KR100423557B1 - Feedforward linear power amplifier - Google Patents

Abstract

The present invention relates to a feedforward linear power amplifier that can improve the second loop in the frequency domain by introducing the concept of analog frequency spectrum to obtain a well-adapted output result even in a high frequency band without the need for a high-speed device or a complex algorithm. Is a feedforward consisting of a first coupler, a first phase and amplitude converter, a main amplifier, a second coupler, a first time delay, a subtraction circuit, a second phase and amplitude converter, an error amplifier, a second time delay and a plus circuit. A linear power amplifier, comprising: a first coupler for separating an input signal, a first phase and amplitude converter for adjusting the phase and amplitude of the signal, a main amplifier for amplifying the signal, and a second for separating the signal A coupler, a first time delay for delaying the signal, a subtraction circuit for combining the two signals, and a phase and amplitude of the signal A second phase and amplitude converter, an error amplifier for amplifying the signal, a second time delay for time delaying the signal, an addition circuit for synthesizing the signal, and a third coupler for separating the output signal of the subtraction circuit. A feedforward linear power amplifier comprising: a fourth coupler for separating an output signal of a plus circuit; A PLL module for generating a local frequency for converting the detected signal to an intermediate frequency, a down converter for synthesizing the incoming signal separated from the fourth coupler and the local frequency generated in the PLL module and converting the signal into an intermediate frequency signal; SAW filter for filtering the distortion signal of the synthesized intermediate frequency through the converter, a log amplifier for converting the distortion signal filtered from the SAW filter to DC level, and an A / D converter for digitalizing the signal output from the log amplifier. An analog spectrum circuit for down-converting, filtering and detecting a signal separated from the fourth coupler including a; And a digital control circuit for controlling the second phase and amplitude converter using the digitally converted DC level of the distortion signal detected from the analog spectrum circuit, and outputting the signal to the PPL module, thereby introducing the analog frequency spectrum concept to provide high frequency. Even in the band, a well-adapted and stable output result is obtained without the need for high-speed devices or complex algorithms.

Description

Feedforward linear power amplifier

The present invention relates to a feedforward linear power amplifier, and more particularly, to introduce and improve the analog frequency spectrum concept of the second loop in the frequency domain to obtain well-adapted output results without the need for high-speed devices or complex algorithms even at high frequency bands. A feedforward linear power amplifier that can

In the field of wireless communication, a feedforward linearization linear power amplifier is necessary to amplify a multi-frequency or CDMA signal to make a large power, and then transmit a signal through an air channel. Linear power amplifier is a high value-added item that occupies a large part of equipment cost such as base station or repeater. It is an amplifying device that maintains optimal call state by preventing intermodulation and distortion of signal generated when multiple frequencies are input. It is used in PCS, cellular and GSM, and will be applied to IMT-2000 service which is commercially available in the future.

The feedforward linear power amplifier has two main applications for the first loop and the second loop control. The first is digital control of the first loop and the analog control of the second loop control. Secondly, digital control is basically used for the first and second loops and complex DSP (Digital Signal Processing) is applied for more stable results.

However, while the first scheme is generally stable in the first loop, adaptive control is difficult for the second loop due to the change of operating conditions of the power amplifier.

The second approach uses a DSP concept to loop control to secure this. This method can achieve more stable results than the first method, but since DSP uses a large amount of fast Fourier transform (FFT) in the DSP algorithm, it is difficult to achieve the desired result unless high speed and expensive devices are selected in the DSP specification. It has the disadvantage of having low efficiency. In addition, there was a problem such as frequency resolution due to the limitation of the A / D converter sampling rate.

The present invention has been made to solve the above-mentioned problems, and the final output is analyzed and controlled in the frequency domain to obtain the stabilization of the output, and the quantization error is reduced compared to the method using the DSP to stabilize the second loop, a large amount of calculation It is to provide a feedforward linear power amplifier that uses Fourier transform using analog frequency spectrum circuit without using algorithms, so that the calculation amount is not taken into consideration, and the production cost is reduced by eliminating the need for high-speed DSP and expensive components.

