JP2003309475A - Radio transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio transmitter capable of controlling power transmitted from an antenna with high accuracy while suppressing an increase in a consumption current and an increase in a manufacturing cost. <P>SOLUTION: The radio transmitter is provided with a compensator 12 for correcting an output of a modulator 11 and transmitting the output to a DA converter 13. A gain control part 18 controls the gain of an amplifier 15 in accordance with power monitored by an AD converter 20 and also controls the correction amount of the compensator 12. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio transmitter that modulates digital data to be transmitted, converts it into an analog signal, further raises the frequency, and transmits from an antenna.

[0002]

2. Description of the Related Art CDMA (Code Division)
Multiple Access: code division multiple access (OFDM) system and OFDM (Orthogonal Fre)
quality Division Multiplex
In a mobile communication system that employs the ing (Orthogonal Frequency Division Multiplexing) technology, an amplifier (VGA: Variable Gain A) whose gain can be adjusted by modulating digital data to be transmitted and converting the digital data into an analog signal
There is known a wireless transmitter that amplifies the signal in mp) and further increases the frequency to transmit from an antenna. In such a wireless transmitter, in order to transmit a signal of specified power from an antenna over a wide dynamic range, the power of the radio wave transmitted from the antenna is monitored, and the power of the amplifier is adjusted according to the monitored power. Gain control, so-called automatic gain control (AGC: Automatic Ga)
in Control) is being performed.

FIG. 7 is a block diagram showing the configuration of a conventional radio transmitter.

The wireless transmitter 100 shown in FIG. 7 is provided with a modulator 101.
Digital data Data to be transmitted is input to 1. The modulator 101 modulates the input digital data Data to generate digital modulation data and outputs it to the DA converter 102. The DA converter 102 is
Digital modulation data from modulator 101 is D / A
The converted analog modulated signal is generated and output to the low pass filter 103. The low-pass filter 103 removes a high frequency component contained in the analog modulation signal from the DA converter 102, and the gain (VGA) 1 whose gain can be adjusted freely.
Output to 04. The amplifier 104 amplifies the analog modulation signal from the low-pass filter 103 and outputs it to the RF converter 105 with a gain adjusted according to an analog control signal from a DA converter 108 described later. The RF converter 105 raises the frequency of the input analog modulation signal to generate an RF (Radio Frequency) signal and transmits it from the antenna 106.

The power of the radio wave transmitted from the antenna 106 is monitored by the AD converter 109. AD converter 10
Reference numeral 9 AD-converts an analog monitor signal corresponding to the monitored power into digital monitor data and outputs the digital monitor data to the gain control unit 107. Information from the modulator 101 is input to the gain control unit 107 in order to control the gain of the amplifier 104 required according to the spreading rate determined by the transfer rate of the digital data Data described above. The gain controller 107 uses this information and the AD converter 109.
The digital control data is generated from the monitor data from and output to the DA converter 108. DA converter 108
Converts the digital control data into a DA signal to generate an analog control signal and outputs the analog control signal to the amplifier 104. In this way, automatic gain control according to the power of the radio wave transmitted from the antenna 106 is performed.

[0006]

[Problems to be Solved by the Invention] CDMA system and OFD
In the M method, a plurality of codes are simultaneously transmitted via a plurality of channels. Here, in order to control the electric power transmitted from the antenna 106 with high accuracy, the modulator 1 that configures the wireless transmitter 100.
01, the DA converter 102, the low-pass filter 103, and the amplifier 104 require linearity with respect to the power of a plurality of codes. However, modulators 101 and D
A converter 102, low-pass filter 103, amplifier 10
If the linearity is lost (non-linearity) in any one of the four, it is difficult to adjust (correct) the non-linearity. The details will be described below.

FIG. 8 is a diagram showing a graph A of ideal linearity and a graph B of non-linearity of a digital data input and an analog output signal in the DA converter of the wireless transmitter.

The horizontal axis of FIG. 8 indicates digital modulation data (a digital value represented by a hexadecimal number from 0 to 3FF) from the modulator 101, which is input to the DA converter 102, for example. Further, the vertical axis of FIG. 8 indicates the output voltage of the analog modulation signal output from the low pass filter 103, for example.

