JPH06350462A - Linear transmission circuit - Google Patents

Abstract

PURPOSE:To provide transmission output with linearity of high accuracy with a simple circuit in a linear transmission circuit. CONSTITUTION:The monitor output of the transmission output is inputted to an envelope detection circuit 117, and a transmission envelope signal voltage Vda is generaged. While, the output of an I/Q signal generator 111 is also inputted to a reference envelope generator 119, and it is changed to a reference envelope signal, and it is inputted to a multiplier 121 together with the output of a data signal generation circuit 120 consisting of a detection characteristic compensation signal generator 1201 and a loop error compensation signal generator 1202. The output of the multiplier goes to an output voltage Vdb2 passing a digital-analog signal converter 122 and a low-pass filter 123, and is inputted to an error amplifier 118 together with the transmission envelope signal voltage Vda, and an output voltage Vdc in which a differential voltage is amplified is supplied to a gain variable circuit control terminal 125 as a control voltage, which controls the gain or attenuation of a gain variable circuit 114.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission circuit used in wireless communication equipment such as mobile communication equipment.

[0002]

2. Description of the Related Art FIG. 4 shows a block diagram of a conventional transmission circuit. In FIG. 4, 1 is an I, Q signal generator, 2 is a quadrature modulator, 3 is a local signal generator, 4 is a gain variable circuit, 5
Is a power amplifier, 6 is a distributor, 7 is an envelope detection circuit, 8 is an error amplifier, 9 is a reference envelope signal generator, 10 is a digital-analog signal converter, 11 is a low-pass filter,
Reference numeral 12 is a detection characteristic compensation circuit, 13 is an adder, 14 is a high frequency signal output terminal, 15 is a DC voltage input terminal, and 16 is a variable gain circuit control terminal.

FIG. 5 is a circuit diagram of the detection characteristic compensation circuit 12 in the transmission circuit. In FIG. 5, 51 is a diode characteristic compensator and a variable load circuit in the detection characteristic compensation circuit,
Reference numeral 52 is a diode characteristic compensator input terminal, 53 is a detection characteristic compensation voltage output terminal, 1142 is a connection terminal, 1141 is a diode characteristic compensator, 1146 is a variable load circuit, and 552.
Is a diode for compensating diode characteristics, 11471, 11
472 is a variable resistance control input terminal, 555, 556, 56
5 is a capacitor for high frequency grounding, 561, 562, 56
3, 564, 568, 569, 571, 572 are fixed resistors, and 566, 567 are variable load circuit on / off control transistors.

With respect to the transmission circuit including the above components, the relationship between these components and the operation thereof will be described below. First, the I, Q output from the I, Q signal generator 1
The Q signal is input to the quadrature modulator 2 and modulated together with the local signal output from the local signal generator 3.
The modulated signal is amplified or attenuated by the variable gain circuit 4, further amplified by the power amplifier 5, and branched by the distributor 6. Of the branched signals, one signal is output as a transmission output from the high frequency signal output terminal 14, and the other signal is input as a monitor output to the envelope detection circuit 7. The high frequency signal input to the envelope detection circuit 7 is subjected to envelope detection and output as a transmission envelope signal voltage.

On the other hand, the output of the I and Q signal generator 1 is also input to the reference envelope signal generator 9 to generate a reference envelope signal. The reference envelope signal is converted into an analog signal by the digital-analog signal converter 10 and has a smooth waveform by the low pass filter 11. The output of the low-pass filter 11 is input to the detection characteristic compensation circuit 12, and the nonlinearity of the diode detector of the envelope detection circuit 7 is added. The output of this detection characteristic compensation circuit and the transmission envelope signal voltage from the envelope detection circuit 7 are both the error amplifier 8
Are input to and the difference voltage between them is amplified. The output voltage of the error amplifier 8 is input to the adder 13 together with the DC voltage externally input from the DC voltage input terminal 15. Then, this adder output is supplied to the variable gain circuit control terminal 16 as a control voltage to control the gain or attenuation of the variable gain circuit 4. In this way, the feedback loop is configured to control the transmission output according to the output of the reference envelope generation circuit 9.

In the detection characteristic compensating circuit 12, the signal inputted from the diode characteristic compensator input terminal 52 is diode characteristic compensated by the diode characteristic compensator 1141, and the diode characteristic compensating current Id proportional to the input voltage is obtained.
Occurs at the connection terminal 1142. Transistor 5 here
When 66 and 567 are in the non-conducting state, the diode characteristic compensation current Id flows into the variable load circuit 1146, and the diode characteristic compensation voltage output terminal 53 has the current value flowing into the variable load circuit 1146 and the resistance value of the fixed resistors 561 and 562. A corresponding diode characteristic compensation voltage is generated.