1 is a block diagram showing a configuration of the present invention.

2 is a block diagram of an analog frequency spectrum circuit of the present invention.

3 is a signal diagram of the main stage of the present invention.

4 is a control flowchart of the present invention.

5 is a flow chart of frequency domain distortion signal processing according to the present invention;

6 is a block diagram of a conventional feedforward linear power amplifier.

<Description of the symbols for the main parts of the drawings>

1: first coupler 2: first phase and amplitude transducer

3: main amplifier 4: second coupler

5: 1st time delay 6: subtraction circuit

7: second phase and amplitude converter 8: error amplifier

9: 2nd time delay 10: plus circuit

11: third coupler 12: fourth coupler

13: analog spectrum circuit 14: digital control circuit

15: PLL Module 16: Down Converter

17: SAW filter 18: log amp,

19: A / D Converter

The present invention includes a first coupler for receiving an input signal and separating the input signal into an amplifier path and a linearization path, and a first phase and amplitude converter for adjusting the phase and amplitude of the input signal separated from the first coupler into the amplifier path. A main amplifier for receiving and amplifying a phase- and amplitude-converted signal from the first phase and amplitude converter, a second coupler for separating the amplified signal from the main amplifier, and a part separated into a linearization path from the first coupler A first time delay for receiving an input signal and time delaying, a subtraction circuit for synthesizing a signal separated from the second coupler and a time delayed signal from the time delay, and a phase and amplitude for adjusting the phase and amplitude of the signal output from the subtracting circuit. A phase and amplitude converted signal is input from the second phase and amplitude converter and the second phase and amplitude converter An error amplifier for outputting, a second time delay for time-delaying the signal separated from the second coupler, and an output signal for the addition circuit and subtraction circuit for combining and outputting the output signal of the second time delay and the output signal of the error amplifier. 13. A feedforward linear power amplifier comprising a third coupler for separating the circuit, comprising: a fourth coupler for separating the output signal of the addition circuit; A PLL module for generating a local frequency for converting the detected signal to an intermediate frequency, a down converter for synthesizing the incoming signal separated from the fourth coupler and the local frequency generated in the PLL module and converting the signal into an intermediate frequency signal; SAW filter for filtering the distortion signal of the synthesized intermediate frequency through the converter, a log amplifier for converting the distortion signal filtered from the SAW filter to DC level, and an A / D converter for digitalizing the signal output from the log amplifier. An analog spectrum circuit for down-converting, filtering and detecting a signal separated from the fourth coupler including a; And a digital control circuit for controlling the second phase and amplitude converter using the digitally converted DC level of the distortion signal detected from the analog spectrum circuit and outputting the signal to the PPL module. It is about.

Hereinafter, the gist of the feedforward linear power amplifier according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a configuration of a feedforward linear power amplifier according to the present invention, FIG. 2 is a block diagram of an analog frequency spectrum circuit of a feedforward linear power amplifier according to the present invention, and FIG. 3 is a feedforward linear power amplifier according to the present invention. 4 is a signal flow diagram of the main stage of the power amplifier, and FIG. 4 is a control flowchart of the feedforward linear power amplifier according to the present invention, FIG. 5 is a flow chart of frequency domain distortion signal processing of the feedforward linear power amplifier according to the present invention, and FIG. Is a block diagram of a feedforward linear power amplifier.