If the linearity of the modulator 101, the DA converter 102, the low-pass filter 103, etc. constituting the radio transmitter 100 is maintained, as shown in Graph A,
For a digital value of 0 to 3FF input to the DA converter 102, for example, the voltage output from the low-pass filter 103 becomes an ideal linearity graph A. However, in general, the modulator 101 and the DA converter 10
2. Since the linearity is not maintained in each part such as the low-pass filter 103, the output voltage becomes a curve graph (graph of non-linearity) as shown in the graph B. Here, in order to effectively use the resolution in DA conversion, for example, the output amplitude of the amplifier 104 is set to a value close to the maximum value with respect to the absolute value of the code. Hence,
In the case of the CDMA system, when the wireless transmitter 100 is applied to wideband communication having a large dynamic range in order to improve the use efficiency of codes in the occupied band, the DA converter 102 having high bit accuracy and the linearity It is necessary to use a high element for the low pass filter 103 and the like. Also, D
The A converter 102 is required to have high integral linearity in addition to differential linearity (that is, in FIG. 8, it is a straight line that passes through the origin with respect to the code absolute value together with the linearity of the local slope. Required). Further, in the CDMA system, in order to transmit a plurality of codes at the same time and independently and finely control the transmission power according to each code, it is necessary to control by multiplying the digital value shown in FIG. The accuracy of the digital value and the accuracy of the analog circuit such as the low-pass filter 103 that are required as a whole are required to be high according to the number of codes. Therefore, the circuit scale of the entire wireless transmitter 100 increases, which leads to an increase in current consumption and an increase in manufacturing cost.

In view of the above circumstances, it is an object of the present invention to provide a radio transmitter capable of controlling the power transmitted from an antenna with high accuracy while suppressing an increase in current consumption and an increase in manufacturing cost. And

[0011]

In the wireless transmitter of the present invention which achieves the above object, the digital data to be transmitted is modulated by a modulator and converted into an analog signal by a DA converter, and the gain can be adjusted freely. In a wireless transmitter that amplifies with an amplifier and increases the frequency with an RF converter for transmission, a power monitor for monitoring the power of the transmitted radio wave and a gain for adjusting the gain of the amplifier according to the power monitored by the power monitor. The gain control unit includes a control unit and a corrector that corrects the output of the modulator and transmits the corrected output to the DA converter. The gain control unit controls the gain of the amplifier according to the power monitored by the power monitor. In addition, it is characterized in that the correction amount by the above-mentioned corrector is controlled.

The radio transmitter of the present invention controls the power transmitted from the antenna, in addition to the gain control of the amplifier,
As shown in an embodiment described later, correction is performed by a corrector in which correction data is stored so as to correct the non-linearity of the components of the wireless transmitter. Therefore, it is possible to relax the requirements such as differential linearity and integral linearity for the constituent elements of the wireless transmitter, and to suppress the power transmitted from the antenna while suppressing the increase in current consumption and the increase in manufacturing cost. Can be controlled with high accuracy.

Here, this radio transmitter is provided with a plurality of modulators having the modulator, the compensator, the DA converter, the amplifier, and the gain control section, and the modulators of the plurality of modulators mutually interoperate. Different modulation is performed, the analog signals output from the amplifiers of the plurality of modulators are combined by a combiner, the RF converter raises the frequency, and the power is transmitted. The power monitor transmits the power of the transmitted radio wave. For each component corresponding to the plurality of modulators, each gain control unit constituting each of the plurality of modulators corresponds to the modulator to which it belongs, which is monitored by the power monitor. It is preferable that the gain of the amplifier of the modulator to which it belongs and the correction amount of the corrector be controlled based on the power component of the radio wave.

The power monitor may monitor the power of the output of the synthesizer instead of monitoring the power of the transmitted radio wave.

In this way, the transmission power can be controlled for each code and the target of transmission power correction can be expanded. Therefore, the power transmitted from the antenna can be controlled with higher accuracy.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a block diagram of a wireless transmitter according to the first embodiment of the present invention.

The radio transmitter 1 shown in FIG. 1 includes a modulator 11, a corrector 12, a DA converter 13, a low-pass filter 14, an amplifier 15, and an RF converter 16.
, Antenna 17, gain control unit 18, and DA converter 1
9 and an AD converter 20 are provided.

Digital data Data to be transmitted is input to the modulator 11. The modulator 11 modulates the input digital data Data to generate digital modulation data. The generated digital modulation data is input to the corrector 12.

