and the transmission power control information. The address generating means may be configured to generate the address using an addition of each bit of the transmission power and the transmission power control information. The address generation means may derive the transmit power for each bit as calculated by adding the instantaneous transmit power and the average of the transmit powers. The transmission signal may be of a slot type, the external transmission power control information may be set for controlling the transmission power every slot, and the address generating means may derive the transmission power every bit by adding an average power value of a transmission slot at a certain time and an instantaneous power value of every bit of a subsequent transmission slot. The transmission power control information may be information for transmission power control for a subsequent transmission slot. The storage device may be a read-only memory.

The transmission power control signals may be separately overlapped in each slot of the signal transmitted by the base station. In the operation of the present invention, a ROM address based on each bit of transmission power of a transmission signal and transmission power control information is generated by an address generating section that generates a compensation data storing ROM address storing nonlinear distortion data which is data to be subjected to nonlinear distortion by a predistortion type linear circuit. In particular, the transmission power control information may reflect a slot that is a control object.

The present invention will be understood more fully from the detailed description of preferred embodiments of the invention given below and from the accompanying drawings, which, however, should not be taken to limit the invention, but are for explanation and understanding only.

FIG. 1 is a block diagram of a preferred embodiment of the present invention;

fig. 2 is an explanatory diagram showing a specific structure of the transmitter of fig. 1;

FIG. 3 is a general flow chart showing the operation of the present invention;

FIG. 4 is an illustrative diagram showing amplitude and phase characteristics of the output power of a power amplifier;

fig. 5 is an explanatory diagram showing a correlation between a reception time slot of a reception side and a transmission time slot of a transmission side;

fig. 6 is an explanatory diagram for explaining an influence on an adjacent channel of another system;

fig. 7 is a block diagram showing a conventional mobile station of the prior art; and

fig. 8 is an explanatory diagram showing a correlation between a transmission frame transmitted by a base station and transmitted transmission power control information.

The present invention will be discussed in detail hereinafter according to preferred embodiments thereof with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details.

Fig. 1 shows a schematic block diagram of the overall structure of a preferred embodiment of the mobile station of the present invention. Referring to fig. 1, for a reception process, a reception signal from an antenna 1 is input to a reception section 3 through an antenna multicoupler 2, and I and Q components of a baseband signal are to be extracted.

Thereafter, the I and Q components thus extracted are input to the demodulation section 4 for demodulation processing (despreading process), and then audible sound is output from the speaker 6 after error correction in the error correction section 5.

On the other hand, the audio signal from the microphone 7 is converted into a digital signal by the transmission signal generating section 8, and then subjected to a linear modulation process (generally, QPSK modulation process), a signal to be caused into I and Q components. Then, linear distortion compensation is performed by the predistortion type linear circuit 9. Then, the transmission processing is performed by the transmission section 10. Thereafter, a radio wave signal as a transmission signal is transmitted through the antenna via the antenna multicoupler 11 and the antenna multicoupler 2.

The transmission signal branched by the directional coupler 11 is obtained in accordance with the average power value of each slot of the transmission signal, and is input to an average power calculation section 12. On the other hand, the I and Q components as the output of the transmission signal generation section 8 are input to the instantaneous power calculation section 13. Thus, the instantaneous transmit power for each bit (symbol) is calculated. Further, the transmission power control information is detected from the output of the error correction section 5 by the transmission power control information detection section 15. It should be noted that the transmission power control information is not supplied to the speaker 6.

Respective outputs of the average power calculating section 12, the instantaneous power calculating section 13 and the transmission power control information retrieving section 15 are supplied to an address generating section 14 for generating an address to access the compensation data storage ROM 16. According to the address thus generated, the compensation data is read out to be supplied to the predistortion type linear circuit 9.

The structure of the transmitting section 10 is shown in fig. 2. The transmitting section 10 is constituted by a D/a converter 501, a quadrature modulator 502, a variable gain amplifier 503, an intermediate frequency passband filter 504, a frequency converter (mixer) 505, a first radio frequency bandpass filter 506, an amplifier 507, a second radio frequency bandpass filter 508, a transmission amplifier 509, a first local oscillator 510, and a second local oscillator 511.

The D/a converter 501 converts the intermediate frequency transmission signal from a digital signal to an analog signal. The quadrature modulator 502 performs quadrature modulation of the base-frequency transmission signal and performs frequency conversion into one transmission signal in the intermediate frequency band. The variable gain amplifier 503 is an amplifier that amplifies a transmission signal according to received transmission power control information. The if band pass filter 504 is a filter that transmits signals through an if band.