The linear power amplifier according to the present invention receives the input signal, the first coupler 1 for separating the input signal into the amplifier path and the linearization path, the phase of the input signal separated into the amplifier path from the first coupler (1) and A first phase and amplitude converter 2 for adjusting the amplitude, a main amplifier 3 for receiving and amplifying a phase and amplitude converted signal from the first phase and amplitude converter, and a signal amplified by the main amplifier. A second coupler (4) for separation, a first time delay (5) for receiving and delaying some input signals separated by a linearization path from the first coupler (1), and a separation from the second coupler (4) A subtraction circuit 6 for synthesizing the signal and the time delayed signal from the first time delayer 5, and a second phase and amplitude converter 7 for adjusting the phase and amplitude of the signal output from the subtraction circuit 6; ) And the second phase and amplitude An error amplifier 8 for receiving and amplifying a signal whose phase and amplitude are converted from the ventilation 7, a second time delay 9 for time delaying the signal separated from the second coupler 4, and An addition circuit 10 for combining and outputting the output signal of the two time delay unit 9 and the output signal of the error amplifier 8; And a third coupler (11) for separating the output signal of the subtraction circuit, the feedforward linear power amplifier comprising: a fourth coupler (12) for separating the output signal of the addition circuit (10); In order to convert the detected signal into an intermediate frequency, the PLL module 15 generates a local frequency, the signal separated from the fourth coupler 12 and the local frequency generated from the PLL module 15 are synthesized. A down converter 16 for converting the signal, a SAW filter 17 for filtering the distortion signal of the intermediate frequency synthesized and converted by the down converter 16, and the distortion signal filtered from the SAW filter 17 to a DC level. Down-converts, filters and detects the signal separated from the fourth coupler 12, including a changing log amplifier 18 and an A / D converter 19 for digitally converting the signal output from the log amplifier 18. An analog spectrum circuit 13; And a digital control circuit 14 for controlling the second phase and amplitude converter using the digitally converted DC level of the distortion signal detected from the analog spectrum circuit 13 and outputting the signal to the PPL module 15. .

Referring to the operation of the feedforward linear power amplifier according to the present invention as follows.

The input signal is divided into two by the first coupler 1 and input into the amplifier path and the linearization path, respectively. The signal input into the amplifier path is converted into phase and amplitude by the first phase and amplitude converter 2 and input to the main amplifier 3, and the main amplifier 3 amplifies the input signal.

The signal amplified by the main amplifier 3 is separated by the second coupler 4, one of which is input to the second time delay 9 and the other of which is input to the subtraction circuit 6. At this time, the signal (point B) input to the subtraction circuit 6 is as shown in FIG.

The signal transmitted to the linearization path by the first coupler 1 is input to the subtraction circuit 6 via a first time delay 5 to ensure that the subtraction circuit 6 has the same time delay between the two input paths. . At this time, the signal (point A) passing through the first time delay unit 5 is shown in FIG.

The two signals input to the subtraction circuit 6 are combined by the subtraction circuit 6 to output the signal of Fig. 3C (point C).

The signal output from the subtraction circuit 6 is separated into the third coupler 11, one of which is input to the digital control circuit 14, so that the first phase and amplitude converter 2 is supplied by the digital control circuit 14. Control, and the other is input to the second phase and amplitude converter 7 so that the phase and amplitude are converted and input to the error amplifier 8, and the error amplifier 8 amplifies the input signal to add the circuit 10. Enter At this time, the signal (point E) amplified by the error amplifier 8 and input to the addition circuit 10 is as shown in FIG.

A signal separated from the second coupler 4 and input to the second time delay 9 is time-delayed by the second time delay 9 so as to have the same time delay between the two input paths in the addition circuit 10. It is input to the addition circuit 10. At this time, the signal (point D) input to the addition circuit 10 by the second time delay unit 9 is shown in FIG.

The two signals input to the addition circuit 10 are combined by the addition circuit 10 to output the signal of Fig. 3 (f) (point F).

The signal output from the addition circuit 10 is separated by the fourth coupler 12, one of which is output as the final output signal, and the other is introduced into the analog frequency spectrum circuit 13.

The analog frequency spectrum circuit 13 receives the signal output from the digital control circuit 14 to process the incoming signal, and controls the signal introduced into the analog frequency spectrum circuit 13 to convert to the intermediate frequency, and the intermediate The data signal obtained by Fourier transforming the frequency signal is input to the digital control circuit 14.

The digital control circuit 14 analyzes the input data signal to control the first and second phase and amplitude converters 2 and 7. In this way, the output signal is monitored through the fourth coupler 12 to continuously control the second loop.