When the transistor 566 is turned on by passing a current through the variable load circuit control terminal 11471, and the transistor 567 is turned off by passing no current through the variable load circuit control terminal 11472. At the diode characteristic compensation voltage output terminal 53, the current value flowing into the variable load circuit 1146 and the fixed resistance 56
A diode characteristic compensation voltage is generated according to the resistance value of 1,562,563.

When a current is passed through the variable load circuit control terminal 11472 to make the transistor 567 conductive, and a current is not passed through the variable load circuit control terminal 11471 to make the transistor 566 non-conductive, At the diode characteristic compensation voltage output terminal 53, the current value flowing into the variable load circuit 1146 and the fixed resistance 561,
A diode characteristic compensation voltage is generated according to the resistance values of 562 and 564.

Further, a current is supplied to both the variable load circuit control terminals 11471 and 11472 to cause the transistor 56 to pass.
When both 6 and 567 are made conductive, a diode characteristic compensation voltage is generated at the detection output terminal 53 according to the current value flowing into the variable load circuit 1146 and the resistance values of the fixed resistors 561, 562, 563 and 564.

Thus, the resistance on / off transistor 5
By turning on and off 66 and 567, the fixed resistance in the variable load circuit 1146 can be selected and the voltage generated at the diode characteristic compensation voltage output terminal 53 can be arbitrarily changed. Can be suppressed so that the diode characteristic compensation voltage does not change significantly even when is changed. The diode 552 used here is of the same type as that used in the envelope detection circuit (for example, Japanese Patent Application No. 4-216981).

[0011]

However, in the above configuration, when the power amplifier 5 is saturated and the transmission output signal is distorted, the output signal branched by the distributor 6 is detected by the envelope detector 7. The difference voltage between the transmission envelope signal voltage containing distortion and the reference envelope signal voltage not containing distortion is detected and amplified by the error amplifier 8, and this signal voltage is used as the control voltage of the gain variable circuit 4, and the power amplifier 5 The gain variable circuit 4 is controlled so that the gain increases only in the distorted portion of the power amplifier 5
In the case of compensating the linearity of, the non-linearity of the envelope detection circuit 7 included in the transmission envelope detection signal is determined by the detection characteristic compensation circuit 1
Since the operating point of the control voltage of the gain variable circuit 4 can be moved by adding the DC voltage to the error amplifier output voltage from the outside by adding the DC voltage to the reference envelope signal by 2.
The effect of the loop error of the feedback loop can also be corrected.

However, the detection characteristic compensating circuit 12 uses a diode of the same type as that of the detection circuit, but if the characteristic of this diode is bad, the linear compensation characteristic becomes poor. Further, the adder 13 alone cannot largely correct the influence of the loop error of the feedback loop. Furthermore, by using the adder 13 and the detection characteristic compensation circuit 12,
There is a problem that the number of parts increases and the circuit scale increases.

In view of the above problems, it is an object of the present invention to provide a linear transmission circuit capable of accurately performing linear compensation with respect to signal distortion due to saturation of a power amplifier, with a simplified circuit.

[0014]

In order to solve the above-mentioned problems, a linear transmission circuit of the present invention is a detection circuit for generating a signal for compensating the non-linearity of an envelope detection circuit instead of an adder and a detection characteristic compensation circuit. A data signal generation circuit including a characteristic compensation signal generator and a loop error compensation signal generator that generates a signal that compensates for a loop error of a feedback loop, and a reference envelope that generates an output of the data signal generation circuit and a reference envelope signal. A multiplier for multiplying the output from the line signal generator is added.

