JP3107680B2 - Linear transmission circuit - Google Patents

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 a wireless communication device such as a mobile communication device.

[0002]

2. Description of the Related Art FIG. 4 shows a block diagram of a conventional transmitting circuit. In FIG. 4, 1 is an I and Q signal generator, 2 is a quadrature modulator, 3 is a local signal generator, 4 is a variable gain circuit,
Is a power amplifier, 6 is a divider, 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,
12 is a detection characteristic compensating circuit, 13 is an adder, 14 is a high-frequency signal output terminal, 15 is a DC voltage input terminal, and 16 is a gain variable circuit control terminal.

FIG. 5 is a circuit diagram of a detection characteristic compensation circuit 12 in a transmission circuit. In FIG. 5, reference numeral 51 denotes a diode characteristic compensator and a variable load circuit in a detection characteristic compensating circuit;
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
Are diodes for compensating diode characteristics, 11471, 11
472 is a variable resistance control input terminal, 555, 556, 56
5 is a high frequency grounding capacitor, 561, 562, 56
Reference numerals 3,564,568,569,571,572 denote fixed resistors, and reference numerals 566,567 denote transistors for controlling the on / off of the variable load circuit.

[0004] The relationship between the components and the operation of the transmission circuit having the above components will be described below. First, 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. One of the split signals is output from the high-frequency signal output terminal 14 as a transmission output, and the other signal is input to the envelope detection circuit 7 as a monitor output. 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 generators 1 is also input to a reference envelope signal generator 9 to generate a reference envelope signal. This reference envelope signal is converted into an analog signal by the digital-analog signal converter 10 and becomes a smooth waveform by the low-pass filter 11. The output of the low-pass filter 11 is input to the detection characteristic compensating circuit 12, to which the nonlinearity of the diode detector of the envelope detection circuit 7 is added. Both the output of the detection characteristic compensating circuit and the transmission envelope signal voltage from the envelope detection circuit 7 are output from the error amplifier 8.
And their difference voltages are 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. The output of the adder is supplied as a control voltage to the gain variable circuit control terminal 16 to control the gain or attenuation of the gain variable circuit 4. In this way, a feedback loop is formed, and the transmission output is controlled according to the output of the reference envelope generating circuit 9.

In the detection characteristic compensating circuit 12, a signal input from a diode characteristic compensator input terminal 52 is subjected to diode characteristic compensation by a diode characteristic compensator 1141, and a diode characteristic compensation current Id proportional to the input voltage.
Occurs at the connection terminal 1142. Where transistor 5
When 66 and 567 are non-conductive, the diode characteristic compensation current Id flows to the variable load circuit 1146, and the diode characteristic compensation voltage output terminal 53 receives the current flowing into the variable load circuit 1146 and the resistance of the fixed resistors 561 and 562. A corresponding diode characteristic compensation voltage is generated.

[0007] Further, 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 not passing a current through the variable load circuit control terminal 11472. The current flowing into the variable load circuit 1146 and the fixed resistor 56 are connected to the diode characteristic compensation voltage output terminal 53.
A diode characteristic compensation voltage is generated according to the resistance values of 1,562,563.

In the case where the transistor 567 is turned on by passing a current through the variable load circuit control terminal 11472 and the transistor 566 is turned off by not passing a current through the variable load circuit control terminal 11471, The diode characteristic compensation voltage output terminal 53 has a current value flowing into the variable load circuit 1146 and a fixed resistance 561,
A diode characteristic compensation voltage according to the resistance values of 562 and 564 is generated.

A current is applied to both variable load circuit control terminals 11471 and 11472 so that transistor 56
When both transistors 6 and 567 are turned on, a diode characteristic compensation voltage is generated at the detection output terminal 53 in accordance with the current value flowing into the variable load circuit 1146 and the resistance values of the fixed resistors 561, 562, 563, and 564.

