JP2002135137A - Transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitter capable of reducing power consumption through control of driving each block therein,corresponding to the inherent number of codes (the output level of a code division multiplexing modulator). SOLUTION: The transmitter includes an amplitude splitting circuit for dividing a signal output from a modulator into a plurality of signals. A plurality of distortion compensating circuits and a plurality of power amplifiers respectively disposed in parallel are successively connected to the amplitude division circuit. Outputs of the plurality of power amplifiers are added to be combined into a single signal, to control to drive with the number of drives in the distortion compensating circuits and the power amplifiers determined, according to the output signal level of the modulator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter, and more particularly to a means for reducing power consumption of a transmitter used in a code division multiple access system.

[0002]

2. Description of the Related Art Recent mobile phones and PHS (Personal Handyph)
2. Description of the Related Art In a mobile communication system such as one system, a time division multiple access (hereinafter, referred to as TDMA) system is adopted in order to secure the number of channels required for the system. The TDMA method is a method of dividing the time axis of this signal and assigning it to each user in order to use a fixed assigned frequency band in common for a plurality of users. However, available frequency bands are limited by frequency allocation, and the number of time divisions is technically limited, so that the number of channels that can be allocated to each user is also limited.

In recent years, with the increase in the number of users of the mobile communication system described above, a code division multiple access (Code Division Multipl.
e Access (hereinafter referred to as CDMA)) has been proposed. CDMA
In the system, each user is identified by a code (unique code) assigned to the user so that the same band can be shared by a plurality of users. Therefore, in order to facilitate identification of the unique code, the unique code is converted into a signal having a clock frequency of about several MHz, which is faster than the information signal, and the information signal is further multiplied by the signal to increase the bandwidth of the transmission signal. The signal is transmitted to the transmission path (with spread spectrum), and the receiving side demodulates the unique code by obtaining the correlation characteristic of the received signal using a matched filter or the like. As described above, the CDMA system has the advantage that the number of users per bandwidth can be increased as compared with the TDMA system, because many users can share the same band.

FIG. 8 is a functional block diagram showing a configuration example of a transmitting device in a CDMA system base station. The transmission apparatus shown in this example includes a code division multiplex modulator (CDM modulator) 101, a distortion compensation circuit 102, and a digital / analog converter (D / A converter) 103
a, 103b and low-pass filter (LPF) 104a for image removal,
The configuration is such that 104b, quadrature modulator 105, and power amplifying unit 110 are sequentially connected. The power amplifying unit 110 includes four power amplifiers 111a to 111d arranged in parallel, three adders 112a to 112c for combining these output signals, and driving of the four power amplifiers 111a to 111d. (ON / OFF).

[0005] The transmitting device shown in this example functions as follows. That is, when the CDM modulator 101 modulates a user-assigned code (unique code) with an information signal to generate and output a digital modulated signal (quadrature signal I, Q), the distortion compensation circuit 102 Removes distortion components and D / A converters 103a, 103b
To supply. The digital modulated signal is converted into an analog signal in the D / A converters 103a and 103b, and the LPFs 104a and 104b
After the image component related to the D / A conversion is removed, the carrier is superimposed on the modulated signal in the quadrature modulator 105. In the power amplifier 110, each of the power amplifiers 111a to 111d
The amplified signal is amplified by the
The operation control circuit 113 drives only a required number of power amplifiers in accordance with the input level of 110.

That is, in the CDMA system, a transmitting device of a base station uses a signal (CDM) code-multiplexed with a large number of unique codes.
When transmitting (modulated signal), the number of unique codes (the number of users) handled by one base station is very large, and the number is constantly fluctuating. The difference from the power (average power) is large, and it is usually operated with transmission power much smaller than peak power. Therefore,
The input level of the power amplifier 110 is monitored by a sensor (not shown), and only the power amplifier necessary to obtain the required transmission power level according to the number of users is controlled by the operation control circuit 11.
By driving by 3, the useless power consumption of the power amplification unit 110 is reduced.

[0007]

However, the transmitting apparatus in the conventional CDMA base station as described above has the following problems. In other words, from the viewpoint of power consumption reduction, the transmitting apparatus controls the number of drives of the power amplifier in the power amplifier, but no other measures are taken. Other than the power amplifier,
The distortion compensation circuit has a large dynamic range characteristic so as to be able to cope with the code multiplexed signal level of the maximum number of unique codes (the maximum number of users). As a result, the number of components in the circuit is increased, and as a result, this is one of the causes for increasing power consumption. The present invention has been made in order to solve the above-described problems related to the conventional transmission device, and has a unique code number (C
An object of the present invention is to provide a transmission device capable of reducing power consumption by controlling driving of each block other than a power amplifier according to a DM modulator output level).