[0015]

According to the present invention, when the voltage amplifier is saturated and the gain becomes insufficient, the present invention compensates for the non-linearity of the envelope detection circuit when the gain compensation circuit compensates the insufficient gain by the variable gain circuit. By multiplying the reference envelope signal by the multiplier, the output of the data signal generating circuit consisting of the detection characteristic compensation signal generator that outputs the signal and the loop error compensation signal generator that generates the compensation signal for the loop error, the transmission envelope It is possible to digitally compensate for the non-linearity of the detector of the line signal and to compensate for the loop error, and it is possible to perform linear compensation accurately with a simplified circuit.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a linear transmission circuit according to the first embodiment of the present invention. In FIG. 1, 11 is a linear transmission circuit, 111 is I,
Q signal generator, 112 quadrature modulator, 113 local signal generator, 114 variable gain circuit, 115 power amplifier, 116 distributor, 117 envelope detection circuit, 118
Is an error amplifier, 119 is a reference envelope signal generator, 120
Is a data signal generation circuit, 1201 is a detection characteristic compensation signal generator, 1202 is a loop error compensation signal generator, 121 is a multiplier, 122 is a digital-analog signal converter, 1
23 is a low-pass filter, 124 is a transmission output terminal, 12
Reference numeral 5 is a variable gain circuit control terminal.

With respect to the linear transmission circuit of the first embodiment having the above components, the relationship between these components and the operation thereof will be described below with reference to FIG. The I and Q signals output from the I and Q signal generator 111 are input to the quadrature modulator 112 and modulated together with the local signal output from the local signal generator 3. This modulated signal is
In the variable gain circuit 114, it is amplified or attenuated by the control signal input to the control terminal 125, and further amplified by the power amplifier 115. The amplified modulated signal is branched by the distributor 116 into a transmission output and a monitor output. The branched monitor output is input to the envelope detection circuit 117, where it is subjected to envelope detection and becomes the transmission envelope signal voltage Vda.

On the other hand, the output of the I and Q signal generator 111 is
It is also input to the reference envelope generator 119 to generate a reference envelope signal. Further, the output of the detection characteristic compensation signal generator 1201 including a memory that stores the input / output characteristic data of the envelope detection circuit 117 and the loop error compensation signal including a memory that stores the loop error characteristic data of the feedback loop. It is combined with the output of the generator 1202 and becomes the output of the data signal generation circuit 120. The output of the data signal generation circuit is input to the multiplier 121 together with the reference envelope signal output from the reference envelope signal generator 119. The output of this multiplier is converted into an analog signal by the digital-analog signal converter 122 to become the analog signal voltage Vdb1 and further has a smooth waveform by the low pass filter 123. The output voltage Vdb2 of the low pass filter 123 is input to the error amplifier 118 together with the transmission envelope signal voltage Vda of the envelope detection circuit 117,
The difference voltage between them is amplified. The output voltage Vdc of the error amplifier 118 is supplied to the variable gain circuit control terminal 125 as a control voltage to control the gain or attenuation of the variable gain circuit 114.

As described above, according to the first embodiment of the present invention, the envelope is not distorted by the feedback loop control so that the transmission envelope signal voltage Vda and the low-pass filter output signal voltage Vdb2 match. The transmission output signal is output from the transmission output terminal 124.

Further, when the power amplifier 115 is saturated and the gain becomes insufficient, in the case of performing linear compensation to compensate for the insufficient gain by increasing the gain of the gain variable circuit 114, the output voltage of the envelope detection circuit 117. Unless the influence of the non-linearity of the envelope detection circuit included in Vda and the influence of the error of the loop gain are removed, the linear compensation cannot be performed accurately. However, in this linear transmission circuit, the reference envelope signal is multiplied by the output of the data signal generation circuit 120 composed of the detection characteristic compensation signal generator 1201 and the loop error compensation signal generator 1202, so that the nonlinearity of the envelope detection circuit is increased. The influence of the noise and the influence of the error of the loop gain can be digitally reduced, and the linear compensation can be accurately performed with a simple circuit. Further, in this method, since complete feedback loop control is performed, stable control is configured even if there are variations in the elements used.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 2 shows a block diagram of a linear transmission circuit in the second embodiment of the present invention, and FIG. 3 shows its timing chart. Note that FIG.
1, the same or equivalent parts as those of the devices and circuit elements in FIG. 1 are designated by the same reference numerals, and the duplicated description will be omitted.

In this embodiment, the data signal generation circuit 120
In addition, a ramping signal generator 1203 is added.
Also, the timing chart of FIG. 3 shows a transmission burst average power waveform 1101 and a ramping signal generator 1203.
The transmission burst control signal 1102, the rising period 1103 of the transmission burst, and the falling period 1104 of the transmission burst are shown.