The frequency converter 505 performs frequency conversion of the intermediate frequency band transmission signal into a radio frequency band transmission signal. The first rf band pass filter 506 and the second rf band pass filter 508 are filters that pass only signals of the transmission band and suppress unnecessary radiation caused in the frequency converter 505 or the amplifier 507.

The amplifier 507 is an amplifier that amplifies a transmission signal. The transmission amplifier 509 is an amplifier for amplifying a transmission signal to power transmitted through an antenna. The first local oscillator 510 is an oscillator for oscillating to generate a local oscillation signal due to frequency conversion in the frequency converter 505. The second local oscillator 511 is an oscillator of a local oscillation signal for oscillating frequency modulation generated in the quadrature modulator 502.

The I and Q component signal inputs of the D/a converter 501 are matched to the I and Q component signal inputs of the transmitting section 10, and the output of the transmission amplifier 509 is matched to the output of the transmitting section 10. The I and Q component signal outputs of D/a converter 501 are connected to the I and Q component signal inputs of quadrature modulator 502. The mid-band signal output of the quadrature modulator 502 is connected to the input of a variable gain amplifier 503. The output of the variable gain amplifier 503 is connected to the input of the intermediate frequency band pass filter 504. The output 504 of the if band pass filter is connected to the if signal input of a frequency converter 505. The radio frequency band output of the frequency converter 505 is connected to the input of a first radio frequency band pass filter 506.

The output of the first rf band-pass filter 506 is connected to the input of an amplifier 507. The output of the amplifier 507 is connected to the input of a second rf band-pass filter 508. The output of the second rf band-pass filter 508 is connected to the input of a transmit amplifier 509. On the other hand, the output of the first local oscillator 510 is connected to the local signal input of the frequency converter 505. The radio frequency band output of the frequency converter 505 is connected to the input of a first radio frequency band pass filter 506.

The output of the first rf band-pass filter 506 is connected to the input of an amplifier 507. The output of the amplifier 507 is connected to the input of a second rf band-pass filter 508. The output of the second rf band-pass filter 508 is connected to the input of a transmit amplifier 509. Furthermore, the output of the first local oscillator 510 is connected to a local signal input of the frequency converter 505. An output of the second local oscillator 511 is connected to a local signal input of the quadrature modulator 502. A gain control signal input terminal of the variable gain amplifier 503 is connected to a transmission power control information output terminal of the transmission power control information modulator 401.

The working of the illustrated embodiment will be discussed below with reference to the flow chart of fig. 3. In the receiving section 3, the time slot Tsi is received from the base station (step S11). In the demodulation section 4, the demodulation process of the time slot TSi is completed (step S12). Subsequently, in the error correction section 5, an error correction process of the time slot TSi is performed (step S13). Then, the next time slot TS (i +1) is received (step S14). After the error correction at step S13, in the transmission power control information detection section 15, the transmission power control information is taken out from the received signal of the slot TSi to be output to the address generation section 14 (step S31). It should be noted that the transmission power control information is a kind of control information for controlling the transmission power of the transmission time slot TS (i +1) at the transmission side.

On the receiving side, when the time slot TSi is received at step S11, signal processing for the transmitted data, such as error correction and the like, is applied to the transmitted data, such as sound for the transmission time slot TS (i +1) and the like, and a transmission frame is generated according to the transmission frame format. Thereafter, the transmission signal is spread using a spreading code. The spread transmission signals are output as I-component and Q-component signals, respectively (step S21).

The transmission signals of the I component and the Q component output from the transmission signal generation section 8 are input to the predistortion type linear circuit 9. In conjunction therewith, the transmission signals of the I component and the Q component are also input to the instantaneous power calculating section 13. In the instantaneous power calculation section 13, the instantaneous powers of the input I component signal and Q component signal are derived (step 32) to be output to the address generator 14.

On the other hand, the I-component and Q-component signals input to the predistortion type linear circuit 9 are subjected to nonlinear distortion compensation by the nonlinear distortion compensation data read out from the compensation data storage ROM16 (step S36), and are output to the transmission section 10. Referring to fig. 2, the operation of the transmitting section 10 will be discussed. The I-component and Q-component signals input to the transmitting section 10 are converted from digital signals into analog signals by the D/a converter 501.