The corrector 12 corrects the digital modulation data from the modulator 11 and transmits it to the DA converter 13. Although details of the corrector 12 will be described later, at the time of manufacturing or operation, the modulator 11 periodically generates a digital signal corresponding to a predetermined analog data output amplitude to transmit the transmission power from the antenna 17 to the AD converter 20. A desired table (or parameter) is created (or updated) in the corrector 12 by feeding back via the feedback. It should be noted that the transmission power is guided to a value determined by the positional relationship with the receiver during operation, and the guided value is changed in a certain cycle. for that reason,
The table (or parameter) of the corrector 12 is also updated according to the change cycle.

The DA converter 13 D / A-converts the digital modulation data corrected by the correction unit 12 to generate an analog modulation signal, and outputs it to the low pass filter 14.

The low-pass filter 14 is a DA converter 13
The high-frequency component contained in the analog modulated signal from is removed and output to the amplifier 15.

The amplifier 15 is an amplifier (VGA) whose gain can be adjusted freely. The amplifier 15 has a gain adjusted according to an analog control signal from a DA converter 19 which will be described later, and a gain from the low-pass filter 14. The analog modulation signal is amplified and output to the RF converter 16.

The RF converter 16 raises the frequency of the input analog modulation signal to generate an RF signal and transmits it from the antenna 17.

The AD converter 20 corresponds to an example of a power monitor according to the present invention, monitors the power transmitted from the antenna 17, AD-converts the analog monitor signal represented by the monitored power, and digitally converts it. Monitor data is generated and output to the gain control unit 18.

In addition to the monitor data from the AD converter 20, the gain control unit 18 transmits the transmission information of the digital data Data input to the modulator 11 described above, for example, the spreading factor determined by the transfer rate or the transmission power information ( In order to control the gain of the amplifier 15 according to transmission power designation information or difference information), the modulator 1
Information from 1 is also entered. The gain control unit 18 generates digital control data from this information and the monitor data from the AD converter 20 and outputs it to the DA converter 19, and also controls the corrector 12 to correct the correction amount of the corrector 12. The correction control data for output is output.

The DA converter 19 DA-converts the digital control data to generate an analog control signal and outputs it to the amplifier 15 described above. Further, the corrector 12 also generates new digital modulation data based on the correction control data and outputs it to the DA converter 13 described above.

Next, the corrector 12 which is a feature of this embodiment.
The configuration of will be described.

FIG. 2 is a diagram showing the configuration of the corrector shown in FIG.

The corrector 12 shown in FIG.
_1 and 12_2, RAMs 12_3 and 12_4, a bus I / F 12_5, and a controller 12_6 are provided. As described above, the signal generated from the modulator 11 is input to the selector 12_1 during manufacturing or operation. A control signal from a CPU (not shown) is input to the bus I / F 12_5. Further, the control unit 12_6 also receives a frame synchronization signal corresponding to the synchronization of the digital data to be transmitted. In this compensator 12, the RAM 1 is responsive to the control signal from the CPU.
The selector 12_1 designates the address of one of the RAMs 2_3 and 12_4 by the selector 12_1, and the controller 1
By the write signal WEN from 2_6, the data from the modulator 11 is transferred to the data line D at the specified address.
Write via i. In this way, RAM12_
3, 12_4 desired table (or parameter)
Create (or update) In the transmission, in the same manner as described above, the desired RAM address is designated, the data is read out to the data line Do, and the data is transferred to the D line via the selector 12_2.
Output to the A converter 13 (see FIG. 1). Here, the transmission power for the digital control data (a certain AGC voltage) from the gain control unit 18 is regularly monitored through the CPU, so that the function for linearization is tabulated, whereby the DA converter 13, The low pass filter 14 is linearized. Further, the table function of the corrector 12 is rewritten by monitoring the ambient temperature, the analog power supply voltage of the low pass filter 14 and the like, the frequency and the like.

Thus, the wireless transmitter 1 of this embodiment
Is for controlling the power transmitted from the antenna 17,
In addition to the gain control of the amplifier 15, correction is performed by the corrector 12 in which a desired table (or parameter) is created so as to correct the non-linearity of the components of the wireless transmitter 1. Therefore, it is possible to relax the requirements for the differential linearity, the integral linearity, and the like of the constituent elements of the wireless transmitter 1. Therefore, the power transmitted from the antenna 17 can be controlled with high accuracy while suppressing an increase in current consumption and an increase in manufacturing cost.