With respect to the linear transmission circuit of the second embodiment having the above components, the relationship between these components and the operation thereof will be described below with reference to FIGS. 2 and 3. The transmission burst control signal 1102 is the rising section 1 of the transmission burst.
At 103, the curve rises with a smooth curve (for example, raised cosine curve), and at the fall section 1 of the transmission burst.
At 104, the curve is made to fall with a smooth curve (for example, raised cosine curve). Transmit burst control signal 1102, which is the output of ramping signal generator 1203
And the output of the detection characteristic compensation signal generator 1201 and the output of the loop error compensation signal generator 1202, which is the combined output of the data signal generation circuit 120 and the output of the reference envelope generation circuit 119. A signal obtained by multiplying a certain reference envelope signal by the multiplier 121 is input to the digital-analog signal converter 122. The output signal voltage Vdb1 of this digital-analog signal converter 122
Is input to the low-pass filter 123, and the output voltage Vdb2 of the low-pass filter 123 is
One of the inputs is one of the inputs, and the feedback loop operates, so that the transmission output signal is the signal burst average power waveform 1
The rising and falling edges of 101 have a smooth burst-like waveform.

As described above, according to this embodiment, a burst-like transmission output signal having a smooth rise and fall can be obtained by the above-mentioned configuration, which is unnecessary in the frequency domain due to the influence of the rise and fall of the burst signal. The spread can be suppressed. Also, the error amplifier 1 after that
The operation after 18 is basically the same as that of the first embodiment.

[0025]

As described above, according to the present invention, in a linear transmission circuit, a data signal generation circuit including a detection characteristic compensation signal generator and a loop error compensation signal generator, and an output of the data signal generation circuit are provided. By providing a multiplier that can multiply the output of the reference envelope generation circuit and digitally reducing the influence of the non-linearity of the envelope detection circuit and the influence of the loop error, accuracy can be improved with a simple circuit. A good linear transmission circuit can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a linear transmission circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a linear transmission circuit according to a second embodiment of the present invention.

FIG. 3 is a timing chart of the linear transmission circuit according to the second embodiment of the present invention.

FIG. 4 is a block diagram of a conventional transmission circuit.

FIG. 5 is a circuit diagram of a detection characteristic compensation circuit in a conventional transmission circuit.

[Explanation of symbols]

 11 Linear Transmission Circuit 111 I, Q Signal Generation Circuit 112 Quadrature Modulator 113 Local Signal Generator 114 Gain Variable Circuit 115 Power Amplifier 116 Distributor 117 Envelope Detection Circuit 118 Error Amplifier 119 Reference Envelope Generation Circuit 120 Data Signal Generation Circuit 1201 Detection characteristic compensation signal generator 1202 Loop error compensation signal generator 1203 Ramping signal generator 121 Multiplier 122 Digital-analog signal converter 123 Low pass filter 124 Transmission output terminal 125 Gain variable circuit control terminal 1101 Transmission burst average power waveform 1102 Transmission burst Control signal 1103 Transmission burst rising period 1104 Transmission burst falling period

Claims (2)

[Claims] 1. An I, Q signal generator for generating baseband I, Q signals, a local signal generator for generating local signals, an output of the I, Q signal generator and the local signal generator. An output is an input, a quadrature modulator that outputs a modulated wave, an output of the quadrature modulator is an input, a gain variable circuit that changes gain or attenuation, and an output of the gain variable circuit is an input, and a high frequency signal is input. A power amplifier for amplification, a distributor for inputting the output of the power amplifier and dividing the high frequency signal into a transmission output and a monitor output, and a monitor output of the distributor for inputting the input high frequency signal to an envelope. An envelope detection circuit that detects the transmission envelope signal voltage and a reference envelope signal generator that receives the outputs of the I and Q signal generators and that generates a reference envelope signal, and an envelope detection circuit of the envelope detection circuit. Input / output A data signal generating circuit including a memory storing characteristic data and loop error characteristic data of a feedback loop; a multiplier for multiplying an output of the reference envelope signal generator by an output of the data signal generating circuit; A digital-analog signal converter for converting a digital-analog signal into a digital-analog signal converter, a low-pass filter for limiting a frequency band of an output signal of the digital-analog signal converter, an output signal of the low-pass filter, and the An error amplifier for detecting and amplifying an error voltage with respect to an output signal of an envelope detection circuit is provided, and the output of the error amplifier is used as a control signal, and the control signal is input to a gain variable circuit control terminal to obtain the gain of the gain variable circuit or A linear transmitter circuit that configures a feedback loop to control the attenuation. 2. The linear transmission circuit according to claim 1, wherein the output signal of the data signal generation circuit takes into consideration a transmission on / off signal having a smooth rise and fall corresponding to a transmission burst signal output. .