As described above, 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 changed arbitrarily. Can be suppressed so that the diode characteristic compensation voltage does not largely change. Note that 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. A difference voltage between a transmission envelope signal voltage including distortion and a reference envelope signal voltage not including distortion is detected and amplified by the error amplifier 8, and this signal voltage is used as a control voltage of the variable gain circuit 4, and the power amplifier 5 The gain variable circuit 4 is controlled to increase the gain only in the portion where
Is compensated for, the nonlinearity of the envelope detection circuit 7 included in the transmission envelope detection signal is compensated by the detection characteristic compensation circuit 1.
2, the operating point of the control voltage of the gain variable circuit 4 can be shifted by adding a DC voltage to the error amplifier output voltage from the outside and adding the DC voltage to the error amplifier output voltage.
The effect of the loop error of the feedback loop can also be corrected.

However, the detection characteristic compensating circuit 12 uses the same type of diode as the detection circuit. However, if the characteristics of the diode are poor, the characteristics of the linear compensation deteriorate. Further, the influence of the loop error of the feedback loop cannot be largely corrected only by the adder 13. Further, 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.

The present invention has been made in consideration of the above problems, and has as its object to provide a linear transmission circuit that can perform linear compensation with high accuracy by using a simplified circuit with respect to signal distortion due to saturation of a power amplifier.

[0014]

In order to solve the above-mentioned problems, a linear transmission circuit according to the present invention comprises a detector for generating a signal for compensating for nonlinearity of an envelope detection circuit, instead of an adder and a detection characteristic compensation circuit. A data signal generation circuit comprising a characteristic compensation signal generator and a loop error compensation signal generator for generating a signal for compensating a loop error of a feedback loop, and a reference envelope for generating 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 saturates and the gain becomes insufficient due to the above-described configuration, when the linear amplifier compensates for the insufficient gain by a variable gain circuit, compensation for the nonlinearity of the envelope detection circuit is performed. The output envelope of the data signal generation circuit, which includes a detection characteristic compensation signal generator for outputting a signal and a loop error compensation signal generator for generating a compensation signal for a loop error, is multiplied by a multiplier to a reference envelope signal, thereby obtaining a transmission envelope. Compensation for the nonlinearity of the detector included in the line signal and compensation for the loop error can be performed digitally, and linear compensation can be performed accurately with a simplified circuit.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an 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 a first embodiment of the present invention. In FIG. 1, 11 is a linear transmission circuit, 111 is I,
Q signal generator, 112 is a quadrature modulator, 113 is a local signal generator, 114 is a gain variable circuit, 115 is a power amplifier, 116 is a divider, 117 is an envelope detector, 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 denotes a gain variable circuit control terminal.

The relationship between the components and the operation of the linear transmission circuit of the first embodiment having the above components 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 together with the local signal output from the local signal generator 3 and modulated. This modulated signal is
In the variable gain circuit 114, the signal 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 split by the divider 116 into a transmission output and a monitor output. The branched monitor output is input to an envelope detection circuit 117, where it is subjected to envelope detection and becomes a transmission envelope signal voltage Vda.

On the other hand, the output of the I and Q signal generators 111 is
The signal is also input to the reference envelope generator 119 to generate a reference envelope signal. An output of a detection characteristic compensation signal generator 1201 composed of a memory storing input / output characteristic data of the envelope detection circuit 117 and a loop error compensation signal composed of a memory storing loop error characteristic data of a feedback loop. The output of the generator 1202 is combined with 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 the multiplier is converted into an analog signal by a digital-analog signal converter 122 to become an analog signal voltage Vdb1, and further a low-pass filter 123 forms a smooth waveform. 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.
Their difference voltage 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, and controls 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 controlling the feedback loop so that the transmission envelope signal voltage Vda and the low-pass filter output signal voltage Vdb2 match. A transmission output signal is output from the transmission output terminal 124.