FIG. 3 is a diagram showing a configuration of a corrector different from the corrector shown in FIG. 2, and FIG. 4 is a diagram showing correction data in the corrector shown in FIG.

The horizontal axis of FIG. 4 represents the data Din (0 to 3FF) forming the signal IN input to the corrector 32 shown in FIG.
Up to the hexadecimal number). The vertical axis of FIG. 4 represents the correction data output from the corrector 32. Further, the data Di that composes the input signal IN
n is divided into areas indicated by dotted lines in FIG.

The corrector 32 shown in FIG.
_1, the parameter table units 32_2 and 32_3,
The primary operation circuit 32_4 is provided. Decoder 3
2_1 and the primary operation circuit 32_4 include the gain control unit 1
8, the signal IN composed of the data Din of 0 to 3FF shown in FIG. 4 is input. The decoder 32_1 is
The data Din forming the input signal IN is assigned to the area shown by the dotted line in FIG. Parameter table section 3
2_2 and 32_3 store the lower limit value and the upper limit value of the correction data in the area allocated by the decoder 32_1. For example, when the data Din of a certain size is input, the decoder 32_1 allocates the data Din to the area corresponding to the data Din. Parameter table section 32_
2, 32_3 output the lower limit value and the upper limit value of the area to the primary operation circuit 32_4. The primary calculation circuit 32_4 obtains a slope (linear function) determined by these lower limit value and upper limit value, and interpolates the correction data corresponding to the data Din input to the primary calculation circuit 32_4 based on the slope. , The DA converter 13 generates correction data corresponding to the input data Din and outputs the correction data as the signal OUT.
Output to. In this way, the data Din is divided into several areas and the correction data is interpolated using the representative points shown by the dotted lines in FIG. 4, thereby reducing the amount of data that must be held as a table and suppressing the circuit scale. May be.

In many cases, when analog-to-digital conversion is performed by the DA converter 13 including the correction amounts of the DA converter 13 and the low-pass filter 14, at most ± several L
Since it is SB, the following corrector in which the region and the representative point are appropriately selected may be used.

FIG. 5 is a diagram showing a configuration of a corrector different from the correctors shown in FIGS. 2 and 3.

The corrector 42 shown in FIG.
_1, the parameter table unit 42_2, and the multiplier 42
_3 is provided. The signal IN including the data Din described above is input to the decoder 42_1 and the multiplier 42_3. The decoder 42_1 converts the data Din forming the input signal IN into the data Din.
The area is allocated according to the size of. The parameter table unit 42_2 stores the representative value (gain) of the correction data in the area allocated by the decoder 42_1. Here, when a certain data Din is input, the decoder 42_1 allocates it to an area according to the size of the data Din. Parameter table section 42_2
Outputs the representative value of the area to the multiplier 42_3. The multiplier 42_3 multiplies the representative value by the data Din input to the multiplier 42_3 to generate correction data corresponding to the input data Din, and outputs it as the signal OUT to the DA converter 13. Output. In this way, the circuit scale may be further reduced.

FIG. 6 is a block diagram of a radio transmitter according to the second embodiment of the present invention.

The wireless transmitter 2 shown in FIG. 6, in which the same components as those of the wireless transmitter 1 shown in FIG. 1 described above are denoted by the same reference numerals, includes a modulator 11, a compensator 12, and a DA converter. 13, a low-pass filter 14, an amplifier 15, a gain control unit 18, and a plurality of modulators 2_1, 2_2, ... Having a DA converter 19 are provided, and the modulator 11 of the plurality of modulators 2_1, 2_2 ,. These different modulators 2_
The analog signals output from the amplifiers 1, 2_2, ... Are combined by the combiner 21, the RF converter 22 raises the frequency, and the combined signal is transmitted from the antenna 17.