The quadrature modulator 502 performs quadrature modulation on the I-component and Q-component signals output from the D/a converter 501 with a local oscillation signal oscillated by the second local oscillator 511, and the transmission signal of the base band is converted into a transmission signal of the intermediate band. The transmission signal converted into the intermediate frequency band transmission signal is amplified by the variable gain amplifier 503 according to the transmission power control information, and then input to the frequency converter 505 through the intermediate frequency band pass filter 504.

The gain of the variable gain amplifier 503 is adjustable in accordance with the transmission power control information output from the transmission power control information detection section 15. The frequency converter 505 converts the input if transmission signal into the rf transmission signal using the local oscillation frequency oscillated by the first local oscillator 510. The radio frequency band transmission signal thus converted passes through the first radio frequency band pass filter 506, the amplifier 507, the second radio frequency band pass filter 508, is amplified by the transmission amplifier 509 to power to be transmitted through the antenna 1, and is then output from the transmission section 10.

So that the transmission signal outputted from the transmitting section is inputted to the directional coupler 11 and outputted from the inserting direction output terminal to be transmitted through the antenna 1 in association therewith, and outputted from the coupling direction output terminal to be inputted to the average power calculating section 12. In the average power calculating section 12, the average power per unit time slot of the inputted transmission signal is obtained, and the detection result for the address generating section 14 is outputted. At this time, on the transmitting side, transmission of the transmission time slot TSi is transmitted (step S23). Thus, the average value of the transmission power of the transmission time slot TSi is obtained at the average power calculation section 12 (step S34), and is output to the address generation section 14.

The address generating section 14 generates an address for accessing the compensation data storage ROM16 using the calculation result output by the instantaneous power calculating section 13, the calculation result output by the average power calculating section 12, and the transmission power control information output by the transmission power control information detecting section 15 (step S35) so as to specify the address of the ROM 16. The ROM16 outputs nonlinear distortion compensation data to the predistortion type linear circuit 9 based on the address designated by the address generation section 14.

In the predistortion type linear circuit 9, the nonlinear distortion of the I-component and Q-component signals is compensated for processing for transmission using the nonlinear distortion compensation data input from the compensation data storage ROM16 (step S23). Then, preparation is made for transmission of the next time slot TS (i +1) (step S24).

Next, the compensation data stored in the compensation data storage ROM16 and its address will be discussed. The signal to be transmitted may be represented as a function of amplitude and phase. The characteristics of the power amplifier in the transmission section 10 are represented as amplitude and phase characteristics as shown in fig. 4. I.e. by increasing the output power, the amplitude and phase characteristics are reduced, causing non-linear distortion. Thus, it can be said that the nonlinear distortion is amplitude distortion for the amplitude of the transmission signal and phase distortion for the phase of the transmission signal. Assuming that the amplitude distortion caused in the transmission section 1O is Δ a and the phase distortion is Δ P, the nonlinear distortion caused in the transmitter 206 can be cancelled by providing- Δ a and- Δ P components to the transmission signal. In other words, the nonlinear compensation data stored in the compensation data storage ROM16 must have characteristics inverse to the amplitude distortion and the phase distortion caused in the transmission section 10.

In other words, as shown in fig. 4, when the transmission power can be seen, the amount of amplitude and phase in the known transmission power can be decided in a simple manner. As a result, the amplitude distortion Δ a and the phase distortion Δ P are determined in a simple manner. Accordingly, by storing the compensation data- Δ a and- Δ P for the transmission power in the ROM16 in advance, the compensation data can be read out from the ROM using the derived transmission power as an address.

Therefore, in the present invention, the bit-by-bit transmission power of the transmission time slot TS (I +1) is obtained using a certain time slot TSi, the average transmission power of the instantaneous power of the I component and Q component to be transmitted in the next time slot TS (I +1), and the transmission power control information for the time slot TS (I + 1). In other words, each bit correction transmission power value to be transmitted last is used to derive each bit transmission power value by adding the instantaneous power value (each bit) transmitted in the time slot TS (i +1) to be compensated to the average transmission power value of the preceding transmission time slot TSi, and the transmission power control information for the transmission time slot TS (i +1) is added to the sum thus derived.