[0008]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the transmitting apparatus according to the present invention,
An amplitude dispersion circuit that divides an output signal of the modulator into a plurality of signals, and a plurality of distortion compensation circuits and a plurality of power amplifiers respectively arranged in parallel are sequentially connected to the amplitude dispersion circuit,
The output signals of the plurality of power amplifiers are added and combined into one signal, and the number of driving of the distortion compensation circuit and the power amplifier is controlled according to the output signal level of the modulator. The invention according to claim 2 of the transmitting apparatus according to the present invention is configured such that in the transmitting apparatus according to claim 1, a code division multiplex modulator is used as the modulator.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a functional block diagram showing an embodiment of a transmitting apparatus according to the present invention.
The transmitting device shown in this example includes a CDM modulator 1, an amplitude dispersion circuit 30 having eight output terminals, four distortion compensation circuits 20a to 20d each arranged in parallel, and eight digital-analog converters (D / A converter) 3a to 3h, eight low-pass filters for image removal (LPF) 4a to 4h, and four quadrature modulators 5a to 5d,
The power amplifying unit 10 is connected sequentially, and an amplitude dispersion circuit
The distortion compensation circuits 2a to 2d, D based on the control signal K from 30
An operation control circuit 6 for controlling the driving (ON / OFF) of the / A converters 3a to 3h and the quadrature modulators 5a to 5d is provided. Also, the power amplifier 1
0 represents four power amplifiers 11a to 11d arranged in parallel, and three adders 12a to 12c for combining these output signals.
And four power amplifiers 11a to 11d
Is also controlled by the operation control circuit 6.

FIG. 2 is a functional block diagram showing a configuration example of the amplitude dispersion circuit 30. Amplitude dispersion circuit 30 shown in this example
Is an amplitude value calculator 31 for obtaining the amplitude value A of the input orthogonal signals X and Y.
And a signal dispersion unit 32 for dispersing the input signal as a maximum of four sets of orthogonal signals based on the A value, and eight delay units 33 for delaying the orthogonal signals for a predetermined time.

FIG. 3 shows the dispersion signals X1, Y1 to X4, Y output with respect to the input signal level (amplitude value A) in the amplitude dispersion circuit 30.
FIG. 4 is a diagram for explaining a control signal K value 4; FIG. 4 is a diagram for explaining the operation of the operation control circuit 6 with respect to the control signal K value output from the amplitude dispersion circuit 30.

The function of the transmitting apparatus according to the present invention shown in FIG. 1 will be described below with reference to FIGS. First, the CDM modulator 1 modulates a user-assigned code (unique code) with an information signal to generate a digital modulated signal (quadrature signal I, Q).
Is generated and output, the amplitude dispersion circuit 30 operates as follows to distribute and output the input signals X and Y.

That is, assuming that the maximum peak amplitude of the input signals X and Y is M, if the amplitude A is smaller than M / 4,
Output K = 1, output the input signals X and Y to the X1 and Y1 terminals as they are, and set the other terminals to zero output. The amplitude A is M
If / 4 or more and less than M / 2, K = 2 as a control signal,
X / 2 is output to the X1 and X2 terminals, and Y / 2 is output to the Y1 and Y2 terminals, and the other terminals are set to output zero. Further, when the amplitude A is equal to or larger than M / 2 and smaller than 3M / 4, K = 3 as a control signal, X1, X
The X / 3 terminal outputs X / 3, the Y1, Y2, and Y3 terminals output Y / 3, and the other terminals output zero. Still further, the amplitude A is 3M /
In the case of four or more, K = 4 is output as a control signal, X / 4 is output to terminals X1, X2, X3, and X4, and Y / 4 is output to terminals Y1, Y2, Y3, and Y4.

After the completion of the control of the driving of each block of the device arranged at the subsequent stage based on the control signal K, each delay unit 33 outputs the scattered orthogonal signals I1, Q1 to Q1 from the amplitude dispersion circuit 30.
Installed to output I4 and Q4. The dispersion quadrature signals I1, Q1 to I4, and Q4 are subjected to distortion components removed by distortion compensation circuits 20a to 20d, converted to analog signals by D / A converters 3a to 3h, and D / A converters at the preceding stage by LPFs 4a to 4h. After the image components related to the A conversion have been removed, the quadrature modulator 5a
Carrier waves are superimposed at ~ 5d. In the power amplifier 10,
After each orthogonal signal is amplified by each of the power amplifiers 11a to 11d, it is combined into one signal by the adders 12a to 12c and output.