Further, the radio transmitter 2 shown in FIG.
A converter 23, an AD converter 24, and a demodulator 25 are provided. The RF converter 23, the AD converter 24, and the demodulator 25 correspond to the power monitor according to the present invention, and the RF converter 23, the AD converter 24, and the demodulator 25 change the power of the radio wave transmitted from the antenna 17, The components corresponding to the plurality of modulators 2_1, 2_2, ... Are monitored. Specifically, the RF converter 23
Inputs the RF signal from the RF converter 22 and outputs a signal having a frequency obtained by reducing the frequency of the RF signal. A
The D converter 24 AD-converts the signal from the RF converter 23.
Convert to generate digital data. The demodulator 25 is A
The digital data from the D converter 24 is converted into a plurality of modulators 2.
It is distributed for each component corresponding to _1, 2_2, ... And is output to each corrector 12 and each gain control unit 18.

Each of the plurality of modulators 2_1, 2_2, ... Each of the correctors 12 and each of the gain control sections 18 that constitute each of the modulators
Is an RF converter 23, an AD converter 24, a demodulator 25
Based on the power component of the radio wave corresponding to the modulator to which the user belongs, the amplifier 1 of the modulator to which the user belongs
The gain of 5 and the correction amount of the corrector 12 are controlled.

As described above, the wireless transmitter 2 of this embodiment
Is to feed back the transmission power for each code by demodulating the transmission output of the RF signal for each code through the RF converter 23, the AD converter 24, and the demodulator 25 for each code. Transmission power control is performed. By doing so, it is possible to perform the feedback location from a location closer to the antenna end and to widen the target of transmission power correction. Also, an inexpensive DA converter 13, low-pass filter 14, amplifier 15 and the like can be used.

Instead of monitoring the power of the radio wave transmitted from the antenna 17, the power of the output of the combiner 21 may be monitored as shown by the dotted line in FIG. In this way, the RF converter 23 can be deleted.

[0044]

As described above, according to the present invention,
While suppressing increase in current consumption and increase in manufacturing cost,
The power transmitted from the antenna can be controlled with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of a wireless transmitter according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a corrector shown in FIG.

FIG. 3 is a diagram showing a configuration of a corrector different from the corrector shown in FIG.

FIG. 4 is a diagram showing correction data in the corrector shown in FIG.

5 is a diagram showing a configuration of a corrector different from the correctors shown in FIGS. 2 and 3. FIG.

FIG. 6 is a block diagram of a wireless transmitter according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional wireless transmitter.

FIG. 8 is a graph A showing ideal linearity of digital data input and analog output signals in the DA converter of the wireless transmitter.
FIG. 4 is a diagram showing a non-linearity graph B.

[Explanation of symbols]

1,2 wireless transmitter 2_1, 2_2 modulator 11 Modulator 12,32 compensator 12_1, 12_2 selector 12_3, 12_4 RAM 12_5 Bus I / F 12_6 Control unit 13,19 DA converter 14 Low-pass filter 15 Amplifier 16,22,23 RF converter 17 antenna 18 Gain control section 20,24 AD converter 21 synthesizer 25 demodulator 32_1, 42_1 decoder 32_2, 32_3, 42_2 Parameter table section 32_4 Primary operation circuit 42_3 multiplier

Claims (3)

[Claims] 1. A radio transmitter in which digital data to be transmitted is modulated by a modulator, converted to an analog signal by a DA converter, amplified by an amplifier whose gain can be freely adjusted, and increased in frequency by an RF converter for transmission. A power monitor that monitors the power of the transmitted radio wave; a gain control unit that adjusts the gain of the amplifier according to the power monitored by the power monitor; and a DA converter that corrects the output of the modulator. The gain control unit controls the gain of the amplifier according to the power monitored by the power monitor, and controls the correction amount by the corrector. And a wireless transmitter. 2. The wireless transmitter comprises the modulator,
A plurality of modulators having the compensator, the DA converter, the amplifier, and the gain control unit are provided, the modulators of the plurality of modulators perform mutually different modulations, and the amplifiers of the plurality of modulators output. The synthesized analog signal is synthesized by a synthesizer, the frequency is raised by an RF converter and transmitted, and the power monitor monitors the power of the transmitted radio wave for each component corresponding to the plurality of modulators. And each gain control section constituting each of the plurality of modulators,
The gain of the amplifier of the modulator to which the user belongs and the correction amount of the corrector are controlled based on the power component of the radio wave corresponding to the modulator to which the user belongs, which is monitored by the power monitor. The wireless transmitter according to claim 1. 3. The radio transmission according to claim 2, wherein the power monitor is for monitoring the power of the output of the combiner, instead of monitoring the power of the transmitted radio wave. Machine.