When the power amplifier 115 saturates and the gain becomes insufficient, linear compensation for compensating for the insufficient gain by increasing the gain of the gain variable circuit 114 is performed by using the output voltage of the envelope detection circuit 117. Unless the effects of the non-linearity of the envelope detection circuit included in Vda and the effects of loop gain errors are removed, linear compensation cannot be performed with high accuracy. However, in this linear transmission circuit, the output of the data signal generation circuit 120 including the detection characteristic compensation signal generator 1201 and the loop error compensation signal generator 1202 is multiplied by the reference envelope signal, so that the nonlinearity of the envelope detection circuit is increased. In this case, the effect of the characteristic and the effect 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 the elements used vary.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram of a linear transmission circuit according to a second embodiment of the present invention, and FIG. 3 is a timing chart thereof. Note that FIG.
In FIG. 1, the same or equivalent components as those of the apparatus and circuit elements in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

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

The relationship between the components and the operation of the linear transmission circuit according to the second embodiment having the above components will be described below with reference to FIGS. The transmission burst control signal 1102 is the rising section 1 of the transmission burst.
At 103, the signal rises with a smooth curve (for example, raised cosine curve), and the falling section 1 of the transmission burst 1
At 104, a fall is made with a smooth curve (for example, a raised cosine curve). Transmission burst control signal 1102 which is the output of ramping signal generator 1203
, The output of the detection characteristic compensation signal generator 1201, the output of the data signal generation circuit 120 which is a combined output of the total of three outputs of the output of the loop error compensation signal generator 1202, 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 the 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
And the feedback loop operates, the transmission output signal has a signal burst average power waveform 1
The rising and falling of 101 has 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 configuration, and unnecessary transmission signals in the frequency domain due to the influence of the rise and fall of the burst signal can be obtained. Spread can be suppressed. In addition, the subsequent error amplifier 1
The operations after 18 are basically the same as those in 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. A multiplier capable of multiplying the output of the reference envelope generation circuit is provided. Digitally reducing the effects of the nonlinearity of the envelope detection circuit and the effects of loop errors, the accuracy can be improved with a simple circuit. , A linear transmission circuit with good

[Brief description of the 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 a linear transmission circuit according to a 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]

 DESCRIPTION OF SYMBOLS 11 Linear transmission circuit 111 I and Q signal generation circuit 112 Quadrature modulator 113 Local signal generator 114 Gain variable circuit 115 Power amplifier 116 Divider 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 Lamping 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 section 1104 Transmission burst falling section

Continuation of the front page (56) References JP-A-3-276923 (JP, A) JP-A-4-156704 (JP, A) JP-A-3-179927 (JP, A) JP-A-4-150523 (JP) JP-A-59-226519 (JP, A) JP-A-61-214825 (JP, A) JP-A-5-3440 (JP, A) JP-A-6-61874 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/04 H04L 27/20 H04L 27/36

Claims (2)

(57) [Claims] 1. An I / Q signal generator for generating baseband I / Q signals, a local signal generator for generating a local signal, an output of the I / Q signal generator, and an output of the local signal generator. An output and an input, a quadrature modulator that outputs a modulated wave, an input of the output of the quadrature modulator, a variable gain circuit that varies gain or attenuation, and an input of the output of the variable gain circuit, A power amplifier to amplify, an output of the power amplifier as an input, a divider for dividing the high-frequency signal into a transmission output and a monitor output, and a monitor output of the distributor as an input, and an envelope of the input high-frequency signal. An envelope detection circuit for detecting and obtaining a transmission envelope signal voltage, a reference envelope signal generator which receives an output of the I and Q signal generators as inputs, and generates a reference envelope signal; Input and output A data signal generating circuit comprising 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-to-analog signal converter that performs a digital-to-analog signal conversion, receives a low-pass filter that limits a frequency band of an output signal of the digital-to-analog signal converter, an output signal of the low-pass filter, An error amplifier for detecting and amplifying an error voltage between the output signal of the envelope detection circuit and an output of the error amplifier as a control signal, and inputting the control signal to a gain variable circuit control terminal to control the gain or the gain of the variable gain circuit. A linear transmission circuit forming a feedback loop to control the attenuation. 2. A data signal generating circuit , comprising:
Rise in a smooth curve in the rising section
Falling with a smooth curve in the falling section of the signal burst
Generates a ramping signal that outputs a burst transmission control signal
2. The linear transmission circuit according to claim 1 , further comprising a live generator .