For example, if the average transmission power value is "10" and each bit instantaneous power value is "15", each bit transmission power value becomes "10" + "15" = "25". Further, to this value, "± 1" or "0" is added as control information (the control information is three kinds of information to which transmission power +1, -1 is set or which remains unchanged). Assuming that the transmission power control information is set to "+ 1", the corrected transmission power per bit becomes "26". By setting the ROM address, it becomes a power value corresponding to "26" of the lateral axis of the characteristic shown in fig. 4. As described earlier, since the respective amplitude values and phase values are obtained, linear distortion corresponding to the amplitude values and phase values can be read out, enabling predistortion.

Using the foregoing method, the operation of the predistortion type linear circuit will be discussed with reference to fig. 5. In fig. 5, (1) indicates control information, (2) indicates transmission power control information, and (3) indicates communication data. On the other hand, the upper layer represents a reception slot, and the lower layer represents a transmission slot.

The transmission power control information received at the reception time slot TS (i +1) is validated at the transmission time slot TS (i + 1). Assuming that the currently transmitted signal is a transmission signal of the time slot TSi, the average power calculated by the average power calculation section 12 becomes the average power of the transmission signal of the transmission time slot TSi. However, the transmission signal of the transmission slot is being transmitted, and therefore naturally, the transmission signal has already passed through the predistortion type linearizer 9. In the linear circuit 9 and the instantaneous power calculation section 13, the transmission signal of the next transmission time slot TS (i +1) is input for distortion compensation.

At this time, a ROM address for obtaining distortion compensation data is generated based on the average power of the transmission signal, the instantaneous power of the transmission signal, and the transmission power control information (to be added). Accordingly, the average power of the transmission signal is the average power of the transmission time slot TSi, the instantaneous power of the transmission signal is the instantaneous power of the transmission time slot TS (i +1), and for this interpolation, the transmission power control information for the transmission time slot TS (i +1) is used.

As explained above, when the predistortion type linear circuit 9 is used to compensate for nonlinear distortion of a transmission signal due to nonlinear distortion of the transmission section 10, nonlinear distortion compensation data of the transmission section 10 is derived in advance and in one-to-one correspondence with transmission power to establish consistency between the transmission power and the compensation data ROM 16. The address of the compensation data storage ROM16, which stores data for compensating for nonlinear distortion, is generated using the instantaneous power calculated from the I-component and Q-component signals to be transmitted, the average transmission power per unit time slot of the transmission signal, and the transmission power control information. Then, nonlinear distortion compensation data is obtained from the compensation data storage ROM16 by the predistortion type linear circuit, and nonlinear distortion compensation is provided for the transmission signal.

As explained above, according to the present invention, nonlinear distortion in the transmission section of a mobile communication device is compensated for each bit (symbol) of transmission power by a predistortion type linear circuit. Further, since the compensation is performed in consideration of the transmission power control information from the base station, a more accurate nonlinear distortion compensation operation can be achieved.

Although the present invention has been described with respect to the embodiments thereof, it should be understood by those skilled in the art that other changes, modifications, additions and subtractions may be made therein without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the foregoing examples, but rather includes all possible embodiments within the scope of the features of the claims and equivalents thereof.

Claims (26)

1. A nonlinear distortion compensation circuit in a transmitting apparatus for controlling transmission power based on external transmission power control information transmitted as a digital signal, comprising:

compensation component generating means for generating a compensation component for nonlinear distortion based on the transmission power of each bit of the digital signal and the transmission power control information; and

and a compensation means for compensating said nonlinear distortion of the transmission signal with said compensation component.

2. The nonlinear distortion compensating circuit as claimed in claim 1, wherein said compensation component generating means generates said compensation component for each bit, and said compensating means performs compensation of said nonlinear distortion based on each bit of said compensation component.

3. The nonlinear distortion compensation circuit of claim 2 wherein said compensation component generating means calculates each bit of transmission power based on the instantaneous transmission power value and the average value of the transmission power, and generates each bit of compensation component based on the calculation result and said transmission power control information.

4. The nonlinear distortion compensation circuit as claimed in claim 1, wherein said compensation component generating means includes storing means for storing in advance compensation data as said compensation component, and address generating means for generating an address of said storing means based on each bit of transmission power and said transmission power control information.

5. The nonlinear distortion compensation circuit of claim 4 wherein said address generation means is configured to generate said address using an addition of said transmission power per bit and said transmission power control information.

6. The nonlinear distortion compensation circuit of claim 5 wherein said address generation means derives each bit transmit power by adding an instantaneous transmit power and an average of the transmit powers.