At this time, based on the control signal K output from the amplitude dispersion circuit 30, the operation control circuit 6
Drives only the distortion correction circuit, D / A converter, quadrature modulator, and power amplifier of the system connected to the terminal from which the dispersed quadrature signals I1, Q1 to I4, and Q4 are output, and connects to the terminal without output Control to turn off the circuits of the other systems. Therefore, only the power amplifier for obtaining the required power level according to the multiplexed modulated signal level output from the CDM modulator 1 corresponding to the number of user-assigned codes is selected and driven, Only the circuits of the system connected to the power amplifier are driven.

As described above, the input dynamic level of each of the distortion compensating circuits 20a to 20d and each of the D / A converters 3a to 3h is reduced to 1/4 as compared with the conventional system, so that the operating dynamic range is 1
/ 4 is enough.

In the transmitting apparatus according to the present invention, although the number of constituent blocks of the apparatus is increased as compared with the conventional apparatus, the power consumption of each block (circuit) can be reduced. 4 systems (dispersed quadrature signals I1, Q1 ~
The probability of driving all of the I4 and Q4 systems is low, and one or two systems (I1, Q1 and I2, Q2) corresponding to output power much lower than the instantaneous peak power are always used. ), So that power consumption can be reduced as compared with the conventional system.

The distortion compensating circuit operates as follows. FIG. 5 is a functional block diagram illustrating a configuration example of the distortion compensation circuit. The distortion compensation circuit shown in FIG.
It comprises an amplitude value calculator 31 for calculating the amplitude values of X, Y (I, Q), two memories 32 and 33 in which distortion correction data is stored, and a vector calculator 34 for performing vector calculation for distortion correction. Is done.

FIG. 6 is a diagram showing an example of input / output characteristics of the power amplifiers 11a to 11d. This characteristic is measured in advance using a single power amplifier. As shown in FIG. 6, when an input signal (input power) passes through a power amplifier, both amplitude characteristics and phase characteristics are generally distorted. FIG. 7 is a diagram showing an inverse characteristic related to the input / output characteristic of the power amplifier shown in FIG.

The operation of the distortion compensation circuit shown in FIG. 5 will be described below with reference to FIGS. 6 and 7. First, Figure 7
Are stored in the memories 32 and 33 as distortion correction data using the input power level (amplitude value) as an address. When the orthogonal signals X and Y are input, the amplitude value calculation unit 3
The amplitude value of the input signal is obtained by 1 and the distortion correction data stored in the memories 32 and 33 is extracted using this value as an address, and the distortion characteristics relating to the power amplifiers 11a to 11d at the subsequent stage are previously determined in the vector operation unit 34. The output is corrected. When this output signal is input to the power amplifiers 11a to 11d via predetermined device configuration blocks, the power amplifier outputs a signal having no distortion (distortion corrected).

[0021]

According to the present invention, as described above, the output signal of the CDM modulator is dispersed into a plurality of signals by using the amplitude dispersion circuit. Therefore, the dynamic range of the distortion compensation circuit and the D / A converter can be reduced, and the modulator can be reduced. Since the drive of each block of the device configuration is controlled in accordance with the output signal level, it is very effective in realizing a transmission device capable of reducing power consumption.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of a transmission device according to the present invention.

FIG. 2 is a functional block diagram of an amplitude dispersion circuit used in the transmission device according to the present invention.

FIG. 3 is a diagram for explaining input / output characteristics of an amplitude dispersion circuit used in a transmission device according to the present invention.

FIG. 4 is a diagram for explaining the operation of an operation control circuit used in the transmission device according to the present invention;

FIG. 5 is a functional block diagram of a distortion compensation circuit used in the transmission device according to the present invention.

FIG. 6 is a diagram showing an example of input / output characteristics of a power amplifier used in the transmission device according to the present invention.

FIG. 7 is a diagram showing an inverse characteristic (an example of correction data) of an input / output characteristic example of a power amplifier used in the transmission device according to the present invention.

FIG. 8 is a functional block diagram showing a configuration example of a conventional transmission device.

[Explanation of symbols]

 1 ... CDM modulator 3a-3h ... D / A converter 4a-4h ... LPF for image removal 5a-5d ... quadrature modulator 6 ... operation control circuit 10 ... power amplifier 11a-11d ... Power amplifiers 12a to 12c Adders 20a to 20d Distortion compensation circuits 30 Amplitude dispersion circuits

Claims (2)

[Claims] An amplitude dispersion circuit for dividing an output signal of a modulator into a plurality of signals, a plurality of distortion compensation circuits and a plurality of power amplifiers respectively arranged in parallel are sequentially connected to the amplitude dispersion circuit, The output signals of the plurality of power amplifiers are added and combined into one signal, and the number of driving of the distortion compensation circuit and the power amplifier is controlled according to the output signal level of the modulator. Transmission device. 2. The transmission apparatus according to claim 1, wherein a code division multiplex modulator is used as said modulator.