Referring to the analog frequency spectrum circuit 13 in detail with reference to Figure 2, the PLL module 15 receives the signal of the digital control circuit 14 output by the signal flowing through the fourth coupler 12, the intermediate frequency Convert to and print it out. The down converter 16, which receives the intermediate frequency converted by the PLL module 15 and the signal flowing through the fourth coupler 12, synthesizes the two signals and converts the two signals into an intermediate frequency signal including a distortion signal. The distortion signal is filtered by the filter 17. The filtered intermediate frequency signal is input to the log amplifier 18 and output as a linearized frequency data signal. The linearized frequency data signal is input to the A / D converter 19 and output as a digital data signal to the digital control circuit 14.

The digital control circuit 14 operates according to the flowcharts of FIGS. 4 and 5, and performs A / D conversion on a Fourier transformed data signal, that is, a distortion signal DC level value (S100).

The A / D converted data signal is analyzed and processed by the flowchart of FIG. 5 (S200). The analysis process S200 will be described in detail with reference to FIG. 5. First, an A / D converted distortion signal DC level value is detected (S201). The arithmetic mean value excluding the maximum value and the minimum value is obtained from the value detected in the step S201 (S202), and the slope value is calculated from the arithmetic mean value obtained in the step S202 (S203). The gradient value calculated in the step S203 is analyzed (S204).

In this way, the lowest slope value is searched among the slope values obtained in the analysis process (S200) (S300). The second loop is continuously controlled such that the slope value of the process S300 becomes the minimum slope value (S400).

In this way, by analyzing and controlling the final output in the frequency domain, the output can be stabilized.

As described above, the feedforward linear power amplifier according to the present invention is a linear power amplifier that analyzes and controls the second loop in the frequency domain for stabilization of the final output stage, and the processing time due to an analog control method or a complex algorithm using a DSP. Constraints, high-speed device selection, and the shortcomings of inefficient design due to high cost have been introduced and improved in the analog frequency spectrum concept to achieve a well-adapted and stable output result even in high frequency bands without the need for high-speed devices or complex algorithms. .

Claims (4)

A first coupler for separating the input signal, a first phase and amplitude converter for adjusting the phase and amplitude of the signal, a main amplifier for amplifying the signal, a second coupler for separating the signal, and a time A first time delay for delaying, a subtraction circuit for combining the two signals, a second phase and amplitude converter for adjusting the phase and amplitude of the signal, an error amplifier for amplifying the signal, a second for delaying the signal 11. A feedforward linear power amplifier comprising a time delay and a third coupler for separating an output signal of said subtraction circuit with an addition circuit for synthesizing a signal, A fourth coupler for separating the output signal of the addition circuit; A PLL module for generating a local frequency for converting the detected signal to an intermediate frequency, a down converter for synthesizing the incoming signal separated from the fourth coupler and the local frequency generated in the PLL module and converting the signal into an intermediate frequency signal; And a SAW filter for filtering the distortion signal of the intermediate frequency synthesized and converted through the down converter, a log amplifier for changing the distortion signal filtered from the SAW filter to a DC level, and digitalizing the signal output from the log amplifier. An analog spectrum circuit for down-converting, filtering, and detecting a signal separated from the fourth coupler, including an A / D converter; And And a digital control circuit for controlling a second phase and amplitude converter using the digitally converted DC level of the distortion signal detected from the analog spectrum circuit, and outputting a signal to the PPL module. delete The digital control circuit of claim 1, wherein the digital control circuit performs A / D conversion on the DC level signal of the distortion signal detected by the analog spectrum circuit, and analyzes the A / D converted signal, and the analyzed gradient value is the lowest value. A feedforward linear power amplifier, characterized in that it continuously controls the second loop to search for an application to be the lowest slope value. The method of claim 3, wherein the signal analysis of the digital control circuit detects a DC level value of the A / D converted distortion signal, obtains an arithmetic mean value excluding a maximum value and a minimum value from the detected value, And a slope value is calculated and analyzed by the calculated slope value.