7. The nonlinear distortion compensation circuit of claim 6 wherein said transmission signal is of a time-slotted type; the external transmission power control information is set for controlling transmission power per slot; the address generating means derives the transmission power of each bit by adding the average power value of the transmission time slot at a certain time and the instantaneous power value of each bit of the subsequent transmission time slot.

8. The nonlinear distortion compensation circuit of claim 7 wherein said transmission power control information is information for controlling transmission power of a subsequent transmission slot.

9. The nonlinear distortion compensation circuit of claim 4 wherein said storage means is a read only memory.

10. A transmitting device, comprising:

a transmitter comprising elements causing non-linear distortion,

a nonlinear distortion compensating circuit in a transmitting apparatus for controlling transmission power in accordance with external transmission power control information in digital signal transmission, the compensating circuit comprising compensation component generating means for generating a compensation component for nonlinear distortion in accordance with transmission power per bit of the digital signal and the transmission power control information, and compensating means for compensating the nonlinear distortion of a transmission signal with the compensation component.

11. The transmitting apparatus according to claim 10, wherein said compensation component generating means generates each of said bit compensation components, and said compensating means performs compensation of said nonlinear distortion based on each of said bit compensation components.

12. The transmission apparatus according to claim 11, wherein said compensation component generating means calculates transmission power per bit based on the instantaneous transmission power value and the average value of the transmission power, and generates compensation components per bit based on the calculation result and said transmission power control information.

13. The transmission apparatus according to claim 10, wherein said compensation component generating means includes storage means for storing in advance compensation data as said compensation component, and address generating means for generating an address of said storage means based on each bit of transmission power and said transmission power control information.

14. The transmitting apparatus of claim 13, wherein said address generating means is configured to generate said address by adding said transmission power per bit and said transmission power control information.

15. The transmitting apparatus of claim 14 wherein said address generating means derives the transmit power of each bit by adding the instantaneous transmit power and the average of the transmit powers.

16. The transmitting device of claim 15, wherein said transmission signal is of a time-slotted type; the external transmission power control information is set for controlling transmission power per slot; the address generating means derives the transmission power of each bit by adding the average power value of the transmission time slot at a certain time and the instantaneous power value of each bit of the subsequent transmission time slot.

17. The transmission apparatus as claimed in claim 16, wherein the transmission power control information is information for controlling transmission power of a subsequent transmission slot.

18. A mobile communication device, comprising:

a receiver that receives a signal from a communication partner, the signal containing transmission power control information;

a transmitting device, comprising: a transmitter including an element that causes nonlinear distortion; a nonlinear distortion compensation circuit in a transmitting apparatus for controlling a transmission power according to an external transmission power control information transmitted as a digital signal, the compensation circuit including a compensation component generating means for generating a compensation component for nonlinear distortion according to a transmission power of each bit of the digital signal and the transmission power control information; and compensation means for compensating said non-linear distortion of the transmission signal by said compensation component.

19. The mobile communication device as claimed in claim 18, wherein said compensation component generating means generates each of said bit compensation components, and said compensating means performs compensation of said nonlinear distortion based on each of said bit compensation components.

20. The mobile communication device of claim 19, wherein the compensation component generating means calculates each bit of transmission power based on the instantaneous transmission power value and the average value of the transmission power, and generates each bit of compensation component based on the calculation result and the transmission power control information.

21. The mobile communication device according to claim 18, wherein said compensation component generating means includes storage means for storing in advance compensation data as said compensation component, and address generating means for generating an address of said storage means based on each bit of transmission power and said transmission power control information.

22. The mobile communication device of claim 21, wherein said address generating means is configured to generate said address using an addition of said transmission power per bit and said transmission power control information.

23. The mobile communication device of claim 22, wherein said address generating means derives each bit transmission power by adding an instantaneous transmission power and an average value of the transmission power.

24. The mobile communication device of claim 23, wherein said transmission signal is of a time-slotted type; the external transmission power control information is set to control transmission power per transmission slot; the address generating means derives the transmission power of each bit by adding the average power value of the transmission time slot at a certain time and the instantaneous power value of each bit of the subsequent transmission time slot.

25. The mobile communication device of claim 24, wherein the transmission power control information is information for controlling transmission power of a subsequent transmission slot.

26. The mobile communication device of claim 18, wherein the transmit power control signals overlap separately in each time slot of a signal transmitted by the base station.